Aaa Mcat Z Comprehensive Mcat Organic Chemistry

Front 1

Lewis Dot Structure

Back 1

Most basic form of structural formula

3 rules:
1. find total # of valence electrons for all atoms in molecule
2. use 1 pair of electrons to form 1 bond between each atom
3. arrange remaining electrons around atoms to satisfy duet rule for H and octet rule for other atoms

Front 2

Valence

Back 2

number of bonds an atom usually forms

C = 4, tetravalent
N = 3, trivalent
O = 2, divalent
H & halogens = 1, monovalent

Front 3

Formula charge

Back 3

number of electrons in the isolated atom, minus # of electrons assigned to the atom in lewis structure

sum of formal charges for each atom in molecule or ion represents total charge on molecule or ion

Front 4

Dash formula

Back 4

shows bonds between atoms

doesn't show 3D structure of molecule

Front 5

Condensed formula

Back 5

does not show bonds

central atoms are followed by atoms that bond to them (even though it is not the bonding order)

ex:
CH3CH2CH2OH

Front 6

Bond-line formula

Back 6

line intersections, corners and endings represent a C atoms, unless other atom is drawn in

H atoms attached to C are not usually drawn but assumed to be present

Front 7

Fischer projection

Back 7

vertical lines are assumed to be oriented into the page

horizontal lines are assume to be oriented out of page

Front 8

Newman projection

Back 8

view straight down axis of 1 of sigma-bonds

both intersecting lines and large circle are assumed to be C atoms

Front 9

Dash-line-wedge formula

Back 9

black wedge is assumed to be coming out of page

dashed wedge assumed to be going into page

lines assumed to be in plane of page

Front 10

ball and stick models

Back 10

ball = atoms
stick = bonds

3D structure of molecules

Front 11

Index of Hydrogen Deficiency

Back 11

# of pairs of H a compound requires in order to become a saturated alkane

saturate alkane contains (2n + 2) # of H, where n = # C

Index of H deficiency = [(2n+2) - x]/2
n: # C atoms
x: # H atoms
count halogens as H, ignore O, count N as 1/2 H

index of H deficiency of saturate alkane = zero

Front 12

Functional groups

Back 12

reactive, non-alkane portions of molecules

List #1:
1. alkane
2. alkene
3. alkyne
4. alcohol
5. ether
6. amine
7. aldehyde
8. ketone
9. carboxylic acid
10. ester
11. amide

Front 13

Alkane

Back 13

C-C single bond

methane

Front 14

Alkene

Back 14

C-C double bond

Front 15

Alkyne

Back 15

C-C triple bond

Front 16

Alcohol

Back 16

R-OH

Front 17

Ether

Back 17

R-O-R

Front 18

Amine

Back 18

Primary amine:
R-N-H2

Secondary amine:
R2-N-H

Tertiary amine:
R3-N

Front 19

Aldehyde

Back 19

R-C-O-H

Front 20

Ketone

Back 20

R-C-O-R

Front 21

Carboxylic acid

Back 21

R-C-O-OH

Front 22

Ester

Back 22

R-C-O-OR

Front 23

Amide

Back 23

R-C-O-NH2

Front 24

Functional groups

Back 24

List #2:
1. Alkyl
2. Halogen
3. gem-dihalide
4. vic-dihalide
5. hydroxyl
6. alkoxy
7. hemiacetal
8. hemiketal
9. mesyl group
10. tosyl group
11. carbonyl
12. acetyl
13. acyl
14. anhydride
15. aryl
16. benzyl
17. hydrazine
18. hydrazone
19. vinyl
20. vinylic
21. allyl
22. nitrile
23. epoxide
24. enamine
25. imine
26. tautomers
27. oxime
28. nitro
29. nitroso

Front 25

Alkyl

Back 25

1 H substituted from an alkane

Front 26

Halogen

Back 26

Halo-

F, Cl, Br or I

Front 27

Hydroxyl

Back 27

-OH

Front 28

alkoxy

Back 28

-OR

Front 29

Prefix = C #s

Back 29

meth = 1
eth = 2
prop = 3
but = 4
pent = 5
hex = 6
hept = 7
oct = 8
non = 9
dec = 10

Front 30

IUPAC rules for nomenclature

Back 30

1. longest C chain with most substituents determines base name
2. end C closest to C with substituent is always 1st C. In case of tie, look to next substituent
3. Any substituent is given same # as its C
4. if same substituent is used more than once, use prefixes: di, tri, tetra, etc
5. order substituents alphabetically

Front 31

Electrostatic force

Back 31

force between electrons and nuclei that creates all molecular bonds

takes 2 electrons to form a bond

electrons are at lowest energy level when they form a bond because they have minimized their distance from both nuclei

each bonded nuclei can donate a single electron to the bond

Front 32

Coordinate covalent bond

Back 32

one nucleus donates both electrons to the bond

Front 33

Sigma-bond

Back 33

forms when bonding pair of electrons are localized directly between 2 bonding atoms

lowest energy, most stable form of covalent bond, strong

always 1st type of covalent bond to formed between any 2 atoms

single bond must be a sigma-bond

any double or triple bond, contains 1 sigma-bond

Front 34

Pi-bonds

Back 34

additional bonds that form between 2 sigma-bonded atoms

orbital of 1st Pi-bond forms above and below sigma-bonding electrons because sigma-bond leaves no room for other electron orbitals directly between atoms

1 pi-bond = double bond (orbital above and below sigma-bond)
2 pi-bonds = triple bond (orbital on either side of sigma-bond)

weaker and more reactive than sigma-bond, but strengthen and shorten overall bond

C, N, O & S form pi-bonds

pi-bonds prevent rotation

Front 35

Bond energy

Back 35

energy necessary to break a bond

Front 36

Atomic orbitals

Back 36

s, p, d and f orbitals

Front 37

Atomic orbitals of lone C atom

Back 37

C has 4 valence electrons

2 electrons in s subshell
2 electrons in 2 orbitals of p subshell

Front 38

Atomic orbitals of C with 4 sigma-bonds

Back 38

4 hybrid orbitals = 4 sigma-bonds

4 electrons in 4 sp hybrid orbitals (equivalent in shape and energy)

hybrid orbital overlap leads to sigma-bond formation in area where orbitals coincide

Front 39

hybrid orbitals

Back 39

types:
1. sp
2. sp^2
3. sp^3

add # of lone pairs of electrons to # sigma-bonds and match total # to sum of superscripts in hybrid name (no superscript = 1)

ex: H2O
2 lone pairs + 2 sigma-bonds = 4
4 = 1 + 3 = sp^3

Front 40

Character

Back 40

superscripts indicate the character as follows:
sp^2 = 1s + 2p = 33% s + 66% p

hybrid orbitals resemble in shape and energy the s and p orbitals from which it is formed to the same extent that s or p orbitals are used

the more s character a bond has, the more stable, stronger, shorter the bond becomes

Front 41

hybridization, bond angles and shape

Back 41

sp = 180 = linear

sp^2 = 120 = trigonal planar

sp^3 = 109.5 = tetrahedral, pyramidal or bent

dsp^3 = 90, 120 = trigonal-bypyramidal, seesaw, T-shaped or linear

d^2sp^3 = 90 = octahedral, square pyramidal or square planar

Front 42

Resonance structure

Back 42

2 or more lewis structures representing molecules with delocalized electrons (bonding electrons spread out over 3 or more atoms)

weighed average of these structures represents real molecule (lower energy than lewis structures)

Front 43

4 rules for resonance structures

Back 43

1. atoms must not be moved (move electrons, not atoms)
2. # of unpaired electrons must remain constant
3. resonance atoms must lie in same plane
4. only proper lewis structures allowed

Front 44

2 conditions exist for resonance structures to occur

Back 44

1. a species must contain an atom either with a p orbital or an unshared pair of electrons
2. that atom must be single bonded to an atom that possesses a double or triple bond (Conjugated unsaturated systems)

Front 45

Aromatic

Back 45

rings that display resonance

Front 46

dipole moment

Back 46

occurs when center of positive charge (center of mass) on molecule or bond doesn't coincide with center of negative charge

represented by arrow pointing from positive charge to negative charge, arrow is crossed at center of positive charge

measure in units of debye (D)
micron = qd
q: magnitude of charge
d: distance between centers of change

Front 47

Polar molecule or bond

Back 47

molecule or bond with dipole moment

results from differences in electronegativity of its atoms

molecules with polar bond may or may not have a dipole moment

Front 48

Nonpolar molecule or bond

Back 48

molecule or bond without dipole moment

Front 49

Induced dipoles

Back 49

weaker than permanent dipoles

dipole moment is momentarily induced in an otherwise nonpolar molecule or bond by a polar molecule, ion or electric field

Front 50

Instantaneous dipole moment

Back 50

electrons in bond move about orbital, and at any given moment may not be evenly distributed between 2 bonding atoms

very short lived and weaker than induced dipoles

can act to induce dipole in neighboring atom

Front 51

Intermolecular attractions

Back 51

attractions between separate molecules

occur solely due to dipole moments

must weaker than covalent forces (1% as strong)

attraction between molecules in proportional to their dipole moments

Front 52

Hydrogen bond

Back 52

intermolecular bond formed when H is attached to a highly electronegative atom (N, O or F) it creates a large dipole moment leaving H with strong partial positive charge. When H approaches N, O or F on another atom, intermolecular bond is formed

Front 53

London Dispersion Forces

Back 53

weakest dipole-dipole force

between 2 instantaneous dipoles

very weak, but are responsible for phase changes of nonpolar molecules

Front 54

Isomers

Back 54

unique molecules with same molecular formula

2 molecules are isomers if they have same molecular formula but are different compounds

Front 55

Conformational isomers (conformers)

Back 55

not true isomers

different spatial orientations of the same molecule

simplest way to distinguish between conformers is with newman projections

Front 56

Structural isomer

Back 56

simplest form of isomer

same molecular formula but different bond-to-bond connectivity

ex:
isobutane and n-butane, both are C4H10, but have different structures

Front 57

Stereoisomers

Back 57

2 unique molecules have same molecular formula and same bond-to-bond connectivity

Front 58

Chirality

Back 58

handedness of a molecule

chiral molecules differ from their reflections

achiral molecules are exactly the same as their reflections

any C is chiral if it is bonded to 4 different substituents

Front 59

Absolute configuration

Back 59

physical description of orientation of atoms about a chiral center (such as a chiral carbon)

2 possible configurations:
1. molecule
2. mirror image of molecule

Determined by R (right) & S (left):
1. atoms attaches to chiral center or #ed from higher (higher atomic weight) to lowest priority (smaller atomic weight)
2. substituents on double and triple bonds are counted 2 or 3 times, respectively
3. lowest priority group faces away
4. circle is drawn from lowest to higher priority
5. clockwise (R) and counter-clockwise (S)
6. mirror image always has opposite absolute configuration

Front 60

Relative configuration

Back 60

not related to absolute configuration

2 molecules have the same relative configuration about a C if they differ by only 1 substituent and other substituents are oriented identically about C

Front 61

Observed rotation

Back 61

direction and degree to which a compound rotates plane-polarized light

Front 62

Polarimeter

Back 62

screens out photons with all but one orientation of electric field

resulting light consists of photons with their electric fields oriented in same direction

Front 63

Plane-polarized light

Back 63

white light that has passed through a polarimeter and now has photons all oriented in same direction

Front 64

Optically inactive

Back 64

may be compounds with no chiral centers or contain equal amounts of both stereoisomers

compound does not rotate light

no single molecular orientation is favored, so there is no rotation of plane of electric field.

Front 65

Racemic mixture

Back 65

optically inactive compound

contains equal amounts of both stereoisomer therefore no rotation of light is observed

Front 66

Optically active

Back 66

compound that rotates light, orientation of electric field is rotated

racemic mixture is separated, resulting in compound containing molecules with no mirror images

if rotates plane-polarized light clockwise = + or d (right)

if rotates plane-polarized light counter-clockwise = - or l (left)

Front 67

Observed rotation

Back 67

direction and # of degrees that electric field in plane-polarized light rotates when it passes through a compound

Front 68

Specific rotation

Back 68

standardized form of observed rotation

calculated from observed rotation and experimental parameters

Front 69

Stereoisomers

Back 69

2 molecules with same molecular formula and same bond-to-bond connectivity that are not same compound

unless geometric isomers, stereoisomers much each contain at least 1 chiral center in same location

2 types:
1. enantiomers
2. diastereomers

Front 70

Enantiomers

Back 70

same molecular formula

same bond-to-bond connectivity

mirror images of each other

not same molecule

opposite absolute configurations at each chiral C

rotate plane-polarized light in opposite directions to an equal degree

same physical and chemical properties except:
1. reactions with other chiral compounds
2. reactions with polarized light

make racemic mixture, when mixed together in equal concentrations

Front 71

Resolution

Back 71

separation of enantiomers

Front 72

Diastereomers

Back 72

same molecular formula

same bond-to-bond connectivity

not mirror images to each other

not same compound

Front 73

Geometric isomer

Back 73

type of diastereomer

exist due to hindered rotation about a bond (ring structure, double or triple bond)

different physical properties

1. 2 substituents on each C are prioritized using atomic weight
2. higher priority substituent for each C on opposite sides = E
3. higher priority substituent for each C same side = Z

Front 74

Cis-isomers

Back 74

diastereomers

geometric isomers

molecules with same side substituents

have dipole moment

stronger intermolecular forces leading to higher boiling points (due to dipole moment)

do not form crystals as readily leading to lower melting points (due to lower symmetry)

steric hindrance (substituents crowd each other) produce higher energy levels resulting in higher heats of combustion

Front 75

Trans-isomers

Back 75

diastereomers

geometric isomers

molecules with opposite-side
substituents

do not have dipole moment

Front 76

Maximum # of optically active isomers

Back 76

2^n
n: # of chiral centers

Front 77

Meso compounds

Back 77

2 chiral centers in a single molecule may offset each other creating an optically inactive molecule

plane of symmetry through their centers which divides them into 2 halves that are mirror images to each other

are achiral and therefore optically inactive

Front 78

Epimers

Back 78

Diastereomers that differ at only 1 chiral C

Front 79

Anomers

Back 79

chiral C is called an anomeric C

distinguished by orientation of substituents

when ring closure occurs at epimeric C, 2 possible diastereomers may be formed

ex:
1. alpha-glucose (OH oriented opposite direction of CH3)
2. beta-glucose (OH oriented same direction of CH3)

Front 80

Alkanes

Back 80

Methane and compounds whose major functional group contains only C-C single bonds

Depending on how many other alkyl groups are attached, C are referred to as:
1. methyl (0 alkyl groups)
2. primary (1)
3. secondary (2)
4. tertiary (3)

Front 81

Physical properties of alkanes

Back 81

boiling point is governed by intermolecular forces

as C are added in single chain, molecular weight increases, intermolecular forces increase, boiling and melting point increases

Branching lowers boiling point but increases melting point

1st 4 alkanes are gases at RT

low density (density increases with molecular weight)

insoluble in water

soluble in hydrocarbons

Front 82

Cycloalkanes

Back 82

alkane rings

some rings structures put strain on the C-C bonds because they bend them away from normal 109.5 degree angle of sp^3 C and cause crowding

Front 83

Ring Strain

Back 83

cyclohexane = 0 but increases as rings become larger or smaller

increases up to 9C ring structure, after which it becomes zero as more C are added

less ring strain means lower energy and more stability

Front 84

Cyclohexane

Back 84

ring straing = 0

3 confomers:
1. chair
2. twist
3. boat

all 3 exist at room temperature, but chair predominates because it is lowest energy

each C in cyclohexane has 2 H

in chair conformation, H are oriented in different directions

Front 85

Equatorial hydrogens

Back 85

H projecting outward from center of ring

substituent groups favored in this position

Front 86

Axial hydrogen

Back 86

H projecting upward or downward

crowding occurs most often in this position with substituents, which raises energy level of ring and causes instability

Front 87

Combustion

Back 87

violent reaction

alkanes mixed with O and energy is added

takes place at high temperatures (inside flame of a match)

generates its own heat and can be self-perpetuation

reactants:
1. alkane
2. oxygen
3. energy, high temperature

products:
1. Carbon dioxide
2. water
3. heat

Front 88

Radical reaction

Back 88

combustion is a type of radical reaction

alkanes reaction with halogens (F, Cl, Br, but not I) in presence of heat or light to form free radicals (each atom in bond retains 1 electron from broken bond)

results in 2 highly reactive species, each with an unpaired electron (free radical)

Front 89

Heat of combustion

Back 89

change in enthalpy (H) of a combustion reaction

can be used to compare relative stabilities of isomers because combustion of isomeric hydrocarbons requires equal amounts of O and produced equal amounts of CO2 and H2O

higher heat of combustion, higher energy level, less stability

Front 90

Halogenation

Back 90

chain reaction with at least 3 steps:
1. initiation
2. propagation
3. termination

exothermic process

stability of alkyl radicals (same as carbocation):
tertiary > secondary > primary > methy

alkyl radical exhibit trigonal planar geometry

Front 91

Initiation

Back 91

halogen starts as diatomic molecule, which is homolytically cleaved by heat or light

resulting in free radicals

Front 92

Propagation

Back 92

halogen radical removes H from alkane

resulting in alkyl radical

alkyl radical reacts with diatomic halogen creating alkyl halide and new halogen radical

may or may not continue indefinitely

stage at which most of product is formed

Front 93

Termination

Back 93

2 radicals bond to end chain reaction or propagation

radical bonds to wall of container to end chain reaction or propagation

Front 94

Reactivity of halogens

Back 94

from most to least reactive:
1. F (can be explosive)
2. Cl
3. Br (requires heat to react)
4. I (nonreactive)

Front 95

Selectivity of halogens

Back 95

how selective a halogen radical is when choosing a position on an alkane

from most to least selective:
1. I
2. Br
3. Cl
4. F

Front 96

Alkene

Back 96

C-C chain that contains a double bond

contain pi-bonds, which are less stable than sigma-bonds, making alkenes more reactive than alkanes

more acidic than alkanes, because pi-bonds are electron-hungry

the more substituted, the more thermodynamically stable

increase molecular weight means increased boiling point

branching decreases boiling point

same physical property trends as alkanes and alkynes

Front 97

Elimination reaction

Back 97

synthesis of alkene

1 or 2 functional groups are removed to form a double bond

base abstracts a H

Front 98

Dehydration of an alcohol

Back 98

E1 reaction, which means rate only depends on 1 species concentration (in this case the alcohol)

alcohol forms alkene in presence of hot concentrated acid

1. acid protonates OH, producing good leaving group H2O
2. (slower, rate determining step) H2O drops off, forming a carbocation (rearrangement may occur if more stable carbocation can be formed)
3. H2O deprotonates carbocation and alkene is formed

major product is most stable, most substituted alkene

Front 99

Carbocation stability

Back 99

follows same trend as radical stability

most to least stable:
tertiary > secondary > primary > methyl

Front 100

Saytzeff rule

Back 100

major product of elimination will be most substituted alkene

Front 101

Dehydrohalogenation

Back 101

E1 if absence of strong base

E2 if high concentration of strong, bulky base

E1: (2 steps)
1. halogen drops off
2. H is removed by weak base

E2: (1 step)
1. Base removes H from C next to halogen-containing C and halogen drops off, leaving alkene

bulky base prevents Sn2 reaction

if base too bulky, Saytzeff rule is violated, resulting in least substituted alkene

Front 102

Substitution reaction

Back 102

nucleophile attacks C

Front 103

Hydrogenation

Back 103

example of addition reaction

heterogeneous catalyst (exists in a different phase than reactants or products, tiny shavings of metal) used

exothermic reaction with high energy of activation

heats of hydrogenation can be used to measure relative stability of alkene

lower heat of hydrogenation, more stable alkene

Front 104

Syn-addition

Back 104

same side addition

hydrogenation

catalyst is usually tiny shavings of metal

1. H and alkene adsorb to surface of catalyst
2. Both Hydrogens add to same size of alkene, forming an alkane

Front 105

Ozonolysis

Back 105

oxidation cleaves alkene at double bond

reactants:
1. alkene
2. ozone (reactive electron pairs with high charge density, very reactive, breaks through alkenes and alkynes)
3. Zinc
4. H2O

products:
1. 2 molecules of O double bonded to C (ketone)

Front 106

Electrophile

Back 106

electron-loving species

partially positive charge

attracted to double bond of alkene because of electron-rich environment

Front 107

Markonikov's rule

Back 107

rule followed when H-halides (HF, HCl, HBr, and HI) are added to alkenes

H will add to least substituted C of double bond

2 steps:
1. H-halide (bronsted-lowry acid) creates positively charged H, which acts as electrophile (slow, rate determining step) and attacks double bond to form carbocation
2. newly formed carbocation picks up negatively charged halide ion

Front 108

Anti-Markovnikov addition

Back 108

If peroxides (ROOR) are present, Br and not H will add to least substituted C

other halogens still follow Markovnikov's rule even in presence of peroxides

Front 109

Hydration of alkene

Back 109

follows Markovnikov's rule

H2O is added to alkene in presence of acid

reverse of dehydration of an alcohol

low temperatures and dilute acid drive reaction toward alcohol formation

high temperatures and concentrated acid drive reaction toward alkene formation

alkene + H2O = alcohol
<--- concentrated acid and heat
---> dilute acid and cold

Front 110

Anti-addition

Back 110

addition from opposite sides of double bond

Front 111

Oxymercuration/demercuration

Back 111

reaction creates alcohol from alkene

follows Markovnikov's rule

1. Hg(OAc)2 partially dissociates to +Hg(OAc), which acts as electrophile, attacking double bone and forming mercurinium ion. Water attacks mercurinium ion to form organomercurial alcohol in anti-addition
2. demercuration to form alcohol by addition of reducing agent or base

in organometallic compounds, metals like to lose electrons and take on full or partial positive charge

Front 112

Hydroboration

Back 112

anti-Markovnikov and syn-addition reaction

produces alcohol from alkene

presence of peroxide

Front 113

Halogenation of alkenes

Back 113

halogens are more reactive toward alkenes and alkynes than alkanes (need heat or light to react)

Br2 and Cl2 add to alkenes via anti-addition to form vic-dihalides (2 halogens connected to adjacent C)

if water present, halohydrin formed (OH and halogen attached to adjacent C)

Front 114

Benzene

Back 114

undergoes substitution and not addition

has resonance, therefore aromatic

flat molecule because resonance atoms are in same plane

stabilized by resonance, therefore C-C bonds have partial double bond character

contains 6 Hydrogens

If contains 1 substituent, remains 5 positions are labeled:
1. ortho (closest to substituent)
2. meta (2nd closest)
3. para (furthest from substituent)

Front 115

Electron withdrawing group

Back 115

is in R position of ring (substituent)

deactivates ring (make less reactive)

directs new substituents to meta position

exception:
halogens are electron withdrawing group and deactivate ring as expected, but direct new substituents to ortho and para positions

Front 116

Electron donating group

Back 116

activates ring (make more reactive)

directs new substituent to ortho and para positions

Front 117

Strongly electron donating group

Back 117

1. O-
2. OH
3. NR2

Front 118

Moderately electron donating group

Back 118

1. OR

Front 119

Weakly electron donating group

Back 119

1. R

Front 120

Strong electron withdrawing group

Back 120

1. NO2
2. NR3+
3. CCl3

Front 121

Moderately electron withdrawing group

Back 121

1. CRO
2. CHO
3. COOR
4. COOH
5. SOOOH
6. CN

Front 122

Weakly electron withdrawing group

Back 122

1. X

Front 123

Benzene compounds

Back 123

1. phenol = benzene-OH
2. aniline = benzene-NH2
3. toluene = benzene-CH3
4. benzoic acid = benzene-COOH
5. nitrobenzene = benzene-NO2

Front 124

Substitution reaction

Back 124

1 functional group replaces another

2 types:
1. SN1
2. SN2

substitution, nucleophilic, unimolecular, bimolecular

# represents order of rate law ans not number of steps

Front 125

SN1 reaction

Back 125

substitution reaction

rate dependent only on 1 of the reactants, independent of nucleophile, directly proportional to concentration of substrate (eletrophile, molecule being attacked by nucleophile)

2 steps:
1. formation of carbocation (Slow, rate determining step), leaving group (group being replaced) breaks away on its own to form carbocation
2. (quick) nucleophile attacks carbocation

only tertiary substrate will undergo SN1

Elimination often accompanies SN1 reactions to produce alkene

strength of nucleophile unimportant

Front 126

SN2 reaction

Back 126

single step

rate dependent on concentration of nucleophile and substrate

1. nucleophile attakcs substrate from behind leaving group and knocks leaving group free while bonding to substrate

results in inversion of configuration on C being attacked by nucleophile

tertiary C sterically hinders nucleophile attack

rate of reaction decreases from:
methyl > primary > secondary

E2 often accompanies SN2 reactions to produce alkene

strength of nucleophile important

Front 127

Nucleophile

Back 127

base always stronger nucleophile (more negative charge and polarizable, less electronegative) than its conjugate acid

basicity not the same as nucleophilicity (decreases up and right on periodic table)

negative charge and polarizability add to nucleophilicity and electonegativity reduces nucleophilicity

nucleophile behaves as base then elimination reaction results

Front 128

Sn1 vs. Sn2

6 things: "the nucleophile and the 5 Ss"

Back 128

1.Nucleophile
2. Substrate
3. Solvent
4. Speed
5. Stereochemistry
6. Skeleton rearrangement

Front 129

Nucleophile

Back 129

Sn2 requires a strong nucleophile

nucleophilic strength doesn't affect Sn1

Front 130

Substrate

Back 130

Sn2 reactions don't occur with sterically hindered substrate

Sn2 requires methyl, primary or secondary substrate

Sn1 requires secondary or tertiary substrate

Front 131

Solvent

Back 131

highly polar solvent increases reaction rate of Sn1 by stabilizing carbocation

highly polar solvent slows down Sn2 reaction by stabilizing nucleophile

Front 132

Speed

Back 132

Speed of Sn2 depends on concentration of substrate and nucleophile

Speed of Sn1 depends only on substrate

Front 133

Stereochemistry

Back 133

Sn2 inverts stereochemistry about chiral center

Sn1 creates a racemic mixture

Front 134

Skeleton rearrangement

Back 134

Sn1 may be accompanied by carbon skeleton rearrangement

Sn2 never rearranges carbon skeleton

Front 135

Elimination

Back 135

Can accompany both Sn1 and Sn2 reactions

occurs when nucleophile behaves as a base rather than a nucleophile (abstracts protons rather than attacking a C)

always results in C-C double bond

E1 and E2 kinetics are similar to Sn1 and Sn2 kinetics respectively

Front 136

Alcohols

Back 136

Boiling point goes up with molecular weight and down with branching

Melting point goes up with molecular weight, unclear trend with branching

boiling and melting points are much higher than alkanes because of hydrogen bonding (increases intermolecular forces, which must be overcome to change phase)

more soluble in water than alkane and alkenes (longer to C chain, the less soluble)

hydroxyl group increases polarity and allows for hydrogen bonding with water

lose proton, therefore act as acid (less acidic than water)

Front 137

Alcohol order of acidity (strongest to weakest)

Back 137

methyl
primary
secondary
tertiary

most stable conjugate base is of strongest acid, weakest negative charge

Front 138

acid & conjugate base

Back 138

H2O --> OH- (water, more acidic)

RCH2OH --> RCH2O- (primary alcohol, neutral)

RCCH3CH3OH --> RCCH3CH3O- (tertiary alcohol, more basic)

Front 139

Grignard Synthesis of an Alcohol

Back 139

1. organometallic compound (strong nucleophile and base) nucleophilic attack on a carbonyl C
2. after acid bath (H3O+), produces an alcohol

Front 140

Reduction Synthesis of an Alcohol

Back 140

nucleophilic attack mechanism

similar to grignard synthesis

hydrides (H-) react with carbonyls to form alcohols

doesn't extend the C skeleton, unlike grignard

NaBH4 & LiAlH4 reduce aldehydes and ketones

only LiAlH4 is strong enough to reduce esters and acetates because carbonyl C has less positive charge because of electron donation and therefore is less attractive to nucleophile

Front 141

Nucleophilic addition

Back 141

1. H2O (alcohol, nucleophile) attacks and connects to substrate
2. positive charged proton will drop off into solution

Front 142

Nucleophilic substitution

Back 142

1. H2O (alcohol, nucleophile) attaches and connects to substrate
2. R group of substrate is kicked off
3. positive charged proton will drop off into solution

Front 143

Oxidation of alcohols

Back 143

primary and secondary alcohols can be oxidized

tertiary alcohols cannot be oxidized

primary alcohols oxidize to aldehydes, which in turn, oxidize to carboxylic acids

secondary alcohols oxidize to ketones

reverse process is called reduction

Front 144

Oxidation or reduction

Back 144

Oxidation:
1. loss of H2
2. addition of O or O2
3. addition of X2 (X = halogens)

Reduction:
1. addition of H2 (or H-)
2. loss of O or O2
3. loss of X2

Neither oxidation nor reduction:
1. addition or loss of H+, H2O or HX

if O to H ratio of a molecule increases, than molecule has been oxidizes

if O to H ratio decreases, than molecule has been reduced

oxidizing agents have lots of O

reducing agents have lots of H

Front 145

alkyl halides from alcohols

Back 145

1. hydroxyl group of alcohol is protonated by Halide and water is good leaving group
2. halide ion (nucleophile) attacks and cinnects to C and kicks off H2O, forming alkyl halide

Sn1 reaction with tertiary alcohol

Sn2 reaction with other alcohols

C-O bond is broken, alcohol is electrophile

O-H bond is broken, alcohol is nucleophile

protonation of hydroxyl group (alcohol) requires strong acid,

Front 146

Formation of sulfonates

Back 146

alcohols form esters called sulfonates

nucleophilic substitution, alcohol acts as nucleophile

tosylates and mesylates are commonly used sulfonates

sulfonate ions are weak bases and excellent leaving groups (Sn1 or Sn2 reactions)

Front 147

Pinacol rearrangement

Back 147

dehydration of an alcohol (vicinal diol) that results in an unexpected product (ketone or aldehyde)

1. 1st OH is protonated and removed by acid to form carbocation
2. methyl group may move to form more stable carbocation, which exhibits resonance
3. water deprotonates most stable resonance (all atoms have octet of electrons) forming pinacolone and regenerating acid catalyst

Front 148

ethers

Back 148

relatively non-reactive (other than epoxides)

hydrogen bond with compounds that contain H attached to N, O or F

polar, soluble in water

organic compounds soluble in ethers (no H need to be broken) making ethers useful solvents

relatively low boiling points, similar to alkanes (making them useful solvents)

undergo one reaction with halo-acids (HI or HBr) to form alcohols or alkyl halides
1. R2O + HBr --> ROH + RBr

oxidized to form peroxides

Front 149

Epoxides

Back 149

3-membered cyclic ethers

more reactive than typical ethers due to ring strain

react with water in presence of acid catalyst to form diols (glycols), in an anti-addition

epoxide O often protonated to form an alcohol, when one of C is attacked by nucleophile

Front 150

acidities of functional groups (weakest to strongest)

Back 150

1. H3C-CH3
2. H2C=CH2
3. H2
4. NH3
5. HC triple bond CH
6. H3CCHO
7. H3C-CH2-OH
8. H2O
9. H3CCOOH

Front 151

Carbonyl

Back 151

C double bonded to an O

double bond is shorter and stronger than double bond of alkene

Include:
Aldehydes (nucleophilic addition), ketones (nucleophilic addition), carboxylic acids (nucleophilic substitution), amides (nucleophilic substitution) and esters (nucleophilic substitution)

1. planar stereochemistry
2. partial positive charge on C, partial negative charge on O

susceptible to nucleophilic attack because of planar stereochemistry

any attack on carbonyl will form a nucleophile because of partial positive charge on C

partial negative charge on O means it is easily protonated

Front 152

Aldehyde and Ketone

Back 152

more polar, higher boiling points than alkanes and alkenes of similar MW

lower boiling points than corresponding alcohols because cannot H-bond with each other

excellent solvents because can H-bond with other compounds

soluble in water with up to 4 C

act as substrate in nucleophilic addition or Bronsted-Lowry acid by donating one of its alpha-H

Front 153

alpha-C

Back 153

C attached to carbonyl C is in alpha position

Front 154

alpha-H

Back 154

H attached to alpha-C

donated by bronsted-lowry acid

forms an enolate ion (alpha-C anion) that is stabilized by resonance

Front 155

beta-C

Back 155

if a carbonyl as well as alpha-C (beta-dicarbonyl), then enol is more stable due to internal H-bonding and resonance

dicarbonyl increases acidity of alpha-H between carbonyls, making it more acidic than water and alcohol

Front 156

tautomers

Back 156

reaction at equilibrium and not resonance

involves proton shift, from alpha-C to carbonyl O

due to properties of alpha-H and carbonyl

aldehydes and ketones exist as tautomers at room temperature

Front 157

Acetals and ketals

Back 157

reaction between aldehydes or ketones with alcohols

form hemiacetals and hemiketals through nucleophilic addition (alcohol acting as nucleophile)

If another second molar concentration of alcohol is added, acetal and ketal are formed from hemiacetal and hemiketal

Front 158

Aldol condensation

Back 158

demonstrates alpha-H activity and susceptibility of carbonyl C to a nucleophile

occurs when:
1. an aldehyde reacts with another
2. a ketone reacts with another
3. an aldehyde reacts with a ketone

reaction is catalyzed by an acid or base

steps:
1. base abstracts alpha-H leaving an enolate ion
2. enolate ion acts as nucleophile and attacks carbonyl C to form alkoxide ion
3. alkoxide is stronger base than OH- ion, thus removes a H from H2O to complete aldol
4. aldol is unstable and easily dehydrated by heat or base to become an enal, which is stabilized by conjugated double bonds

Front 159

Halogenation of ketones

Back 159

Halogens add to ketones at alpha-C in presence of acid or base

base makes it difficult to prevent halogenation at more than 1 alpha positive

base is consumed by reaction with H2O as by-product

acid acts as true catalyst and is not consumed by reaction

Front 160

Haloform reaction

Back 160

if base is used with methyl ketone, alpha-C will become completely halogenated

trihalo product reacts with base to produce carboxylic acid and haloform

Front 161

haloform

Back 161

1. chloroform, CHCl3
2. bromoform, CHBr3
3. iodoform, CHI3

Front 162

Wittig Reaction

Back 162

converts ketone (or aldehyde) to alkene

phosphorous ylide is used (neutral molecule with negative charged carboanion)

1. ketone undergoes nucleophilic addition from ylide to form betaine
2. betaine is unstable and breaks down to triphenylphosphine oxide and alkene

mixture of cis and trans isomers are formed

Front 163

Carboxylic Acid

Back 163

behaves as acid or as substrate in nucleophilic substitution reaction

stereochemistry makes it susceptible to nucleophiles

OH group is protonated, forming to good leaving group water and substitution results

strong organic acids, conjugate base is stabilized by resonance

electron withdrawing groups on alpha-C help stabilize conjugate base and thus increases acidity of acid

know:
1. formic acid, methanoic acid
2. acetic acid, ethanoic acid
3. benzoic acid

salt of acids are named with suffix "ate" which replaced "ic"

Front 164

Physical properties of Carboxylic acids

Back 164

make strong double H-bonds to form dimers

dimer increases boiling point by doubling MW of molecules leaving liquid phase

melting point is lowered by double bonds of unsaturated carboxylic acids because impede crystal lattice
saturate carboxylic acids, more than 8 C, are solids

4C or less = water soluble
5C or more = less soluble in water
10C or more = insoluble in water

soluble in nonpolar solvents

Front 165

Decarboxylation

Back 165

when carboxylic acid loses CO2

exothermic, high activation energy

lower activation energy when beta-C is carbonyl because of anion stabilization by resonance or stable cyclic intermediate

final products are tautomers

Front 166

Acyl Chlorides

Back 166

derivatives of carboxylic acids contain acyl groups

RC=O

acyl chlorides form from reaction of inorganic acid chlorides (SOCl2, PCl3, PCl5) with carboxylic acids by nucleophilic substitution

bronsted-lowry acids, donate alpha-H

stronger acids than aldehydes

Front 167

Acid Chlorides

Back 167

most reactive of carboxylic acid derivatives because of stability of Cl- leaving group

love nucleophiles

carboxylic acid derivatives (acid chloride, ester, amide, anhydride) hydrolyze to form carboxylic acids

Front 168

Ester

Back 168

form from reaction of carboxylic acids with alcohols through nucleophilic substitution

strong acid catalyzes reaction by protonating OH of carboxylic acid

process called esterification

Front 169

transesterification

Back 169

alcohols react with esters

an alkoxy group (OR) is substituted for another

Front 170

Acetoacetic ester synthesis

Back 170

production of keton from acetoacetic ester due to strong acidic properties of alpha-H

acidity of alpha-H between carbonyls is increased in beta-dicarbonyl compounds

1. base removes alpha-H resulting in enolate ion
2. enolate ion is alkylated by alkyl halide or tosylate, forming alkylacetoacedic ester
3. alkylacetoacedic ester, a beta-keto ester, is decarboxylated by addition of acid, leaving a ketone

Front 171

amides

Back 171

formed when amine (nucleophile) substitutes at carbonyl of carboxylic acid or one of its derivatives

Front 172

reactivity of carboxylic acid derivatives

Back 172

most (weak base, good leaving group) to least (strong base, poor leaving group) reactive:
1. acyl chloride
2. acid anhydride
3. carboxylic acid
4. ester
5. amide

Front 173

Amines

Back 173

derivatives of ammonia (NH3)

primary amine: NH2R
secondary amine: NHR2
tertiary amine: NR3
quaternary amine: NR4+

nitrogen can take 3 (lone pair of electrons) or 4 bonds (positive charge)

ammonia and amines act as weak bases, donating lone pair electrons

electron withdrawing substituents decrease basicity of amines

electron donating substituents increase basicity of amines

bulky substituents decrease basicity

like to donate negative electrons to stabilize carbocation

Front 174

3 considerations with N-containing compounds

Back 174

1. act as lewis base, donating lone pair electrons
2. act as nucleophile, lone pair attacks positive charge
3. N can take on 4th bond (positive charge)

Front 175

Amine basicity

Back 175

highest to lowest, when functional groups are electron donating

1. secondary
2. primary
3. amonia

Front 176

aromatic amine

Back 176

amines attached to benzene ring

much weaker bases than amines nonaromatic amines because electron pair can delocalize around benzene ring

substituents that withdraw electrons from benzene ring will further weaken aromatic amine

Front 177

physical properties of amines

Back 177

H-bond which raises boiling point and increases solubility

optically inactive, both enantiomers exist

higher boiling point than water, but lower boiling point than alcohol

Front 178

imines and enamines

Back 178

form from reaction of amines with aldehydes and ketones losing water

imine and enamines exist as tautomers

Front 179

Condensation with Ketones

Back 179

1. amine acts a nucleophile, attacking electron deficient carbonyl C of ketone
2. ketone undergoes nucleophilic addition
3. acid catalyst protonates ketons to form unstable intermediate
4. intermediate loses water and proton to produce either enamine or imine

if original amine is secondary, has no proton to give, ketone loses alpha-H and results in enamine (2 substituents)

if original amine is primary, gives up H to form imine (1 substituent)

reaction inhibited with too much acid, because amine is protonated and become weak nucleophile

Front 180

Wolff-Kishner Reduction

Back 180

reduces ketone or aldehyde by removing O and replacing it with 2 H

1. hydrazine (nucleophile) attacks ketone in nucleophilic addition, to produce hydrozone
2. hot strong base deprotonates N and produces desired product with N gas and water as by-products

same thing can be accomplished by adding hot acid, however some ketones and aldehydes cannot survive hot acid

Front 181

Hofmann elimination

Back 181

E2 mechanism

elimination of quaternary ammonium hydroxide to form an alkene (least stable)

Front 182

Amine alkylation

Back 182

alkylation of an amine by alkylhalides

nucleophilic substitution

amine acts as nucleophile

can be made into quarternary ammonium salt by repeated alkylations

amine is a poor leaving group

quarternary ammonium salt is good leaving group

Front 183

diazotization of an amine

Back 183

formed from reaction of primary amines with nitrous acid

1. nitrous acid is protonated by strong acid to form nitrosonium ion
2. nitrosonium ion react with primary amine to form N-nitrosoammonium (unstable)
3. N-nitrosoammonium deprotonates to form N-nitrosoamine
4. N-nitrosoamine tautomerizes to diazenol
5. diazenol, in presence of acid, dehydrates to diazonium ion

diazonium ion can be replaced by a variety of other groups

Front 184

Amides

Back 184

weak acid or base

less basic than amines, due to electron withdrawing properties of carbonyl

amines are hydrolyzed by strong acids or bases

amides with H attached to N are able to H-bond with each other

no substituents on N = primary amides

most stable of carboxylic acid derivatives

Front 185

Lactams

Back 185

cyclic amides

highly reactive due to ring strain

nucleophiles easily react with lactams

Front 186

Hofmann degradation (rearrangement)

Back 186

primary amides react with strong basic solution of chlorine or bromine to form primary amines with CO2 as a by-product

1. amine is deprotonated by strong base
2. deprotonated amine picks up halogen atom, leaving a halide ion and producing N-haloamide
3. N-haloamide is deprotonated
4. rearrangement occurs: R gourp of amine migrates to N to form isocyanate
5. isocyanate reacts with H2O to form carbamic acid
6. carbamic acid decarboxylates, giving off CO2 and leaving amine

can produce amines with a primary, secondary, or tertiary alkyl position

Front 187

Phosphoric acids

Back 187

when heated, form phosphoric anhydrides

react with alcohols to form esters

Front 188

Fatty acids

Back 188

long carbon chains with a carboxylic acid end

3 functions:
1. hormones and intracellular messengers
2. components of phospholipids and glycolipids of cell membranes
3. act as fuel for body, stored in form of tryacylglycerols which can be hydrolyzed to form glycerol and corresponding fatty acids

carbonyl C is assigned #1
C next to carbonyl is a-C (alpha-C)
C at opposite end of chain is w-carbon (omega carbon)

pKa = 4.5, exist in anion form in cellular environment

C chains can be saturated or unsaturated

amphipathic molecules, nonpolar

enter Krebs cycle 2 C at a time

Front 189

lipolysis

Back 189

hydrolysis of tryacylglycerols into glycerols and corresponding fatty acids

reverse of esterification

tryacylglycerols can be cleaved by addition of NaOH

Front 190

saponification

Back 190

tryacylglycerols can be cleaved by addition of NaOH

production of soap

Front 191

triacylglycerols

Back 191

form in which fatty acids are stored in adipose cells (fat cells)

lipolysis takes place inside adipose cells

Front 192

Krebs cycle

Back 192

acetyl CoA (2C) enters Krebs cycle for further oxidation by condensation with oxaloacetate

Front 193

Amino acids

Back 193

building blocks of proteins

single proteins consists of 1 or more chains of amino acids strung end to end by peptide bonds

Front 194

peptide bonds

Back 194

holds amino acids end to end to form chain, resulting in proteins

N is comfortable with 4 bonds and O is comfortable with partial negative charge, thus electrons delocalize creating resonance that results in partial double bond character of peptide bond

prevents bond from rotating freely

affects secondary and tertiary structure of polypeptide

Front 195

polypeptide

Back 195

chain of multiple amino acids, held together end to end by peptide bonds, forming proteins

secondary and tertiary structure affected by double bond characteristic of peptide bonds

Front 196

amide

Back 196

functional group created by peptide bond

an amine connected to a carbonyl C

formed via condensation of 2 amino acids

reverse reaction is hydrolysis of peptide bond

N-C=O

Front 197

a-amino acids

Back 197

alpha amino acids

amino acids used by body

amine group attached to C which is alpha to carbonyl C (similar to a-H of ketones and aldehydes)

Front 198

Side chains

Back 198

R groups on amino acids

each amino acids differs only in R groups, which have different chemical properties, divided into 4 categories:
1. acidic (polar)
2. basic (polar)
3. polar
4. nonpolar

20 a-amino acids
10 essential amino acids

Front 199

Acidic Amino acids

Back 199

polar, side chain contains carboxylic acid

isoelectric point below pH 7

1. aspartic acid
2. glutamic acid

Front 200

Basic Amino acids

Back 200

polar, side chain contains amines

isoelectric point above pH 7

HAL:
1. histidine
2. arginine
3. lysine

Front 201

Polar amino acids

Back 201

hydrophilic

will turn to face an aqueous solution, such as cytosol

affect protein's tertiary structure

1. valine
2. isoleucine
3. proline
4. methionine
5. alanine
6. leucine
7. tryptophan
8. phenylalanine
9. glycine

Front 202

Nonpolar amino acids

Back 202

hydrophobic

will turn away from aqueous solution, such as cytosol

affect protein's tertiary structure

1. serine
2. threonine
3. cysteine
4. tyrosine
5. glutamine
6. asparagine

Front 203

3 forms in which amino acids exist:

Back 203

1. low pH, acidic, positive charge on N
2. pH 7, neutral, negative charge on O of OH and positive charge on N, zwitterion (dipolar ion)
3. high pH, basic, negative charge on O of OH and H removed from N (no charge)

Front 204

isoelectric point (pI)

Back 204

when all protons (H+) have been removed from all carboxylic acids from amino acid

pH where the population has no net charge and max # of species are zwitterions

more acidic the side chain, the lower pI

the more basic the side chain, the greater pI

Front 205

Carbohydrates

Back 205

carbon and water

for each C atom there exists 2 H

Cn(H2O)n

most common: glucose or fructose

named for # of C they posses:
3 C = triose
4 C = terose
5 C = pentose
6 C = hexose
7 C = keptose

labeled D or L depending on chirality:
D = OH on highest # chiral C points to R on fischer projection
L = OH on highest # chiral C points to L on fischer projection

Front 206

Hexoses

Back 206

6 C carbohydrates

ex:
1. glucose (aldehyde)
2. fructose (ketone)

Front 207

aldoses

Back 207

polyhydroxyaldehydes

ex:
glucose

Front 208

ketoses

Back 208

polyhydroxyke-tones

ex:
fructose

Front 209

aldohexose

Back 209

carbohydrates, polyhydroxyaldehydes, aldehydes, with 6C

ex:
glucose

Front 210

anomeric C

Back 210

only C attached to 2 O because its OH may point upwards or downwards on ring resulting in alpha or beta anomer

in carbohydrate, OH on chiral C farthest from carbonyl may act as nucleophile and attack carbonyl, resulting in nucleophilic addition to aldehyde or ketone, forming hemiacetal, creating ring structure

C 1 is called anomeric C

Front 211

carbohydrate cyclic ring structure nomenclature

Back 211

named according to # of ring members (including O)

5 member ring = furanose
6 member ring = pyranose

ex: glucose ring = glucopyranose

names of reducing sugars end in "ose" = hemiacetals

names of nonreducing sugars end in "oside" = acetals (reducing blocking agents)

Front 212

Sucrose

Back 212

1,1' glycosidic linkage: glucose and fructose

linkage is alpha with respect to glucose

linkage is beta with respect to fructose

Front 213

Maltose

Back 213

alpha - 1,4' glucosidic linkage: 2 glucose molecules

Front 214

lactose

Back 214

beta- 1,4' galactosidic linkage: galactose and glucose

Front 215

cellulose

Back 215

beta- 1,4' glucosidic linkage: chain of glucose molecules

Front 216

amylose

Back 216

alpha- 1,4' glucosidic linkage: chain of glucose molecules

Front 217

amylopectin

Back 217

alpha- 1,4' glucosidic linkage: branched chain of glucose molecules with alpha- 1,6' glucosidic linkages formed the branches

Front 218

glycogen

Back 218

alpha- 1,4' glucosidic linkage: branched chain of glucose molecules with alpha- 1,6' glucosidic linkages forming the branches

Front 219

Lab techniques

Back 219

1. spectroscopy
2. spectrometry
3. separations

Front 220

Spectroscopy

Back 220

1. nuclear magnetic resonance (NMR)
2. infrared spectroscopy (IR)
3. ultraviolet spectroscopy (UV)

Front 221

Spectrometry

Back 221

1. Mass spectrometry (Mass Spec)

Front 222

Separations

Back 222

1. Chromatography
2. Distillation
3. Crystallization
4. Extraction

Front 223

Nuclear Magnetic Resonance (NMR)

Back 223

observes nuclear spin exhibited by nuclei (hydrogen) with odd atomic # or odd mass #

frequency of electromagnetic radiation is held constant, while magnetic field strength is varied

protons with a compound absorb electromagnetic energy of same frequency at different magnetic field strengths

Front 224

NMR spectrum

Back 224

graph of magnetic field strengths absorbed by H of a specific compound at a single frequency

field strength is measured in parts per million (ppm) and increases from left (downfield) to right (upfield)

upfield is peak at 0 ppm due to reference compound

each peak represents chemically equivalent hydrogens

splitting of peaks is created by "neighboring hydrogens"

Front 225

chemical shift

Back 225

difference between resonance frequency of chemically shifted H and resonance frequency of H on reference compound (tetramethylsilane)

enantiotropic H are repesented by same peak in NMR spectrum and have same chemical shift

Front 226

area under peak of NMR spectrum

Back 226

represents # of H represented by peak

the more chemically equivalent H, the greater the are

tallest peak doesn't correspond to greatest area

Front 227

integral trace

Back 227

line drawn above peaks that rises each time goes over a peak

rise of integral trace is proportional to # chemically equivalent H in peak beneath it

ratio of H from 1 peak to another can be determine, but not exact # of H

Front 228

electron shielding

Back 228

H with less shielding have peak downfield (left), electron withdrawing groups

H with more shielding have peak upfield (right), electron donating groups

Front 229

Splitting

Back 229

spin-spin splitting

results from neighboring H that are not chemically equivalent

# of peaks due to splitting = n + 1
n: # of neighboring H that are not chemically equivalent

Front 230

neighboring hydrogens

Back 230

H that is on an atom adjacent to atom to which H is connected

Front 231

NMR steps:

Back 231

1. identify chemically equivalent H
2. identity and count neighboring H that are not chemically equivalent, use n+1 to figure out splitting for chemically equivalent H
3. if necessary, identify electron withdrawing/donating groups near chemically equivalent H

aldehyde protons = 9.5 ppm

C-13 is only C isotope to register on NMR (ignore splitting)

Front 232

Infrared radiation

Back 232

when exposed to IR, polar bonds within compound stretch and contract in vibration motion

different bonds vibrate at different frequencies

Front 233

IR spectroscopy

Back 233

IR slowly changes frequency of infrared light shining upon a compound and record frequencies of absorption in reciprocal centimeters (cm^-1 = number of cycles per cm)

if a bond has no dipole moment, IR does not cause vibration and no energy is absorbed

Front 234

IR spectrum

Back 234

predictable section: 1600 - 3500 cm^-1 region

C=O: sharp dip, 1700 cm^-1
O-H: broad dip, 3200-3600 cm^-1

1. Carboxylic acid: O-H (2500-3500), C=O (1710)
2. Aldehyde: saturated C-H (2800-3000), aldehyde C-H (2700, 2800), C=O (1710)
3. alcohol: O-H (3300), saturated C-H (2800-3000)
4. Amine: N-H (short, 3300), saturated C-H (2800-3000)
5. Nitrile: saturated C-H (2800-3000), C triple bond N (2200)
6. Amides: N-H (long, 3300), saturated C-H (2800-3000), C=O (1710)

greater mass = lower frequencies
stiffer bonds = higher frequencies

Front 235

fingerprint region

Back 235

2 compounds do not have exactly same IR spectrum

region where complex vibrations that distinguish 1 compound from similar compound are found (600-1400)

unique to all compounds

Front 236

Ultraviolet light

Back 236

wavelength between 200 and 400 nm

shorter and much higher energy level than infrared light

Front 237

ultraviolet spectroscopy (UV)

Back 237

detects conjugated double bonds (double bonds separated by one single bond) by comparing intensities of 2 beam of light from same monochromatic light source

difference in radiant energy between sample and solvent is recorded as UV spectrum of sample compound

Front 238

UV spectrum

Back 238

UV starts around 217nm with butadiene

30 to 40nm increase for each additional conjugated double bond

5nm increase for each additional alkyl group

isolated double bonds do not increase absorption wavelength

carbonyls, C=O, also absorb light in UV region

Front 239

Visible spectrum

Back 239

if compound has 8 or more double bonds, its absorbance moves into visible spectrum

Front 240

complementary color

Back 240

beta-carotene (11 conjugated bonds) absorbs at 497nm (blue-green light), giving complementary color of red-orange

Front 241

Mass Spectrometry

Back 241

gives the MW and molecular formula

molecules of sample are bombarded with electrons, causing them to break apart and to ionize

largest ion is size of original molecule minus 1 electron

ions are accelerated through magnetic field and resulting force deflects ions around curved path

magnetic field strength is altered to allow passage of different size ions through flight tube

computer records # of ions at different magnetic field strengths as peaks on chart

Front 242

mass to charge ratio

Back 242

m/z ratio of ion

establishes radius of curvature of the ion's path

most ions have charge of +1

Front 243

Base peak

Back 243

largest peak on mass spec graph

Front 244

parent peak

Back 244

peak made by molecular ion that didn't fragment

all the way on right of spectrum

Front 245

Chromatography

Back 245

resolution (separation) of mixture by passing it over/through matrix that absorbs different compounds with different affinities, altering the rate at which they lose contact with the resolving matrix

mobile phase: solution into which mixture is dissolved
resolving matrix: solid surface
stationary phase: compounds from mixture absorbed by surface

compounds with greater affinity for surface move more slowly

more polar compounds move more slowly because of greater affinity for stationary phase

results in establishment of separate and distinct layers, 1 pertaining to each component mixture

Front 246

Different types of chromatography

Back 246

Solid to liquid:
1. column chromatography
2. paper chromatography
3. thin layer chromatography

gas to liquid:
1. gas chromatography

Front 247

Column chromatography

Back 247

solution containing mixture is dripped down a column containing solid phase (glass beads)

more polar compounds travel more slowly, separating compounds

compound are collected as elutes with solvent, dripping out of bottom of column

Front 248

paper chromatography

Back 248

sample is spotted onto paper, one end of paper is placed in solvent, solvent moves up paper via capillary action and dissolves sample as it passes over it

more polar components move slowly because they are attracted to polar paper

less polar components move more quickly

results in series of colored spots representing different components of sample with most polar near bottom and least polar near top

Front 249

Rf factor

Back 249

can be determined for each component

divide distance traveled component by distance traveled by solvent

nonpolar components have Rf factors close to 1

polar components have Rf factors lower than 1

always between 0 and 1

Front 250

thin layer chromatography (TLC)

Back 250

similar to paper chromatography except coated glass or plastic plate is used instead of paper

results are visualized via iodine vapor chamber

Front 251

gas chromatography

Back 251

liquid phase is stationary phase

mixture dissolved into heated carrier gas (He or N) and passes over liquid phase bound to column

compounds in mixture equilibrate with liquid phase at different rates and elute as individual components

Front 252

Distillation

Back 252

separation based upon vapor pressure

solution with 2 volatile liquids with boiling points that differ by 20 degrees or more may be separated by slow boiling

compound with lower boiling point (higher vapor pressure) will boil off and be captured and condensed in cool tube

Front 253

fractional distillation

Back 253

more precise method of distillation

vapor runs through glass beads allowing compound with higher boiling point to condense and fall back into solution

Front 254

Crystallization

Back 254

based upon principle that pure substances form crystals more easily than impure substances

very inefficient method of separation, very difficult to arrive at pure substance

crystallization of salts is an exothermic process

ex:
iceberg = pure water (no salt)

Front 255

Extraction

Back 255

based upon solubility due to similar polarities

likes dissolve likes

1. organic mixture on top of aqueous layer (different polarities)
2. add strong acid and shake. acid protonates bases like amines in organic layer, making them polar. polar amine dissolve in aq layer and are drainer off
3. add weak base. base deprotonates only strong acids like carboxylic acids, making them polar. polar carboxylic acids dissolve in aq layer and drain off.
4. add strong base. strong base reacts with rest of acids (weak acids). acids dissolve in aq layer and drain off.