Organic Chemistry I (Part 2-3)

Front 1

alkyl halide

Back 1

simply has halogen atom bonded to one of the sp3 hybrid carbon atom of alkyl group

Front 2

vinyl halide

Back 2

has a halogen atom bonded to one of the sp2 hybrid carbon atoms of an alkene

Front 3

Aryl halide

Back 3

has a halogen atom bonded to one of the sp2 hybrid orbital of an aromatic ring.

Front 4

Rank the alkyl halides in the order of increasing dipole moment

Back 4

C-I < C-Br < C-F < C-Cl

Front 5

Alkyl Halide (haloalkane)

Back 5

a derivative of an alkane in which one or more of the hydrogen atoms has been replaced by a halogen

Front 6

allylic halogenation

Back 6

substitution of a halogen for a hydrogen at the allylic position

Front 7

allylic

Back 7

the saturated position adjacent to a carbon to carbon double bond

Front 8

allylic shift

Back 8

a rearrangement that results from reaction at either end of a resonance stabilized allylic intermediate

Front 9

anti

Back 9

adding to (or eliminating from) opposite faces of a molecule
anti-coplanar: Having a dihedral angle of 180
Syn-coplanar: having a dihedral angle of 0

Front 10

aprotic solvent

Back 10

a solvent that has no acidic protons; a solvent with no O-H or N-H groups

Front 11

aryl halide

Back 11

an aromatic compound (benzene derivative) in which a halogen is bounded to one of the carbon atoms of the aromatic ring

Front 12

acid/ base

Back 12

acid donate a proton
base, an electron rich species that can abstract a proton

Front 13

concerted reaction

Back 13

a reaction in which the breaking of bonds and the formation of new bonds occur at the same time (in one step)

Front 14

dehydrohalogenation

Back 14

an elimination in which the two atoms lost are a hydrogen atom and a halogen atom

Front 15

electrophile (Lewis acid)

Back 15

A species that can accept an electron pair from a nucleophile, forming a bond

Front 16

Elimination

Back 16

a reaction that involves the loss of two atoms or groups from substrate usually resulting in the forming of a pi bond

Front 17

E1 reaction (elimination, unimolecular)

Back 17

a mulitstep elimination where the leaving group is lost in a slow step then a proton is lost in a second step Zaitsev orientation is generally preferred

Front 18

E2 reaction (elimination, bimolecular

Back 18

a concerted elimination involving a transition state where the base is abstracting a proton at the same time that the leaving group is leaving the anti co planar transition state is generally preferred

Front 19

geminal dihalide

Back 19

a dihalide with both halogens on the same carbon atom

Front 20

halogen exchange reaction

Back 20

a substitution where one halogen atom replaces another commonly used to form fluorides and iodides

Front 21

Hydride Shift

Back 21

movement of a hydrogen atom with a pair of electrons from one atom usually carbon to another. Hydride shifts are examples of rearrangements that convert carbocations into more stable carbocation

Front 22

inversion of configuration

Back 22

a process in which the groups around a chiral carbon atom are changed to opposite spatial configuration usually as an result of back side attack, the SN2 reaction usually goes with this

Front 23

leaving group

Back 23

the atom or group of atoms that departs during substitution and elimination it can be charged or uncharged but it leaves with a pair of elections that are originally bonded to the group to the remainder of the molecule

Front 24

methyl shift

Back 24

rearrangement of methyl group with the pair of electrons from one atom usually carbon to another

Front 25

nucleophile

Back 25

a lewis base an electron rich species that can donate a pair of electrons to form a pi bond

Front 26

nucleophilic substitution

Back 26

a reaction where a nucleophile replace another group or atom in a molecule

Front 27

polarizable

Back 27

having electrons that are easily displaced toward a positive charge

Front 28

1*, 2*, and 3* halide

Back 28

these terms specify the substitution of the halogen bearing carbon atom called the head carbon

Front 29

protic solvent

Back 29

a solvent containing acidic protons usually O-H or N-H groups

Front 30

Racemization

Back 30

a loss of optical activity that occurs when a reation shows neither clean retention of configuration no clean inversion of configuration

Front 31

reagent

Back 31

the compound that serves as the attacking species in a reaction

Front 32

rearrangement

Back 32

a reaction involving a change in the bonding sequence within a molecule. these are common in reaction such as SN1 and E1 involving carbocation intermediates

Front 33

retention of configuration

Back 33

formation of product with the same configuration as the reactant in a substitution retention of configuration occurs when the nucleophile assumes the same stereochemical position in the product as the leaving group occupied

Front 34

solvolysis

Back 34

a nucleophilic substitution or elimination where the solvent serves as the attacking reagent solvolysis literally means cleavage by a solvent

Front 35

stereocenter

Back 35

an atom that gives rise to stereoisomers when its groups are interchanged the most common being asymmetric carbon atoms and a double bonded carbons in cis trans alkenes

Front 36

stereospecific reaction

Back 36

a reaction in which different stereoisomers react to give different stereoisomers of the product

Front 37

substitution

Back 37

a reaction in which an attacking species (nucleophile, electrophile, or free radical) replaces another group

Front 38

SN2 reaction

Back 38

substitution, nucleophilic, bi molecular) the concerted displacement of one nucleophile by another on an sp3 hybrid carbon atom

Front 39

SN1 reaction

Back 39

a two step interchange of nuclophiles with bond breaking preceding bond formation. the first step is ionization to form a carbocation the second step is the reaction of the carbocation with a nucleophile

Front 40

substrate

Back 40

the compound that is attacked by the reagent

Front 41

vicinal dihalide

Back 41

a dihalide with the halogens on adjacent carbon atom

Front 42

vinyl halide

Back 42

a derivative of an alkene in which one (or more) of the hydrogen atoms on a double bonded carbon atoms has been replaced by a halogen

Front 43

Zaitsev's rule

Back 43

an elimination usually gives the most substituted alkene product

Front 44

Relative Nucleophilicity of Common Nucleophiles (in Methanol)

Back 44

Reactivity Classification Nucleophile
Very Good Iodide(I-), Hydrogen Sulfide(HS-), Alkyl Sulfides(RS-)

Good Bromide(Br-), Hydroxide(HO-), Alkoxides(RO-), Cyanide(CN-), Azide(N3-)

Fair Ammonia(NH3), Chloride(Cl-), Fluoride(F-), Carboxylates(RCO2-)

Weak Water(H2O), Alcohols(ROH)
Very Weak Carboxylic Acids(RCO2H)

Front 45

a compound of formula CH2X2

Back 45

this is a methylene group with two halogens and is called a methylene halide
iupac: dichloromethane

Front 46

a compound of formula CHX3

Back 46

this is called a haloform
iupac: trichloromethane

Front 47

a compound formula CH4

Back 47

carbon tetrahalide
iupac: tetrachloromethane

Front 48

Describe Radical Halogenation

Back 48

it is not an effective method in the synthesis of alkyl halides because they produce a mixture of products. Bromination can be selective mostly predominatly at 3*

Front 49

Allylic Bromination

Back 49

bromination is highly selective, with only the most stable radical being formed.
the initiation step bromine absorbs light, causing the formation of radicals
then first bromination step where bromine radical abstracts an allylic hydrogen making a allylic radical
the second propagation step the allylic radical reacts with bromine

Front 50

Show how free radical halogenation might be used to synthesis this compound why would you only epect a single major product

Back 50

bromine atom will abstract the hydrogen giving the most stable radical in this case the intermediate will be stabalized by the resonance with the benzene ring

Front 51

When discussing the SN1 mechanism explain why it is a first order reaction

Back 51

SN1 takes place in steps unlike SN2 where the formation of the new bond and the new bond is not concerted the first step is the breaking of a bond without the formation of a new bond so it is endothermic and therefore the rate determining step the second step is fast because it is no breaking of bonds so it is highly exothermic therefore the reaction rate is only determined by the concentration of the alkyl halide

Front 52

TOPIC: Stereochemisty
compare the possibilities when talking about SN1 and SN2 reactions and the most accurate

Back 52

3 possibilities
1)inversion of configuration
2)retention of configuration
3) Racemic mixture
in a SN2 reaction inversion predominates because of back side attack this mechanism is happening concerted
in a SN1 reaction the carbocation is an intermediate and is planar thus being achiral in nature and H20- can approach from any side and will result in a racemic mixture of product

Front 53

When dealing with secondary systems in substitution reaction how can you distinguish between SN2 or SN1

Back 53

the main factor will be the strength of the nucleophile because the nucleophile is present in the SN2 rds but not in SN! the stronger the nucleophile will tend to proceed via SN2 mechanism

Front 54

Explain the solvent effect on the SN1 and the SN2 reaction

Back 54

in a SN2 reaction an increase in solvent polarity preferentially stabilizes the reactants thus slowing the reaction because the nucleophile is more strongly stabalized by the polar solvents than the transition state
SN1 the TS has ionic character and is more stabalized by polar solvent solvation than is the reactant so the reaction rate is increased

Front 55

The effect of the leaving group

Back 55

the leaving group that holds that electrons best is the best therefore a weaker base will be the best because weaker bases stabilizes the negative charge better so the electron density thus making it more stable I->Br->Cl->F-

Front 56

What is the general concept of an elimination reaction

Back 56

Involves the loss of two atoms or groups from the substrate, usually with formation of pi bond elimination usually accompany and compete with substitutions

Front 57

E2 Elimination reaction general mechanism

Back 57

this can be termed by elimination in which a proton which is beta to a leaving group is removed by a base
the reaction produces alkenes. the reaction is concerted the transition state has alkene character

Front 58

The E1 mechanism

Back 58

E1 indicated a elimination, unimolecular reaction, where rate= k[R-LG] this implies that the rate determining step depends on the decomposition of a single molecular species and this is a multi step process with the following two critical steps the loss of the leaving group to generate a carbocation intermediate and second the loss of a proton H+, from the carbocation to form the p-bond

Front 59

In an E1 reaction what is the reactivity order of the substrate

Back 59

(CH3)3C- >(CH3)2CH- > CH3CH2- >CH3
recall that the rate determining step is the loss of the leaving group to form a carbocation so the more stable it is the easier it is to form

Front 60

What is the effect of the leaving group in the E1 reaction

Back 60

the only event in the rate determing step is the decomposition and breaking of the C-LG bond therefore there is a very strong dependence on the strength of the leaving group the better the leaving group the faster the reaction will take place

Front 61

what is the effect of the Base in an E1 reaction

Back 61

since the base is not involved in the rate determining step in an E1 reaction the nature is unimportant in the E1 reaction but the more reactive the base the more likely an E2 reaction comes

Front 62

Explain the selectivity in an E1 reaction

Back 62

the E1 reaction usually favors the more stable alkene as the major product more highly substituted and Trans>cis

Front 63

The E1 reactin pathway is most common with

Back 63

good leaving groups
stable carbocations
weak bases

Front 64

Describe the E1 reaction for alkyl halides

Back 64

step 1: cleavage of the polarized C-X bond allow the loss of the good leaving group, a halide ion, to give a carbocation intermediate this is the rate determining step (bond breaking is endothermic)
Step 2: an acid/base reaction. Deprotonation by a base from a C atom adjacent to the carbocation center leads to the creation of the Carbon carbon double bond

Front 65

Explain mechanism of the E2 reaction

Back 65

an elimination bimolecular reaction where the
rate=k[b][R-LG] this implies that the rate determining step involvees an interaction between these two species, the base and the organic substrate this reaction is concerted so simultaneous removal of the proton H+ by the base and the loss of the leaving group LG and formation of the pi bond

Front 66

What are the effects of the R-group in an E2 reaction

Back 66

the reaction transform 2 sp3 Carbon atoms into sp2 atoms this moves substituents further apart decreasing any steric interactions so more highly substituted systems undergo E2 eliminations more rapidly

Front 67

wHAT Is the important thing to note when discussing elimination reactions when it comes to the base

Back 67

the base is involved in the rate determining step in an E2 reaction so it is important so the more the reactive the base the more likely an E2 reaction will occur

Front 68

The E2 pathway is most common

Back 68

high concentration of a strong base poorer leaving groups
R-LG that would not lead to stable carbocations (when the E1 mechanism will occur)

Front 69

Competition between the E2 and SN2 reactions

Back 69

since the base is also a nucleophile (the requirements for both are an unshared pair of electrons) if the base is much stronger as a nucleophile than a base like as a sulfur or halide type anions the SN2 reaction will naturally dominate
if the leaving group is attached to a primary carbon the sn2 will predominate any way because of the great rapidity of this mechanism at a primary carbon however secondary or tertuary system usually lead to predominant elimination

Front 70

E1 reaction competes with SN1

Back 70

if the nucleophile is quite basic then elimination product predominates high temperature favors elimination
if we have a non basic but good nucleophile gives substitution product as the major product ex I-

Front 71

Topic: Physical Properties of Alkenes
Explain the trends in boiling point and density

Back 71

boiling points are close to 0 degree with densities close to 0.7 g/cm as with alkanes increase boiling points increase with molecular weights
increased branching leads to greater volatility and lower boiling points 1

Front 72

Topic: Physical properties of alkenes
explain the polarity

Back 72

relatively non polar insoulble in water but tend to be slightly more polar than alkane for two reasons
1. the more weakly held electrons in the pi bonds are more polarizable (contributing to instantaneous dipole moments) and the vinylic bonds tend to be slightly polar ( contributing to a permanent dipole moment)
alkyl groups are slightly electron donating toward a double bond helping to stabalize it thus making it have a slight postive on the alkyl group cis will have a vector sum trans will cancel out

Front 73

Topic Preperation of Alkene
Dehydration of alcohols summary

Back 73

When heated with strong acids catalysts (most commonly H2SO4, H3PO4), alcohols typically undergo a 1,2-elimination reactions to generate an alkene and water.
Also known as dehydration since it involves the removal of a molecule of water.
Alcohol relative reactivity order : 3o > 2o > 1o
Regioselectivity : major product is usually the more highly substituted alkene (alkene stability) Zaitsev's Rule.
Stereoselectivity : trans- > cis- again controlled by stability
Reaction of secondary or tertiary alcoholsusually proceeds via an E1 mechanism which proceeds via a carbocation intermediate, that can often undergo rearrangement.
Primary alcohols will proceed via an E2 mechanism since the primary carbocation is highly unfavorable.
Other common strong acids such as HCl, HBr or HI are less suitable catalysts as nucleophilic substitution reactions will probably interfere.

Front 74

Topic: preperation of alkene
dehydrohalogenation of alkyl halides summary

Back 74

When heated with strong bases, alkyl halides typically undergo a 1,2-elimination reactions to generate alkenes.
Typical bases are sodium or potassium hydroxides or alkoxides in the alcohol as solvent.
Alkyl halide relative reactivity order : I > Br > Cl > F (nb. elimination of F is rarely used).
Product distribution:
Regioselectivity is usually controlled by the relative stability of the product alkenes (Zaitsev's rule).
Stereoselectivity due to the preferred antiperiplanar (180o) arrangment of -H and -X in the transition state.

Front 75

alkene

Back 75

a hydrocabon with one or more carbon to carbon double bond
diene- two double
triene- three double
tetraene- 4 double

Front 76

allyl group

Back 76

a vinyl group plus a methylene group: CH2=CH-CH2

Front 77

Bredt's rule

Back 77

a stable bridgehead bicyclic compund cannanot have a double bond at a bridgehead position unless one of its rings contain atleast eight carbon atoms

Front 78

dehalogenation

Back 78

the elimination reaction of a halogen X2 from a compound

Front 79

dehydration

Back 79

elimination of water from a compound usually acid catalyzed

Front 80

dehydrogenation

Back 80

the elimination of hydrogen (H2) from a compund usually done in the presence of a catalyst

Front 81

dehydrohalogenation

Back 81

the elimination of a hydrogen halide (HX) from a compound usually base promoted

Front 82

double bond isomers

Back 82

constitutional isomers that differ only only in the position of the double bond to give the same alkane

Front 83

element of unsaturation

Back 83

a structural feature that results in two fewer hydrogen atoms in the molecular formula
halogens treated like hydrogen
oxygen ignore
nitrogencount like half a carbon

Front 84

geminal dihalide

Back 84

a compound with two halogen atoms on the same carbon atoms

Front 85

hofmann product

Back 85

the least highly substituted alkane product

Front 86

hydrogenation

Back 86

addition of hydrogen to a molecule

Front 87

trans-diaxial

Back 87

an antil and co planar arrangement allowing E2 elimination of two adjacent substituents on a cyclohexane ring

Front 88

vicinal dihalide

Back 88

a compound with halogens on adjacent carbon atoms

Front 89

this shows step 1 of an oxymercuration-demercuration reaction explain whats going on here

Back 89

The p electrons act as the nucleophile with the electrophilic Hg and loss of an acetate ion as a leaving group, forming the mercurinium ion.

Front 90

This shows step 2 of the oxymercuration- demercuration reactions what is happening

Back 90

Water functions as a nucleophile and attacks one of the mercury substituted carbons resulting in cleavage of the C-Hg bond.

Front 91

This is step 3 of Oxymercuration-demercuation reaction explain whats going on

Back 91

The acetate ion functions as a base deprotonating the oxonium ion to give the alcohol. This completes the oxymercuration part of the reaction.

Front 92

this shows the final step in the oxymercuration demercuration whats happening here

Back 92

:(mechanism not shown)
The hydride reduces the Hg off, creating a C-H bond while breaking the C-Hg bond. This is the demercuration part of the process.

Front 93

What is a general summary for a oxymercuration - demercuration
Reaction type?
Typical Reagent?
Catalyst?
regioselectivity?
Stereoselective?

Back 93

Overall transformation C=C to H-C-C-OH
This is an alternative method for hydrating alkenes to give alcohols
Typical reagents are mercury acetate, Hg(OAc)2 in aqueous THF
Unfortunately, mercury compounds are generally quite toxic
Regioselectivity predicted by Markovnikov's rule (most highly substituted alcohol)
The reaction is not stereoselective
Reaction proceeds via the formation of a cyclic mercurinium ion (compare with bromination of alkenes)

The mercurinium ion is opened by the attack of water to complete the oxymercuration.
When the water attacks, it does so at the more highly substituted carbon.
Demercuration is effected by a reduction using sodium borohydride, NaBH4
If the reaction is carried out in the presence of an alcohol rather than water, then ethers are obtained.

Front 94

Topic: hydroboration/oxidation
write a summary for this reaction mechanism

Back 94

Reaction type: Electrophilic Addition
Summary.

Overall transformation : C=C to H-C-C-OH
Reagents (two steps) 1. BH3 or B2H6 then 2) NaOH/ H2O2
Regioselectivity : Anti-Markovnikov, since the B is the electrophile.
Stereoselectivity : Syn since the C-B and C-H bonds form simultaneously from the BH3.
The alcohol is formed over a series of steps involving the B center (see below), with retention of configuration at the C.
Compliments simple hydration with opposite regiochemistry and stereospecificity

Front 95

topic: Reactions of alkene
what is the definition of addition

Back 95

a reaction involving an increase in the number of groups attached to the alkene and a decrease in the number of unsaturation

Front 96

define: anti addition and ehat kind of reaction is this seen in

Back 96

an addition in which two groups add to opposite faces of the double bond as in addition of Br2 which results from the bromonium ion mechanism (back side attack)

Front 97

define: Electrophillic addition

Back 97

an addition in which the electrophile (electron pair acceptor) bonds to one of the double bonded carbons first followed by a nucleophile

Front 98

define: syn addition

Back 98

an addition in which two groups add to the same face of the double bond as in Osmium tetroxide hydrooxylation

Front 99

define: alkoxymercuration

Back 99

the addition of mercuric acetate to an alkene in an alcohol solution, forming an alkoxymercurial intermediate. demercuration gives an ether

Front 100

define: alpha elimination

Back 100

the elimination of two atoms or groups from the same carbon atom freq used to form carbenes

Front 101

define: beta elimination

Back 101

the most common form of an elimination with two atoms or groups are removed from adjacent carbon atoms

Front 102

define: carbene

Back 102

a reactive intermediate with a neutral carbon atom having only two bonds and two non bonding pairs of electrons

Front 103

define: demercuration

Back 103

the removal of a mercury species from a molecule productof oxymercuration and alkoxymercuration usingsodium borohydride

Front 104

epoxide (oxirane)

Back 104

a three membered cyclic ether

Front 105

define: halogenation

Back 105

the addition of a halogen(x2) to a molecule or the free radical substitution of an x for an H

Front 106

define: halohydrin

Back 106

a beta halo-alcohol with a halogen and a hydroxyl group on adjacent carbon atoms

Front 107

define: Halonium ion

Back 107

a reactive, cationic intermediate with a three membered ring containing a halogen atom cl br i

Front 108

hydration

Back 108

the addition of water to a molecule

Front 109

hydroboration

Back 109

the addition of borane (BH3) or one of its derivative (BH2-THF) to a molecule

Front 110

hydrogenation

Back 110

the addition of hydrogen to a molecule the most common is a catalytic hydrogenation

Front 111

hydroxylation

Back 111

the addition of two hydroxyl groups one at each carbon of the double bond formally an oxidation

Front 112

Markovnikov's rule

Back 112

when a proton adds to the double bond of an alkene the proton adds to the carbon that already has more hydrogen atmos --> in an electrophilic addition to an alkene the electrophile adds in such a way as to generate the most stavle intermediate

Front 113

oxidative cleavage

Back 113

the cleavage of a carbon carbon bond through oxidation commonly by ozonolysis/reduction or by arm, concentrated permanganate

Front 114

oxymercuration

Back 114

the addition of aqueous mercuric acetate to an alkene

Front 115

define: ozonolysis

Back 115

the use of ozone, usually followed by reduction to cleave a double bond

Front 116

define: peroxide effect

Back 116

the reversal of orientation of HBr addition to alkenes in the persence of peroxides. a free radical mechanism is responsible for the peroxide effect

Front 117

define: regioselective reaction

Back 117

a reaction in which one direction of bond making or bond breaking occurs preferentially over all other directions addition of HCL is regioselective hydroboration-oxidation is regioselective (anti markovikov)

Front 118

define: simmons-smith reaction

Back 118

a cyclopropanation of an alkane using the carbenoid reagent generated from diiodomethane and the zinc copper couple

Front 119

define: sterospecific rotation

Back 119

a reaction that converts different stereoisomers of the starting material into different stereoisomers of the product

Front 120

Topic: Reactions of alkenes
how many different types of Electrophilic addition reactions can occur name them

Back 120

5 that we spoke about
a. addition of hydrogen halides
b.acid catalyzed hydration
c. oxymercuration-demercuration
d. alkoxymercuration-demercuration
e. Hydroboration- oxidation

Front 121

what is the reduction reaction when discussing reactions of alkene

Back 121

catalytic hydrogenation

Front 122

what is the addition of carbenes most useful for

Back 122

cyclopropanation

Front 123

how many oxidative additions are there when discussing reactions of alkenes name them

Back 123

there are three in which we spoke about
1. addition of halogens
2. halohydrin formation
3. syn hydroxylation

Front 124

name all the oxidative cleavage reaction

Back 124

a. ozonolysis
b. potassium permanganate (warm)

Front 125

Back 125

Front 126

Back 126

Step 1: protonation of the double bond forms a secondary carbocation
step 2: nucleophillic attack by water
step 3: deprotonation gives the alcohol

Front 127

Explain the trend of increasing nucleophilicity of halide ions influenced by solvent effect

Back 127

the key word here is polarizable
in a polar protic solvent the trend is Cl<Br<I because of the tight shell will block the hard base from reacting as a nucleophile but a soft base will not in a polar apotic solvent the trend is reversed

Front 128

Explain the steric effect of a nucleophile

Back 128

this is the greatest effect and occur when groups attached to a nucleophillic atom are too large to allow the nucleophile to react they usually act more as bases