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158 Cards in this Set

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CH4
methane
CH3CH3
ethane
CH3CH2CH3
propane
CH3CH2CH2CH3
butane
11 carbon chain
undecane
12 carbon chain
dodecane
formula for a straight chain alkane
C(n)H(2n+2)
n-propyl
n = normal, or unbranched compound... so CH3CH2CH2 is the substitutent
t-butyl
C(CH3)3
neopentyl
CH2-C(CH3)3
isopropyl
CH(CH3)2
sec-butyl
CH(CH3)CH2CH3
isobutyl
CH2CH(CH3)2
alphabetizing substituents?
ignore di, tri, tetra, tert/t, sec, n; but cyclo-, iso-, and neo- are used
olefin
alkene (CC double bonds)
common name of ethene
ethylene
common name of propene
propylene
vinyl-
monosubstituted ethylenes
chloroethene
vinyl chloride
allyl-
propylene substituted at the C3 position (2-propenyl-)
3-bromo-1-propene
allyl bromide
methylene-
refers to -CH2, e.g. "methylene cyclohexane"
conjugated system
a carbon backbone with alternating single and double bonds; conjugation stabilizes through electron delocalization.
acetylene
ethyne
t-butyl bromide
2-bromo-2-methylpropane
2-iodopropane
isopropyl iodide
when there are both double and triple bonds?
y-root-en-x-yne" where y is position of the double bond and x is the position of the triple bond. Choose so that x+y is minimized and y is the smallest number possible; ex: 2-hexen-4-yne
alcohol or multiple bond when giving number priority?
alcohol
methyl alcohol
methanol
glycol
diols = molecules with 2 hydroxyl groups
vicinal
diols with hydroxyl groups on adjacent carbons
geminal
diols with hydroxyl groups on the same carbon
hydrates
geminal diols, not commonly observed because they spontaneously dehydrate to produce carbonyl compounds
ether
common name for diethyl ether
oxiranes
epoxides, or three-membered cyclic ethers
ethyl methyl ether
methoxyethane
name of the ether functionality..
alkoxy- (where alk = the smaller alkyl group)
ethylene oxide
oxirane
propylene oxide
2-methyloxirane
THF
tetrahydrofuran
methanal
formaldehyde
ethanal
acetaldeyhde
propanal
propionaldehyde
prefix for a substituent ketone
oxo-
acetone
2-propanone or dimethyl ketone
3-butene-2-one
methyl vinyl ketone
formic acid
methanoic acid
acetic acid
ethanoic acid
propionic acid
propanoic acid
ethanamine
CH3CH2NH2
ethylpentylamine
N-ethylpentanamine
IUPAC prefix/suffix for an ester
alkoxycarbonyl- / -oate
IUPAC prefix/suffix for an amide
(R-CONH2) amido- / -amide
IUPAC prefix/suffix for cyanide
(R-CN) cyano- / -nitrile
imine, general
R2 - C=NR'
sulfide, general
R2S
nitro, general
R-NO2
azide, general
R-N3
diazo, general
R-N2+
IUPAC prefix/sufix for a thiol
(RSH) sulfhydryl- / -thiol
isomers
compounds with same molecular formula but different structure - in atomic connectivity, rotational orientation, or the 3D position of the atoms
structural isomers
or constitutional isomers; only share the molecular formula. Since they differ in atomic connectivity, they may have very different chemical properties
stereoisomers
same connectivity, different orientation - includes diastereomers (geometric isomers), enantiomers, and conformational isomers.
geometric isomers
isomers that differ in the position of substituents attached to a double bond (cis, trans, Z, or E)
Z or E?
highest priority (determined by atomic #) on same side = Z (zusammen); opposite sides = E (entgegen)
chiral
an object that is not superimposable upon its mirror image, e.g. the left and right hands
enantiomers
chiral objects that are non-superimposable mirror images
R or S?
R = high to low priority is clockwise (rectus = right); S = counterclockwise (sinister = left)
orienation in a Fischer projection
horizontal lines project out, vertical point into the page
diastereomers
isomers that differ in their chirality but are not mirror images
meso compounds
contain chiral centers but are not optically active due to an internal mirror plan of symmetry
chemical properties of enantiomers?
are identical except for they rotate plane-polarized light in opposite directions
specific rotation
[alpha] = observed rotation(alpha) / concentration(g/mL) * length(dm)
a compound that rotates plane-polarized light to the right is called...
dextrorotatory or (+), vs. levorotatory (-)
racemic modification
or racemic mixture = a mixture of equal concentrations of both (+) and (-) enantiomers resulting in no optical activity
for n chiral centers, there are ____ possible stereoisomers
2^n
conformational isomers
compounds that differ only by rotation about one or more single bonds; can be depicted by Newman projection
straight-chain conformations
staggered or anti (lowest energy) -- eclipsed (methyl and hydrogen groups overlap) -- gauche (2 methyl groups are 60* apart) -- totally eclipsed (the two methyl groups overlap = highest energy)
cause of ring strain in cycloalkanes
angle strain (bond angles deveiate from ideal values), torsional strain (eclipsed interactions), and nonbonded strain or van der Waals repulsion (due to competition for same space)
envelope conformation"
cyclopentane
comformations of cyclohexane
chair, boat, and twist/skew-boat
conformation of cyclobutane
puckered (a "V" shape)
axial vs. equatorial position
perpendicular to the plan of the ring vs. parallel
boat vs. chair confomations
all atoms are eclipsed vs. all three types of strain are eliminated
bulky groups and ring conformation?
bulky groups prefer equatorial positions and can prevent chair "flipping"
trans in a chair conformation?
place substituents so that they point in opposite directions relative to the plan of the ring
a node (as related to orbitals)
an area where the probability of finding an electron is zero
number of nodes for a p vs. d orbital
1 and 2, respectively
energy of a bonding orbital?
lower than the molecular orbitals that add to make the bonding orbital
double bond consists of...
a sigma bond and a pi bond; with sp2 hybridization; the three sp2 orbitals are 120* apart
can a pi bond exist independently?
no, only after the formation of a sigma bond will the p orbitals of adjacent carbons be parallel; without the bond the three p orbitals are orthogonal to one another.
are pi or sigma bonds stronger?
sigma bonds are stronger
a triple bond consists of...
a sigma and two pi bonds; sp hybridized orbitals are 180* apart
alkanes
fully saturated hydrocarbons, consisting only of hydrogen and carbon atoms joined by single bonds
isobutane
HC(CH3)3
neopentane
C(CH3)4
as chain length of an alkane increases...
bp, mp, and density increase
at RT, straight-chain alkanes are in what state?
C1-4 are gases, C5-16 are liquids, and >16 are waxes and harder solids
increased branching in an alkane...
lowers bp (decreased surface area = decreased van der Waals) and density
symmetry and melting point?
the more symmetric molecule will have the higher mp (easier to pack into a tight, 3D structure)
free radical halogenation
initiation (homolytic cleagage of a diatomic halogen by heat or light) -- propagation (Xradical attacks RH to form XH and an alkyl radical, which attacks X2, regenerating the halogen radical) -- termination (two free radicals combine to form a stable molecule)
bromine and free radical halogenation?
Br radicals react fairly slowly and primarily attack the most substituted carbon atom
combustion
alkanes + O2 = carbon dioxide + water + heat
pyrolysis
also called cracking, most commonly used to reduce average MW of heavy oils and increase the production of the more desirable volatile compounds (C-C bonds are cleaved by heat and produce smaller-chain alkyl radicals that can recombine)
disproportionation
a radical transfers a hydrogen atom to another alkyl radical, producing an alkane and an alkene
nucleophiles and electrons
nucleophiles are electron rich (and thus are attracted to positively polarized atoms)
nucleophilicity and basicity
roughly correlated if the attacking atom is the same
nucleophilicity of oxygen-containing nucleophiles
RO- > HO- > RCO2- > ROH > H2O
solvent and nucleophilicity
large atoms are better in protic solvents (they can shed their solvent molecules and are more polarizable), but more basic compounds are better in aprotic solvents
nucleophile strength of halides
in an aprotic solvent, correlated to basicity: F- > Cl- > Br- > I- (the opposite is true in a protic or polar solvent)
size order of typical nucleophiles
CN- > I- > RO- > HO- > Br- > Cl- > F- > H2O
best leaving groups?
are the weak bases, because these can accpet an electron pai and dissociate to form a stable species (largest > smaller halides)
Sn1
unimolecular (rate is dependent on only one species... usually the formation of the carbocation or carbonium ion) nucleophilic substitution
solvents and carbocations
carbocations are stabilized by polar solvents that have lone electron pairs to donate (e.g. water, acetone)
increasing the rate of an SN1 rxn
in order to accelerate the formation of the carbocation consider 1) structural factors = more substitution means more charge delocalization; 2) solvent effects = polar protic solvents stabilize the intermediate and isolate ions; 3) nature of the leaving group = wk bases dissociate more easily
Sn2
bimolecular nucleophilic substitution
transition state of an SN2 rxn
Nu attacks the reactant from the backside to form a trigonal bipyramidal transition state
isobutylene
(CH3)2C=CH2
degree of unsaturation
number of double bonds or rings (for a compound CnHm), N = 1/2(2n +2 - m)
physical properties of alkenes vs. alkanes
alkenes show similar trends to alkanes - mp and bp increase with MW and are similar in value to the corresponding alkane
physical properties of trans vs. cis-alkenes
trans generally have higher mp (higher symmetry allows better packing in the solid state) and lower bp (less polar)
E1
unimolecular elimination, favored by highly polar solvents, highly branched carbon chains, good leaving froups, and weak nucleophiles in low concetration.
E1 and SN1
same factors favor both, so directing the rxn is difficult although high temperatures tend to favor E1
E2
bimolecular elimination; rate is dependent on the concentration of the substrate and the base
E2 mechanism
strong base (e.g. ethoxide ion) removes a proton while a halide ion anti to the proton leaves. If there are two possible products, the more substituted double bond is formed preferentially.
E2 vs SN2
steric hindrance does not greatly affect E2 rxns, and strong base favors E2 over SN2 (strong nucleophiles, or weak Lewis bases, favor SN2).
synthesis of an alkene
elminitation of either alcohol (with H+, heat) or alkyl halide (with base, heat) -- see E1 or E2
catalytic hydrogenation
the reductive process of adding molecular hydrogen to a double bond with the aid of a metal catalyst such as Pt, Pd, or Ni (usually Raney nickel, a special powdered form), but also Rh, In, or Ru; This is a syn addition.
syn addition
both atoms are added to the same face of the double bond
electrophilic additions
since the electrons of the pi bond are somewhat exposed, they are easily attacked by molecules that seek to accept an electron pair = Lewis acids or electrophiles
alkene + HX
proton accepts electrons of the double bond (acting as a Lewis base) to yield a carbocation which combines with the halide ion. This addition follows Markovnikov's rule b/c the initial protonation proceeds to produce the most stable carbocation.
Markovnikov's rule
the addition of something to the most substituted carbon in the double bond
alkene + X2
(a rapid process, often used to establish the presence of double bonds) Dbl bond acts as nucleophile and attacks an X2 molecule, displacing X- and forming a cyclic halonium ion. X- then attacks in a standard SN2 displacement - therefore the addition is anti
addition of X2 and the solvent
in a nucleophilic solvent, the solvent molecules can compete in the displacement step, producing different products (other than the dihalo compound).
alkene + H2O
only under acidic conditions!! Double bond is protonated according to Markovnikov's rule, carbocation formed, water attacks. Also performed at low temperature b/c the reverse reaction is an acid-catalyzed dehydration favored by high temp.
better way to add water to a double bond?
use mercuric acetate (Hg(CH3COO)2)
alternative mechanism to add HX to an alkene
through a free radical addition when there are peroxides, oxygen or other impurities present. The halide radical adds first to the double bond (so the addition is anti-Markovnikov). This rxn is useful for HBr but not HCl or HI.
presence of peroxides
think free radical reactions (that do not follow Markovnikov's rule)
hydroboration
diborane (B2H6) is a Lewis acid and attaches to the less sterically hindered C, followed by oxidation-hydrolysis with peroxide and aqueous base to produce an alcohol with overall anti-Markovnikov, syn orientation
potassium permanganate
KMnO4
oxidation of alkenes with potassium permanganate
if cold, dilute, aqueous KMnO4 used -- vicinal diols (glycols) with syn orientation produced + MnO2 (s); if a hot basic solution is used, followed by acid, then nonterminal alkenes are cleaved to form 2 molar equivalents of carboxylic acid and terminal alkenes ar ecleaved to form a carboxylic acid and CO2 (if the nonterminal double bonded carbon is disubstituted, a ketone is formed)
ozonolysis
1) alkene + O3, CH2Cl2, 2) reduction by zinc and water = cleavage of the double bond produces aldehydes -- or -- 2) reduction by soidum borohydride in methanol = cleavage of double bonds produces alcohols
sodium borohydride
NaBH4
examples of peroyxcarboxylic acids
peroxyacetic acid (CH3CO3H) and m-chloroperoxybenzoic acid (mcpba)
oxidation of alkenes by peroxycarboxylic acids
alkene + mcpba = oxirane or epoxide
polymerization of an alkene
ethylene + alkyl radical (R*), heat, high pressure = R-CH2-CH2-(CH2CH2)n-CH2CH2-R
methylacetylene
propyne (CH3CCH)
physical properties of alkynes
similar to analogous alkanes/alkenes; shorter-chains are generally gases that have higher bp than corresponding alkenes; have asymmetrical distribution of e- density = small dipole moments
effect of position of triple (double) bonds on physical properties
internal alkynes have higher bp than terminal alkynes; and terminal alkynes are fairly acidic with a pKa's around 25.
synthesis of an alkyne
1) elimination of 2HX from a geminal or vicinal dihalide, use heat and base -- or 2) convert a terminal triple bond into a nucleophile by removing the acidic proton with a strong base (e.g. n-BuLi), which can then perform nucleophilic displacements on alkyl halids at RT
Lindlar's catalyst
Pd on barium sulfate (BaSO4) with quinoline
reduction of alkynes to alkenes
1) H2, Lindlar's catalyst = cis-alkene -- or 2)sodium in liquid ammonia below -33* (Na, NH3) = trans-alkene via a free radical mechanism
boiling point of ammonia
is -33 degrees celsius
electrophilic addition to alkynes
occur according to Markovnikov's rule, use 1 equivalent of Br2 to stop at alkene stage
free radical addition to alkynes
anti-markovnikov orientation; product is usually the trans alkene isomer because the intermediate vinyl radical can isomerize to its more stable form
hydroboration of an alkyne
B adds first (can coordinate to three substrate molecules) in a syn mechanism; the B atom can be replaced with a proton from acetic acid to produce a cis alkene -- or a disubstituted borane (R2BH) can be used to prevent further boration of the vinylic intermediate which is then oxidatively cleaved with H2O2 to create an intermediate vinyl alcohol, which rearranges to the more stable carbonyl compound
aldehyde from an alkyne
(for a terminal alkyne) use R2BH, hydrogen peroxide, base -- produces a vinyl alcohol which can undergo keto-kenol tautomerism to form the aldehyde.
oxidation of alkynes
vis basic potassium permangenate (followed by acidification) -- or -- ozone, CCl4 (follow with water); both cleave the multiple bonds to produce carboxylic acids