Chapter 16

Question 1

carbonyl group

Answer 1

consists of 1 sigma bond formed by overlap of sp2 hybrid orbitals and 1 pi bond

Question 2

functional group of aldehyde

Answer 2

carbonyl + H atom + C atom

Question 3

functional group of ketone

Answer 3

carbonyl group + 2 carbons

Question 4

IUPAC of aldehyde

Answer 4

• parent chain is longest chain that contains carbonyl
• suffix from -e to -al
• unsaturated aldehyde infix from -an- to -en-
• cyclic: carbaldehyde

Question 5

IUPAC ketone

Answer 5

• suffix -e to -one

- # chain o give c=o lowest #

Question 6

physical properties of aldehydes and ketones

Answer 6

• C=O is polar
• both are polar
• have higher boilingpoints

Question 7

protonation

Answer 7

makes carbonyl a better electrophile (more partially +)

Question 8

reaction of aldehyde/ketone with a proton or Lewis acid

Answer 8

• forms a resonance stabilized cation
• protonation increases the electron deficiency of the carbonyl carbon and make sit more reactive toward nucleophilic
• neutral nucleophiles are “wimpy”

Question 9

cyanide ion

Answer 9

HCN adds to C=O group of aldehyde or ketone to give cyanohydrin

Question 10

cyanohydrin

Answer 10

molecule containing -OH group and CN group bonded to same carbon

Question 11

addition of water to carbonyl group

Answer 11

give geminal diol (hydrate)

Question 12

addition of alcohol to C=O group

Answer 12

gives hemiacetal

Question 13

hemiacetal

Answer 13

molecule containing -OH & -OR or -OA at same C

Question 14

hemiactel + alcohol

Answer 14

form acetals

-w/ ethylene glycol and other glycols they produce a 5 membered cyclic acetal

Question 15

acetals

Answer 15

a molecule containing 2 -OR or -OAr

• act like ethers - stable to organometallics
• can be protecting group

Question 16

addition of nitrogen nucleophiles to aldehydes/ketones

Answer 16

-ammonia, primary aliphatic amines, and primary aromatic amines react w/ carbonyl group of aldehydes and ketones to give imines (Schiff bases)

Question 17

imines

Answer 17

-value: carbon-nitrogen double bond can be reduced to a carbon-nitrogen single bond

Question 18

wittig reaction

Answer 18

very versatile synthetic method for synthesis of alkenes from aldehydes and ketones

Question 19

ylid

Answer 19

molecule, which when written as a Lewis acid, has positive and negative charges

• normally cis (Z) product
• if negative carbon is stabilized, mostly trans (E)

Question 20

phosphonium ylids formed in two steps

Answer 20

1. nucleophilic displacement of I by (Ph)3P

2. treatment of phosphonium salt w/ a very strong base (BuLi, NaH, NaNH2)

Question 21

Horner-Emmons-Wadsworth modification

Answer 21

• use a phosphonester
• use trimethylphosphate, rather than triphenylphosphine
• 2nd SN2 to get intermediate

Question 22

acidity of alpha hydrogens

Answer 22

• hydrogens alpha to a carbonyl group are more acidic than hydrogens of alkanes, alkenes, & alkynes
• less acidic than hydroxyl hydrogen of alcohols

Question 23

enol

Answer 23

protonated enolate

Question 24

keto-enol tautomerism

Answer 24

1. proton transfer to carbonyl oxygen

2. proton transfer to Base

Question 25

racemization at alpha carbon

Answer 25

may be catalyzed by acid or base

Question 26

alpha halogenation

Answer 26

two types:

1. in dilute acid - typically one halogen added
2. in base - all alpha H’s replaced

Question 27

after 3x halogenation

Answer 27

loss of leaving group

-methyl ketones may be converted to carboxylic acids w/ loss of carbon atom via haloform reaction

Question 28

oxidation of aldehydes

Answer 28

• aldehydes are oxidized to carboxylic acids by variety of agents (H2CrO4)
• also oxidized by Ag+ in aqueous ethanol or THF
• oxidized by O2 in radical chain reaction
• sensitive to air, must be stored in N2

Question 29

oxidation of ketones

Answer 29

• very hard
• not oxidized by H2CrO4
• oxidized by powerful oxidants at high temp and high conc of acid or base

Question 30

reductions

Answer 30

H- sources metal hydride reactions NaBH4 & LiAIH4

Question 31

NaBH4 reduction

Answer 31

• carried out in aqueous or pure methanol or ethanol

- 1 mol reduces 4 mol aldehyde or ketone

Question 32

catalytic hydrogenation

Answer 32

• not as easy as C=C reduction

- selectively possible