Aldehydes and ketones

Question 1

Carbonyls

Answer 1

Carbonyl groups are a C=O double bond found in aldehydes, ketones, and carboxylic acids.
They are good electrophiles due to partial positive charge on the C.

Question 2

Carbonyls

Defined as the carbon next to the carbonyl group. α-hydrogens are the H attached to the α-carbon.

Answer 2

α-carbons

Question 3

Carbonyls

Aldehydes

Answer 3

Contain a carbonyl C=O group and use the suffix -al
Aldehydes are more reactive toward nucleophilic substitutions.

Question 4

Carbonyls

Ketones

Answer 4

Contain a carbonyl C=O group and use the suffix -one
Aldehydes have the carbonyl group on the terminal C vs ketones on the non-terminal C (connected to two alkyl chains).

Question 5

Carbonyls

Reactivity difference of ketones and aldehydes toward nucleophilic substitutions

Answer 5

Ketones are less reactive toward nucleophilic substitutions, due to steric hindrance and instability of alpha carbon.

Question 6

Aldehydes - reactions

Formation

Answer 6

Aldehydes are formed by oxidation of primary alcohols, specifically using a weak agent like PCC.

Question 7

Aldehydes - reactions

Oxidation

Answer 7

Aldehydes get oxidized to carboxylic acids.

Question 8

Aldehydes - reactions

Reduction

Answer 8

Aldehydes get reduced to primary alcohols by hydrides (ie LiAlH4).

Question 9

Aldehydes - reactions

Reaction with alcohol

Answer 9

Aldehyde + one equivalent of alcohol = hemiacetal.

Aldehyde + two equivalents of alcohol = acetal

Question 10

Ketones - reactions

Formation

Answer 10

Ketones are formed by oxidation of secondary alcohols.

Question 11

Ketones - reactions

Oxidation

Answer 11

Ketones cannot be further oxidized.

Question 12

Ketones - reactions

Reduction

Answer 12

Ketones get reduced to secondary alcohols by hydrides (ie LiAlH4), the same reagents used to reduce aldehydes.

Question 13

Ketones - reactions

Reaction with alcohol

Answer 13

Ketone + one equivalent of alcohol = hemiketal.
Ketone + two equivalents of alcohol = ketal
Similar reaction to aldehydes.

Question 14

Carbonyls - reaction

Nucleophilic addition reactions

Answer 14

Aldehydes and ketones have poor leaving groups, nucleophilic attacks result in protonation forming alcohols.
Carboxylic acids have good leaving groups, nucleophilic attacks result in reformation of compound.

Question 15

Carbonyls - reaction

Imine reactions

Answer 15

Nitrogen + carbonyls = imines. This can be reversed by using water to hydrolyze the imine.

Question 16

Carbonyls - reaction

Imine tautomerization

Answer 16

Imines can undergo a tautomerization reaction to form its tautomer enamines