Lecture 8 Flashcards
(5 cards)
Aldehydes and Ketones
Aldehydes and ketones are incorporated a carbonyl functional group (C=O)
The carbon atom of this group has two remaining bonds that may be occupied by
hydrogen, alkyl or aryl substituents.
• Carbon is sp2 hybridized.
• C=O bond is shorter, stronger and more polar than C=C bond in alken
Functional Groups: Carbonyl Compounds
A carbonyl group consists of an oxygen atom bound to a carbon atom by a double covalent
bond (C=O). An acyl group consists of a carbonyl group attached to an alkyl group or to an aryl group.
Oxygen lone pairs make the group polar as the carbon is partially positive, and the oxygen is
partially negative. Carbon is susceptible to attack by negative nucleophiles.
Carbonyl compounds are regarded as:
Class I - contain a group that can be replaced by
another group and undergo nucleophilic acyl
substitution reactions with these nucleophiles.
Class II - do not contain a group that can be replaced
by another group and undergo nucleophilic acyl addition reactions
Part. 2
In aldehydes the carbonyl group is at the end of the carbon chain and so has at least
one hydrogen attached to it.
The carbonyl group (>C=O) is the functional group found in compounds such as
aldehydes, ketones, and will be present carboxylic acids.
In ketones the carbonyl group is in the middle of a carbon chain and so has two alkyl
groups attached to it.
If at least one of these substituents is hydrogen, the compound is an aldehyde. If neither is
hydrogen, the compound is a ketone
Naming Aldehydes
- Aldehydes take their name from their parent alkane chains
- IUPAC: Replace –e (from the end of alkane) with -al.
- The aldehyde carbon is number 1.
- If -CHO is attached to a ring, use the suffix -carboxaldehyde.
- Aldehyde priority is higher than ketone
Naming Ketones
A ketone carbonyl function may be located anywhere within a chain or ring (position is
usually given by a location number)
The common names for ketones are formed by naming both alkyl groups attached to the
carbonyl then adding the suffix -ketone. The attached alkyl groups are arranged in the name
alphabetically.
1. Replace -e with –one and indicate the position of the carbonyl
with a number.
2. Number the chain so that carbonyl carbon has the lowest number.
3. For cyclic ketones, the carbonyl carbon is assigned the number 1