Organic Chemistry

formaldehyde

acetaldehyde

acetone

Section 18.2 Relative Reactivities of Carbonyl Compounds 735

BUTANEDIONE: AN UNPLEASANT COMPOUND

Fresh perspiration is odorless. Bacteria that are always present on our

skin produce lactic acid, thereby creating an acidic environment that

allows other bacteria to break down the components of perspiration, producing com-

pounds with the unappealing odors we associate with armpits and sweaty feet. One

such compound is butanedione.

CH 3 C

CH 3

butanedione

C

O

O

PROBLEM 1

Why are numbers not used to designate the positions of the functional groups in propanone

and butanedione?

PROBLEM 2

Give two names for each of the following compounds:

a. d.

b. e.

c. f.

PROBLEM 3

Name the following compounds:

a. b. c.

18.2 Relative Reactivities of Carbonyl Compounds

We have seen that the carbonyl group is polar because oxygen, being more electronega-
tive than carbon, has a greater share of the electrons of the double bond (Section 17.5).
The partial positive charge on the carbonyl carbon causes carbonyl compounds to be
attacked by nucleophiles. The electron deficiency of the carbonyl carbon is indicated by
the blue areas in the electrostatic potential maps.

An aldehyde has a greater partial positive charge on its carbonyl carbon than does a
ketone because a hydrogen is electron withdrawing compared with an alkyl group
(Section 4.2). An aldehyde, therefore, is less stable than a ketone, which makes it more
reactive toward nucleophilic attack.

C

O

RR(H)

−Nu

δ−

δ+

CH 3 CH 2 CHCH 2 CNH 2

O

CN HC O

O

CH 3 CHCH 2 CH 2 CCH 2 CH 3

O

OH

CH 2 CHCCH 2 CH 2 CH 2 CH 3

O

CH 3 CHCH 2 CCH 2 CH 2 CH 3

O

CH 3

CH 3 CH 2 CHCH 2 CH 2 CH

CH 2 CH 3 O

CH 3 CH 2 CH 2 CCH 2 CH 2 CH 3

O

CH 2 CH 2 CH 2 CH

O

CH 3 CH 2 CHCH 2 CH

O

CH 3