Organic Chemistry

Section 18.1 Nomenclature 733

Notice that the terminal “e”is not removed in hexanedial; the “e”is removed only to
avoid two successive vowels.
If the aldehyde group is attached to a ring, the aldehyde is named by adding
“carbaldehyde”to the name of the cyclic compound.

In Section 8.1, we saw that a carbonyl group has a higher nomenclature priority
than an alcohol or an amine group. However, all carbonyl compounds do not have the
same priority. The nomenclature priorities of the various carbonyl groups are shown
in Table 18.1.
If a compound has two functional groups, the one with the lower priority is indicated
by its prefix. The prefix of an aldehyde oxygen that is part of the parent hydrocarbon is
“oxo.”The prefix of a one-carbon aldehyde group that is not part of the parent hydrocar-
bon is “formyl.”

H

C

O

CH 3

H

trans-2-methylcyclohexanecarbaldehyde benzenecarbaldehyde

benzaldehyde

systematic name:
common name:

C

O

increasing

priority

Table 18.1 Summary of Functional Group Nomenclature

Class

Carboxylic acid

Ester

Amide

Nitrile

Aldehyde

Ketone

Alcohol

Amine

Alkene

Alkyne

Alkane

Ether

Alkyl halide

Suffix Name

-oic acid

-oate

-amide

-nitrile

-al

Aldehyde -al

-one

-ol

-amine

-ene

-yne

-ane

—

—

Prefix Name

Carboxy

Alkoxycarbonyl

Amido

Cyano

Formyl

Oxo

Hydroxy

Amino

Alkenyl

Alkynyl

Alkyl

Alkoxy

Halo

( CH O)

( O)

Oxo( O)

HC

H OCH 3

O

ethyl 4-formylhexanoate

O O

CH 3 CH 2 CHCH 2 CH 2 OCH 2 CH 3

3-hydroxybutanal methyl 5-oxopentanoate

CH 3 CHCH 2 H

C

O

OH

C

O

CH 3 CHCH 2 H CH 3 CHCH 2

C

O

H H

H

C

O

systematic name:
common name:

3-chlorobutanal

-chlorobutyraldehyde

3-methylbutanal

isovaleraldehyde

Cl CH 3 O

O

hexanedial