Organic Chemistry

Section 21.2 Amine Inversion 885

(in alphabetical order) that have replaced the hydrogens of ammonia. Systematic
names employ “amine”as a functional group suffix.

A saturated cyclic amine—a cyclic amine without any double bonds—can be
named as a cycloalkane, using the prefix “aza”to denote the nitrogen atom. There are,
however, other acceptable names. Some of the more commonly used names are shown
here. Notice that heterocyclic rings are numbered so that the heteroatom has the low-
est possible number.

Heterocycles with oxygen and sulfur heteroatoms are named similarly. The prefix for
oxygen is “oxa”and that for sulfur is “thia.”

PROBLEM 1

Name the following compounds:

a. c. e.

b. d. f.

21.2 Amine Inversion

The lone-pair electrons on nitrogen allow an amine to turn “inside out”rapidly at room
temperature. This is called amine inversion. One way to picture amine inversion is to
compare it to an umbrella that turns inside out in a windstorm.

CH 2 CH 3

O

CH 3

S

N

H

CH 2 CH 3

CH 3

O CH^3

CH 3

HN

H

N

CH 3

CH 3

OO

O

tetrahydropyran 1,4-dioxane

oxacyclopropane

oxirane

ethylene oxide

O

thiacyclopropane

thiirane

S O

O

oxacyclobutane

oxetane

oxacyclopentane

tetrahydrofuran

a tertiary amine

ethylmethylpropylamine

N-ethyl-N-methyl-1-propanamine

a secondary amine

butylethylamine

N-ethyl-1-butanamine

a primary amine

pentylamine

1-pentanamine

common name:
systematic name:

CH 3 CH 2 CH 2 CH 2 CH 2 NH 2 CH 3 CH 2 CH 2 CH 2 NHCH 2 CH 3 CH 3 CH 2 CH 2 NCH 2 CH 3

CH 3

CH 3

CH 2 CH 3

N

H

N

H

N

CH 3

3-methylazacyclopentane

3-methylpyrrolidine

2-methylazacyclohexane

2-methylpiperidine

azacyclopropane
aziridine

azacyclobutane

azetidine

N-ethylazacyclopentane

N-ethylpyrrolidine

N

H NH