preface to fifteenth edition

ORGANIC COMPOUNDS 1.39
sulfamic acids or by theprefix sulfoamino- to denotethegroup HO 3 S9NH9. Thegroups
9N"SO and 9N"SO 2 are named sulfinylamines and sulfonylamines, respectively.
Sultones and Sultams. Compounds containing thegroup 9SO 2 9O9 as part of thering are
called -sultone. The 9SO 2 9 group has priority over the 9O9 group for lowest-numbered locant.
Similarly, the 9SO 2 9N" group as part of a ring is named by adding -sultam to the name of
thehydrocarbon with thesamenumber of carbon atoms. The9SO 2 9 has priority over 9N" for
lowest-numbered locant.
1.1.4 Stereochemistry
Concepts in stereochemistry, that is, chemistry in three-dimensional space, are in the process of
rapid expansion. This section will deal with only the main principles. The compounds discussed will
be those that have identical molecular formulas but differ in the arrangement of their atoms in space.
Stereoisomers is the name applied to these compounds.
Stereoisomers can be grouped into three categories: (1) Conformational isomers differ from each
other only in the way their atoms are oriented in space, but can be converted into one another by
rotation about sigma bonds. (2) Geometric isomers are compounds in which rotation about a double
bond is restricted. (3) Configurational isomers differ from one another only in configuration about
a chiral center, axis, or plane. In subsequent structural representations, a broken line denotes a bond
projecting behind the plane of the paper and a wedge denotes a bond projecting in front of the plane
of the paper. A line of normal thickness denotes a bond lying essentially in the plane of the paper.
1.1.4.1 Conformational Isomers. A molecule in a conformation into which its atoms return
spontaneously after small displacements is termed a conformer. Different arrangements of atoms
that can be converted into one another by rotation about single bonds are called conformational
isomers (see Fig. 1.1). A pair of conformational isomers can be but do not have to be mirror images
of each other. When they are not mirror images, they are called diastereomers.
FIGURE 1.1 Conformations of ethane.
(a) Eclipsed; (b) staggered.
Acyclic Compounds. Different conformations of acyclic compounds are best viewed by construction
of ball-and-stick molecules or by use of Newman projections (see Fig. 1.2). Both types of
representations are shown for ethane. Atoms or groups that are attached at opposite ends of a single
bond should be viewed along the bond axis. If two atoms or groups attached at opposite ends of the
bond appear one directly behind the other, these atoms or groups are described as eclipsed. That
portion of the molecule is described as being in the eclipsed conformation. If not eclipsed, the atoms