to A and B is designated by the term diastereomer. Diastereomers may be defined
as stereoisomers that are not enantiomers. Since C and D are enantiomers, they
must have identical properties, except as noted on p. 138; the same is true for A
and B. However, the properties of A and B are not identical with those of C and
D. They have different melting points, boiling points, solubilities, reactivity, and all
other physical, chemical, and spectral properties. The properties are usually similar,
but not identical. In particular, diastereomers have different specific rotations;
indeed one diastereomer may be chiral and rotate the plane of polarized light while
another may be achiral and not rotate at all (an example is presented below).
It is now possible to see why, as mentioned on p. 138, enantiomers react at different
rates with other chiral molecules, but at the same rate with achiral molecules.
In the latter case, the activated complex formed from the (R) enantiomer and the
other molecule is the mirror image of the activated complex formed from the (S)
to A and B is designated by the term diastereomer. Diastereomers may be defined
as stereoisomers that are not enantiomers. Since C and D are enantiomers, they
must have identical properties, except as noted on p. 138; the same is true for A
and B. However, the properties of A and B are not identical with those of C and
D. They have different melting points, boiling points, solubilities, reactivity, and all
other physical, chemical, and spectral properties. The properties are usually similar,
but not identical. In particular, diastereomers have different specific rotations;
indeed one diastereomer may be chiral and rotate the plane of polarized light while
another may be achiral and not rotate at all (an example is presented below).
It is now possible to see why, as mentioned on p. 138, enantiomers react at different
rates with other chiral molecules, but at the same rate with achiral molecules.
In the latter case, the activated complex formed from the (R) enantiomer and the
other molecule is the mirror image of the activated complex formed from the (S)
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