Answer to Question #177599 in Organic Chemistry for Sam

Question

Explain stereoisomerism and the different types that exist (i.e. geometric and optical). Give simple and naturally occurring examples of each type to illustrate your explanations, including structural formulae and photographs of 3D models of stereoisomers. For geometric stereoisomerism, include cis and trans (Z and E) stereoisomers of unsaturated fatty acids (e.g. oleic acid and elaidic acid). For optical isomerism, include amino acids (e.g. L-alanine and D-alanine), sugars (e.g. glucose and galactose) and starch with cellulose. Compare different stereoisomers of the same molecular formula, considering any difference in physical or chemical properties that exist. 

Answer 1

Stereoisomerism, or spatial isomerism, is a form of isomerism in which molecules have the same molecular formula and sequence of bonded atoms (constitution), but differ in the three-dimensional orientations of their atoms in space. This contrasts with structural isomers, which share the same molecular formula,

There are two kinds of stereoisomers: enantiomers and diastereomers. Enantiomers are mirror images, like one’s hands, and diastereomers are everything else.