Answer to Question #175610 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 & displayed formulae and 

• photographs of 3D models of stereoisomers (draw the optical isomers in 3D). 

• 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) – draw the linear structures for the monosaccharides

• and starch with cellulose. Compare different stereoisomers of the same molecular formula, considering any difference in physical or chemical properties that exist.

Answer 1

Stereoisomers are isomers that have the same composition but that differ in the orientation of those parts in space.

Types

Geometric isomers are two or more coordination compounds which contain the same number and types of atoms, and bonds but which have different spatial arrangements of the atoms.i.e1,2-dichloroethene

Optical isomers are two compounds which contain the same number and kinds of atoms, and bonds and different spatial arrangements of the atoms, but which have non-superimposable mirror images.

i.e Carbon with four different groups bonded to it.

There are two ways in which isomers can differ. When they differ in the way the atoms are connected, they are called constitutional isomers. Butane and isobutane, for example, are constitutional isomers. Constitutional isomers have similar chemical properties but different physical properties.