Question

discuss the conformational isomers of 1,2 dihydroxy ethane​

Answer 1

Answer:

Recap: Some isomers have already been encountered � constitutional isomers (eg 1-butene and 2-butene); conformational isomers (e.g. staggered and eclipsed forms of ethane) and diastereomers such as (Z)- and (E)-2-butene or cis- and trans-1,2-dimethylcyclobutane.

Conformational isomers are one type of stereoisomer which generally can not be separated from one another at room temperature. Another class is configurational isomers, which can be separated from one another, as interconversion requires breaking of bonds. There are two types of configurational isomers: diastereisomers and enantiomers. Enantiomers are non-superposable mirror images.

Chiral molecules (optical isomers) can be identified in this way: when a molecule and its mirror image are not identical (not superposable) the substance is chiral

A pair of molecules which are not identical but are mirror images of each other are called enantiomers

Almost all of the physical and chemical properties of a pair of enantiomers are identical (melting point, boiling point, solubility etc.)

Structures of Chiral Compounds

A sp3 hybridised carbon atom has a tetrahedral arrangement of bonds about it

In molecules where there are four different groups attached to one carbon centre, there are two non-superposable mirror images. Such a carbon atom is called a stereogenic centre and the molecule is said to be chiral.

Example:

In molecules where there are not four different groups attached to a single carbon centre then any mirror image is identical to the original, just drawn in a different way.

Example:

Enantiomers differ only in (i) the way that they interact with other chiral molecules, (ii) the way that they interact with polarised light.

A sample of one enantiomer of a pair will rotate the plane of polarised light in a clockwise direction (labeled (+)) and an equal amount of the other enantiomer will rotate the plane of light to the same extent in a counter-clockwise direction (labeled (-))

Molecules which rotate plane polarised light are called optically active molecule

It is not currently possible to predict the direction or the magnitude of optical rotation from the molecular structure