Stereochemistry

Question 1

define isomer

Answer 1

compounds with the same atomic composition but with different structural or stereochemical formula, and hence different physical and/or chemical properties.

Question 2

Define stereoisomers

Answer 2

Molecules with the same structural formula, same atom connectivity, but different orientation of their atoms in space.

Question 3

what do geometric isomers have

Answer 3

Geometric isomers have different cis/trans configurations and result from restricted rotation about a bond.

Question 4

where does the E/Z notation come from

Answer 4

The E/Z notation comes from the German terms Engegen (opposed to) and Zusammen (together) and should be preferred to cis/trans, as the latter only applies to disubstituted alkenes.

Question 5

what are enatiomers

Answer 5

Enantiomers are pairs of molecules which are mirror images of each other and non-superimposable.

Question 6

what is a stereogenic centre

Answer 6

A stereogenic centre is a quaternary atom with four different substituents

While stereogenic centres are often found in chiral molecules, the presenc of a stereogenic centre is not a sufficient, not necessary condition for chirality.

Question 7

what are chiral molecules

Answer 7

Chiral molecules are non-superimposable to their mirror images; such molecules do not possess elements of symmetry of the second kind, i.e. mirror planes and centers of inversion.

Question 8

what is the CIP convention used to distinguish

Answer 8

Using the CIP convention, it is possible to distinguish stereogenic centres with opposite configuration.

Question 9

what does the CORN law allow

Answer 9

The CORN law allows to establish whether amino acids are (L) or (D).