Lecture 21 - Stereochemistry

A series of flashcards based on the lecture notes about stereochemistry, covering key concepts such as chirality, enantiomers, optical activity, and isomerism.

What are configurational isomers and how do they arise?

Configurational isomers arise due to the absence of rotation about a double bond or when an sp3 atom has four different bonding partners.

What defines a chiral object?

A chiral object is one that is not superimposable upon its mirror image.

What makes a molecule chiral?

A molecule is chiral if it contains a stereogenic centre, which is a carbon atom bonded to four different groups.

What are enantiomers?

Enantiomers are pairs of molecules that are mirror images of each other and are not superimposable.

What labeling conventions are used for chiral centres?

Chiral centres can be labeled as R or S in modern convention, and as L or D in older convention.

Why does chirality matter in pharmaceuticals?

Chiral molecules are common in pharmaceuticals, with around 40% being chiral, and often only one enantiomer is active.

What is optical activity?

Optical activity refers to the rotation of plane polarized light by a chiral compound; one enantiomer rotates light clockwise and the other anti-clockwise.

What are diastereoisomers?

Diastereoisomers are stereoisomers that are not mirror images of each other.

What is the relationship between the number of stereogenic centres and isomers?

A molecule with n stereogenic centres can form 2^n isomers, leading to a rapid increase in the number of isomers with additional chiral centres.

What distinguishes stereoisomers from constitutional isomers?

Stereoisomers differ in the arrangement of groups in space, while constitutional isomers differ in the nature or sequence of their bonds.