Unit 2-Stereochemistry

Question 1

What are structural isomers?

Answer 1

Same molecular formula but different structural formulae (different connectivity).

Question 2

What are stereoisomers?

Answer 2

Same molecular and structural formula but different 3D arrangement.

Question 3

What types of stereoisomerism exist?

Answer 3

Geometric and optical.

Question 4

What causes geometric isomers?

Answer 4

Restricted rotation around a C=C bond or within a ring.

Question 5

What condition is required for geometric isomerism?

Answer 5

Each carbon in the restricted bond must have two different groups attached.

Question 6

What does cis mean?

Answer 6

Groups on the same side of the restricted bond.

Question 7

What does trans mean?

Answer 7

Groups on opposite sides of the restricted bond.

Question 8

Why does propene not show geometric isomerism?

Answer 8

One carbon of the double bond does not have two different groups.

Question 9

What causes optical isomers?

Answer 9

A chiral carbon with four different groups attached.

Question 10

What is a chiral carbon?

Answer 10

A carbon attached to four different groups.

Question 11

What are enantiomers?

Answer 11

Non superimposable mirror images.

Question 12

What is plane polarised light?

Answer 12

Light vibrating in only one plane.

Question 13

What does optically active mean?

Answer 13

Enantiomers rotate plane polarised light in opposite directions.

Question 14

What is a racemic mixture?

Answer 14

A 50:50 mixture of enantiomers that is optically inactive.

Question 15

Why do enantiomers behave differently in biological systems?

Answer 15

Biological systems are chiral and often interact with only one enantiomer.