Isomerism in Organic Chemistry

Question 1

Define Structural isomerism

Answer 1

• the same molecular formula
  - different structural formula

Question 2

Define Stereoisomers

Answer 2

• the same structural formula
  - different arrangements of atoms in space.

Question 3

What are the key points of optical isomerism (3)

Answer 3

• Optical isomerism is a form of stereoisomerism.
• Stereoisomers have the same structural formula but a
  different arrangement of atoms in space.
• Optical isomers are non-superimposable mirror images.

Question 4

What is optical isomerism (4)

Answer 4

• Molecules with chiral centres
• That are non-superimposable mirror images
• Rotate the plane of polarised light in opposite directions
• One isomer will rotate it clockwise, the other isomer will rotate it anti-clockwise.

Question 5

Chiral

Answer 5

A molecule which can exist as a pair of optical isomers is said to be CHIRAL

Question 6

Chiral Centre

Answer 6

The carbon which is attached to four different groups is called the CHIRAL CENTRE

Question 7

Stereogenic Centre

Answer 7

Another name for a chiral centre is a STEREOGENIC CENTRE

Question 8

Asymmetric Carbon

Answer 8

Another name for a chiral centre is an ASYMMETRIC CARBON

Question 9

Enantiomer

Answer 9

Each optical isomer can also be called an ENANTIOMER

Question 10

Enantiomerically Pure

Answer 10

If a sample contains only one optical isomer it is said to be ENANTIOMERICALLY PURE

Question 11

Optically Active

Answer 11

An enantiomerically pure compound is OPTICALLY ACTIVE as it will rotate the plane of polarised light in one direction only.

Question 12

Racemic Mixture

Answer 12

A mixture which contains equal quantities of enantiomers is called a RACEMIC MIXTURE.