25.2- OPTICAL ISOMERISM

Question 1

What are isomers?

Answer 1

compounds with same molecular formula but have different molecular structures or different arrangement of atoms in space

Question 2

Examples of structural isomers?

Answer 2

different functional groups

functional group attached at different points on main chain

different arrangement of carbon atoms in skeleton of molecule

Question 3

What is stereoisomerism?

Answer 3

two (or more) compounds have same structural formula

differ in arrangement of bonds in space

Question 4

What are the two types of stereoisomers?

Answer 4

E-Z isomerism

optical isomerism

Question 5

When does optical isomers occur?

Answer 5

when there are four different substituents attached to one carbon atom

Question 6

When there are four different substituents attached to one carbon, what does this result in? (optical isomerism)

Answer 6

results in two isomers that are non-superimposable mirror images of one another, but not identical

Question 7

How do two isomers that are non-superimposable mirror images of one another differ?

Answer 7

differ in way they rotate plane of polarisation of polarised light- either clockwise ( (+) isomer) or anticlockwise ( (-) isomer)

Question 8

What are optical isomers said to be?

Answer 8

chiral

Question 9

What are the two isomers of optical isomers called?

Answer 9

pair of enantiomers

Question 10

What is the chiral centre/ asymmetric carbon atom of an optical isomer?

Answer 10

carbon bonded to four different groups

Question 11

How is the chiral centre indicated on formulae?

Answer 11

by *

Question 12

Why do optical isomerism happen?

Answer 12

as the isomers have three-dimensional structures so it can only be shown by three-dimensional representations or by models

Question 13

What does light consist of?

Answer 13

vibrating electric and magnetic fields

Question 14

What can light be thought of as?

Answer 14

waves with vibrations occurring in all directions at right angles to direction of motion of light wave

Question 15

What happens when light passes through a special filter, called a polaroid?

Answer 15

all the vibrations cut out except those in one plane

Question 16

What can be used to measure optical rotation?

Answer 16

polarimeter

Question 17

Where is polarised light passed through- measuring optical rotation using a polarimeter #1

Answer 17

polarised light passed through two solutions of same conc. , each containing different optical isomer of same substance

Question 18

What will each solution do?- measuring optical rotation using a polarimeter #2

Answer 18

one solution rotate plane of polarisation through particular angle, clockwise
other by same angle, anticlockwise