Isomerism

Question 1

geometrical isomerism

Answer 1

same structural formula but atoms occupy different area in space

due to restricted rotation of double bond

Question 2

assigning E and Z isomers - Priority rules

Answer 2

1. look at atomic number
2. look at atomic weight
3. multiple bonds are treated as single bonds

Question 3

evidence that dichloromethane (CH2Cl2) is tetrahedral

Answer 3

if it was square planar, 2 distinct isomers would form with different configurations - could only be interconverted by breaking and re-making chemical bonds

however, only one form of this compound has ever been found

Question 4

enantiomers

Answer 4

a pair of non-superimposable mirror molecules

Question 5

chiral

Answer 5

4 distinct groups

non-superimposable mirror images

Question 6

stereogenic centre

Answer 6

atom whose substituent groups give rise to chriality

Question 7

name of mixture comprising of a single enantiomer only

Answer 7

enantiomerically pure

Question 8

name of mixture with equal amounts of each enantiomer

Answer 8

racemic mixture / a racemate

Question 9

how to distinguish between enantiomers

Answer 9

[ labelled as (S) or (R) ]

assign priorities to 4 groups attached to carbon

• > highest = 1
• > lowest = 4

view molecule with lowest priority group away in background and other 3 coming forward in a triangle

decide direction of rotation
R = clockwise
S = anticlockwise