organic chem intro

Question 1

Which alkene shows E–Z isomerism?
A 2,3-dimethylbut-2-ene
B 4-methylpent-2-ene
C methylpropene
D pent-1-ene

Answer 1

E/Z isomerism only occurs if the groups bonded to each carbon atom in the C=C bond are different

B

Question 2

Which does not contain an asymmetric carbon atom?
A CH3CH(CH3)CH2CH3
B CH3CH2CH(CH3)CH2CH2CH3
C CH3CH(OH)CH2OH
D CH3CH2CHClCH

Answer 2

A

asymmetric carbon atom connected to 4 different atoms / groups

Question 3

How many isomers are there of C3H9N?

Answer 3

4

You can put the nitrogen atom on top of a carbon and in the middle connected to other carbon atoms

Question 4

Another structural isomer of J is shown below.
Explain how the Cahn-Ingold-Prelog (CIP) priority rules can be used to
deduce the full IUPAC name of this compound.

Answer 4

Stage 1: consider the groups joined to right hand carbon of the C=C
bond
Extended response
Maximum of 5 marks for answers which do not
show a sustained line of reasoning which is
coherent, relevant, substantiated and logically
structured.
Consider the atomic number of the atoms attached
M1 can be scored in stage 1 or stage 2
1
C has a higher atomic number than H, so CH2OH takes priority
1
Stage 2: consider the groups joined to LH carbon of the C=C bond
Both groups contain C atoms, so consider atoms one bond further
away
1
C, (H and H) from ethyl group has higher atomic number than H, (H
and H) from methyl group, so ethyl takes priority
1

Stage 3: conclusion
The highest priority groups, ethyl and CH2OH are on same side of
the C=C bond so the isomer is Z