Question 3
1. Remember the rule: select the longest chain as the parent
chain
- counting horizontally from left to right gives five
carbons in the chain and the parent name Pent.
Since only hydrocarbon groups are involved, the parent name will be Pentane.
2. Number from the end of the chain to give the smallest
number in naming
- ie counting from
left to right places the two CH3 groups at position 2 and
not 4 if the chain was numbered from the
right hand side.
3. Since one more similar group (methyl) is attached at
position 4, this will be grouped with the others.
This gives trimethyl - two groups at position 2 and one
group at position 4
Full name use option A
Question 4
1. If the molecule shows optical activity, it should form two non- superimposable isomers that
are mirror images of each other. To do this the molecule must have a chiral centre. This is a
carbon centre (atom) which has four different groups attached to it
2. Search the examples given for a carbon fitting this
description.
3. To answer
i. Eliminate II this molecule is symmetrical.
ii. Eliminate III this will have similar (methyl) groups on
the central carbon atom.
iii. I and IV fit the description and we have seen these in
our text books before
Option B is the
answer
