| Date | November 2016 | Marks available | 1 | Reference code | 16N.2.hl.TZ0.6 |
| Level | HL | Paper | 2 | Time zone | TZ0 |
| Command term | Suggest | Question number | 6 | Adapted from | N/A |
Question
One structural isomer of C4H9Br is a chiral molecule.
Draw the three-dimensional shape of each enantiomer of this isomer showing their spatial relationship to each other.
[2]
a.
When one enantiomer undergoes substitution by alkaline hydrolysis approximately 75 % of the product molecules show inversion of configuration. Comment on the mechanisms that occur.
[2]
b.
Suggest why the rate of alkaline hydrolysis of an enantiomer of iodopropane is greater than that of an enantiomer of bromopropane.
[1]
c.
Markscheme
correct isomer
mirror image shown clearly
a.
SN2 would give inversion of configuration «almost 100%»
OR
SN1 would give «approximately» 50% of each
so mechanism is a mixture of both mechanisms
b.
C–I bond «longer, so» weaker «than C–Br bond»
OR
I– is a better leaving group than Br–
c.
Examiners report
[N/A]
a.
[N/A]
b.
[N/A]
c.
