Thank you!
If you're doing further maths, then I would say that your maths ability would've sharpened up enough in this year so that it would be very unlikely that you wouldn't get 90UMS+ in C4, so taking C3 again would be redundant. However, I would also argue that with minimal work, you'll be able to do exceedingly better at C3 anyway, so overall I think it shouldn't matter whether or not you take both again, but personally I would retake both for redundancy's sake (ending up with 100 UMS in both C3 and C4 was a nice little bonus for me as well
)
As for the personal statement, I explicitly stated stuff on:
- Ring closing reactions involving internal nucleophiles
- Frontier molecular orbital theory
- The Diels-Alder reaction
- Charge transfer complexes, eg. ferrocene
- The effect of steric hindrance on antibiotic resistance (as part of my EPQ)
And the two books I already mentioned I read this stuff on.
At interview, they had asked me all of the aforementioned stuff and to expand on some of it, eg. the sine wave pattern in the molecular orbitals of butadiene as an expansion of FMO theory, or an example mechanism on ring closing involving internal nucleophiles and how to catalyse such a reaction. They expect you to fully know everything you've written and to solve problems involving it, and it takes a lot of hard graft.
On the plus side, I can explain the Woodward-Hoffmann rules for cycloaddition reactions down to a pin now, almost anyway