[yourdeath01]

All 3 reactions: https://imgur.com/xQqgecC

For part a: Basically Thiamine hydrochloride (vitamin B1) in presence of NaOH it losses 2 protons to become nucleophilic and adds (with a proton) to carbonyl of benzaldehyde.
Then: thiamine residue is electron withdrawing which increase acidity of adjacent hydrogen atom, which makes it so that the base can attack the hydrogen to yield a carbanion, which attacks the carbonyl of another benzaldehyde molecule. Loss of thiamine residue from product produces benzoin

Here is my mechanism for part a:

page 1: https://imgur.com/tBm17Yq

page 2: https://imgur.com/rHKO4J3

Is my mechanism in terms of arrow pushing and everything else all good?!

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For part b: Benzoin is then converted to benzil through the use of NH4NO3 (ammonium nitrate) through the use of copper (II) acetate catalyst which will oxidize the benzoin

Here is my mechanism for part b: https://imgur.com/8d0bUux

Alternative method: https://imgur.com/KiAnWzj

Mechanism all good? Is the alternative better to use here or stay on the one above it?

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For part C: The benzil is treated with KOH which will make it go through molecular rearrangement discovered by von Liebig How the rearrangement happens? KOH makes Nu attack on 1 of the C= O and then it makes its phenyl group move to other carbonyl. This yields initially potassium benzilate but this dissolves after the mixture is heated

Mechanism for part C:

https://imgur.com/rwxzsE6

Again, is this mechanism all good?

I am probably overthinking this lol, but I don't want to lose out points on silly mistakes, so let me know if I should make adjustment to any of the 3 parts/mechanisms I posted above.

[AWK]

Reaction of copper(I) oxidation is unbalanced.
Google - Copper-Catalyzed Oxidation of Benzoin to Benzil

10.1021/ed065p553