Chemistry Olympiad

does anyone have any tips for the chemistry olympiad? and any methods that actually help approach the question

It depends on what types of questions you are struggling with.
Post a few here and I'll talk you through how I would go about solving them.

there’s not any specific ones, i can attempt the questions i just don’t necessarily get to right answer and it’s takes a while to understand.
is doing past papers the best way to practice?

Past papers are definitely the best form of practice- I’d say at the very least aim to get the four or five most recent papers done and marked (if you have doubts or find the MS hard to understand, ask here for a clarification).

Past papers are definitely the best form of practice- I’d say at the very least aim to get the four or five most recent papers done and marked (if you have doubts or find the MS hard to understand, ask here for a clarification).

Can I do so too?

Can I do so too?

anyone done it ?

did anyone the last bit on question 5?
I got the OH- and Br2 made an acid but had no idea what CH2N2 did, apparently it makes ester

(Note that I didn’t do the paper - I’m a chemistry undergraduate)
I’d need to see the question, but I’m guessing you have a reaction between a carboxylic acid and diazomethane.
Essentially the acid protonates the CH2 bit of diazomethane to give the CH3N2^+ cation and then the carboxylate does a nucleophilic substitution on the cation to give a methyl ester and N2 (g).

Also, if I had to guess, OH^- and Br2 is a bromoform reaction, so presumably you started off with something that had a COCH3 or C(OH)CH3 as part of it’s structure

Yeah
From what I remember it was this, starting from the top left
(Last step was either grignard or lithium 2eq, can't remember)
I got all the reactions except the ch2n2 so I just put carboxylic acid for everything after that, so 0 marks I guess?? And also if it was methyl ester surely it would go back to acid after HCl?? Maybe I just missed a step

Esters generally require heating in order to hydrolyse - HCl alone doesn’t necessarily indicate you’ve hydrolysed it.
I would imagine the acid is to deprotect the ketal only.
When the paper is released, I’ll give it another look and maybe share my thoughts here

Esters generally require heating in order to hydrolyse - HCl alone doesn’t necessarily indicate you’ve hydrolysed it.
I would imagine the acid is to deprotect the ketal only.
When the paper is released, I’ll give it another look and maybe share my thoughts here