Question 1

What is the difference between an alcohol and a phenol?

Accepted Answer

In an alcohol, the hydroxyl (–OH) group is attached to a saturated carbon atom (part of an alkyl group). In a phenol, the –OH group is attached directly to a carbon atom within a benzene ring. This difference leads to significantly different chemical properties, particularly in terms of acidity.

Question 2

Can I use acidified potassium manganate(VII) to oxidise alcohols?

Accepted Answer

Yes, potassium manganate(VII) ($KMnO_4$) is a powerful oxidising agent and will oxidise primary and secondary alcohols. The colour change is from purple ($MnO_4^-$) to colourless ($Mn^{2+}$). However, it is less selective than dichromate(VI) and can easily cause cleavage of C-C bonds, especially under harsh conditions. For A-Level purposes, acidified potassium dichromate(VI) is the standard reagent you should refer to unless specified otherwise.

Question 3

Why is a catalyst needed for esterification?

Accepted Answer

Esterification is a slow, reversible reaction. The strong acid catalyst (e.g., concentrated $H_2SO_4$) serves two purposes: it speeds up both the forward and reverse reactions, allowing equilibrium to be reached faster. It also acts as a dehydrating agent, removing the water produced, which shifts the equilibrium position to the right (according to Le Chatelier's principle), increasing the yield of the ester.

Alcohols

What you need to know

Alcohols: The Reactive Hydroxyl