What feature is required for a molecule to show optical isomerism?

A chiral carbon bonded to four different groups

Why does benzene undergo substitution rather than addition?

Substitution preserves the stable delocalised ring of electrons

The phenoxide ion is stabilised by delocalisation of its charge into the ring

The nitrogen lone pair can accept a proton

By a sharp melting point at the expected value

The number of hydrogens on neighbouring carbon atoms is n

11questions. Pick an answer and you'll see why right away.

What feature is required for a molecule to show optical isomerism?
Why does benzene undergo substitution rather than addition?
What is the electrophile in the nitration of benzene?
Why is phenol more acidic than ethanol?
Which reagent gives a silver mirror with an aldehyde but not a ketone?
What type of reaction occurs when hydrogen cyanide adds to a carbonyl group?
What is the catalyst for the esterification of a carboxylic acid with an alcohol?
Why do amines act as bases?
How is the purity of a recrystallised organic solid checked?
In infrared spectroscopy, an absorption near $1700$ cm $^{-1}$ indicates which bond?
In proton NMR, what does the splitting of a peak into n+1 lines tell you?