Question

Explain the mechanism for the reaction between methyl chloride and aqueous KoH

Answer 1

“The best explanation we have for what happens in this reaction is that it proceeds through what organic chemists refer to as a backside attack.

Answer 2

Answer:

Explanation:

The best explanation we have for what happens in this reaction is that it proceeds through what organic chemists refer to as a backside attack. The nucleophile approaches the alkyl halide 180° from the C-Br bond, and as the C-(nucleophile) bond forms, the C-(leaving group) bond breaks.** At the transition state of the reaction, there are partial C-(nucleophile) and C-(leaving group) bonds (denoted by dashed lines). Note the geometry too – instead of tetrahedral, it’s trigonal bipyramidal. This is 5-coordinate carbon – if only for a femtosecond or two.

And in an analogy you’ll no doubt hear many times, then, like an umbrella in a strong wind, the three groups flip over as the leaving group leaves, resulting in inversion of configuration. Note that inversion happens at carbons without stereocenters too – it’s just that we can’t observe it because there’s no way to detect the change in configuration.

This umbrella metaphor for the backside attack mechanism is so fundamental and well known in organic chemistry that you can tweet about it and people will know exactly what you mean