Formation of 3-chloromethylbenzene VS 3-chloromethylbenzene VS 4-chloromethylbenzene

Question

For methylbenzene (with the methyl group at position 1), is it easier for chlorine to substitute the hydrogen at position 2, 3 or 4?

I was thinking somewhere along the lines of different charge densities around the benzene ring, and that the charge density closest to the already existing methyl group has been diminished due to the methyl group itself. However, I am unable to explain it properly enough.

I just corrected a little typo in the product names, but i left them wrong for didactic purposes ;) See below for an explanation :) — Klaus-Dieter Warzecha, Feb 26 '14 at 16:30

score 2 · Answer 1 · answered Feb 26 '14 at 16:31

It very much depends on the reagents and reaction type you are using to halogenate the aromatic ring, however, the most common method taught during organic chemistry is electrophilic hologenation, which in this case the methyl will be para directing.

http://en.wikipedia.org/wiki/Electrophilic_halogenation#Scope

Klaus-Dieter Warzecha · Accepted Answer · 2014-02-26T16:40:56.047

2

We are talking about the electrophilic aromatic substitution of methylbenzene (A) with chlorine.

EAS

The possible products are 2-methylchlorobenzene (2), 3-methylchlorobenzene (3), and 4-methylchlorobenzene (4)

Chloromethylbenzene (B) is something different, also known as benzylchloride. Chloromethyl is the name for the $\ce{-CH2Cl}$ substituent :)

Please have a look at this site for an animated explanation of the mechanism and the selectivities.

edited Feb 26 '14 at 16:40

answered Feb 26 '14 at 16:34

Klaus-Dieter Warzecha

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In order to emphasize the differences, you might want to consider using the systematic IUPAC names 1-chloro-2-methylbenzene (2), 1-chloro-3-methylbenzene (3), 1-chloro-4-methylbenzene (4), and (chloromethyl)benzene (B). – Jul 08 '15 at 09:26

Formation of 3-chloromethylbenzene VS 3-chloromethylbenzene VS 4-chloromethylbenzene

2 Answers2