Friedel Crafts alkylation of arenes
Description: In the presence of a catalyst such as FeCl3 or AlCl3 treatment of an aromatic with an alkyl chloride provides an aromatic alkane. This reaction is called “Friedel-Crafts alkylation” .
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Real-Life Examples:
Org. Synth. 1939, 19, 36
DOI Link: 10.15227/orgsyn.019.0036
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Org. Synth. 1934, 14, 34
DOI Link: 10.15227/orgsyn.014.0034
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Org. Synth. 1948, 28, 42
DOI Link: 10.15227/orgsyn.028.0042
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I have a question, but Ive heard FC alkylation reaction makes multi-substitution product. And is it right if there is Halogen already in Benzene, FC makes only one-substitution product??
Thanks.
Yes, that is correct. Friedel-Crafts alkylation results in a more electron-rich aromatic ring, which can then compete with the starting aromatic ring for the electrophile. It’s a Cookie Monster reaction. If there is an electron-withdrawing substituent (like Cl) this will be less likely to happen.
Mechanism is spelled Mecbanism. I’m an orthographist by night.
in example 2, I thought aryl halides didn’t react in Friedel crafts alkylation?
They generally don’t occur when meta-directing groups are present, but FC alkylations are possible when a single halogen atom is present.