Oxidizing Alkyl substituents on Benzene (-1 C?)

[bchang57]

According to DAT Achiever, a benzene ring with an ethyl at C-1, and a methyl at C-4 undergoes oxidation with NaCr2O7, H+, and heat to yield a benzene ring with 2 COOH groups at the 1 and 4 position.

I thought the methyl would become COOH and the ethyl would become CH2COOH.

Does someone know the reason as to why the ethyl group loses a carbon?

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[Msmouth]

The COOH goes on the benzylic carbon (closest to the ring) every time, and it doesn't matter how long the chain is.

 

[Dotoday]

This is a side chain oxidation reaction. Whenever you have a benzylic carbon with a benzylic hydrogen, it gets oxidized to cooh using Group 1 metal with MnO4 or K2Cr2O7. Hope this helps.

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[bchang57]

ahh im still lost as to why the ethyl becomes COOH instead of CH2COOH

 

[Msmouth]

ahh im still lost as to why the ethyl becomes COOH instead of CH2COOH

The benzyllic carbon is the carbon closest to the benzene ring......no matter how long the chain is, the COOH will be 1 away from benzene and the rest will disappear.

 

[Dotoday]

Yes. It is like a tree branch that has little branches. Once you cut the big branch off, all the little branches will go with it.

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