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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: michaelaaaaa on March 17, 2012, 01:21:13 AM

Title: Friedel Crafts mechanism problem help
Post by: michaelaaaaa on March 17, 2012, 01:21:13 AM

http://26.media.tumblr.com/tumblr_m10jt7PUmr1qzof18o1_500.png

Ok so the problem is written at the top its a benzene with a och3 on it, you use reagents:
1. ch3co2coch3, AlCl3, CS2
2. HCl, H2O
to get the product (sorry the picture is so small)

my problem is I got the product before using the second step reagents (HCl, and H2O) so what is the function of the HCl and H2O?

Anyone?

Title: Re: Friedel Crafts mechanism problem help
Post by: Potla on March 21, 2012, 03:23:28 AM

Quote from: michaelaaaaa on March 17, 2012, 01:21:13 AM

my problem is I got the product before using the second step reagents (HCl, and H2O) so what is the function of the HCl and H2O?

I think HCl and H₂O means dil. H⁺, which acts as a catalyst for the process. In case of anhydrides, I think two moles of AlCl₃ is required, one mole is used for liberating the acid chloride from the anhydride:
R-CO-O-CO-R + AlCl₃ --> RCOCl +RCOOAlCl₂.
The second mole, forms the sigma complex with C₆H₆OMe and then the O-Al^-Cl₃ might take H⁺ and liberate one mole of HCl. Then the complex may lose a proton to regain aromaticity, followed by which the Cl may (intramolecular) attack the -AlCl₂, causing breakage of O-Al bond and C-Cl bond through a 4-membered transition state.
This may be possible. I don't really know if all of this is correct or not, since I am a beginner. Hope I could be of some help. :)