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Homework Help: Mechanism for reaction of Grignard reagent

  1. Jul 14, 2010 #1
    I am in an organic chemistry lab course and my lecture and lab do not align nicely. I need to write out the full mechanism for the reaction of malachite green and crystal violet dyes. The reaction starts by preparing a Grignard reagent from 4-bromo-N,N-dimethylaniline with magnesium/thf. The Grignard reagent then reacts with 1. ethyl carbonate/HCL or 2. methyl benzoate/hcl.

    Could anyone write out the mechanisms for me for these two chemical pathways? I have no idea what I'm doing!!

    Thank you!!
  2. jcsd
  3. Jan 19, 2017 #2


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    The Grignard reagent RMgX is synthetically equivalent to the synthon R-. The negatively charged synthon will attack the partial positive charge on the carbonyl (or carbonate) carbons. To synthesize these two dyes, you need multiple molar equivalents of the dimethylaniline magnesium Grignard (2 or 3, depending on which dye you're making). Eventually, you'll saturate the carbonyls, giving a tertiary alcohol with 3 phenyl groups around it. The final step is a wash with HCl, which protonates the alcohol and eliminates the resulting water.
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