The correct sequence of reagents for the following conversion will be

Reaction image

(1) $\ce{CH3MgBr, H+/CH3OH, [Ag(NH3)2]+OH-}$

(2) $\ce{CH3MgBr, [Ag(NH3)2]+OH-, H+/CH3OH}$

(3) $\ce{[Ag(NH3)2]+OH-, CH3MgBr, H+/CH3OH}$

(4) $\ce{[Ag(NH3)2]+OH-, H+/CH3OH, CH3MgBr}$

I think the correct option is (3), however, the key says it is (4).

The first step is definitely the oxidation of the $\ce{-CHO}$ group to $\ce{-COOH}$ using Tollen's reagent. But I think that the second step should be to use Grignard reagent to form tertiary alcohol and then acidify it. Because if we first acidify and then use Grignard reagent, the $\ce{CH3MgBr}$ will react with the leftover acid and the $\ce{CH3OH}$ due to its mildly acidic proton.

Also, I am rather doubtful that the $\ce{CH3MgBr}$ will even react with the acid formed in the first step since it will be in the form of $\ce{R-COO^-Ag+}$, which is not electrophilic.

So what is the correct answer? And how would the $\ce{CH3MgBr}$ react with the acid? Thank you.

  • $\begingroup$ In case you are wondering, this question appeared in the JEE Main exam on 2nd April 2017. $\endgroup$ – FreezingFire Apr 18 '17 at 17:54
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    $\begingroup$ That is not an acidification, it is an esterification. In any case, the steps are separate, it does not mean you leave the MeOH there and then add the Grignard (which is a complete waste of time for the reasons you mentioned!). You will somehow extract the organic product, re-dissolve it in a different (aprotic) solvent, then only add the Grignard. That is what is implied by the separate steps (2) H+, MeOH (3) CH3MgBr. $\endgroup$ – orthocresol Apr 18 '17 at 18:06
  • $\begingroup$ @orthocresol Oh! Duh. You are right. You should add that as an answer! The ester will also react more effectively with CH3MgBr, so their answer is correct. $\endgroup$ – FreezingFire Apr 19 '17 at 2:32
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    $\begingroup$ I'll try to answer if I get the time, but no guarantees $\endgroup$ – orthocresol Apr 19 '17 at 12:12
  • $\begingroup$ @orthocresol if we follow the steps mentioned in option 4, then we will obtain a compound like this i.stack.imgur.com/jNewl.jpg . Final compound will only be obtained after hydrolysis, so why is option 4 correct? $\endgroup$ – user66707 Jan 30 '19 at 17:18

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