I'm trying to work out a possible mechanism for the reaction of a methyl glycinate hydrochloride salt in toluene (it is insoluble) with an acid chloride, reacting through the N-terminus. As the amine is protonated (hydrochloride salt), it is non-nucleophilic and insoluble in the toluene. The question states that upon addition of the acid chloride and heating under reflux for 4 hrs the insoluble salt slowly goes into solution.

Given the salt is non-nucleophilic, I am struggling to see a way that the reaction could take place. My current thoughts are that a small amount of the salt must exist in the non-polarised form (an amine + HCl) and this is what reacts as the amine is a nucleophile and so able to react with the acid chloride, forming a soluble product hence the gradual dissolving over time. Would this be correct, or am I missing something? Any suggestions much appreciated!

Edit: There is no base such as Et3N in the solution, although I imagine that could solve the problem quite nicely!

  • 2
    $\begingroup$ Your logic seems sound to me. The heating should support conversion to the more thermodynamically stable product. It would help if the HCl byproduct was being removed from the system, but that doesn't seem to be the case. $\endgroup$ Mar 14 at 14:02
  • $\begingroup$ @electronpusher thank you - that would seem to make sense about the heating promoting formation of the more thermodynamically stable product which then can react. $\endgroup$
    – gd99
    Mar 14 at 20:21

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