I've just started with EAS. I wanted to write down a mechanism for acylation of a cyclic anhydride (for some reason the formation of the carbocation is not given in my textbook). So I wish to know whether this mechanism is correct or now. Since this is my first attempt at writing one, I don't know whether it's correct.

The reaction:

Reaction scheme

What I came up with:

enter image description here

  • $\begingroup$ @orthocresol I haven't really made any nontrivial contributions to Chemistry SE. Once I have contributed something of value, I will perhaps be in a position to post proposals and suggestions on Meta. I have deleted my previous comments as they're off-topic here. $\endgroup$ – Rodrigo de Azevedo Jul 1 at 16:15
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    $\begingroup$ @RodrigodeAzevedo, I think (I hope) that meta here is fairly open, and tags are a pretty easy topic to get introduced to meta rather than commenting on heavyweight topics like closure etc. But of course, it's up to you! $\endgroup$ – orthocresol Jul 1 at 16:54

The mechanism shown in the question seems reasonable enough to me. I would note that ring opening before the attack on the $\pi$-system is likely, but not absolutely necessary. Loss of $\ce{AlCl3}$ may not occur until workup. Direct proton transfer seems unlikely, but is a inconsequential detail. Note however, that the electron pushing arrow is drawn opposite to what it needs to be for that transfer.

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    $\begingroup$ I didn't quite understand what you meant by 'workup' $\endgroup$ – Avyansh Katiyar Jan 11 '18 at 20:33
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    $\begingroup$ Workup = quenching the reaction usually with ice/water $\endgroup$ – Waylander Jan 12 '18 at 0:38
  • $\begingroup$ are you sure that the top oxygen's lone pair forms the complex and not the middle ones' ? $\endgroup$ – Archer Mar 23 '18 at 15:07
  • $\begingroup$ Seems more likely to me, but the mechanism would then still work. $\endgroup$ – TAR86 Mar 23 '18 at 17:15

Your mechanism is almost correct. In your first intermediate, you have a red arrow in the wrong place. Since this ring is opening up, you want the arrow showing movement of the ring electrons (those between the lower carbonyl and the ring oxygen). Ideally, you would show those electrons becoming the new CO double bond of the aluminum carboxylate.

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