The following reaction mechanism contains mistakes. Which of the following statements correctly describes the curved arrows consistent with the reaction?
A) The curved arrow should start at the carbonyl oxygen atom
B) The curved arrow should start at the hydride, go to the hydrogen connected to oxygen and a second arrow should start from the O-H covalent bond and go to the oxygen
C) The curved arrow should start at the oxygen atom of the OH
D) There should be two more arrows

Question

The following reaction mechanism contains mistakes. Which of the following statements correctly describes the curved arrows consistent with the reaction? 
A) The curved arrow should start at the carbonyl oxygen atom 
B) The curved arrow should start at the hydride, go to the hydrogen connected to oxygen and a second arrow should start from the O-H covalent bond and go to the oxygen 
C) The curved arrow should start at the oxygen atom of the OH 
D) There should be two more arrows

Quizplus · Accepted Answer

The mechanism shown in the diagram involves the attack of a hydride ion on the carbonyl carbon atom, followed by proton transfer from the oxygen to the nitrogen atom. There should be another curved arrow showing the second proton transfer from the nitrogen to the oxygen. Choice A is incorrect because the curved arrow should show the movement of electrons, so it should start from the donor atom (hydride) and end on the acceptor atom (oxygen). Choice C is also incorrect because the proton transfer should occur from the oxygen to the nitrogen, not the other way around. Choice D is incorrect because there are no missing arrows in the mechanism shown in the diagram.

The Following Reaction Mechanism Contains Mistakes