Difficult Chen MCAT question

This forum made possible through the generous support of SDN members, donors, and sponsors. Thank you.

SonhosDaVida

Full Member
7+ Year Member
Joined
May 23, 2014
Messages
265
Reaction score
37
Why is the answer C? Can someone draw out a mechanism for how C and D work?

Members don't see this ad.
 
This question
 

Attachments

  • IMG_8441.PNG
    IMG_8441.PNG
    189.1 KB · Views: 93
If I remember correctly from orgo I, I think it's because KMnO4 is not specified as hot and concentrated. When it is cold and reacted with a base, it will form syn diols. If KMnO4 and H+ were to react with added heat, it would cleave and the resulting product would not be hexanoic acid. Although the question didn't specify conditions, I don't believe you would get hexanoic acid either way. Hopefully this helps. Someone please correct me if I'm wrong.


Sent from my iPhone using SDN mobile
 
Members don't see this ad :)
The option C, the double bond will be broken up and further oxidized into two carboxylic acid on two ends.

All other options will give you the target compound gradually.
 
Canada to the rescue: https://home.cc.umanitoba.ca/~hultin/chem2220/Support/oxidative_cleavage.pdf

@hellocakes appears to be correct. C will produce two carboxylic acid groups on opposite ends of an alkyl chain, which would not be hexanoic acid.

The mechanism for D is that KMnO4 just oxidizes the hell out of the alkyne group. KMnO4 is a very strong oxidizing agent and appears to generally always progress to COOH if appropriate substrate material is available.
 
Top