leia03

7+ Year Member
Jan 4, 2010
18
2
Status
Pre-Dental
This is one of the ACS questions.
I do not understand why the answer is D instead of B.

According to ACS, mechanism of hydration of carbonyl molecule with benzene ring and ester as a substituents is following:
Hydride attack carbonyl carbon to make amine group leave and form aldehyde and then, aldehyde further gets reduced to primary alcohol.

Using same mechanism, the answer should be B, but seems like hydride just reduces carbonyl group, why is it? Why two are going under different mechanism?

your help will be highly appreciated.
 

Attachments

Aug 22, 2013
56
5
Status
Pre-Dental
This is one of the ACS questions.
I do not understand why the answer is D instead of B.

According to ACS, mechanism of hydration of carbonyl molecule with benzene ring and ester as a substituents is following:
Hydride attack carbonyl carbon to make amine group leave and form aldehyde and then, aldehyde further gets reduced to primary alcohol.

Using same mechanism, the answer should be B, but seems like hydride just reduces carbonyl group, why is it? Why two are going under different mechanism?

your help will be highly appreciated.
From my understanding LiAlH4, Et2O an reducing reagent that can reduce aldehyde , ketone, esters, and acids Usually by replacing them with an Alcohol group. However in an amide (which is in this problem) it gets rid of the =O completely and the NH2 group is attached to form a primary amine.. Hope this helped a little!
 
Sep 26, 2013
36
2
Status
Pre-Health (Field Undecided)
You can read the wiki
http://en.wikipedia.org/wiki/Amide_reduction

Amide reduction in chemistry is the organic reduction of amides.[1] The main reaction product in this functional group interconversion is an amine. The reagents are lithium aluminium hydride,[2][3][4][5][6] Ether and catalytic hydrogenation (requires high temperatures and pressures).



N,N-disubstituted amides can be reduced to aldehydes by using an excess of the amide:

R(CO)NRR' + LiAlH4 → RCHO + HNRR'
With further reduction the alcohol is obtained.