e withdrawing or donating?

[sdnstud]

is beneze an electron withdrawing or electron donating group? is amide an electron withdrawing or electron donating group

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[PRamos]

The easiest thing to consider is the allylic (or phenylic) carbon attached to the <pi>-system. If the atom has a lone pair, then it is donating. If it is part of a <pi>-bond, then it is withdrawing.

Both an amide and benzene can be either donating or withdrawing, depending on what they're attached to.

If the N is attached, then it is mildly donating. If the carbonyl carbon is attached, then it is withdrawing. Benzene is whatever it needs to be. It is donating when added to an electron poor carbon and withdrawing when added to an electron rich carbon.

Given that benzene chemistry is not on the MCAT, why are you asking? The only spot I saw that stuff tested in my materials was with the Diels-alder reaction. Is there somewhere else, like acidity and basicity?

 

[sdnstud]

electrophilic aromatic substitution. if the beneze or the amide group is the director...are they e donating or e withdrawing?

 

[PRamos]

electrophilic aromatic substitution. if the beneze or the amide group is the director...are they e donating or e withdrawing?

EAS is no longer tested on the MCAT, so I haven't reviewed it.

But, if I remember correctly, an amide is a meta-director when the carbonyl carbon is bonded to the benzene ring but an ortho,para-director when the nitrogen is bonded to the benzene ring.

A benzene on another benzene is electron donating in EAS, because the reactive site takes on a positive charge in its intermediate, so the substituent benzene donates electron density to stabilize the intermediate.

 

[Leonine]

EAS is no longer tested on the MCAT, so I haven't reviewed it.

.

I thought i saw a question related to that on the Kaplan Fl # 4 today. 😕

 

[ifailedmcat]

A benzene attached to another benzene is electron donating, as are all alkyl groups.

An amide group on a benzene is electron withdrawing.

Hope this helps 👍.