Question

Given that benzaldehyde is a meta- director, in the same Marvin editor draw all three resonance structures for the carbocation intermediate that results from STEP 2 in the electrophilic aromatic substitution reaction when benzaldehyde reacts with Br2 in the presence of FeBr3. If you do not remember the structure of the benzene derivative, consult the L3 complete lecture notes slides #21 - 24.

Answer 1

The reaction of FeBr3/Br2 with benzaldehyde will yield a major product in which the -Br is attached to the benzaldehyde at the meta position.

Step-by-step explanation:

In chemistry, resonance is a way of describing bonding in certain molecules or ions by the combination of several contributing structures into a resonance hybrid in valence bond theory. Resonance structures often explain the formation of certain major and minor products in organic chemistry reactions.

Aromatic aldehydes and ketones undergo electrophilic substitution reactions such as nitration, sulphonation and halogenation. Since the aldehydic group (-CHO) and ketonic group (-COR or -COAr) are electron-withdrawing, they are deactivating and m-directing.

In benzaldehyde, the ring becomes deactivated at ortho & para positions due to an electron withdrawing aldehyde group. Hence electrophilic substitution is favored at Meta position.

This implies that the reaction of FeBr3/Br2 with benzaldehyde will yield a major product in which the -Br is attached to the benzaldehyde at the meta position.