Problem 4.91


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Michelle_Nguyen_3F
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Joined: Wed Sep 21, 2016 2:59 pm

Problem 4.91

Postby Michelle_Nguyen_3F » Tue Nov 08, 2016 12:10 am

Hello!

The question says: Benzyne, C6H4, is a highly reactive molecule that is detected only at low temperatures. It is related to benzene in that it has a six-membered ring of carbon atoms; but, instead of three double bounds, the structure is normally drawn with two double bonds and a triple bond. (a) Draw a Lewis structure of benzene molecule. Indicate on the structure the hybridization at each carbon atom. (b) On the basis of your understanding of bonding, explain why this molecule might be highly reactive.

I know how to do part (a), but I am unsure of what the answer to part (b) is. I read the answer in the solution manual, but I would still like some more clarification. Thank you!

Rachel_Smith_3D
Posts: 21
Joined: Wed Sep 21, 2016 2:58 pm

Re: Problem 4.91

Postby Rachel_Smith_3D » Tue Nov 08, 2016 12:47 am

The wording in the solutions manual is a little confusing, but the gist is that the triple-bonded carbons both have only 2 regions of electron density. Therefore they are sp hybridized. Sp hybridized atoms generally form linear arrangements with bond angles of 180 degrees. However, the shape of benzyne forces those bonds to bend to a 120 degree angle. The other carbons have bonds to hydrogen that cause them to be sp2 hybridized, so 120 degrees is the natural bond angle (they are trigonal planar) whereas this is strained in the triple-bonded carbons.

Because these bond angles are so strained, the carbons will readily bond with something to make them sp2 hybridized. This means that they're highly reactive.


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