Triple vs. double bonds

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Sophie 1I
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Joined: Fri Sep 29, 2017 7:04 am

Triple vs. double bonds

Postby Sophie 1I » Sun Nov 19, 2017 6:09 pm

On a homework problem for writing the lewis structure for ClCN, why would Carbon form a triple bond with nitrogen and a single bond with chlorine instead of a double bond with both Nitrogen and chlorine?

Carlos Gonzales 1H
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Joined: Fri Sep 29, 2017 7:05 am
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Re: Triple vs. double bonds

Postby Carlos Gonzales 1H » Sun Nov 19, 2017 6:16 pm

If the Carbon were to have a double bond with both chlorine and nitrogen then the formal charge of carbon would be 0, but the formal charges of chlorine and nitrogen would be +1 and -1, respectively. When making lewis structures we want to have the formal charges to be as close to 0 as possible. When carbon has a triple bond with nitrogen, the formal charges of nitrogen and carbon are both 0. The single bond formed between chlorine and carbon will also result in chlorine having a formal charge of 0.

Kathleen Vidanes 1E
Posts: 62
Joined: Fri Sep 29, 2017 7:07 am

Re: Triple vs. double bonds

Postby Kathleen Vidanes 1E » Sun Nov 19, 2017 6:18 pm

Carbon would form a triple bond with Nitrogen and a single bond with Chlorine in order to satisfy the formal charges for each atom in the Lewis Dot Structure. When it is drawn in this way and you calculate the formal charge for each atom, each one should have a formal charge of zero, which is what we want, since the overall molecule does not have a positive or negative charge.

If there was a double bond for both Nitrogen and Chlorine, then the formal charges would be +1 for Chlorine and -1 for Nitrogen. Even though these numbers would cancel to equal 0, Nitrogen usually prefers a triple bond whenever it is bonded to another atom.


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