Question 24 Passage 4, Section 1 TBR Ochem

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Sikara

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What is the geometry of the following molecule:

HCONH2

The answer key says the six atoms are coplanar, because resonance allows the Nitrogen to donate its lone pair to the carbonyl group, thus giving it sp2 character. The carbon also has sp2 character, thus we have 2 trigonal planars joined.

But isn't this resonance, where the actual configuration lies between sp2 and sp3? Thus, it wouldn't be correct to say that the nitrogen is sp2, it also has some larger amount of single bond character due to the dominant resonance form.

Therefore, why wouldn't the nitrogen portion be bent in a slightly tetrahedral orientation? Thanks for any input!

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What is the geometry of the following molecule:

HCONH2

The answer key says the six atoms are coplanar, because resonance allows the Nitrogen to donate its lone pair to the carbonyl group, thus giving it sp2 character. The carbon also has sp2 character, thus we have 2 trigonal planars joined.

But isn't this resonance, where the actual configuration lies between sp2 and sp3? Thus, it wouldn't be correct to say that the nitrogen is sp2, it also has some larger amount of single bond character due to the dominant resonance form.

Therefore, why wouldn't the nitrogen portion be bent in a slightly tetrahedral orientation? Thanks for any input!

the emphasis is on the carbonyl carbon, which is sp2.

the partial double bond character between the nitrogen and carbon make it a planar bond and therefore it couldn't be tetrahedral orientation since the nitrogen is only attached to 3 atoms and its non-bonding electrons are tied up in conjugation.

atoms adopt the electron configuration of lowest energy, and therefore the nitrogen's sp2 hybridization is the dominant form
 
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