gen chem, kaplan FL type

[amar21]

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which choice correctly lists the energy level of the C-H bonds from lowest to highest?

answer
c2h2 < c6h6 < ch4

how? is it because sigma bonds have more energy than pie bonds? Thats kidn of confusing, because in orgo you learn that a triple bond requires more energy to break than a single bond?

 

[rocuronium]

What you are talking about is the strength of C-C bonds, while the question is referring to C-H bonds.

If I recall correctly, the answer to this question lies in the amount of s character of the bonds. s orbitals have lesser energy than p orbitals, so the more s character that a bond has, the lower energy it will have.

If you look at the molecules in the question, the C-C triple bond is sp hybridized while the CH4 molecule is sp3 hybridized. The sp bond has more s character than the sp3 bond, and therefore less energy.

 

[amar21]

ahhh i see! thanks