TBR - Section I Exam Passage Question 29 General Chemistry - Bond Lengths

[Romz]

Hey guys.

I'm a little confused over the answer that TBR gives regarding Bond lengths.

Question 29. Which of the following compounds has the weakest C-C bond?

I understand that the weakest bond will be the longest bond. However, TBR uses the hybridization of the two carbons involved in the bond to determine the bond length and I have no idea what theory/principles they are applying to reach these conclusions.

I thought that a bond between an sp hybridized and sp3 hybridized carbon would be weakest (most unequal distribution of e- density). However, TBR says it's between sp2 and sp3 hybridized carbon atoms.

A little clarification would be immensely appreciated! Thanks!

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[BerkReviewTeach]

If you like the idea of bond length to determine the bond strength, then consider that an sp-hybrid is shorter than an sp2-hybrid which is shorter than an sp3-hybrid. A sigma bond between an sp-carbon and sp3-carbon will be shorter than a sigma bond between an sp2-carbon and sp3-carbon, because the orbitals involved in the bond are shorter.

 

[Romz]

If you like the idea of bond length to determine the bond strength, then consider that an sp-hybrid is shorter than an sp2-hybrid which is shorter than an sp3-hybrid. A sigma bond between an sp-carbon and sp3-carbon will be shorter than a sigma bond between an sp2-carbon and sp3-carbon, because the orbitals involved in the bond are shorter.

Derp. Very clear explanation. Thank you!