Originally Posted by andy96
On page 11 of berkeley review organic chemistry book, example 1.4, the correct answer is C "bond C is stronger than bond A, despite both sharing an sp2 and sp3 carbon, because bond C contains more highly substituted carbon"
However, on page 19,example 1.7 asks for the most stable bond, the correct answer is A,"an sp2-carbon to a primary sp3-carbon". But I think according to answer to example 1.4, "a sp2-carbon to a secondary sp3-carbon" seems more reasonable.
The question on page 19 tells you to refer to a table, not to past knowledge or knowledge of a specific case. Based on the table alone, an sp2-primary sp3 bond is the most stable. On page 11 the problem is not involving a vinyl group (CH2=CH-R), it is involving a tetra-substituted alkene. The reason bond c is weaker than bond a is because if you cleaved bond a you would end up with a methyl carbocation, which is much less stable than the isopropyl carbocation you would get if you cleaved bond c.