Contradiction in TBR? Acid strength and bond length?

[altogether]

"given that longer bonds are weaker bonds (in both a homolytic and heterolytic fashion), the acidity of a cmpd directly depends on the length and strength of the bond"--Talking about size of atom attached to acidic proton.

"the hybridization of an atom affects the bond length and the distribution of electron density within a bond... the relationship is not obvious in that it is not true that longer bonds lead to stronger acids as is the case with most other acids??. in fact, the relationship between length and acid strength is exactly the opposite. as the hybrid orbital gets smaller, the electrons are held closer to the nucleus of the atom bonded to hydrogen, so the bond can be cleaved in a heterolytic fashion more easily."

I completely understand the second statement. But how does that fit in with the first statement? Should I completely disregard bond length and bond strength? And instead say that larger conj. base is more stable?

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[DougTPR]

It is a matter of what examples you are talking about...

"given that longer bonds are weaker bonds (in both a homolytic and heterolytic fashion), the acidity of a cmpd directly depends on the length and strength of the bond"--Talking about size of atom attached to acidic proton.

Compare H-F < H-Cl < H-Br < H-I and you see longer bond is stronger acid.

"the hybridization of an atom affects the bond length and the distribution of electron density within a bond... the relationship is not obvious in that it is not true that longer bonds lead to stronger acids as is the case with most other acids??. in fact, the relationship between length and acid strength is exactly the opposite. as the hybrid orbital gets smaller, the electrons are held closer to the nucleus of the atom bonded to hydrogen, so the bond can be cleaved in a heterolytic fashion more easily."

Compare C(sp3)-H < C(sp2)-H < C(sp)-H and you see shorter bond is stronger acid.

I completely understand the second statement. But how does that fit in with the first statement? Should I completely disregard bond length and bond strength? And instead say that larger conj. base is more stable?

You are correct in that it is not as simple just to relate acidity to bond length or bond strength.

The more complete idea is the ability of the conjugate base to stabilize the resulting negative charge.