Which C-H bond has lowest bond energy in allylic carbanions?

[gpavanb]

Homework Statement

Look at the diagram accompanying the question. Which has least C-H bond energy?

The Attempt at a Solution

On cleavage of a C-H bond, a carbanion is formed as carbon is more electronegative than hydrogen. So cleavage of (b) results in a carbanion stabilized by resonance

 

[chemisttree]

Homework Statement

Look at the diagram accompanying the question. Which has least C-H bond energy?

The Attempt at a Solution

On cleavage of a C-H bond, a carbanion is formed as carbon is more electronegative than hydrogen. So cleavage of (b) results in a carbanion stabilized by resonance

You can form 2 allylic (stabilized by resonance) carbanions (a and b). Which one is most stable?

 

[gpavanb]

Cleavage of a results in a vinylic carbanion. b forms the more stable allylic carbanion

 

[chemisttree]

Sorry, I read that wrong. It should have been position 'b' and 'd' produce the allylic carbanions. Which one is most stable?