HELP Ochem question/reasonance hybrid

[Mrbubbles]

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ok...WHY is the answer B???? this is from Kaplan's practice test (OCHEM #1).

i chose C because I thought the most electronegative element should carry the - charge.

http://i5.photobucket.com/albums/y156/eyesparkles637/ochem-1.jpg here is the link if u can't see it thanx!

 

[WayneSU]

Choice a has five bonds to carbon, thus least stable

choice b has more bonds than both choices c and d, making it the most stable

also, all atoms in choice b satisfy octect rule

 

[Mrbubbles]

oh..lol. duh is houdl have counted the valences. thanx dude.

 

[drgreen]

choice A has 5 bonds on carbon
choice C has a primary Carbocation (not great)

choice D vs. choice B, choice B is favored because the + is stabilized by the - charge