Carbocation and Radical stability

[americanpierg]

Allyl radical is more stable than tertiary, but tertiary carbocation is more stable than allyl carbocation?

Why is this?

Also, are benzyl radicals more stable than tertiary?

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[uclaDDS101]

According to most DAT study material ive seen, allyl and benzyl radicals/carbocations are more stable than tert, due to delocalization of the positive charge/radical. I, too, was taught otherwise in my ochem class, but i'm just going to stick with the convention stated above. In studying for the DAT, Ive realized that ive had to throw out some of the info ive been taught in my classes, and adopt different ones presented by DAT study materials.

 

[wantVCUdental]

I would think that because bonds are electron sharing systems, having a carbocation is highly unstable, so a tertiary (sharing between 4 carbons) is definitely going to be more stable than allyl (sharing between 3 carbons)
Now a radical is an extra electron, that electron can participate in bonding and the alkene in allyl systems allow for resonance structure while a tertiary doesn't, so an allyl radical is more stable.

 

[americanpierg]

According to most DAT study material ive seen, allyl and benzyl radicals/carbocations are more stable than tert, due to delocalization of the positive charge/radical. I, too, was taught otherwise in my ochem class, but i'm just going to stick with the convention stated above. In studying for the DAT, Ive realized that ive had to throw out some of the info ive been taught in my classes, and adopt different ones presented by DAT study materials.

Well I found the answers, though some differ, and chose the one that appeared most frequently lol.

Just in case anyone else was wondering.

Radical--- benzyl, allyl, tert, etc
Carbocation--- tert, benzyl = allyl, secondary, etc