[vivekrai]

I've been told by my instructor that 3 degree alkyl cabocations are more stable than 1 degree alkyl or benzyl. I tried to look it up on google but it didn't yield some productive work.

So I would like to ask the members here to offer some explanation for it, or any reference text.

[Schrödinger]

Yeah, that's what I heard from my professor too. It might be hard to believe that although the positive charge is delocalized over an aromatic ring, the tertiary carbocation is more table. But that's the hard truth. I guess inductive effect from all 3 alkyl groups (and maybe hyperconjugation) is a good enough reason.

[discodermolide]

I've been told by my instructor that 3 degree alkyl cabocations are more stable than 1 degree alkyl or benzyl. I tried to look it up on google but it didn't yield some productive work.

So I would like to ask the members here to offer some explanation for it, or any reference text.

You didn't find this link?
http://www.chem.ucalgary.ca/courses/350/Carey5th/Ch08/ch8-3.html
Benzyl is similar to tertiary in stability due to the resonance stabilization of the aromatic ring.

[vivekrai]

What's given in the link is too obvious. It doesn't makes a comparison on the two I had sought for. I agree with Schrödinger that it is hard to believe because In general the Mesomeric effects are considered superior to the Inductive and Hyperconjugative. effects.
I wish to know how chemists came to be aware of this fact? I mean how did they determine it?

[Arctic-Nation]

The simplest method is to measure the rate of reaction. If you take benzyl chloride and tert-butyl chloride and let them react under SN1 conditions (because benzyl chloride can react via SN2, too), you'll find that tBuCl reacts much faster.

It might be important to consider that a benzyl cation is still a primary carbocation, and stabilization only comes through the loss of aromaticity. Tertiary cations have triple hyperconjugation that comes at the apparently lower cost of weakened C-C and/or C-H bonds.

[james_a]

Although my copy isn't on me at the moment (so I can't quote from it) in March's Advanced Organic Chemistry you will find a list of rates for the ionization of various alkyl halides in water (primary, secondary, tertiary, benzylic, allylic). There you will find your answer

I've been told by my instructor that 3 degree alkyl cabocations are more stable than 1 degree alkyl or benzyl. I tried to look it up on google but it didn't yield some productive work.

So I would like to ask the members here to offer some explanation for it, or any reference text.