[martin4sifon]

Please House, I need your answers to this:

why is it that racemic sec-butyl chloride would be obtained if:
a) the sec-butyl radical were not flat, but pyramidal
b) Chlorination did not involve a free sec-butyl radical at all, but proceeded by a mechanism in which a chloride atom displaced a hydrogen, taking the position n the carbon atom formerly occupied by that hydrogen

[sjb]

Please House, I need your answers to this:

why is it that racemic sec-butyl chloride would be obtained if:
a) the sec-butyl radical were not flat, but pyramidal
b) Chlorination did not involve a free sec-butyl radical at all, but proceeded by a mechanism in which a chloride atom displaced a hydrogen, taking the position n the carbon atom formerly occupied by that hydrogen

Any thoughts of your own?

[martin4sifon]

@ Sjb

It is a stereo chemistry question gotten from Organic Chemistry Textbook by Morrison and Boyd (3rd Edition). it is a practice question for my exams. I know that racemic mixture is formed by a planar shape through Sn1 reaction mechanism because the flat shape allows for equal chance of attack of the radical for the back and front.

In this case, I really dont know why this will happen in a pyramidal sec-buty radical

[spirochete]

Explanation for part A:

Alkyl radicals are shallow pyramids, so they are somewhat in between sp2 and sp3 hybridization. I think closer to sp2.

But this doesn't matter very much, because even if the intermediate radical is chiral, it is configurationally unstable. This means that it is rapidly interconverting between two configurations: R and S so to speak. So the intermediate is a rapidly interconverting racemic mixture of radicals.

You may have learned about configurational instability in the context or amines. Here is a link with information about amines: http://web.chem.ucla.edu/~harding/tutorials/nitrogen_inversion.pdf