Alcohol rxns Reagents and stereochemistry

[nwu]

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Hi I am having trouble finding a textbook that will tell me about the possible stereochemical of using these reagents during alcohol reactions.

Of all the reagents I looked at: TsCl and MsCl and Hbr (Hbr provides protons so that OH can turn into H20 and leave) they all turn the OH into a good LG so that a halide or Nu can come in and attack. These guys follow the same rules of Sn1 and Sn2, inversion and racemization are possible depending on the stereochemistry provided.

The only exception I found is SoCl2, this reagent is used specifically to retain stereochemistry so there is no inversion. Is this correct?

 

[amy_k]

You are correct that there is usually retention of stereochemistry with SOCl2 as it goes through the SNi mechanism, but there can be retention of stereochemistry depending on conditions -such as in the presence of a lewis base (commonly pyridine) in which case the reaction proceeds through SN2. There is still some ambiguity on whether we would get 100% inversion/retention though, so its very unlikely that you would be tested on the stereochemistry of this reaction, and just be given an achiral molecule.