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I have a question regarding using $\ce{SOCl2}$ to convert an alcohol into a alkyl halide. The Klein book mentions that $\ce{SOCl2}$ is only used for primary and secondary alcohol; however, in the solutions for one of their problems (Klein), it uses $\ce{SOCl2}$ to convert tertiary alcohol into an alkyl halide.

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Is it even possible to use $\ce{SOCl2}$ with tertiary alcohol?

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  • $\begingroup$ This is not $\mathrm{S_N1}$ or $\mathrm{S_N2}$. This follows $\mathrm{S_N i}$ mechanism. Implying, carbocation formation is absent. $\endgroup$ Commented Jan 1 at 15:30
  • $\begingroup$ In future please use $\LaTeX$ environments for formatting. Chemical formulae are written in the $\ce{}$ environment. Refer to the edited version (and of course Community Wiki) for more details. $\endgroup$ Commented Jan 1 at 15:34
  • $\begingroup$ en.wikipedia.org/wiki/SNi - Refer. $\endgroup$ Commented Jan 1 at 15:35

1 Answer 1

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There is no real barrier against thionyl chloride reacting with a tertiary alcohol. The mechanism described by Ouellette and Rawn[1] does not depend on cleavage of a carbon-hydrogen bond and is even illustrated with a tertiary alcohol substrate.

Hydrogen chloride as the electrophilic reagent may provide a good alternative with tertiary alcohols because this alternative can proceed through a relatively stable tertiary carbocation (the thionyl chloride reaction does not form a carbocation). Carbocation formation would be more difficult with a primary or secondary alcohol.

Reference

  1. Robert J. Ouellette, J. David Rawn, "16 - Alcohols: Reactions and Synthesis", Editor(s): Robert J. Ouellette, J. David Rawn, Organic Chemistry (Second Edition), Academic Press, 2018, Pages 463-505, ISBN 9780128128381, https://doi.org/10.1016/B978-0-12-812838-1.50016-5.
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