\begin{align} \ce{Propanol + SOCl2 &-> Expected~ alkyl~ halide~ product}\\ \ce{Propanoic~ acid + SOCl2 &-> Expected ~acid ~chloride ~product}\\ \ce{Acetone ~enol + SOCl2 &-> doesn't~ work ~in~ the ~expected ~manner}\\ \end{align}
My prof says the $\ce{SOCl2}$ only works on $\ce{sp^3}$ substrates.
But ... both propanoic acid and acetone enol involve an $\ce{sp^2}$ carbon bound to an alcohol group ... why does $\ce{SOCl2}$ work in one case but not in the other?
I think it instead has to do with the nucleophilicity of the electrons involved with oxygen ... the mechanism starts with electrons associated with oxygen attacking thionyl chloride. A regular alcohol has an oxygen with lone pairs that aren't fairly "free," so to speak. An carboxylic acid has resonance donation enhancing the nucleophilicity of one oxygen's lone pairs. In acetone, however, there is no resonance donation ....... (inductive donation, sure).
So does the $\ce{sp^2}$ vs. $\ce{sp^3}$ explanation hold water?