2
$\begingroup$

The basic strength is determined by the ability of an ion or molecule to accept a proton. How do I know whether RSH is more stable than ROH? (R is an alkyl group)

$\endgroup$
  • 3
    $\begingroup$ My recent answer to this question is quite relevant, with the small difference that one hydrogen gets swapped for an alkyl group. Just remember that stronger acids create weaker conjugate bases. $\endgroup$ – Nicolau Saker Neto Mar 26 '15 at 12:42
  • 5
    $\begingroup$ I think it's the other way around. Thiols are more acidic than alcohols so the conjugate base of a thiol is a weaker base than the alcohol conjugate base. $\endgroup$ – RobChem Mar 26 '15 at 15:31
3
$\begingroup$

RobChem has already pointed out in his comment that your assumption is not quite correct.

Take a look at $\mathrm{p}K_\mathrm{a}$ values for $\ce{ROH}$ and $\ce{RSH}$ in water from the CRC Handbook of Chemistry and Physics and/or other online sources, such as this or that.

\begin{array}{lrr} \mathbf{R} & {\ce{\mathbf{OH}}} &\ce{\mathbf{SH}}\\ \hline \ce{H} & 15.7 &7.0\\ \ce{Et} & 15.9 & 10.6\\ \ce{(H3C)3C} & 18.0 & 11.7\\ \ce{C6H5} & 9.9 & 6.6\\ \end{array}

In all the cases above, the $\mathrm{p}K_\mathrm{a}$ value for $\ce{RSH}$ is smaller than that of $\ce{ROH}$.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.