# Why is RS- more basic than RO-?

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)

• 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. – Nicolau Saker Neto Mar 26 '15 at 12:42
• 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. – RobChem Mar 26 '15 at 15:31

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