When comparing the acidity of ethanethiol with the -OH group in ethanol and the -SH group in H₂S, we find that ethanethiol is a stronger acid. This is because the sulfur (S) atom has a larger atomic radius and lower electronegativity, resulting in a weaker attraction to the S-H bond and a lower S-H bond energy. Therefore, in H₂O solution, the S-H bond dissociates more easily, making ethanethiol a stronger acid than ethanol.
Conversely, when comparing the acidity of ethanethiol with H₂S, we observe that ethanethiol is a weaker acid. This is because the ethyl group has an electron-donating effect relative to the hydrogen atom, increasing the electron cloud density on the S atom and making it less likely for the hydrogen atom to dissociate. Therefore, CH₃CH₂-SH is a weaker acid than H₂S.
Furthermore, it is worth noting that the electronegativity of the sulfur (S) atom is lower than that of the oxygen (O) atom, and the S atom has a larger radius, which leads to a weaker polarity of the S-H bond, further affecting the acidity of ethanethiol. The -SH bond in H2S has a weak dissociation ability, which is also due to the weak polarity of the -SH bond, making H2S a weak acid.
