Thiols vs. Alcohols

[qw098]

Hello:

From what I know, Thiols are more acidic than Alcohols.

I was wondering: Do thiols experience more hydrogen bonding than Alcohols or vice-versa?

Thank you,
qw098

 

[Raiden2012]

Thiols do not experience H bonding. Remember that H bond only involves the really electronegative atome F,O,N

 

[qw098]

Thiols do not experience H bonding. Remember that H bond only involves the really electronegative atome F,O,N

Excellent, thank you kindly!

 

[lastt]

I wouldn't expect to see it on the MCAT, but thiols & alcohols surely do hydrogen bond as both acceptors and donors. As to which would be stronger, that depends on what they're H-bonding to. Think overlap and availability of electron pairs.

 

[Raiden2012]

Above poster is right. Thiols do experience hydrogen bonding but it is so weak that it cannot be compared to alcohols since S is weakly electronegative. But for MCAT purposes, treat it as none.

 

[CodeRedDew]

Above poster is right. Thiols do experience hydrogen bonding but it is so weak that it cannot be compared to alcohols since S is weakly electronegative. But for MCAT purposes, treat it as none.

Thiols do not experience any significant hydrogen bonding. The sulfur is simply just not electronegative enough to withdraw the electron cloud away from the hydrogen so that it can act as a hydrogen bond donor.

The reason why thiols are more acidic than alcohols is due to the size of the sulfur atom. The conjugate base of a thiol leaves you with a negative charge on the sulfur, whereas the conjugate base of an alcohol leaves you with a negative charge on the oxygen. The negative charge is more stable on the larger atom (sulfur) because the concentration of charge is not as high as it is on the smaller oxygen atom. Therefore, as the general rule of acidity goes - a more stable conjugate base equates to a stronger acid.