Acidity of TsOH and HCN

1. Oct 8, 2004

maverick280857

Which is more acidic: TsOH or HCN? (Ts is p-MeC6H4SO2-).

2. Oct 8, 2004

movies

TsOH. TsOH has a pKa around -7, HCN is around 9.

3. Oct 8, 2004

chem_tr

You may think from the reverse side; if you have the basic equivalents of these acids, the basicities are reversed. Let me give an example, sodium salts of these acids are bases, but sodium cyanide is a very strong base whereas sodium tosylate is not that strong.

4. Oct 8, 2004

maverick280857

Yeah I was working on this substitution reaction when this came along so I wanted to compare the leaving abilities of TsO- and CN- hence this problem. I did not know anything about their basic strengths. Instead we've been told to make acids from these anions (conjugate) and compare their acidic strengths. The stronger the acid, we weaker its conjugate base and correspondingly, the greater its leaving ability in a SN2 rxn.

Thanks and Cheers
Vivek