The sdphonation of pyridine-N-oxide with fuming sulphuric acid and mercuric sulphate as a catalyst yields, together with the 3-sulphonic acid as chief product, the 2- and 4-isomers. ... There is a remadcable discrepancy in the behaviour of pyridine-N- oxide towards electrophilic reagents. While the N-oxide is nitrated easily by heating with fuming nitric acid and sulphuric acid to 4-nitro- pyridinedN-oxide * and mercurated with mercuric acetate to products ...
