Abstract: | The thioacetanilide negative molecular ion (produced by secondary electron capture) is stable, but it fragments after collisional activation to yield C6H5NH]? by cleavage α to the C?S grouping. The negative molecular ions of (substituted) o-nitrothioacetanilides undergo a series of extremely complex rearrangement reactions. For example, the molecular anion derived from o-nitro-N-methylthioacetanilide yields both acetate and thioacetate anions as major fragment ions. |