Abstract Unimolecular hydroxyl (OD) loss from regio-and stereo-specifically labelled o- nitrostyrenes 1a, 1c and 1d results in the formation of an ion which upon collisional activation gives identical mass spectra. Suggestions are made which aim at explaining:(i) the loss of stereochemical integrity of the diastereotopic methylene hydrogens in the course of hydroxyl elimination; and (ii) to account for the collision induced losses of CO and HNC ...
