Publication costs assisted by the National Science FoundationProcedures are developed in which the reversed-sector double-focusing mass spectrometer is employed to monitor signals due to specified ionic reactions. These procedures are employed to determine chlorine isotope effects for positive and negative ions fragmenting both unimolecularly and on collision at high velocity. Values of the 35C1/37C1 isotope effect are measured for reactions involving C1. and HC1 elimination and are found to range from unity to 1.2. A dependence is noted upon the internal energy of the ion and, in the case of chlorobenzenes, on the nature of the para substituent. Fragmentations of positive ions which are subject only to secondary chlorine iostope effects are monitored to provide internal standards and as a check upon possible isotope effects in the chemical ionization source. The magnitudes of the kinetic heavy atom isotope effects for positive ions are rationalized in terms of the strength of the C-Cl bond as determined chiefly by the contribution of the chloronium (>C=Cl+) resonance form. A value of 1.19 f 0.01 (95% confidence) is recorded as the secondary chlorine isotope effect for HCl elimination from the negative ions formed by chloride ion attachment to benzoic acid. The error in this determination is no more than 5%.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.