Influence of Sulfur for Oxygen Substitution in the Solvolytic Reactions of Chloroformate Esters and Related Compounds

International Journal of Molecular Sciences

Malcolm J. D’Souza²  Dennis N. Kevill¹ 

[1] Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb, IL 60115-2862, USA;Department of Chemistry, Wesley College, 120 N. State Street, Dover, DE 19901-3875, USA

关键词: chloroformate;    chlorothioformate;    chlorothionoformate;    chlorodithioformate;    carbamoyl chloride;    thiocarbamoyl chloride;    Grunwald-Winstein equation;    addition-elimination;    ionization;   

DOI  :  10.3390/ijms151018310

来源: mdpi

【 摘 要 】

The replacement of oxygen within a chloroformate ester (ROCOCl) by sulfur can lead to a chlorothioformate (RSCOCl), a chlorothionoformate (ROCSCl), or a chlorodithioformate (RSCSCl). Phenyl chloroformate (PhOCOCl) reacts over the full range of solvents usually included in Grunwald-Winstein equation studies of solvolysis by an addition-elimination (A-E) pathway. At the other extreme, phenyl chlorodithioformate (PhSCSCl) reacts across the range by an ionization pathway. The phenyl chlorothioformate (PhSCOCl) and phenyl chlorothionoformate (PhOCSCl) react at remarkably similar rates in a given solvent and there is a dichotomy of behavior with the A-E pathway favored in solvents such as ethanol-water and the ionization mechanism favored in aqueous solvents rich in fluoroalcohol. Alkyl esters behave similarly but with increased tendency to ionization as the alkyl group goes from 1° to 2° to 3°. N,N-Disubstituted carbamoyl halides favor the ionization pathway as do also the considerably faster reacting thiocarbamoyl chlorides. The tendency towards ionization increases as, within the three contributing structures of the resonance hybrid for the formed cation, the atoms carrying positive charge (other than the central carbon) change from oxygen to sulfur to nitrogen, consistent with the relative stabilities of species with positive charge on these atoms.

【 授权许可】

CC BY   
© 2014 by the authors; licensee MDPI, Basel, Switzerland.