Tautomeric Equilibria of Thio-Analogues of Nucleic Acid Bases. Part 1. 2-Thiouracil: Background, Preparation of Model Compounds, and Gas Phase Proton Affinities

摘要

The preparation is reported of all four of the mono-alkyl derivatives of 2-thiouracil, and of four of the six possible dialkyl derivatives required as models for study of the tautomeric equilibria by physical methods. Gas phase proton affinities are determined using ion cyclotron resonance mass spectrometry, and used to provide quantitative estimates of individual tautomer stabilities in the vapor state. These quantitative results agree well with qualitative deductions of predominant structures for the monoalkyl derivatives from IR spectroscopy. (AW)