Size Matters: Barrier Heights and Widths in the Kinetics Of Tautomerisation and Rotamerisation of Thiotropolone and Its Five‐ and Three‐Membered Cyclic Analogues

ABSTRACT Recent experiments by Nunes et al. have demonstrated that unprecedented control of chemical reactions is possible by narrowband infrared vibrational photo‐excitation at low temperatures in inert matrices. The generated higher energy level conformers may then undergo rotamerisation and tautomerisation reactions which provide extremely useful benchmarks for studying the chemical kinetics of reactions proceeding at low temperatures in which quantum mechanical tunnelling plays a major role and which may deepen our understanding of reactions taking place in the interstellar medium. A seven‐membered alkene ring system with adjacent C═S and O─H groups, thiotropolone, and its five‐ and three‐membered cognates are explored and we show how barrier heights and widths affect in detail the chemical kinetics of both tautomerisation and rotamerisation reactions at temperatures less than 300 K.