Journal of Physical Organic Chemistry

Three novel diarylethenes were synthesised and their photochemical properties examined in four different solvents. While the UV spectra are almost insensitive to the substitution pattern and to the solvent effects, the kinetics of ring opening/cycloreversion reactions exhibit a more complex behavior. The whole reaction scheme can be explained by the presence of two conformers of the open form, a parallel and an antiparallel conformation.

Methionine (2-amino-4-(methylthio)butanoic acid) is a sulfur-containing essential α-amino acid. Despite its importance, its enthalpy of formation is contentious. From the analysis of experimental enthalpy of formation measurements, the group increment temperature adjusted enthalpy of sublimation, quantum chemical calculations, and difference quantity derived enthalpy estimates, our recommended value for the gas phase enthalpy of formation of methionine is -(430 ± 10) kJ·mol-1.