The dimerization of formamide (FMA) has been investigated by matrix isolation spectroscopy, static ab initio calculations, and ab initio molecular dynamics (AIMD) simulations. Comparison of the experimental matrix IR spectra with the ab initio calculations reveals that two types of dimers A and C are predominantly formed, with two and one strong NH...O hydrogen bonds, respectively. This is in accordance with previously published experiments. In addition, there is also experimental evidence for the formation of the thermally labile dimer B after deposition of high concentrations of FMA in solid xenon. The AIMD simulations of the aggregation process show that in all cases dimer C is initially formed, but rearrangement to the more stable doubly hydrogen-bonded structures A or B occurs for a fraction of collisions on the sub-picosecond time scale.

Triplet phenylphosphinidene was prepared by light-induced elimination of ethylene from the corresponding phenylphosphirane and was characterized by IR and UV/vis spectroscopy together with matching of its spectral data with density functional theory computations. The photolysis of phenylphosphirane in P-O doped matrices enabled the spectroscopic identification of a hitherto unknown phenyldioxophosphorane, the long elusive phosphorus analogue of nitrobenzene.

We present the first spectroscopic identification of hitherto unknown 1,1‐ethenediol, the enol tautomer of acetic acid. The title compound was generated in the gas phase through flash vacuum pyrolysis of malonic acid at 400 °C. The pyrolysis products were subsequently trapped in argon matrices at 10 K and characterized spectroscopically by means of IR and UV/Vis spectroscopy together with matching its spectral data with computations at the CCSD(T)/cc‐pCVTZ and B3LYP/6–311++G(2d,2p) levels of theory. Upon photolysis at λ=254 nm, the enol rearranges to acetic acid and ketene.

Conformational control of organic reactions is at the heart of the biomolecular sciences. To achieve a particular reactivity, one of many conformers may be selected, for instance, by a (bio)catalyst, as the geometrically most suited and appropriately reactive species. The equilibration of energetically close-lying conformers is typically assumed to be facile and less energetically taxing than the reaction under consideration itself: this is termed the 'Curtin-Hammett principle'. Here, we show that the trans conformer of trifluoromethylhydroxycarbene preferentially rearranges through a facile quantum-mechanical hydrogen tunnelling pathway, while its cis conformer is entirely unreactive. Hence, this presents the first example of a conformer-specific hydrogen tunnelling reaction. The Curtin-Hammett principle is not applicable, due to the high barrier between the two conformers.

That's radical! A photochemical reaction between the phenyl radical and water results in the abstraction of a hydrogen atom from water and the formation of a hydroxyl radical. The hydroxyl radical forms an OHpi hydrogen bond with benzene (see picture) and does not react with benzene thermally under the conditions of matrix isolation.