Hydrogen atom transfer reactions of N+2with H2, HD, and D2from thermal to 10 eV center of mass

Gas-phase basicity of 2-furaldehyde

2-Furaldehyde (2-FA), also known as furfural or 2-furancarboxaldehyde, is an heterocyclic aldehyde that can be obtained from the thermal dehydration of pentose monosaccharides. This molecule can be considered as an important sustainable intermediate for the preparation of a great variety of chemicals, pharmaceuticals and furan-based polymers. Despite the great importance of this molecule, its gas-phase basicity (GB) has never been measured. In this work, the GB of 2-FA was determined by the extended Cooks's kinetic method from electrospray ionization triple quadrupole tandem mass spectrometric experiments along with theoretical calculations. As expected, computational results identify the aldehydic oxygen atom of 2-FA as the preferred protonation site. The geometries of O-O-cis and O-O-trans 2-FA and of their six different protomers were calculated at the B3LYP/aug-TZV(d,p) level of theory; proton affinity (PA) values were also calculated at the G3(MP2, CCSD(T)) level of theory. The experimental PA was estimated to be 847.9 ± 3.8 kJ mol(-1), the protonation entropy 115.1 ± 5.03 J mol(-1) K(-1) and the GB 813.6 ± 4.08 kJ mol(-1) at 298 K. From the PA value, a ΔH°(f) of 533.0 ± 12.4 kJ mol(-1) for protonated 2-FA was derived.

Theoretical investigations of the N2H2+ cation and of its reactivity

Accurate ab initio calculations have been performed in order to investigate both the stable isomers and the reactivity of the N(2)H(2)(+) cation. In addition to the trans-HNNH(+) isomer already observed in the photoelectron studies, a formaldehyde type (isodiazene cation) and H(2)O(2)-like isomers are found. At the coupled cluster level of theory, the isodiazene cation is calculated to be as stable as trans-HNNH(+). We have also studied the reactivity of N(2)H(2)(+) and its implication on the reactive processes involving N(2)/N(2)(+) and H(2)(+)/H(2), H/H(+) and HN(2)(+)/HN(2), and HN and HN(+) by performing suitable one-dimensional cuts of the six-dimensional potential energy functions of the lowest electronic states of H(2)N(2)(+). We have pointed out the crucial role of this tetratomic intermediate cation and the importance of the short range internuclear distances during these processes. In the case of N(2)/N(2)(+) and H(2)(+)/H(2) reactions, we have shown that the initial orientation of the reactants may influence the N(2)H(2)(+) tetratomic intermediate: One can expect to form the trans isomer preferentially if the internuclear axes of the H(2)/H(2)(+) and the N(2)(+)/N(2) molecules are parallel to each other when these diatoms are colliding and after intramolecular isomerization process. However, if the internuclear axes of the diatomics are perpendicular to each other, the isodiazene cation is formed preferentially. Different branching ratios are expected for each collision scheme. These reactive processes are found to involve vibronic, Renner-Teller and spin-orbit couplings between the electronic states of N(2)H(2)(+). These interactions mix these electronic states, leading to the formation of atomic, diatomic, and triatomic species via the decomposition of the N(2)H(2)(+) intermediate complex.

Mass spectrometry--not just a structural tool: the use of guided ion beam tandem mass spectrometry to determine thermochemistry

Guided ion beam tandem mass spectrometry has proved to be a robust tool for the measurement of thermodynamic information. Over the past twenty years, we have elucidated a number of factors necessary to make such thermochemistry accurate. Careful attention must be paid to the reduction of the raw data, ion intensities versus laboratory ion energies, to a more useful form, reaction cross sections versus relative kinetic energy. Analysis of the kinetic energy dependence of cross sections for endothermic reactions can then reveal thermodynamic data for both bimolecular and collision-induced dissociation (CID) processes. Such analyses need to include consideration of the explicit kinetic and internal energy distributions of the reactants, the effects of multiple collisions, the identity of the collision partner in CID processes, the kinetics of the reaction being studied, and competition between parallel reactions. This work provides examples illustrating the need to consider this multitude of effects along with details of the procedures developed in our group for handling each of them.