A time-dependent, quantum reaction dynamics approach in full dimensional, six degrees of freedom was carried out to study the energy requirement on reactivity for the HBr + OH reaction with an early, negative energy barrier. The calculation shows both the HBr and OH vibrational excitations enhance the reactivity. However, even this reaction has a negative energy barrier, the calculation shows n...

The internal rotation in ammonia borane (AB) was studied on the basis of natural orbitals for chemical valence (NOCV) and eigenvectors for Pauli repulsion (NOPR). We found that the total hyperconjugation stabilization (ca. 5 kcal mol(-1)), based on the charge transfer from the occupied σ (B-H) orbitals into the empty σ*(N-H), slightly favors the staggered conformation over the eclipsed one; how...

The barrier for rotation about an N-alkylcarbamate C(carbonyl)-N bond is around 16 kcal/mol. In the case of an N-phenylcarbamate, the rotational barrier is lowered to 12.5 kcal/mol, but with N-(2-pyrimidyl)carbamates the barriers are so low (<9 kcal/mol) that the syn and anti rotamers cannot be observed as separate signals by 500 MHz NMR spectroscopy at 183 K. X-ray and computational data show ...

Spectral and kinetic behavior of thermal cis-to-trans isomerization of 4-aminoazobenzene (AAB) is examined in various solvents of different polarities. In contrast to azobenzene (AB), it is found the rate of thermal isomerization of AAB is highly dependent on solvent polarity. Accelerated rates are observed in polar solvents as compared to nonpolar solvents. Moreover, a decrease in the barrier ...

Mass transport at a surface is a key factor in heterogeneous catalysis. The rate is determined by excitation across a translational barrier and depends on the energy landscape and the coupling to the thermal bath of the surface. Here we use helium spin-echo spectroscopy to track the microscopic motion of benzene adsorbed on Cu(001) at low coverage (θ ∼ 0.07 ML). Specifically, our combined exper...

A series of sixand eight-membered ring-fused aminothiophenes 1-8 was investigated in terms of the height of the rotational barrier of the amino group by dynamic H NMR spectroscopy and quantum chemical methods. The restricted rotation around the N-C(sp) bond depends only on steric influences of the fused ring. The compounds with the eight-membered fused ring show a decreased barrier to rotation....

Classical trajectories on rotational energy surfaces and coherent-state quantum projections have been used to study an asymmetric-top molecule containing a freely rotating internal symmetric top whose symmetry axis is not coincident with a principal axis of the molecule. Stationary points on the rotational energy surface, which strongly influence the trajectories, increase in number from two to...

The dependence of CS2 predissociation upon rotational quantum number K at vibrational levels below the barrier to linearity of the 1B2(1Sigmau+) state has been investigated in detail with laser spectroscopy, by using a heated supersonic source to increase the intensities of hot band transitions. Predissociation lifetimes were determined from rotational contour simulations of 13 vibronic bands i...