Transition state

About: Transition state is a research topic. Over the lifetime, 4978 publications have been published within this topic receiving 117965 citations. The topic is also known as: transition state of elementary reaction.

Reactivity of Sc+(3D,1D) and V+(5D,3F): Reaction of Sc+ and V+ with Water

Abstract: The study of the reaction of water with the early first-row transition metal ions has been completed in this work, in both high- and low-spin states. In agreement with experimental observations, the only exothermic products are the low-lying states MO+ + H2; formation of other endothermic products is also examine. An in-depth analysis of the reaction paths leading to each of the observed products is given, including various minima and several important transition states. All results have been compared with existing experimental data and our earlier work covering the Ti+ + H2O reaction in order to observe existent trends for the early first-row transition metal ions.

Theoretical studies of inorganic and organometallic reaction mechanisms. 2. The trans effect in square-planar platinum(II) and rhodium(I) substitution reactions

Abstract: Ab initio calculations with an effective core potential have been used to study the mechanism of substitution reactions for square-planar transition-metal complexes. Pseudo-trigonal-bipyramidal transition states with rather small entering-ligand to metal to leaving-ligand angles were found for the substitution reactions investigated in this paper. The stability of the transition state is determined by both σ and π effects of the ligands

Energy and structure of the transition states in the reaction OH + CO → H + CO2

Abstract: Two, quite different, experimental studies have been carried out on the reaction between OH and CO at low total pressures. In the first, rate constants have been determined at 82 and 106 K. At the lower temperature, measurements were made at 2 and 5 Torr total pressure, yielding k=(1.0 ± 0.12)× 10–13 cm3 molecule–1 s–1 and (0.91 ± 0.1)× 10–13 cm3 molecule–1 s–1, respectively. At 106 K and 4 Torr, k=(0.98 ± 0.08)× 10–13 cm3 molecule–1 s–1. Theoretical considerations show that the reaction must be in its low-pressure limit, yielding H + CO2, and that the vibrational ground-state adiabatic barrier to formation of HOCO must be <200 cm–1, significantly lower than estimated previously.In the second series of experiments, a tunable diode laser has been used to observe transient absorptions on transitions in the ν3 infrared bands of the CO2 product of the reaction, when it is initiated by flash photolysis at room temperature. There is no excitation of the ν3 mode, and the overall vibrational distribution corresponds to an averaged vibrational energy yield of only 6%. It is concluded that energy is released largely as repulsion following passage through a transition state in which the OCO angle is ca. 171° and the O—C, C—O bond distances are very similar to those in isolated CO2.

Theoretical study of the activation of carbon-carbon bonds by transition metal atoms

Abstract: Quantum chemical model studies have been performed for the transition metal activation of C-C bonds in ethane, cyclopropane, and cyclobutane. Both the ethane and cyclobutane reactions have been studied for the entire second row of transition metal atoms, for both equilibrium states and transition states. For cyclobutane the first transition metal series has also been studied. The cyclopropane reaction has only been fully studied for rhodium and palladium. The quantum chemical calculations include a size-consistent treatment of electron correlation of all the valence electrons with fairly large basis sets including f functions on the metal. The geometries have been fully optimized. Palladium is found to have the smallest barriers for the C-C bond breaking reaction, and the C-C bond in cyclopropane is easiest to break, in line with general experimental experience for transition metal complexes. 38 refs., 6 figs., 11 tabs.