Ruthenium Olefin Metathesis Catalysts with Frozen NHC Ligand Conformations

The catalytic behavior of Grubbs and Hoveyda–Grubbs II type ruthenium complexes bearing N-heterocyclic carbene (NHC) ligands with syn-phenyl groups on the backbone and syn- or anti-oriented o-tolyl N-substituents was evaluated in a series of olefin metathesis transformations. Further advance in the synthesis of the best-performing syn catalysts and a deeper investigation into the solution-state structure of the Hoveyda–Grubbs type II complex with anti N-tolyl groups by 2D-NMR and DFT studies are also reported. Of particular interest, syn complexes emerged among the best-performing catalysts in all of the explored metathesis reactions, especially in the ring-closing metathesis (RCM) of hindered olefins, allowing also for the difficult formation of macrocyclic trisubstituted alkenes. An important unexpected result was obtained in the RCM of linalool, where both syn and anti catalysts appeared to be involved in the dehydration reaction of the cyclization product (1-methylcylopent-2-en-1-ol). This process all..

Kinetic modeling of jet propellant-10 pyrolysis

A detailed kinetic model for the thermal decomposition of the advanced fuel Jet-Propellant 10 (JP-10) was constructed using a combination of automated mechanism generation techniques and ab initio calculations. Rate coefficients for important unimolecular initiation routes of exo-TCD were calculated using the multireference method CAS-PT2, while rate coefficients for the various primary decompositions of the exo-TCD-derived monoradicals were obtained using CBS-QB3. Rate-of-production analysis showed the importance of four dominating JP-10 decomposition channels. The model predictions agree well with five independent experimental data sets for JP-10 pyrolysis that cover a wide range of operating conditions (T = 300-1500 K, P = 300 Pa-1.7 x 10 (5) Pa, dilution = 0.7-100 mol% JP-10, conversion = 0-100%) without any adjustment of the model parameters. A significant part of the model comprises secondary conversion routes to aromatic and polyaromatic hydrocarbons and could thus be used to assess the tendency for deposit formation in fuel-rich zones of endothermic fuel applications