Enhanced activity and selectivity in cyclohexane autoxidation by inert H-bond acceptor catalysts.

Herein, we demonstrate that the chain-initiating dissociation of cyclohexyl hydroperoxide, CyOOH, is substantially accelerated by H-bond acceptors (e.g. Teflon), which assist O-O bond breaking by stabilising the leaving *OH radical. This is a completely new approach to boost the chain-propagating radical concentration. Indeed, up to now, literature has remained focussed on transition metal catalysis. In addition to this initiation effect, we demonstrate how inert perfluorinated compounds are also able to steer the selectivity at the molecular level, by promoting the conversion of the intermediate cyclohexyl hydroperoxide to the most desired end-product, cyclohexanone. This effect is explained by an enhanced, H-bond-assisted, hydroperoxide propagation. This hitherto overlooked hydroperoxide propagation was recently presented by us as the dominant cyclohexanone and cyclohexanol source. We herein thus confirm our previously reported autoxidation scheme, and illustrate its usefulness as a solid basis for designing new catalytic systems.     

Edge-Ends in Countable Graphs

We introduce the notion of an edge-end and characterize those countable graphs which have edge-end-faithful spanning trees. We also prove that for a natural class of graphs, there always exists a tree which is faithful on the undominated ends and rayless over the dominated does.     

Electrostatic Potential Field and Nucleophilicity of 3, 5, 8, 10-Tetramethyl-aceheptylene

The electrostatic potential (EP.) for aceheptylene (I) is calculated using ab-initio wavefunctions. In addition, the EP. around I is approximated by a monopole expression, using wavefunctions from various semiempirical procedures as a basis. It is found that the previously noted discrepancy between the thoretical prediction of differential nuclophilicity of the individual unsaturated C-atoms in 3,5,8,10-tetramethyl-aceheptylene(II) and the experimental results of protonation is removed, if instead of local atomic charges, the EP. around II, approximated by that of I is considered.     

Elastic anomalies in 1T-TaS2

The temperature dependence of the resonant period in 1T-TaS₂ was measured using the resonant flexural vibration technique. From the close study on the effect of thermal cycles, it is suggested that the anomalous regions observed both on cooling down (183–193 K) and on warming up (218–282 K) were associated with the nearly commensurate-commensurate charge density waves (CDW's) phase transition.     

Internal motion in 1-methylnaphthalene. A variable temperature NMR study using C and H spin—lattice relaxation time measurements

¹³C nuclear spin—lattice relaxation times of 1-methylnaphthalene and ²H nuclear spin—lattice relaxation times of the perdeuterated species, both in deuterochloroform solutions, were measured at several different temperatures. The effects of isotopic substitution on the effective correlation times are discussed. The Woessner approach to extracting the internal jump rates of the CH₃ and CD₃ groups from these relaxation times was used. Activation energies for the internal motions were calculated by fitting the temperature dependent jump rates to an Arrhenius type expression. The differences between the activation energies of the two isotopic species are discussed.