Wendell F. Smith

Application of molecular orbital theory to the electronic absorption spectra of schiff bases

Abstract The linear combination of atomic orbitals-molecular orbital (LCAO-MO) method with inclusion of overlap has been applied to benzylideneaniline. The energy levels, electron densities and bond orders were calculated and the results applied to an interpretation of the electronic absorption spectra of benzylideneaniline and some of its derivatives. It is concluded that the anomalous spectrum of benzylideneaniline can be explained on the basis of twisting of the aniline ring out of the plane of the molecule.

Induced decomposition of benzoyl peroxide by the benzophenone ketyl radical

Abstract Benzophenone ketyl radicals [(C6H5COH] induce the decomposition of benzoyl peroxide in benzene at 25°. In the presence of benzhydrol, the resulting benzoyloxy radicals (C6H5COO·) abstract hydrogen from the alcohol, resulting in the formation of benzoic acid and more benzophenone ketyl radicals. Chain lengths are short. Termination is principally between phenylcyclohexadienyl radicals (or possibly between phenylcyclohexadienyl and benzoyloxy radicals), indicating that the rate determining step is the hydrogen abstraction from alcohol. This result is contrasted with the results of thermolysis of benzoyl peroxide in alcohols at higher temperatures. By comparing the reactivity of the benzophenone ketyl radical with its O-Me analog, it is concluded that the transition state for the induced decomposition probably involves a partial hydrogen transfer from the ketyl radical to one of the peroxide O atoms.

Biplot Displays for Looking at Multiple Response Data in Mixture Experiments

In the analysis of mixture experiments it is not unusual to have many response variables (or physical characteristics of the end product) under investigation simultaneously. Generally these responses are correlated with one another, and the analyst must compromise by concentrating on what he or she considers the most important characteristics, at the expense of others, in selecting the optimum formulation. Furthermore, in those situations in which some responses are positively correlated while others are negatively correlated, it can be very difficult to understand the relative importance of the different components. In such situations, a biplot display can help the analyst not only to understand the underlying structure of the data better but also to understand the roles played by the different components. Biplots are so named because both row (mixture formulation) and column (response) information are displayed in a single plot. This graphical technique has been applied successfully to mixture experimen...

The photosensitized decomposition of benzoyl peroxide in benzene

Abstract The mechanism of the benzophenone and 2-acetonaphthone sensitized decomposition of benzoyl peroxide in benzene has been investigated. When benzophenone is the sensitizer, the yield of acid resulting from peroxide decomposition increases as the initial peroxide concentration decreases. We interpret this to mean that benzophenone ketyl radicals are formed by hydrogen abstraction from solvent benzene at low peroxide concentrations, and the ketyl radicals then induce the decomposition of peroxide. When 2-acetonaphthone is the sensitizer, the acid yield is unaffected by peroxide concentration, but does depend upon the 2-acetonaphthone concentration and the light intensity. At the same light intensity, the acid yield with 2-acetonaphthone as sensitizer is less than half the yield when benzophenone is the sensitizer in the region of peroxide concentrations where the latter sensitizer should not form ketyl radicals. This can be rationalized by assuming (i) induced decomposition of benzoyl peroxide by benzophenone, but not 2-acetonaphthone, triplets; (ii) vertical and nonvertical energy transfer, with multibond cleavage occurring preferentially from the non-spectroscopic peroxide triplet; or (iii) quenching of sensitizer triplets by benzoyloxy radicals. These may not be mutually exclusive, and additional data are needed to clarify these points.

Radical efficiency from azo-p-cymene

Abstract The first-order rate constants (ki) and efficiencies of radical formation (e) for azo-p-cymene were measured in ten solvents spanning 80-fold in absolute viscosity and 30-fold in dielectric constant. Although viscosity plays a major role in the cage effect, specific solvation of p-cymyl radicals must also be considered. The ki exhibit little change with solvent viscosity or dielectric constant, and no trend is apparent. Activation parameters were measured in the most polar solvent (propylene carbonate) and one of the least polar solvents (n-heptadecane). The results indicate either a lack of solvent participation in the thermolysis, or similar solvation of the ground and transition states in both solvents.