Electron transfer in the reduction of primary halides by metal hydrides

The reactions of various main-group metal hydrides with 1-halo-5-hexenes and with 1-halo-2,2-dlmethyl-5-hexenes produce both straight chain and cyclized reduction products. The formation of cyclic hydrocarbons clearly indicates the presence of radical intermediates during the course of these reactions.     

Substitution reactions of 4-methyldibenzothiophene

Succinoylation, acetylation and nitration of 4-methyldibenzothiophene yields 2-substituted products. Bromination however, gave 3-bromo-4-methyldibenzothiophene as the major product along with a small amount of the 2-isomer. The bromo-compounds were used to prepare related derivatives via lithium exchange. 4-Methyldibenzothiophene 5,5-dioxide was also shown to nitrate in the 3-position. The structures of the derivatives were determined by NMR analyses. An alternative synthesis of 4-methyldibenzothiophene is described.     

A non-isothermal kinetic study of the thermal decomposition of magnesium alkoxides and amides

The thermal decomposition of alkoxides and amides of magnesium have been studied by vacuum TGA under both isothermal and non-isothermal conditions. These compounds were found to follow a unimolecular decay law, which in integrated form is ln(1  α)  kt, where α is the fraction of material reacted, and k is the Arrhenius rate constant. The rate-controlling process is random nucleation, one nucleus on each particle. Energies of activation calculated by isothermal and non-isothermal methods agree to within ±20%.     

Irreducible half-integer rank unit spherical tensors

A new class of half-integer rank spherical tensors is introduced. The motivation for investigating this new class of tensors originated from a desire to be able to partition matrices using mixtures of fictitious integer and half-integer spin labels. However, it is shown that they can also be used as annihilation/creation operators for spin-1/2, 3/2, etc., particles. In particular, half-integer rank tensors can be used to add/subtract a spin-1/2 particle from a given ensemble. Thus they can be viewed as the natural generalization of the raising and lowering operatorsI _±, in that they change bothI andM, simultaneously.The concept of a universal rotator is introduced and it is demonstrated that half-integer rank tensors obey the same contractional and rotational properties as their integer counterparts, but with half-integer rank. In addition, it is shown that half-integer rank tensors can be used to factorize the Pauli spin matrices. Finally, an example of the use of half-integer rank tensors in the block-diagonalization of a simple 3 x 3 matrix is presented and discussed.     

Metal foams: A survey

The current state-of-the-art in the development of cellular metal foams is reviewed, with focus on their fabrication, mechanical/thermal/acoustic properties, and potential applications as lightweight panels, energy absorbers, heat exchangers, and acoustic liners. Foam property charts with scaling relations are presented, allowing scoping and selection through the use of material indices.     

Effect of pH on the fluorescence and absorption spectra of hypericin in reverse micelles

The well-characterized, monodispersed nature of reverse micelles formed by sodium bis(2-ethylhexyl)sulfosuccinate/heptane and their usefulness in approximating a membrane-like environment have been exploited to investigate the effect of pH and water pool size on the photophysical properties of hypericin (Hyp). Our measurements reveal two titratable groups of pKa approximately 1.5 and approximately 12.5. These are assigned to the HypH+/Hyp equilibrium (the deprotonation of a carbonyl group) and the Hyp-/Hyp2- equilibrium (the deprotonation of a peri hydroxyl group). The low-energy absorbance maxima of HypH+, of Hyp and Hyp- and of Hyp2- are 583, 594 and 613 nm, respectively. Neither at pH 13 nor at 1 M HCl is the system entirely in the Hyp2- or the HypH+ forms. Ours is the first study of Hyp in reverse micelles as well as the first time-resolved study of Hyp as a function of pH.     

Reactions of phenyllithium with lithium aluminum hydride in diethyl ether

Reactions of phenyllithium with LiAlH₄ in diethyl ether have been studied in detail. Lithium hydride, as an insoluble solid, and LiAlPh_n H_4?n (where n = 2 or 3)_in solution, are formed when the PhLi to LiAlH₄ ratio is 2/1and 3/1. However, Li₃AlH₆ is formed when LiAlH₄ is added to an equimolar solution of PhLi in diethyl ether. The integrity of the products have been established by IR, NMR and X-ray powder diffraction pattern.