EP morphisms

The concept of an EP matrix is extended to a morphism of a category C with involution. It is shown that an EP morphism has a group inverse iff it has a Moore-Penrose inverse, and in this case the inverses are identical. On the other hand, if a morphism has a Moore-Penrose inverse that is a group inverse, then C is a full subcategory of a category in which φ is EP. Also, if C is an additive category with involution 1 and with 1-biproduct factorization, then a morphism of φ of C is EP iff there is a 1-biproduct J ⊕ K and an invertible morphism θ : J → J such that φ is congruent to a morphism of the form

$\text{θ 0}\text{0 0}\text{: J⊕K → J⊕K.}$

In particular, a square matrix over a principal-ideal domain with involution is EP iff it is congruent to a matrix of the form dg(θ, 0) with θ invertible.     

Multiply charged ions in the mass spectra of aromatics

The prominence of multiply charged molecular and fragment ions upon electron-impact in the mass spectrometer is proposed as an experimental, empirical indication of aromatic character. The effects of electron withdrawing and donating substituents on the production of multiply charged ions are considered and appearance potentials are noted for several species.     

Poly[tris(diorganophosphinato)alanes]

Poly[tris(diorganophosphinato)alanes], [Al(OPRR′O)₃]_n, were synthesized in which the organic moieties (R,R′) contained from one to eighteen carbon atoms. Polymeric properties depended upon the organic moieties; polymers were fusible, tractable, and flexible when the organic moieties contained six or more carbon atoms. Soluble polymers were prepared by using mixtures of symmetrical and unsymmetrical phosphinates. One polymer, poly{bis[n-butyl(benzyl)phosphinato]di-n-octylphosphinatoalane}, exhibited a degree of polymerization greater than 1000 and an exceptionally high intrinsic viscosity of 37 dl/g. The properties of the different polymers are discussed, and feasible structures are proposed.     

Highly efficient and selective epoxidation of alkenes by photochemical oxygenation sensitized by a ruthenium(II) porphyrin with water as both electron and oxygen donor

Visible light irradiation of a reaction mixture of carbonyl-coordinated tetra(2,4,6-trimethyl)phenylporphyrinatoruthenium(II) (Ru(II)TMP(CO)) as a photosensitizer, hexachloroplatinate(IV) as an electron acceptor, and an alkene in alkaline aqueous acetonitrile induces selective epoxidation of the alkene with high quantum yield (Phi = 0.6, selectivity = 94.4% for cyclohexene and Phi = 0.4, selectivity = 99.7% for norbornene) under degassed conditions. The oxygen atom of the epoxide was confirmed to come from a water molecule by an experiment with H(2)(18)O. cis-Stilbene was converted into its epoxide, cis-stilbeneoxide, without forming trans-stilbeneoxide. trans-Stilbene, however, did not exhibit any reactivity. Under neutral conditions, an efficient buildup of the cation radical of Ru(II)TMP(CO) was observed at the early stage of the photoreaction, while an addition of hydroxide ion caused a rapid reaction with the cation radical to promote the reaction with reversion to the starting Ru(II)TMP(CO). A possible involvement of a higher oxidized state of Ru such as Ru(IV), Ru(V), Ru(VI) through a dismutation of the Ru(III) species was excluded by an experiment with Ru(VI)TMP(O)(2). Decarbonylation of the Ru complex was also proven to be invalid. A reaction mechanism involving an electron transfer from the excited triplet state of Ru(II)TMP(CO) to hexachloroplatinate(IV) and subsequent formation of OH(-)-coordinated Ru(III) species, leading to an oxo-ruthenium complex as the key intermediate of the photochemical epoxidation, was postulated.     

PM3-SM3: A general parameterization for including aqueous solvation effects in the PM3 molecular orbital model

Our recently proposed scheme for including aqueous solvation free energies in parameterized NDDO SCF models is extended to the Parameterized Model 3 semiempirical Hamiltonian. The solvation model takes accurate account of the hydrophobic effect for hydrocarbons, as well as electric polarization of the solvent, the free energy of cavitation, and dispersion interactions. Eight heteroatoms are included (along with H and C), and the new model is parameterized accurately for the water molecule itself, which allows meaningful treatments of specifically hydrogen bonded water molecules. The unphysical partial charges on nitrogen atoms predicted by the Parameterized Model 3 Hamiltonian limit the accuracy of the predicted solvation energies for some compounds containing nitrogen, but the model may be very useful for other systems, especially those for which PM3 is preferred over AM1 for the solute properties of the particular system under study. © 1992 by John Wiley & Sons, Inc.     

Simultaneous determination of trace concentrations of saturated and α,β-unsaturated carbonyl compounds in organic systems

A method for the simultaneous determination of trace concentrations of saturated and α,β-unsaturated carbonyl compounds in complex systems is presented. Carbonyl as the alkaline 2,4-dinitrophenylhydrazone is determined spectrophotometrically at 2 selected wavelengths of 480 and 426 nm. The apparent total carbonyl concentration is obtained from prepared calibration curves at the selected wavelengths based on known concentrations of n-heptaldehyde. From the observed relative response of known concentrations of n-heptaldehyde and 2-ethyl-2-hexenal, the true concentration for saturated and α,β-unsaturated carbonyl is obtained by a simple calculation. The method has been used extensively for alcohol systems ranging up to tetracontanol but is equally useful for hydrocarbons, aromatic oxygenates and hydrocarbons, petroleum distillates and kerosenes, organic acids and esters, and some ethers.