Fluorescence decay of tertiary aliphatic amines

The fluorescence decay of the tertiary aliphatic animes trimethylamine (TMA), triethylamine (TEA) and tri-n-propylamine (TPA) in the vapour phase excited between 260 and 215 nm has been shown to consist of a single, wavelength-dependent, component when the first excited state is uniquely excited, but two components when the first and second excited states are simultaneously excited. This dual exponentiality persists at pressures as low as 10 mTorr, and it is argued that the two-component decay does not arise from collisional vibrational relaxation.     

The noncumulative effect of methyl substituents on the rate of addition of benzeneselenenyl chloride to olefins1

The rates and products of addition of benzeneselenenyl chloride to ethylene and its six Me substituted derivatives have been determined in methylene chloride at 25°. Unlike the addition of 4-chlorobenzenesulfenyl chloride to this same series of compounds, the effect of Me groups on the rates of addition is not cumulative. Also the regiochemistry of the product is different. For arenesulfenyl chloride additions, products of anti-Markownikoff orientation are formed preferentially under conditions of kinetic control. Under similar conditions regiospecific formation of the Markownikoff adduct is observed for the addition of benzeneselenenyl chloride to methylpropene and 2-methyl-2-butene. These data indicate a difference in both rate and product determining transition states between additions of arenesulfenyl and selenenyl chlorides to alkenes.     

Molecule formation and energy transfer processes in a vapor with high density of 3P-excited sodium atoms

A rich fluorescence spectrum extending between 4000 and 8200 Å has been observed whenever sodium vapor is excited by dye laser light tuned to the 3²S → 3²P transition. Molecule formation due to collisions between excited and unexcited atoms is manifested by the presence of an emission band of sodium in the spectral range 4160–4570 Å.     

The electronic Raman spectrum of cobalt doped MgO

The energies of the ⁴T_1g states of Co²⁺ as a dilute substitutional impurity in MgO relative to the ground Λ_6g doublet have been found by low temperature Raman spectroscopy to be two Λ_8g states at 305 ± 3 cm^?1 and 930 ± 3 cm^?1; the remaining Λ_7g energy is predicted to be in the 980–1010 cm^?1 range the corresponding Λ_6g → Λ_7g Raman transition being weak and buried in the extensive two-phonon background. A second-order perturbation calculation which couples the spin-orbit states to both E_g and T_2g modes of vibration gives a weak but important Jahn-Teller stabilization energy for the Λ_8g states.     

Electrophilic additions to allenes—II : The reaction of benzeneselenenyl chloride with some 1,3-disubstituted allenes

Benzeneselenenyl chloride reacts with 1,3-dialkyl-substituted allenes in methylene chloride solution to give 1:1-adducts. Attack by selenium is found to occur exclusively at the central allenic carbon. In contrast to the analogous reaction of arenesulphenyl chlorides, the preferential formation of the Z-alkene is observed. A mechanism involving the preequilibrium formation of alkylideneseleniranium ions and/or alkylideneepiselenuranes which, in the product-determining step, collapse to products via an anti attack of chloride at the methine carbon of the ring is proposed to account for the preferential formation of the Z-isomers.     

Spectral and thermal studies of some 4-(O-acetyl)glycopyranosylaminopyrimidine derivatives

A spectral study (IR and UV spectroscopies) of seven 4-(O-acetyl)glycopyranosylaminopyrimidine derivatives has been carried out. The thermal study of the compounds allowed us to characterize the following processes: (i) desolvations, (ii) solid-solid transitions, (iii) melting, (iv) pyrolytic decompositions. Through the IR spectral study it was established that pyrolytic decompositions of all the compounds start with the acetyl groups. The reaction orders and activation energies of the deacetylation processes have been calculated.     

Azole chemistry : XI. 3-Dimethylsila-2H-imidazo[1,2-a]benzimidazoles

2-Aminobenzimidazole, and its 5,6-dichloro, 5,6-dimethyl, and 5,6-dinitro derivatives react with bromomethyldimethylchlorosilane in anhydrous tetrahydrofuran at room temperature to give the new heterocycles, 3-dimethylsila-2H-imidazo [1,2-a]benzimidazoles, in good yields. The spectral properties of these heterocycles are discussed.     

A SCF Xα SW study of the shake-up in TiCl4

The Ti 2p electron shake-up spectrum in TiCl₄ is calculated using SCF Xα SW method. Results showed that the low-energy satellite can be ascribed to ligand → metal charge-transfer transitions. However, the nature of the intense peak at 9.8 eV cannot be explained within the one-electron model. An anomaly is noted in the eiperimental spectra of the titanium halides.     

Calculation of molecular polarizabilities: the indo method applied to some aromatic hydrocarbons1

Molecular polarizabilities calculated by the all valence electron INDO method are reported for benzene, naphthalene, anthracene, phenanthrene, biphenyl and p-terphenyl. For these molecules INDO is better than other semi-empirical methods at predicting the polarizability anisotropy.