Second virial coefficients of asymmetric top molecules

A short self-contained derivation is given for the second virial coefficient B2(T) of a gas consisting of identical interacting asymmetric rigid rotors. The resulting expression is correct through variant Planck's over h2. First, the canonical partition function is derived by means of an variant Planck's over h expansion of exp[-H/(k(B)T)] due to Friedmann [Adv. Chem. Phys. 4, 225 (1962)]. The present work applies angular momentum operators and known facts from angular momentum theory. It is considerably more accessible than Friedmann's exposition, which is not based on angular momentum operators, but instead on explicit derivatives with respect to Euler angles. The partition function obtained from the variant Planck's over h expansion is applied to the derivation of an expression for B2(T) that is identical in appearance to the expression for symmetric rotors of T Pack [J. Chem. Phys. 78, 7217 (1983)]. The final equation in this work is valid for rigid rotors of any symmetry.     

Acetylenic amides. 3. The synthesis of 5-methylene-2,4-imidazolidinediones from 2-propynamides and isocyanates

2-Propynamides react with aryl isocyanates in the presence of triethylamine to give 5-methylene-2,4-imidazolidinediones 5 in good yields. If the propynamide contains a terminal trimethylsilyl group, Z-trimethylsilylidenehydantoin ( 7 ) is produced.     

Analysis of inter-ring coupling effects in N-heterobicyclic π-systems using a structural definition of aromaticity

A purely structural definition of aromaticity based on the average ring bond length and -bond order is proposed. The definition is illustrated for N-heterocycles by reference to theoretical STO-3G and 3-21G geometries and charges for some pteridine derivatives. The treatment focuses on the gross structural changes (i.e., ring size, overall degree of π-electron delocalization, and net ring charges), accompanying chemical changes, such as substitution, tautomerization, ring reduction, and deazination, as well as the structural interdependence of the two rings in a bicyclic ring system.     

Organolithium and organosodium compounds of n-substituted 2-alkylbenzimidazoles

Organolithium and organosodium compounds of 1,2-dimethyl-, 1-methyl-2-ethyl-, 1-methyl-2-propyl-, and 1-phenyl-2-methylbenzimidazole, containing the metal in the alkyl group at position C(₂), were obtained by metallation. It was found that metallation can be complicated by the addition of the metalling reagent at the C=N bond of the heterocycle. It was shown that the obtained organometallic compounds can be used for the synthesis of various derivatives of benzimidazole.The calculation was performed with the standard bond lengths. A planar model was used for the carbanion.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1073–1077, August, 1986.     

INVESTIGATION OF THE ANTIVIRAL ACTION OF THE PHOTOACTIVE COMPOUND PHENYLHEPTATRIYNE

Abstract— Murine cytomegalovirus, a herpes virus, was used as a model virus to investigate the mechanism of the anti-viral action of phenylheptatriyne in long wave ultraviolet light. The genome and proteins of the inactivated virus penetrated the nuclei of susceptible cells normally. Furthermore, the viral genome did not contain extra single strand breaks or cross-links. However, cells infected with the treated virus did not synthesize late viral proteins, as determined by polyacrylamide gel electrophoresis. nor did they synthesize late viral RNA and viral DNA according to nucleic acid hybridization tests. Thus the compound may interfere with an early viral function so that the replication cycle cannot proceed.     

Isolation of nonprotamine proteins from the nuclei of the gonad cells of the Russian sturgeonAcipenser güldenstadti

Eight nonprotamine proteins have extracted from the nuclei of the cells of the gonads of the Russian sturgeon with 0.35 M sodium chloride solution followed by fractionation of carboxymethyl-Sephadex G-25 and desalting on Bio-Gel P-2, and their amino acid compositions have been determined.     

Determination of potential-energy surface of molecules in an applied field on the basis of virial relations

The quantum-mechanical virial theorem (in diagonal and nondiagonal forms) for molecules in an external, weak, uniform electric field is used for obtaining the analytical expression of the potentialenergy surface in the Hartree–Fock–Roothaan one-determinantal approximation. The polarizability tensor components of the H₂O molecule are computed on this basis. The dependence of basing the atomic orbitals upon the intensity of the applied field lead to good coincidence of results with the data of near Hartree–Fock calculations.     

Chlorine nitrate photolysis by a new technique: very low pressure photolysis

Very low pressure photolysis (VLPØ) of chlorine nitrate was performed in a quartz Knudsen cell. The light source was a 2500 W high-pressure xenon lamp, and a modulated molecular-beam mass spectrometer was used to monitor the concentration of ClONO₂ and photolysis products. Because of the low pressures used (? 10^?3 torr) and the short residence time in the cell (≈1 s), secondary reactions were unimportant and the primary products could be directly identified. The primary photolysis products (λ ≈ 2700 Å) are atomic chlorine and NO₃ free radical. Chlorine atoms were identified both by the appearance of Cl₂ (wall recombination product; the walls were not poisoned) and by HCl produced when C₂H₆ was added to the cell. Nitrate free radical was directly identified as a mass peak at m/e = 62, as well as by chemical titration with nitric oxide: NO₃ + NO → 2NO₂. It was verified by direct tests that the peak at m/e = 62 did not arise from possible HNO₃ contamination or from N₂O₅, a possible secondary product. This titration reaction was used to measure quantitatively a lower limit to the primary quantum yield, φ ? 0.5 ± 0.3. This represents a lower limit because of the unknown extent of the secondary photolysis of NO₃ under our conditions. We believe this to be the first observation using mass spectrometry of the NO₃ free radical. The quantum yield for atomic chlorine is φ = 1.0 ± 0.2. N₂O was used to test for O(¹D) according to the reaction, O(¹D) + N₂O → products; none was observed. Triplet oxygen, O(³P) was observed to the extent of ≈ 10% by the reaction O(³P) + NO₂ → NO + O₂, but this yield can also be due to the photolysis of NO₃ free radical produced in the primary step. We conclude that the predominant reaction pathway is

.     

High-pressure silicate pyrochlores,Sc2Si2O7 and In2Si2O7

The silicate compounds Sc₂Si₂O₇ and In₂Si₂O₇ have been converted from thortveitite type to pyrochlore type at 1000°C, 120 kbar, with resulting cell constants of 9.287(3) and 9.413(3) Å, respectively. Invariant reflection intensities in the X-ray powder diffraction patterns allowed precise absorption corrections to be made, and refinement of thermal parameters and of the single structural parameter x gave values of 0.4313(21) and 0.4272(15), respectively. The corresponding six-coordinate SiO distances were 1.761(7) and 1.800(5) Å, and the average eight-coordinate distances for ScO₈ and InO₈ were 2.267 and 2.275 Å. Values of structure-refined bond lengths for compounds containing six-coordinate silicon are surveyed, and overall weighted average octahedral distances of 1.782(14) Å for SiO and 2.520(18) Å for OO are derived. Pyrochlore phases were not produced from rare-earth disilicate or monosilicate phases subjected to the same reaction conditions as the Sc and In compounds.     

The synthesis of some new derivatives of 1, 7-dimethylxanthine

We have synthesized a group of new 8-substituted 1, 7-dimethylxanthines which are of interest for biological investigation as very close structural analogs of some 8-substituted theobromine derivatives obtained previously. In particular, we have carried out the conversion of 8-hydroxymethyl-1, 7-dimethlxanthine (I) [1] into 8-chloromethyl-1, 7-dimethylxanthine (II) and from this, by heating it for 6 hours with an excess of diethylamine or by condensing it with sodioacetylaminomalonic ester in ethanol we have obtained 8-diethylaminomethyl-1, 7-dimethylxanthine (III) and its hydrochloride (compare [2]) or 8-(-acetylamino-, -diethoxycarbonylethyl)-1, 7-dimethylxanthine (IV). The hydrolytic cleavage of the latter, accompanied by partial decarboxylation, led to 1, 7-dimethyl-8-xanthinylalanine (V) (cf. [3]).