Preparation and thermal properties of polyquinazolone containing 4-substituted phenyl groups on the quinazolone ring

Polyquinazolones containing 4-substituted phenyl groups (H, Cl, CH₃, CH₃O, NO₂) on the quinazolone ring were synthesized in m-cresol and their thermal properties were studied by using dynamic thermogravimetry and isothermal weight loss in nitrogen and air. Polyquinazolones were synthesized with intrinsic viscosities in the range of 0.2–0.7 dL/g when phosphorus pentoxide was used as a catalyst. In TGA studies, there was a difference in the initial decomposition temperature of polyquinazolones with varying substituted groups. The introduction of substituted groups reduced oxidative thermal stability of the polymers. Furthermore, the thermal degradation mechanism was investigated by infrared spectrophotometry.     

Unique hydrogenation activity of supported tin catalyst: Selective hydrogenation catalyst for unsaturated aldehydes

Selective hydrogenation of unsaturated aldehydes, crotonaldehyde (CH₃CH=CHCH=O) and cinnamaldehyde (C₆H₅CH=CHCH=O), has been studied over SiO₂-supported monometallic Sn and bimetallic Rh---Sn catalysts in the liquid phase. Over a silica-supported monometallic Rh catalyst, Rh/SiO₂, no unsaturated alcohol (crotyl alcohol or cinnamyl alcohol) was formed, whereas considerable amounts of the corresponding saturated aldehyde and saturated alcohol were obtained. The selectivity to the unsaturated alcohol was improved over the Rh---Sn bimetallic catalyst. The selectivity to the corresponding unsaturated alcohol attained ca. 65% over the Rh---Sn bimetallic catalysts. On the other hand, The supported Sn catalyst showed markedly high selectivity to the unsaturated alcohols. The selectivity of the Sn/SiO₂, attained 95% to crotyl alcohol and 100% to cinnamyl alcohol, respectively. Although the conversion of each unsaturated aldehyde over Rh---Sn/SiO₂ catalysts was greater than that over Sn/SiO₂ catalysts, the selectivity of Sn/SiO₂ catalysts to the corresponding unsaturated alcohols was superior to that over Rh---Sn/SiO₂. The selectivity of Sn/SiO₂ was also compared with that of Rh---Sn/SiO₂ at a similar conversion of the unsaturated aldehydes. The selectivity of Sn/SiO₂ was significantly greater than that of the Rh---Sn bimetallic catalyst. These results indicate that the high selectivity over Sn/SiO₂ was ascribed not to low conversion but to intrinsic selectivity of the Sn catalyst.     

1,2,4-Triazoles. V. Nuclear magnetic resonance study of N-Methyl derivatives of 1,2,4-triazoles

The chemical shifts of the N-methyl protons of a number of N-methylated-1,2,4-triazoles were studied. Substitution of methyl and methylthio groups in position 3 causes upfield shifts of the N-methyl signals, while substitution of α-pyridyl, γ-pyridyl, and phenyl groups causes downfield shifts. In 3,5-disubstituted 1,2,4-triazoles, substituents in positions 3 and 5 have additive effects on the chemical shifts of N-methyl groups, so that the chemical shifts of the N-methyl groups of such compounds can be calculated. In this way, it was possible to assign the peaks of mixtures of N-monomethylated derivatives obtained by methylation of 1,2,4-triazoles.     

Somatic-cell mutation induced by UVA and monochromatic UV radiation in repair-proficient and -deficient Drosophila melanogaster

Near-ultraviolet light (UVA: 320-400 nm) constitutes a major part of sunlight UV. It is important to know the effect of UVA on the biological activities of organisms on the earth. We have previously reported that black light induces somatic-cell mutation in Drosophila larvae. To investigate which wavelength of the UVA is responsible for the mutation we have now carried out a series of monochromatic irradiations (310, 320, 330, 340, 360, 380 and 400 nm) on Drosophila larvae, using the large spectrograph of the National Institute for Basic Biology (Okazaki National Research Institutes, Okazaki, Japan). Mutagenic activity was examined by the Drosophila wing-spot test in which we observe mutant wing hair colonies (spots) on the wings of adult flies obtained from the treated larvae. The induction of mutation was highest by irradiation at 310 nm and decreased as the wavelength became longer. Neither the 380 nor the 400 nm light was mutagenic. Excision repair is known to protect cells from UV damage. In the excision-repair-deficient Drosophila, the mutagenic response induced by 310 nm irradiation was 24-fold higher than that of the wild-type (7.2 +/- 1.5 spots/wing/kJ vs 0.3 +/- 0.08 spots/wing/kJ), and at 320 nm the difference of the response was 14-fold (0.21 vs 0.015 +/- 0.005). In the case of irradiation at 330 and 340 nm the difference of the response was only two-fold (at 330 nm, 6.9 +/- 2.9 x 10(-3) vs 3.1 +/- 1.1 x 10(-3) spots/wing/kJ; at 340 nm, 3.5 +/- 0.9 x 10(-3) vs 2.0 +/- 0.7 x 10(-3). These results suggest that the lesion caused in the larvae by 320 nm irradiation may be similar to the damage induced by 310 nm and that the lights of 330 and 340 nm may induce damage different from the lesions induced by shorter-wavelength lights.     

Effective gauge theory and the effect of heavy quarks in Higgs boson decays

A general framework is given for evaluating the contributions of as yet undiscovered heavy quarks to the gluonic decay rate of the Weinberg-Salam type Higgs boson. Since the Yukawa coupling of the Higgs boson to a quark pair is proportional to the quark mass, loop graphs involving heavy quarks have a non-vanishing effect on the gluonic decay width of the Higgs boson. This effect of heavy quarks with massesM _j(j=t,...) much greater than the Higgs boson massm _H is calculated in an effective gauge theory. The effects of two different kinds of large logarithms, lnM _j ² /μ m _h ² /μ ² are separated and summed up by the renormalization group method. It is found that the higher order QCD corrections are large and that the gluonic contribution to the hadronic decay width is significant if there are more than three generations. The Higgs decay width can therefore be used to probe the number of generations of heavy quarks.     

DFT investigation of the mechanism of CH2CO + O(3P) reaction

A detailed theoretical survey of the potential energy surface (PES) for the CH₂CO + O(³P) reaction is carried out at the QCISD(T)/6‐311+G(3df,2p)//B3LYP/6‐311+G(d,p) level. The geometries, vibrational frequencies, and energies of all stationary points involved in the reaction are calculated at the B3LYP/6‐311+G(d,p) level. More accurate energy information is provided by single‐point calculations at the QCISD(T)/6‐311+G(3df,2p) level. Relationships of the reactants, transition states, intermediates, and products are confirmed by the intrinsic reaction coordinate (IRC) calculations. The results suggest that P1(CH₂+CO₂) is the most important product. This study presents highlights of the mechanism of the title reaction. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

Photo-induced radical formation in cellulose

The characteristics of cellulose radicals produced by photo-irradiation were studied from their ESR spectra. All spectra of the irradiated samples contained a singlet spectrum with a line width of 28 gauss. Spectra consisting mainly of a single absorption line were observed in the initial stage of irradiation. With the elapse of irradiation time, two absorption lines with a line width of 8 gauss were added to the original singlet spectrum, leading to the three absorption lines widths of 8, 28, and 8 gauss, respectively, of which the middle line with a line width of 28 gauss showed the maximum intensity. This three-line spectrum was easily produced when hydrogen peroxide or metallic ions such as Fe³⁺, Ag⁺, Fe²⁺, and Ce⁴⁺ were used as sensitizers. The observed ESR spectra consisted of a singlet with a line width of 28 gauss and a triplet with a line width of 8 gauss and a splitting factor of 28 gauss. The triplet component was more unstable toward warming, as compared with the singlet component. Based on the experimental results, it was suggested that cellulose radicals due to the scissions of cellulose chains corresponding to the ESR spectra with a single line could be the most important factor for the initiation of graft copolymerization.     

Determination of arsenic content in natural water by graphite furnace atomic absorption spectrometry after collection as molybdoarsenate on activated carbon

A sample solution containing less than 0.5 μg of As was adjusted to pH 2. As in the solution was collected on activated carbon (AC) as molybdoarsenate. The AC was directly introduced as an AC suspension into a graphite furnace atomizer, and the concentration of As was determined by atomic absorption spectrometry (AAS). This method is relatively free from interference caused by coexisting ions. The calibration curve was linear up to 0.1 mg l⁻¹, and limit of detection of As was 0.004 mg l⁻¹. When 1000 ml of sample solution is preconcentrated to 5 ml (enrichment factor is 200-fold) 0.02 μg l⁻¹ of As could be determined, and relative standard deviation was below 4.0% (by the deuterium background correction system). The method was applied to sea water and well water, and the sum of As(III) and As(V) was determined with satisfactory results.