摘要:

Fluorescence and phosphorescence are observed when 2,3-pentanedione in the gaseous state is excited at 365, 405, and 436°nm. The phosphorescence lifetime has been investigated as a function of temperature (298 to 363 °K) and concentration of the diketone (0.5 to 90 × 10−4 M). A mechanism that explains the experimental data is proposed. Apart from the radiative process and an intersystem crossing to the ground state, the triplet state 2,3-pentanedione molecules are removed by two other processes. One is a unimolecular reaction with a rate constant of 1 × 1011exp (−11.0/RT) s−1(consistent with an intramolecular hydrogen atom abstraction), and the other is an interaction with ground state molecules. The photochemistry of the triplet state of 2,3-pentanedione is compared with that of biacetyl to consider the effect of substitution of a hydrogen atom by the methyl group on the radiationless processes in diketones.

ISSN:0008-4042    

DOI:10.1139/v71-164

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

The photochemical reactions of tetraphenyldiphosphine, triphenylphosphine, and diphenylphosphine in alcohol were studied by flash photolysis and product analysis. The primary photochemical process of all three phosphines studied appeared to be the formation of diphenylphosphinyl radicals which subsequently abstract α-H atoms from the solvent alcohol. The relationship between the rate constants of the abstraction and the α-H bond energies of various alcohols was examined.

ISSN:0008-4042    

DOI:10.1139/v71-165

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

The description of chemical reaction rates, in terms of the language of nonequilibrium thermodynamics, is compared with the conventional language of chemical kinetics. It is concluded that the formalism of nonequilibrium thermodynamics possesses considerable disadvantages, even in the regime where the rate is a linear function of affinity; this conclusion also holds for cases where chemical rates are coupled to diffusion processes. Some of the difficulties involved are illustrated using the experimental data of Nebeker and Pings (28).

ISSN:0008-4042    

DOI:10.1139/v71-166

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

An investigation into the gettering powers of aluminum, barium, magnesium, and misch metal for removing oxygen from liquid samples has been carried out. The liquids treated with each getter are: H2O, CH2Br2, CH2Cl2, CH2I2, and CH3OH. The results show that aluminum is more suitable for all these liquids even though the other getters are also effective. It appears that as long as there is no strong reaction, any of these getters can be used to remove oxygen from any liquid.

ISSN:0008-4042    

DOI:10.1139/v71-167

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

A series of silylphthalimides containing silicon substituents —H, —CH3, —C2H5, —CH2CH=CH2, and —C6H5have been prepared and characterized. The compounds areN-silylated and found to be monomeric in the liquid and gas phase. The i.r. spectroscopic studies in dilute (10−1 M) chloroform solution showed a decrease (approximately 40 cm−1) in the carbonyl stretching frequency on silylation, but relatively small changes (± 7 cm−1) on changing silicon substituents. The major effect appears to be electron donation by silyl groups. The N15isotopomers were prepared and C—N and Si—N vibrations identified.Mass spectrometric studies of methyl- and phenylsilylphthalimides, including N15substitution, are reported. A possible mechanism of formation of methyl- and phenylbiphenylene silicon ions, involving loss of methyl or phenyl, carbon dioxide, and hydrogen cyanide, is suggested.

ISSN:0008-4042    

DOI:10.1139/v71-168

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

An arabinan and the previously characterized arabinogalactan and acidic polysaccharide complex have been isolated by extraction of defatted and deproteinized soybean cotyledon meal with water. Methylation analysis involving gas chromatography – mass spectrometry of methylated alditol acetates formed from the methylated arabinan has shown that the parent polysaccharide is highly branched and of the same structural type as other arabinans associated with pectins. Methylated derivatives of mustard seed and lemon-peel arabinans and of soybean arabinogalactan have been similarly analyzed.

ISSN:0008-4042    

DOI:10.1139/v71-169

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

The reaction of hydrogen atoms, produced by electric discharge, with vinyl chloride vapor has been studied at four widely different temperatures. Since the maximum yields of HCl at both 328 and 494 °C exceeded the flow rates of atomic hydrogen, the reaction was observed to have limited chain characteristics. The products were hydrogen chloride, ethylene, methane, and ethane. The specific reaction rate for HCl production was found to be aboutand that for production of ethylene plus ethane was found to be about.

ISSN:0008-4042    

DOI:10.1139/v71-170

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Treatment of the ketonitrile2awith sodium borohydride gave the lactone3awhich underwent ammonolysis to give 10,11-dihydro-5,10-(iminomethano)-5H-dibenzo[a,d]cyclohepten-13-one (5a). This compound was used to prepare a number of 12- and 11,12-disubstituted derivatives of the ring system.

ISSN:0008-4042    

DOI:10.1139/v71-171

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

The decarboxylation of pyrrole-2-carboxylic acid in aqueous buffers at 50° and ionic strength 1.0 has been found to be first order with respect to substrate at a fixed pH. As the pHis decreased, the rate constant increases slightly in the pHrange 3–1, then rises rapidly from pH1 to 10 MHCl. The13C-carboxyl kinetic isotope effect is 2.8% in 4 MHClO4and negligible at pH~ 3. These observations can be accounted for by a mechanism, previously proposed for the decarboxylation of anthranilic acid, in which the species undergoing decarboxylation is the carboxylate ion protonated at the 2-position of the pyrrole ring. This intermediate can be formed both by ring-protonation of the carboxylate anion and by ionization of the ring-protonated acid. At low acidities ring-protonation is rate determining, but at higher acidities the rate of protonation exceeds that of decarboxylation.

ISSN:0008-4042    

DOI:10.1139/v71-172

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Ca3(AsO4)2crystallizes in the rhombohedral space groupR3cwith unit cell parametersa = 14.05(1) Å, α = 45.05(2)°, andZR = 7. The equivalent hexagonal axes area = 10.77(1) andc = 37.81(3) Å withZH = 21. The structure was refined, using 769 symmetry independent reflections and a full matrix least squares program from a trial structure obtained from Patterson functions, to a finalRvalue of 0.063. The structure consists of interconnected chains of CaOnpolyhedra and AsO4tetrahedra paralleling thecaxis. The six chains surrounding the three-fold axes are each much like those in Ba3(PO4)2with 3Ca followed by two AsO4groups per half cell. The chain on the three-fold axis has only one AsO4per half cell with one and half cations between adjacent arsenic atoms. The mean As—O bond lengths are 1.69, 1.65, and 1.69 Å for the three independent tetrahedra. The cation sites show coordination to 6, 7, or 8 oxygen atoms in contrast to the 10 or 6 + 6 found in Ba3(PO4)2. These structural differences arise primarily from the shorter cation – oxygen atom bond lengths in this compound. This structure is the same as that of Ca3(VO4)2and although closely related to that of Whitlockite differs from it because of the need to accommodate hydrogen atoms in the latter compound.

ISSN:0008-4042    

DOI:10.1139/v71-173

出版商:NRC Research Press    

年代:1971

数据来源: NRC