摘要:

The hydration of soluble ribonucleic acid, of two forms of polyriboadenylic acid, and of nucleohistone was determined gravimetrically as a function of relative humidity (r.h.). The curves are smooth functions of r.h., similar to those obtained earlier for deoxyribonucleic acid. The general similarity of the hydration curves of the polynucleotides so far investigated is in agreement with the suggestion that the ionic phosphate groups are the primary hydration sites in polynucleotides. The hydration data fit the Brunauer–Emmett–Teller equation up to about 75% r.h. and the Harkins–Jura equation at higher values. Both equations yield a value of about 2.0 molecules of H2O per nucleotide for the "monolayer content" for all the polynucleotides investigated.

ISSN:0008-4042    

DOI:10.1139/v66-167

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

Absolute rate constants for the copolymerization of α-methylstyrene and oxygen have been measured from 13 to 50 °C. The propagation and termination rate constants can be represented byExperiments with 2,6-di-t-butyl-4-methylphenol at 65 °C have shown that C6H5C(CH3):CH2and C6H5C(CD3):CD2have the same propagation rate constant but that chain termination involves a deuterium isotope effect (kt)H/(kt)D ≈ 1.5.Absolute rate constants for the copolymerization of oxygen with β-methylstyrene and with indene at 30 °C showed that a significant fraction of the oxidation chains were terminated by a kinetically first order process (rate constantkx). The rate constants for β-methylstyrene and indene at 30 °C arekp = 51 and 142 l mole−1s−1,kt = 1.6 × 107and 2.5 × 107l mole−1s−1, andkx = 0.61 and 1.2 s−1, respectively. The propagation rate constant for indene can be separated into a rate constant for the copolymerization with oxygen (kadd = 128 l mole−1s−1) and a rate constant for hydrogen atom abstraction (kabstr = 14 l mole−1s−1). In the presence of heavy water the first order process for indene had a deuterium isotope effect (kx)/(kx)D2O ≈&ens

ISSN:0008-4042    

DOI:10.1139/v66-168

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

Absolute rate constants have been measured for the autoxidation of five hydrocarbons under a variety of conditions. The propagation (kp) and termination (kt) rate constants at 30 °C (in l mole−1s−1) are: tetralin in chlorobenzene 6.3 and 3.8 × 106respectively, cyclohexene in chlorobenzene 6.1 and 2.8 × 106, diphenylmethane 4.8 and 8.0 × 107, ethylbenzene 0.11 and 2.0 × 107, and allylbenzene 10 and 2.2 × 108. Measurements on tetralin, α-methylstyrene, and allylbenzene in different solvents indicate that the effect of solvents on oxidation rates is mainly connected with changes in the rate of termination rather than propagation. Experiments with α,α-d2-diphenylmethane gave isotope effectskH/kD~5.1 forkpand ~1.4 forkt. The rate constant for hydrogen atom abstraction from 2,6-di-t-butyl-4-methylphenol by peroxy radicals decreases in the order expected if steric effects are important, i.e., primary peroxy > secondary peroxy > tertiary peroxy radical.The co-oxidation method of estimating chain termination constants is criticized on the grounds that it can only be used to distinguish the fairly large changes inktcommonly encountered between hydrocarbons giving tertiary peroxy radicals and those giving secondary or primary radicals.The effect of hydrocarbon structure on bimolecular chain termination rate constants is reviewed. There is a gradation inktfrom ~2 × 108] mole−1s−1for primary peroxy radicals, through the range 8 × 107to 1 × 106for secondary radicals, to the range from 3 × 105to 3 × 102for tertiary peroxy radicals.

ISSN:0008-4042    

DOI:10.1139/v66-169

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

A theoretical method, which allows one to determine the effect of the Pauli exclusion principle on the electron density distribution, is used to test the concepts underlying the electron pair repulsion theory of molecular geometry. It is shown that pictures of overlapping orbitals frequently do not correspond to the actual effect which the Pauli principle has on the three-dimensional charge density. An alternative electrostatic approach, involving the concept of a binding region for a polyatomic molecule, is proposed to account for the observed molecular geometries.

ISSN:0008-4042    

DOI:10.1139/v66-170

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

The sorptions of hydrogen and of oxygen on freshly prepared and on gas-treated cadmium oxide were measured from 0 to 250 °C. The data suggest that hydrogen chemisorption predominates near 26°, where it is the precursor of water formed on the surface. Surface reduction occurs at temperatures as low as 50°. At least two types of oxygen sorption exist. The isobar has a minimum near 50°. Chemisorption occurs below 50° and the sorption kinetics indicates the presence of two types. The incorporation of oxygen into the bulk may account for the observed increased sorption above 150°.

ISSN:0008-4042    

DOI:10.1139/v66-171

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

The real and imaginary parts of the complex dielectric constant of the composite system ethyl chloride adsorbed on porous glass have been determined over a range of temperature, namely −20 to −190 °C in the frequency range 1 000 to 4 000 Mc/s. The porous glass was treated to remove the majority of the silanol groups. The dielectric constants of the adsorbate are also reported. The major finding was that removal of the silanol groups eliminated the second linear section (of lower slope) of the usual plots. The behavior of the polar adsorbate is then shown to be quite similar to that of polar adsorbates on nonporous rutile. Loss curves as functions of frequency and temperature are given and discussed. There is insufficient evidence to discriminate between Debye-type loss and that of an oscillator or resonator.A method is given of obtaining the dielectric parameters from the standing wave data with greater accuracy than can be obtained from use of Von Hippel plots.

ISSN:0008-4042    

DOI:10.1139/v66-172

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

Attempts to measure the actual lifetime of N2(A3∑u+) in active nitrogen resulted only in a very small upper limit of ≈5 × 10−4 s. This result is consistent with quenching of theA3∑u+state by atomic nitrogen in an atom–atom interchange process,having a rate coefficient ofIt is suggested that similar processes are involved in determining the distribution of excited states observed in atom associatio

ISSN:0008-4042    

DOI:10.1139/v66-173

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

The radiolysis of dilute solutions of ethane-dϵ, propane-d8, andn-butane-d10in liquid hydrocarbons at 195 °K results in the production of D2and HD in amounts which are determined by the relative ionization potentials of solvent and solute. Solvents of higher ionization potential enhance the production of D2and HD from deuterated solutes of lower ionization potential. When the ionization potentials are in the reverse order the yields are diminished. This solute–solvent interaction, which is ionic in nature, is a general phenomenon in the radiolysis of mixtures of saturated hydrocarbons in the liquid phase and is consistent with charge transfer between solvent and solute.

ISSN:0008-4042    

DOI:10.1139/v66-174

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

The volume changes on mixing of the three binary mixtures, acetone–chloroform, benzene–chloroform, acetone–benzene, and the ternary mixture, acetone–chloroform–benzene, and their molar refractivities and viscosities, were determined.Determinations of total and partial vapor pressures were made. The systems acetone–chloroform and benzene–chloroform show negative deviations from Raoult's law. The system acetone–benzene shows positive deviations.The excess Gibbs free energies of mixing have been calculated for all systems. By combining these data with previously measured heats of mixing (1), the excess entropy has also been calculated. The curves representing zero excess volume, zero heat of mixing, zero excess free energy of mixing, and zero excess viscosity as functions of composition in the ternary system do not coincide. It, therefore, must be concluded that they result from compensating effects and do not represent ideality.

ISSN:0008-4042    

DOI:10.1139/v66-175

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

The kinetics of the thermal decomposition of purified pyrite to pyrrhotite and sulfur in a dynamic argon atmosphere have been studied over the temperature range 600 to 653 °C. The reaction was followed by the rate of weight loss as indicated by a quartz spring balance and also by the rate of progression of the pyrite/pyrrhotite interface into a cylindrical, compressed, polycrystalline pellet. The temperature coefficient of the reaction was found to be 69.5 ± 5.9, 64.7 ± 3.3, and 66.9 ± 5.1 kcal mole−1, when the results were processed in three different ways. The pyrite/pyrrhotite interface was found to progress at a linear rate into the pellet at a given temperature; equations were derived to express the variation of reaction rate with temperature. Attempts to follow the early nucleation stage of the decomposition, using massive mineral crystals, proved unsuccessful.

ISSN:0008-4042    

DOI:10.1139/v66-176

出版商:NRC Research Press    

年代:1966

数据来源: NRC