摘要:

The inactivation of myosin adenosine triphosphatase activity was studied in 0.6 Mpotassium chloride solution at pH ranging from 7.0 to 10.8 and for 5 °C to 40 °C. The inactivation is a first-order process with respect to time and 0.6th order with respect to the concentration of protein. The rate of inactivation is independent of the pH for pH 7.0 to pH 8.5 at 35 °C and increases rapidly with pH at higher pH. At 12 °C, close to pH 10.4, the rate is inversely proportional to the 4.5th power of the hydrogen ion concentration. The energies of activation are 56 kcal mole−1at pH 8.0 and 58 kcal mole−1at pH 10.5. A discussion of the data stresses the importance of structural changes and indicates a possible role for the electrostatic charge in the inactivation process.

ISSN:0008-4042    

DOI:10.1139/v61-032

出版商:NRC Research Press    

年代:1961

数据来源: NRC

摘要:

2-Imino-1,3-oxathiolane, in the free state, evolves cyanic acid spontaneously and gives rise to ethylene sulphide. This rearrangement is characteristic of all substituted 2-imino-1,3-oxathiolanes. It has now been found that rearrangement of the next higher homologue, 2-imino-1,3-oxathiane, does not give the anticipated trimethylene sulphide but only tris-3-mercaptopropyl cyanurate. The mechanism of this rearrangement is discussed.

ISSN:0008-4042    

DOI:10.1139/v61-033

出版商:NRC Research Press    

年代:1961

数据来源: NRC

摘要:

The oxidation of di-t-butyl peroxide has been investigated in a static system at low conversion at 124 °C with sufficient oxygen present to suppress completely the formation of methane and ethane. The decomposition of thet-butoxy radical is unaffected by the presence of oxygen. A major product of the oxidation is formaldehyde whose yield rapidly approaches a stationary value. It is postulated that the major source of formaldehyde is the decomposition of methyl peroxy radicals, which may also abstract hydrogen from formaldehyde to form methyl hydroperoxide, and that this competition leads to the stationary concentration of formaldehyde actually observed. Methyl hydroperoxide was demonstrated to be unstable in the system and the predominant decomposition product was methanol, a compound also found in high yields in the oxidation. Experiments with added formaldehyde-C13showed that formaldehyde can be converted to carbon monoxide in the system and indicated that formaldehyde was a likely precursor to the carbon monoxide found in the oxidation.

ISSN:0008-4042    

DOI:10.1139/v61-034

出版商:NRC Research Press    

年代:1961

数据来源: NRC

摘要:

The synthesis of a series of meta- and para-substituted anthranilic acids is reported with their rates of decarboxylation in nitrobenzene solution at 210.5 °C. The reaction is second order with respect to anthranilic acid. The rate is increased by electron-releasing substituents and decreased by deuterium in the functional groups. The relative rates are interpreted by means of the Hammett equation and its extensions and it is concluded that the rate-determining step involves attack by proton from one anthranilic acid molecule on carbon 1 of a second molecule.

ISSN:0008-4042    

DOI:10.1139/v61-035

出版商:NRC Research Press    

年代:1961

数据来源: NRC

摘要:

The face-centered cubic phase π(Fe,Co,Ni,S) has been shown to exist, at room temperature, within wide composition limits in or close to theM9S8section of the quaternary system Fe–Co–Ni–S. TheM:S ratio of the binary phase π (Co,S) is 9:8 with very narrow homogeneity ranges on both sides of Co9S8, but in π (Fe,Co,Ni,S) the ratio is somewhat higher and appears to increase with decreasing cobalt content. Stoichiometric Co9S8probably contains a small number of vacancies in both sublattices. It is quite lilcely that the sulphur sublattice is nearly fully occupied and that departures from stoichiometry are caused by the varying degree of occupancy of the metal sublattice.The crystal structure, which was proposed for Co9S8and for the mineral pentlandite by Lindqvistetal., has been confirmed for these two substances and for π (Fe,Co,Ni,S) in general by X-ray and neutron powder diffraction. The present evidence does not support the crystal structure suggested for natural pentlandite by Eliseev; Eliseev's model does not, in fact, account for the diffraction data of any of the substances examined in this work.Replacement of cobalt in π (Co,S) by iron or nickel or both results in an expansion of the unit cell, the maximum increase in a(π) amounting to about 3%. Cobalt in π (Co,S) cannot be replaced completely by iron or by nickel in samples prepared by dry synthesis, but if the substitution is simultaneous, the π structure will be preserved over a considerable range of compositions even on total replacement. The stability limits of π (Fe,Ni,S) have been found somewhat wider than those stated by Lundqvist.In π phases with the compositions Co8MS8the metal atoms can conceivably be present in ordered sublattices. This possibility was explored by neutron diffraction in slowly cooled Co8NiS8. Unlike in spinels, where nickel shows a strong preference for octahedral co-ordination, the cobalt and nickel atoms were found to be distributed at random.

ISSN:0008-4042    

DOI:10.1139/v61-036

出版商:NRC Research Press    

年代:1961

数据来源: NRC

摘要:

The stereochemistry of molecules in which there are five or six pairs of electrons in the valency shell of a central atom is discussed in terms of the repulsions that exist between pairs of electrons in the valency shell as a consequence of the operation of the Pauli exclusion principle. An explanation is given for the difference in lengths of the axial and equatorial bonds in molecules such as PCl5and ClF3whose structures are based on the trigonal-bipyramidal arrangement of five valency-shell electron pairs. The fact that in molecules with a central atom with a valency shell of six electron pairs, one of which is a lone pair and which have the structure of a square pyramid, the central atom always lies below rather than in, or above, the base of the square pyramid, is also accounted for.

ISSN:0008-4042    

DOI:10.1139/v61-037

出版商:NRC Research Press    

年代:1961

数据来源: NRC

摘要:

Measurement of the transmission of electronic effects through square-planar complexes of platinum has provided evidence of double bonding to halogen and nitro ligands. The nuclear magnetic resonance chemical shift of the β-protons in pyridine ligands serves as an indicator of electron drift in the complexes. Justification is thus provided for the assumed mechanism of the trans effect involving π-bonding. The observations are in accord with the assumption that the increase in trans-directing powers with atomic number of the halogen is due to an increasing tendency to acceptd-electrons from the central atom.

ISSN:0008-4042    

DOI:10.1139/v61-038

出版商:NRC Research Press    

年代:1961

数据来源: NRC

摘要:

Solution properties of a series of hexaoxyethyleneglycol ethers having 8 to 16 carbon atoms in a paraffin chain along with a number of diethers were assessed in ethanol at 48 and 60 °C. The molecular weights at infinite dilution indicated that the compounds are unassociated. Solvation effects were observed for the monoethers having 14 or more carbon atoms in the hydrophobic portion of the molecule, but were absent for those molecules containing 12 carbon atoms or less. The apparent micellar weights suggested that association did not proceed beyond a dimer for most of the hexaoxyethyleneglycol compounds. The diethers obeyed Raoult's law up to the critical micelle concentration while different apparent association patterns were observed beyond this concentration.

ISSN:0008-4042    

DOI:10.1139/v61-039

出版商:NRC Research Press    

年代:1961

数据来源: NRC

摘要:

Boron trifiuoride does not form a stable adduct with hexamethyldigermoxane. Instead, cleavage of the Ge—O—Ge linkage occurs with quantitative formation of trimethylfluorogermane and boron trioxide. Trimethylmethoxygermane and boron trifiuoride form a 1:1 addition compound which sublimes without decomposition. Dativedπ–pπbonding, if present in the Ge—O linkage of trimethylmethoxygermane, does not appear to affect appreciably the electron-donor activity of the oxygen atom toward boron trifiuoride. The preparation and some properties of CH3GeH2Br, CH3GeHCl2, (CH3)3GeCl, (CH3)3GeF, [(CH3)3Ge]2O, and (CH3)3GeOCH3are described.

ISSN:0008-4042    

DOI:10.1139/v61-040

出版商:NRC Research Press    

年代:1961

数据来源: NRC

摘要:

Three different kinetic isotope effects have been measured in the thermal decomposition of S-methyl-trans-2-methyl-1-indanyl xanthate: the S32/S34effect for the thio-ether sulphur atom, the S32/S34effect for the thion sulphur, and the C12/C13effect for the carbonyl carbon. The results of these measurements provide strong support for a two-step mechanism, in which the rate-determining step is the removal through a cyclic transition state of the cis beta hydrogen atom by the thion sulphur atom.

ISSN:0008-4042    

DOI:10.1139/v61-041

出版商:NRC Research Press    

年代:1961

数据来源: NRC