摘要:

A series of complexes of the type Rh(cyclam)X2+and Rh(cyclam)XYn+have been prepared and characterized, where cyclam represents 1,4,8,11-tetraazacyclotetradecane and X and Y represent OH−, H2O, Cl−, Br−, I−, N3−, NCS−, and NO2−. The infrared and electronic spectra are discussed with respect to assignment of thecisandtransisomers, the linkage isomers, and the Rh–ligand stretching frequencies above 250 cm−1. The thermodynamictranseffect is related to shifts in the Rh–ligand stretching frequencies. The intensities of the d–d transitions are related to distortion of the octahedral field to support thecisandtransassignments, and compared to show the decrease in bond constraint for propylene linkages in place of ethylene. Steric constraint accounts for the single case of stereoisomerization bycis-Rh(cyclam)I2+.

ISSN:0008-4042    

DOI:10.1139/v70-243

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

The photolysis of cyanogen bromide with cyclohexane yielded cyclohexyl bromide, hydrogen cyanide, and small amounts of cyanogen, while the benzoyl-peroxide-promoted reactions of cyanogen bromide with various alkanes yielded approximately equal amounts of alkyl bromides and alkyl cyanides, often in high yields. Both hydrogen cyanide and hydrogen bromide were shown to react with benzoyl peroxide and an added hydrocarbon to yield the corresponding alkyl cyanide and alkyl bromide. Possible reaction mechanisms for these reactions are discussed.

ISSN:0008-4042    

DOI:10.1139/v70-244

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Enzymes behave differently when attached to solid supports for four main reasons: (1) their conformations when they are supported may differ from those in free solution, (2) they act upon substrates in a different environment, (3) there will be partitioning of substrate between the support and the free solution, and (4) there will be effects due to diffusion of the substrate in the support. The present paper examines effects (3) and (4) and shows how rates will vary with substrate concentration. If factors (1) and (2) do not enter, rates in the limit of high substrate concentrations will be the same for the supported enzyme as in free solution. At low substrate concentrations, rates will be less for the supported enzyme if the substrate is less soluble in the support than in free solution, and the apparent Michaelis constant,Km(app.), will be greater; conversely, for higher solubility in the support, rates will be greater andKm(app.) smaller. Effect (4) leads to lower rates and higherKm(app.) values, except in the limit of high substrate concentrations. At a sufficiently low thickness of the support, depending upon the activity of the enzyme, the kinetic behavior becomes identical with that in free solution.

ISSN:0008-4042    

DOI:10.1139/v70-245

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

The yield of ozone from the radiolysis of gaseous oxygen has been measured at 1026–1027 eV g−1s−1to beG(O3) = 12.8 ± 0.6, in reasonable agreement with the value of 13.8 of Ghormley, Hochanadel, and Boyle (2a). At 1016 eV g−1s−1, our results and re-examination of previous data giveG(O3) = 6.2 ± 0.6. The same value is obtained at the high dose rates by the addition of electron scavengers. The difference in yields on going from high to low dose rates and the decrease with electron scavengers at the high dose rate is explained by differences in ion neutralization processes. These are supported by computer calculations. The mechanism of the neutralization steps is discussed in terms of the applicability of the electron jump theory and the effect of clustering of the ions.The proportion of energy lost to ionization, excitation, and subexcitation electrons is calculated. This is based on theWvalue, relative cross sections for ionization, and the potential energy curves for O2+ions. A predicted yield on this basis is G(O3) = 14.0 ± 0.9, in fairly good agreement with the experimental yield.

ISSN:0008-4042    

DOI:10.1139/v70-246

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Air and other mixtures of nitrogen and oxygen containing from 0.1 to 100% oxygen have been irradiated with single, 0.12 Mrad electron pulses at a dose rate of 2 × 1026 eV g−1s−1. The major product formed in these irradiations is ozone. For air from 400–1500 Torr,G(O3) = 10.3 ± 0.5, the addition of SF6reduces this by 5.8 ± 0.5 G units. The yield of ozone from other nitrogen–oxygen mixtures varies with the concentration of oxygen. At both 700 and 1500 Torr total pressure for 1 Torr of O2,G(O3) ≈ 4. This increases with oxygen concentration to a maximum ofG(O3) = 12.8 for pure oxygen. For all the above conditions the yield of nitrogen dioxide is below the limits of detection.A mechanism is proposed based on known possible ionic and neutral reactions and their rate constants. Detailed computer calculations using this mechanism give results which compare well with the experimental yields. These results are consistent with an assumed yield ofG(N) = 6 from processes involving neutral species in the radiolysis of pure nitroge

ISSN:0008-4042    

DOI:10.1139/v70-247

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Ultraviolet irradiation of 3-carene-2,5-dione1in acetone has been found to yield three cyclobutanetype photodimers. A detailed spectroscopic study of these compounds has shown that the two most abundant dimers possess thehead-to-headorientation. Thehead-to-headdimers have been shown to possess theanti-anti-antiandsyn-anti-synstructures10and8respectively, while the minor,head-to-tailproduct has one of the corresponding structures9or11. In all three cases, the cyclobutane and cyclohexane rings arecis-fused. Nuclear Overhauser effects enable structures8and10to be specifically assigned to dimerBand dimerA, respectively.

ISSN:0008-4042    

DOI:10.1139/v70-248

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

A ring expanded lactone is obtained on electrochemical oxidation oft-BuOOH in presence of tetracyclone. The same product is formed on chemical oxidation of a mixture oft-BuOOH and tetracyclone with cerie ammonium sulfate or on heating the mixture to dryness.

ISSN:0008-4042    

DOI:10.1139/v70-249

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

The state of water in the hydration shell of DNA was studied by infrared spectroscopy. The stretching bands of isotopically dilute HDO adsorbed on DNA have nearly the same band profiles as those of HDO in liquid water. This indicates a distribution of hydrogen-bond strengths similar to that in liquid water. At low temperatures, the spectra show that an inner layer of about 10 water molecules per nucleotide is incapable of crystallization, even when the surrounding water crystallizes into ice I. The biopolymer hydration shells are not "ice-like" in the sense of crystalline ordering into an ice-like structure.

ISSN:0008-4042    

DOI:10.1139/v70-250

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Amine oxides, azoxybenzenes, and nitrones are deoxygenated in good yields by iron pentacarbonyl in hot butyl ether. Substituted nitro- and nitrosobenzenes are reduced under these conditions to azo and/or amino compounds, depending on the nature and location of the substituents; some evidence for nitrene or nitrene-like intermediates in these reactions is presented.

ISSN:0008-4042    

DOI:10.1139/v70-251

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

The Friedel–Craftst-butylation of methyl 2-pyrrolecarboxylate and of 2-acetylpyrrole have been investigated. The results are found to be consistent with the mechanistic pathway suggested in earlier isopropylation papers. Evidence is presented that alkylation of similarly substituted furans may be interpreted in the same way.

ISSN:0008-4042    

DOI:10.1139/v70-252

出版商:NRC Research Press    

年代:1970

数据来源: NRC