摘要:

In the presence of vast excess of ferrocyanide, over the pHrange 1.76–2.65, the reaction between iodate and ferrocyanide ions follows the rate lawwherekaandkbhave values of 1.97 × 103M−2min−1and 4.08 × 105 M−3 min−1, respectively, at an ionic strength of 1.18 Mand a temperature of 25.0 ± 0.1 °C.K1is the formation constant of monoprotonated ferrocyanide. The "overall activation energy" of the reaction was found to be 15.8 kcal/mol. Rate-determining steps consistent with the kinetics have been proposed.

ISSN:0008-4042    

DOI:10.1139/v74-289

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Detailed measurements of the low-frequency Raman spectra of the crystals of [ZnPy2Cl2] and [ZnPy2Br2] at room temperature, where Py is the pyridine molecule, and the far-infrared spectrum of the crystal of [ZnPy2Cl2] at liquid nitrogen temperature have been made. The vibrational frequencies for the single molecule and for the complete crystal of these two complexes have been calculated and compared with the observed spectra, and the distribution of the potential energy of the normal modes has also been calculated to assist the refinement of the calculation and the interpretation of the spectra. Apparently, the skeletal Zn–ligand vibrations of the individual molecule couple with the lattice vibrations in the crystal, except for the normal modes at 326 cm−1for [ZnPy2Cl2] and at 250 cm−1for [ZnPy2Br2] which are dominated by the Zn–halogen stretching vibrations. Reasonably good Zn–ligand stretching force constants were obtained. The nature of the coordination bonds of these complexes has been discussed.

ISSN:0008-4042    

DOI:10.1139/v74-290

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The preparation of the complexes BX3•R3PY (X=Cl, Br, I; R=Me, Ph, cyclohexyl; Y=S, Se) is reported. The corresponding BF3adducts could not be isolated. The infrared spectra for all complexes are presented as well as the n.m.r. spectra for the methyl adducts. The shifts in ν(P—Y) upon co-ordination are amongst the largest ever reported for these ligands when they function as non-bridging species, and are in fact comparable to shifts observed in bridging situations. The spectral data are consistent with an increase in the B—Y bond strength as the atomic weight of X increases.

ISSN:0008-4042    

DOI:10.1139/v74-291

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Cobalt(II) and nickel(II) halide complexes with thiomorpholin-3-thione and thiazolidine-2-selenone have been prepared. Infrared and far infrared spectra, electronic spectral studies, and magnetic susceptibility measurements indicate that the cobalt derivatives are tetrahedral in structure, nickel chloro- and bromo-thiomorpholin-3-thione derivatives are octahedral while [Nits2I2] and all nickel thiazolidine-2-selenone complexes have a pseudo-tetrahedral symmetry. The probable site of bonding in the ligands is nitrogen in all the complexes studied here, except the nickel derivatives of thiazolidine-2-selenone. These results are confirmed by n.m.r. measurements. Spectroscopic parameters for the complexes have been calculated and compared against similar chromophores containing MN2X2and MS2X2chromophores.

ISSN:0008-4042    

DOI:10.1139/v74-292

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

One known (1) and eight new (3,5,6a,7,8a,15,16, and19b) diterpenoids have been isolated from a chemically distinct subgroup within the speciesSolidagoserotinaAit. The constitution and stereochemistry of the new compounds are deduced from their spectroscopic properties and chemical reactions. Of key importance are the conversions of (i)6aand8ainto8b, which has been synthesized from methyl kolavenate (9); (ii)1and15into3; and (iii)15and19binto16. Also discussed are the cleavages of the epoxides10and15with boron trifluoride which result in rearrangement, the products being12and a mixture of16,17a, and17b, respectively.

ISSN:0008-4042    

DOI:10.1139/v74-293

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

An indirect thermochemical estimate of the equilibrium constant for the aldol condensation of acetaldehyde suggested that this reaction was much less irreversible than has been believed. The rate of the hydroxide catalyzed retroaldol reaction has been measured;k21 = 2.8 × 10−3 M−1 s−1at 25°, so that the equilibrium constant is 4.0 × 102 M−1. The γ value for acetaldehyde as addend is 0.40. The enthalpy change for the aldol reaction is −9.84 kcal/mol.

ISSN:0008-4042    

DOI:10.1139/v74-294

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The carbon-13 n.m.r. spectra of a series of 1,4-oxathianes, including the 4-oxide and 4,4-dioxide of 1,4-oxathiane, are reported. The results corroborated conclusions reached previously, on the basis of proton n.m.r. studies, concerning the conformational equilibria. The work also permitted a structural differentiation of the two nucleosides 6-chloro-9-(1,4-oxathian-2-yl)-9H-purine (1) and 6-chloro-9-(1,4-oxathian-3-yl)-9H-purine (2).

ISSN:0008-4042    

DOI:10.1139/v74-295

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The crystal structure of the compound I2+Sb2F11−has been determined from three-dimensional X-ray counter data. Crystals are monoclinic witha = 13.283(5),b = 8.314(3),c = 5.571(2) Å; β = 103.75(2)°;V = 579.5 Å3;Z = 2 andDc = 3.92 g cm−3. The structure has been refined in the space groupC2 with a final conventionalRfactor of 0.055 for 365 independent reflections withI ≥ 3σ(1). The structure consists of discrete I2+cations and Sb2F11−anions, each with a crystallographic two-fold rotation axis through the center. The I—I bond length is 2.557(4) Å while the Sb—F bridge length is 2.00(1) Å with a bridge angle of 166(3)° in the symmetric anion.

ISSN:0008-4042    

DOI:10.1139/v74-296

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Reversible inhibition of the hydrolysis ofO-hippuryl-L-3-phenyllactic acid by carboxypeptidase A has been studied for a series of decarboxylic acids at 25°, pH7.5, and ionic strength 0.2. All inhibitors studied displayed either strictly competitive or partially competitive inhibition kinetics. For the series CO2H(CH2)nCO2H, strictly competitive inhibition was observed forn = 1, 3, 4, 8, 10, whereas partially competitive inhibition occurs forn = 2, 5, 6, 7. A series of 11 alkyl- and aryl-substituted malonic acids were all strictly competitive inhibitors; for a series of six alkylmalonic acids the inhibition constants are correlated with the Hansch π-parameter by the equation –logK1 = 2.257π + 1.75; arylmalonic acids are poorer inhibitors than expected on the basis of their π-parameters, in accord with a similar observation for monocarboxylic acids. Phthalic acid is a strictly competitive inhibitor (K1 = 1.7 mM), whereas the isomeric isophthalic and terephthalic acids cause relatively little inhibition even at 0.1 M; maleic acid is a partially competitive inhibitor, whereas the isomeric fumaric acid gives only 15% inhibition at 0.1 M. Homophthalic acid and 2,2-dimethyl- and 3,3-dimethylglutaric acids were also investigated.The characteristics of partially competitive inhibition displayed by all dicarboxylic acids and also monomethyl succinate and succinamic acid are consistent with a scheme which assumes the formation of an E.I2complex. The observed specificity of dicarboxylic acid binding is used to postulate a schematic diagram for binding of these species to the enzyme, and an interpretation of this diagram is suggested on the basis of the crystallographically determined structure of the enzyme.

ISSN:0008-4042    

DOI:10.1139/v74-297

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The structure of a new cranberry alkaloid, 12-methyl-1,2,3,4,6,7,12,12b-octahydroindolo[2,3-a]quinolizine was established using mass spectroscopy and by synthesis.

ISSN:0008-4042    

DOI:10.1139/v74-298

出版商:NRC Research Press    

年代:1974

数据来源: NRC