摘要:

The reduction of the title compound,by chromium(II) is first order in Cr(II) and obeys the rate lawkobsd = k1Ka′/(Ka′ + [H+]) at 25.0 °C andI = 1.0 mol L−1(LiClO4) withk1 = (2.9 ± 0.1) × 104L mol−1s−1andKa′ = 0.86 ± 0.03 mol L−1. In the rate law,k1refers to reduction of the 3+ ion above and theKa′ is the acid dissociation constant for the protonated form of1. The reduction occurs by a remote attack inner-sphere mechanism with complete transfer of the organic ligand to chromium.

ISSN:0008-4042    

DOI:10.1139/v86-138

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The electron donor–acceptor (EDA) interaction between methyl viologen (MV2+) and 1-naphthylamine (1NA), 2-naphthylamine (2NA), andN,N-dimethyl-1-naphthylamine (DMA) was studied in water and in aqueous sodium dodecyl sulphate (SDS). The experimental values of the association constants in water were 8.9, 9.8, and 2.8 M−1for 1NA, 2NA, and DMA, respectively. In the presence of SDS the observed values were very much higher and strongly dependent upon the detergent concentration. The enhancement in the interaction is due to an increase in the local concentration of the partners in the micellar pseudophase. MV2+itself was shown to strongly interact with the micelles. A new absorption is present at the red tail of the spectrum of MV2+in the presence of SDS micelles. An association constant of 1700 M−1was obtained from this absorption.

ISSN:0008-4042    

DOI:10.1139/v86-139

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The reaction of arsenic pentafluoride with benzo-2,1,3-thiadiazole,1, or benzo-1,2,3-thiadiazole,2, in liquid SO2gave 1:1 adducts that were characterized spectroscopically (infrared and13C nmr) and by X-ray crystallography. Crystal data: for1•AsF5, monoclinic, space groupP21/n,a = 6.932(1),b = 9.113(1),c = 15.136(2) Å, β = 98.035(7)°,V = 946.8(2) Å3,Z = 4; for2•AsF5, monoclinic, space groupP21/a,a = 7.573(2),b = 13.101(2),c = 9.514(3) Å, β = 90.95(2)°,V = 943.9(4) Å3,Z = 4. The coordination of AsF5to one of the nitrogen atoms in1introduces asymmetry in the heterocyclic ring, with the longer bond lengths being associated with the coordinated nitrogen atom,d(S—N) = 1.633(5) and 1.577(6) Å,d(C—N) = 1.364(7) and 1.339(8) Å. The quinonoid character of the benzene ring is still apparent in the adduct. In2•AsF5, the AsF5molecule is coordinated to the nitrogen atom that is bonded to carbon.

ISSN:0008-4042    

DOI:10.1139/v86-140

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Base-promoted ring cleavage of 9,10- and 8,10-dibromocamphor provides chiral intermediates for natural product synthesis.

ISSN:0008-4042    

DOI:10.1139/v86-141

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The analytical methods for estimating forms of sulfur in coals are reviewed on the basis of sulfur analyses of Western Canadian low sulfur subbituminous coals. The reasons for the variance in analyses are examined, and a novel method of analysis is recommended for evaluation

ISSN:0008-4042    

DOI:10.1139/v86-142

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Metal–ligand association constants of 1:1 binary (ML) and 1:1:1 ternary (MAL) complexes of the type(where M = La3+, Ce3+, Pr3+, Nd3+, or Sm3+; A = primary ligand = EDTA; L = secondary ligand = O—O, O—N, O—S donor aliphatic or aromatic ligand) have been determined potentiometrically by the Irving–Rossotti titration technique at ionic strength 0.2 (mol dm−3NaClO4) and 25 °C. Differences between logKMLand logKMALare negative; this may be chiefly due to electrostatic repulsion between the primary binary complex and the incoming secondary ligand during the formation of the mixed-ligand complexes. The relative complexing tendencies of various secondary ligands have been found to follow the sequence O—O donor (aromatic) > O—N donor > O—O donor (aliphatic) ≥ O—S donor.

ISSN:0008-4042    

DOI:10.1139/v86-143

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The kinetics of triethylamine (TEA) catalyzed deydrochlorination of a series ofN-aryl-C-ethoxycarbonylformohydrazidoyl chlorides1a–mhave been studied under pseudo-first-order conditions in 4:1 (v/v) dioxane–water solution at 30 °C. For all compounds studied, the kinetics followed the rate law:kobs = k2(TEA). The values of the overall second-order rate constants for the studied compounds were correlated by the equation: logk2 = 0.533σ−-0.218. The results are compatible with a mechanism involving a fast reversible deprotonation step leading to the anion of1, followed by rate-determining step involving the loss of the chloride ion from the anion. The reaction constants of these two steps were estimated to be 0.845 and −0.312, respectively.

ISSN:0008-4042    

DOI:10.1139/v86-144

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The crystals of C17H19NO5belong to the monoclinic space groupP21/nwitha = 15.793(3),b = 4.089(4),c = 24.649(5) Å, β = 97.56(3)°V = 157 8(2) Å3, andZ = 4. The structure was solved by MULTAN 78 and refined by full-matrix least-squares to a finalRof 0.053 for 1863 observed reflections. X-ray crystallography has revealed that the molecule is the Δ3isomer and not the Δ5isomer suggested originally from nmr spectroscopy. The piperidyl nitrogen issp2hybridized with its electron lone pair involved in conjugation with the carbonyl groups. The piperidone ring adopts a distorted boat conformation. An interesting feature of the structure is the formation of two C(ethylenic)—H … O(keto) intramolecular hydrogen bonds which stabilize the molecular conformation.

ISSN:0008-4042    

DOI:10.1139/v86-145

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The pinacolisation of ketones is enhanced when a bivalent transition metal cation is present. This phenomenon is general and occurs with Cr2+, Mn2+, Fe2+, Co2+, Zn2+but not with Ni2+. The cathodic reduction leads to α-glycols with a good yield, without any resin production, and at a less negative potential than that of the ketone itself. The distribution of all isolated compounds is dependent on the Lewis character-acidity and complexing power of the metallic cation. Thus, for the dimerization, the greatest specificity is generally observed when Fe2+is present. For the chalcone, the better stereoselectivity is obtained with Zn2+. No evidence of initial carbonyl complex of the metal ion was shown.

ISSN:0008-4042    

DOI:10.1139/v86-146

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The electrochemical behaviour of the Zn(II)–Zn(Hg) system in aqueous ethylene glycol (EG) solutions containing 5.0 × 10−2 MLiClO4has been studied by polarography and cyclic voltammetry. The reversible half-wave potentials, the diffusion coefficients and the Walden products for Zn(II) have been polarographically determined. The standard free energies of transfer of 1 mol of Zn(II) ions from water to EG–water mixtures,, obtained from the reversible half-wave potentials vs. the ferrocene electrode scale, are always negative, indicating a greater stability of Zn(II) in EG–water mixtures than in pure water. The splitting of thevalues into electrostatic and chemical contributions shows that the mixtures are more basic than water. The analysis of the variation of the Walden product with solvent composition indicates an enhancement of the solvent structure in the water-rich region. The diffusion coefficient for Zn in mercury, the transfer coefficients for Zn(II) electroreduction, and the apparent standard rate constants of the Zn(II)–Zn(Hg) system have been determined by cyclic voltammetry. The change in the kinetics with solvent composition is discussed in terms of existing models.

ISSN:0008-4042    

DOI:10.1139/v86-147

出版商:NRC Research Press    

年代:1986

数据来源: NRC