摘要:

The kinetics of the direct chlorination of cyclopentanone (cp) and cyclohexanone (ch) in carbon tetrachloride, catalyzed by hydrogen chloride, was studied. The rate of chlorination, measured by flow and stopped-flow techniques, is zero order in chlorine; the order in cp and ch increases from 1 at [cp] and [ch] of 0.01 Mconcentration to 2 at concentrations of 1 M. This is explained by self-association of the ketones in carbon tetrachloride solutions. The order in hydrogen chloride is 1. Since this compound is one of the products, the reaction isautocatalytic. Deuterium isotope effects and the kinetic data strongly point to a mechanism in which the oxygen-protonatedmonomericketone is α-carbon deprotonated in a rate-determining step. This step, which is catalyzed by the bases cp or ch, respectively, leads to the corresponding enol as intermediate. The enol is then chlorinated very rapidly. In addition to the chloro ketone, very reactive chloride anions are formed. A small fraction of these anions deprotonate α- or α′-carbon atoms of the oxygen-conjugate acid of the monochloro ketone. The remainder are captured by HCl to form energetically more favored Cl--(HCl)ncomplexes withn = 1, 2, or 3. This explains why, even at low conversions of the ketones, substantial amounts of the various dichloro isomers are formed in addition to monochloro products. A rate expression is derived, which excellently describes the experimentally obtained rates of chlorination of cp and ch over a range of reaction rates of more than three decades.

ISSN:0008-4042    

DOI:10.1139/v86-277

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The kinetics of the direct chlorination of 2-chlorocyclopentanone (2-mccp) and 2-chlorocyclohexanone (2-mcch) in carbon tetrachloride, catalyzed by hydrogen chloride, were studied. Reaction products are all the possible 2,2-, 2,5-, and 2,6-dichloro compounds. The ratios depend on the concentrations of the monochloro compound and hydrogen chloride. Surprisingly, even at conversions of the monochloro compound as low as 2%, 2,2,5-trichlorocyclopentanone and 2,2,6-trichlorocyclohexanone, respectively, are also formed. The chlorination reaction of both monochloro ketones shows zero order in chlorine. The order in hydrogen chloride is 1.3. The order in 2-mccp and 2-mcch varies somewhat with the concentration of the ketone and was found to be roughly 1.7. The variation in reaction order is explained by a partial self-association of the ketones. The ketones act as substrates as well as basic catalysts in the rate-determining α- or α′-carbon deprotonation. General base catalysis is clearly demonstrated by a strong increase in the rate of chlorination of 2-mccp upon addition of cyclopentanone (cp) to the reaction mixture, which agrees with the mechanism as presented in a previous paper. Kinetic equations derived from the reaction models for the "separate" and "mixed" ketone chlorinations accurately describe the observed rates of the chlorination of 2-mccp and 2-mcch in the concentration range of 0.04–1.0 M.

ISSN:0008-4042    

DOI:10.1139/v86-278

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The preparation, crystal structure, and vibrational spectra of the title compound are reported. The compound crystallizes in the triclinic space groupwitha = 7.386(2),b = 8.637(1),c = 16.546(2) Å, α = 97.40(1)°, β = 95.51(2)°, γ = 112.91(2)°,V = 951.6 Å3, ρobs = 2.43 g cm−3,Z = 2, ρcalcd = 2.424 g cm−3(MoKα, λ = 0.71069 Å). The structure was solved by direct methods and electron density maps, and refined by full-matrix least squares to the finalR = 0.038 for 3343 observed reflections. The structure consists ofN,N,N′,N′-tetramethylpiperazonium cations containing a six-membered C4N2heterocycle, InBr5(OH2)2−anions, and additional H2O solvent molecules. Infrared and Raman spectral bands of the InBr5(OH2)2−complex are assigned on the basis ofC4vskeletal symmetry, and the H2O molecule of crystallization is also detected spectroscopically.

ISSN:0008-4042    

DOI:10.1139/v86-279

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Mixed anhydrides derived from carboxylic and amidophosphoric acids, (RO)(R′2N)P(O)OC(O)R″ (1), undergo unimolecular fragmentation yielding carboxyamides, R″C(O)NR′2, and metaphosphate esters, ROPO2. The mechanism of the amino group transfer was studied for substrate1a(1, R = R′ = Me; R″ = Ph); solvent as well as substituent effects indicate little (if any) charge development in the transition state. The effects of solvents and Lewis acids on the reaction rate and the activation parameters determined for1acan be explained best in terms of stabilizing interactions with either carboxyamide or metaphosphate being formed in the course of reaction. The transfer of a functional group from one acyl center to another was investigated for other anhydride systems and the relative contributions of the fragmentation vs. disproportionation of substrates are discussed.

ISSN:0008-4042    

DOI:10.1139/v86-280

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Benzoate displacement of the 2-triflyl derivative of methyl 3-azido or 3-O-benzoyl-4-deoxy-α-DL-thero-pentopyranoside (1or4) occurs with a pyranose to furanose contraction reaction at C-2. This contraction is not observed with an azido displacement.

ISSN:0008-4042    

DOI:10.1139/v86-281

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

MNDO calculations are reported for the series of closed shell aromatic and heteroaromatic molecules and cations1to7. The 14π dipyrido-dications1aand2aare considerably less stable than their dihydro-analogues1band2band perhaps should not be considered to be "aromatic" cations.

ISSN:0008-4042    

DOI:10.1139/v86-282

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Reaction of 1,3,5-trinitrobenzene (TNB) with the malononitrile anion in methanol yields a carbon-bonded σ-adduct, (3). Ionisation of the remaining exocyclic hydrogen is favourable and yields the dianion (4). The initial reaction of 1-chloro-2,4,6-trinitrobenzene similarly occurs at an unsubstituted ring position, but is followed by slower nucleophilic attack at the 1-position yielding the substituted product. A major difference in the reaction of the ethyl malononitrile anion with TNB is that the adduct formed (11) has no readily dissociable proton. Hence, here, conversion to the carbon-bonded adduct is less favourable. Kinetic and equilibrium data are reported for these reactions and are compared with data for adduct formation involving methoxide ions.

ISSN:0008-4042    

DOI:10.1139/v86-283

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Enthalpies of solution of urea in binary mixtures of isopropanol,s-butanol, and ethoxyethanol with water have been measured at high water content. Those in the binaries isopropanol + water and ethoxyethanol + water show endothermic maxima at 8 and 4 mol% alkanol, respectively. Enthalpic pair interaction coefficients are calculated for the interactions between urea and the alkanols and discussed in connection with these coefficients for interactions between urea and other nonelectrolytes and betweenN,N-dimethylformamide and several nonelectrolytes. The enthalpic pair interaction coefficients correlate linearly with the heat capacity change on hydration of the nonelectrolytes and with the enthalpy of hydrophobic hydration of the alkanols.

ISSN:0008-4042    

DOI:10.1139/v86-284

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The oxidation of 2,5-disubstituted 1,2,4,3-triazaphospholes with amines gives 1,2 addition products by an equilibrium reaction. This equilibrium has been proved by temperature lowering and also by chemical reaction: addition of sulfur, selenium, or azide (X) shifts the equilibrium to the 1,2 addition products:The thermodynamical parameters associated with this equilibrium have been determinated in some cases.

ISSN:0008-4042    

DOI:10.1139/v86-285

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

A fuel-rich, methane–oxygen, premixed flame at atmospheric pressure was doped with 0.2 mol% of OCS. More than 40 different sulphurous cations were observed in the mass range < 100 u by sampling the flame into a flame-ion mass spectrometer. Ion concentration profiles along the flame axis are presented, together with mass spectra at fixed points in the flame. In the reaction zone, primary sulphur ions CHxS+(x = 1, 3, 5) undergo extensive ion–molecule reactions (association and condensation) with CH4/CH3, C2H2, and OCS to form a considerable variety of secondary sulphurous cations. Just downstream of the reaction zone, the ion chemistry is somewhat different; it appears to be dominated by reactions of primary sulphur ions including HxS+(x = 0–3) with C2H2present as an intermediate. A few ions (HxS+, OS+, S2+) persist throughout the burnt gas region in equilibrium with the natural flame ions CHO+and H3O+. These sulphurous cation signals show the evolution of the sulphur chemistry, both ionic and neutral, through the flame reaction zone into the burnt gas downstream where H2S, not SO2, is the major product in fuel-rich combustion.

ISSN:0008-4042    

DOI:10.1139/v86-286

出版商:NRC Research Press    

年代:1986

数据来源: NRC