摘要:

The role of steric and electronic effects during the rate and product determining steps for the addition of arenesulphenyl chlorides to 1,3-disubstituted allenes has been briefly examined. Both effects appear to be generally of minimal importance during the rate determining step. The available rate data indicate the presence of little, if any, build up of positive charge on sulphur. These results are interpreted in terms of an SN2 attack on bivalent sulphur leading to an alkylidenethiiranium ion intermediate. Steric effects are of greater importance in the product determining step, particularly when the sulphenyl chlorides possess two bulkyorthosubstituents, as in the case of 2,4,6-triisopropylbenzenesulphenyl chloride.

ISSN:0008-4042    

DOI:10.1139/v80-438

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The reactions of benzeneselenenyl chloride, bromide, and 2,4,6-trimethylbenzeneselenenyl bromide with alkyl 1,3-disubstituted allenes in methylene chloride solution have been investigated. While kinetic data are in accord with similar rate determining transition states, exhibiting strong steric effects for ail three species, the product distributions show changes in both chemoselectivity and configurational-selectivity in accord with two different types of steric interaction mechanisms during the product determining transition states. A mechanism involving rate limiting formation of alkylideneseleniranium ions and/or alkylideneepiselenuranes, followed by isomerization between the alkylideneseleniranium ions by a path not involving allylic ions, prior to the product determining transition states, is proposed.

ISSN:0008-4042    

DOI:10.1139/v80-439

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Substituent effects in some autoxidation and hydrogen abstraction reactions have been studied in terms of the field (Fk) and resonance (Rk) components proposed by Swain and Lupton and the unique positional weighting factorsfjandrjincorporated by Williams and Norrington with the aid of the following equation:wherePi's are the rate parameters,Pi0being that for a standard reference compound. The correlations are found to be quite satisfactory, showing the general validity of the above equation for the types of reactions considered. From the information obtained from the present correlation studies, an attempt has been made to resolve the conflict with regard to the nature of the transition state involved in the hydrogen abstraction reactions – that is, whether or not there is charge separation in the transition state. The results of the present studies seem to suggest that both the differences in the resonance stabilization energies of the ring-substituted benzyl radical and the contribution of polar structures to the transition state are to be invoked to explain the observed data.

ISSN:0008-4042    

DOI:10.1139/v80-440

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

o-Hydroxybenzenethiol reacts with one equivalent of acetic anhydride to give a mixture of starting materiel, diacylated material, andO- orS- monoacylated products as determined by nmr. The same products are obtained by equilibration of a mixture ofo-hydroxybenzenethiol and its diacetate. The mixture does not contain detectable amounts of 2-methylbenzothioxolan-2-ol.

ISSN:0008-4042    

DOI:10.1139/v80-441

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Two new crystalline products were isolated from the chlorination ofm-cresol in cold alkaline solution. These products have been identified asE,Z-2-chloro-5-methyl muconic acid and 5Z-carboxymethylene-3-chloro-4-methyl-2(5H) furanone.

ISSN:0008-4042    

DOI:10.1139/v80-442

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The protoberberine skeleton has been prepared in two steps fromN-benzyl-3,4-dihydroisoquinolinium salts. Treatment of the salts with the anion of methyl methylthiomethylsulfoxide yields mixtures of diastereomeric adducts that cyclize on heating with concentrated hydrochloric acid to dihydroprotoberberines. The latter compounds may be reduced to their tetrahydro analogues with sodium borohydride, oxidized to protoberberinium salts with iodine, or converted to 13-methyltetrahydroprotoberberines by treatment with formaldehyde according to an established procedure. The method has been applied successfully to the synthesis of (±)-tetrahydropalmatine, palmatine iodide, (±)-xylopinine, (±)-sinactine, and (±)-corydaline.N-Benzylisoquinolinium salts may be used in place of their dihydro analogues as starting materials in this synthesis, thereby extending the range of substitution patterns potentially available.

ISSN:0008-4042    

DOI:10.1139/v80-443

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

A short synthesis of the title compound is reported. It can be used to transform aldehydes to the corresponding α,β-unsaturated ketene dithioacetals, the sulfoxides of which can be converted to α,β-unsaturated aldehydes.

ISSN:0008-4042    

DOI:10.1139/v80-444

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The reactions of ethyl(trichloromethyl)carbinol, dimethyl(trichloromethyl)carbinol, (trichloromethyl)vinylcarbinol, ethynyl (trichloromethyl)carbinol, and 1,1,1,-triehloro-3-nonyn-2-ol have been studied with the following reagents.Methanolicpotassiumhydroxide: α-methoxy acids are formed in 70 and 79% yields with the ethyl- and vinylcarbinols respectively. Double bond migration to the conjugated position was observed with the vinylcarbinol.Thiourea: substituted 2-imino-4-thiazolidinones are formed in 27 to 66% yield with the first three carbinols with double bond migration in the case of the vinylcarbinol.Cyanamide: the saturated carbinols were converted to substituted ethy] 2-imino-4-oxo-1-imidazolidinecarboximidates in 30 to 60% yield.Aqueouspotassiumhydroxide: α-chloro acids were formed from the ethyl- and vinylcarbinols in 23 and 24% yields respectively, again with double bond migration in the case of the vinylcarbinol.The results are discussed in terms of the known parallel reactions with phenyl (trichloromethyl)carbinol, and provide information which illustrates the usefulness and defines the limits of certain known synthetic reactions when applied to the alkyl, alkenyl, and alkynyl trichloromethylcarbinols.

ISSN:0008-4042    

DOI:10.1139/v80-445

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The adsorption of tripropylphosphate, triethylphosphate, and trimethylphosphate at the dodecane–water interface has been studied at temperatures from 293 to 313 K. Standard free energies of adsorption were obtained from the lowering of interfacial tensions in the low (< 10−4) solute mole fraction region. Standard enthalpies and entropies of adsorption were then obtained from the temperature variation of the standard free energies of adsorption.Standard free energies of adsorption from dodecane showed little variation with solute chain length, with the exception of trimethylphosphate. On the other hand, free energies of adsorption from water decreased by 3.45 kJ/mol for each methylene group added, again with the exception of trimethylphosphate. Enthalpies of adsorption increased linearly with increasing solute chain length for adsorption from either phase. For each methylene group added, the enthalpy of adsorption from dodecane increased by 2.9 kJ/mol, while that from water increased by 2.4 kJ/mol.Results for tripropylphosphate adsorption and for triethylphosphate adsorption at higher temperatures could be adequately described by the Schofield–Rideal equation of state, but not by simple two-dimensional solution models. Results for trimethylphosphate adsorption and for triethylphosphate adsorption at lower temperatures could not be fitted adequately by either type of equation of state.

ISSN:0008-4042    

DOI:10.1139/v80-446

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

A recently developed gc–calorimetry procedure involving a combination of gas chromatography and heat of solution measurements has been used to measure heats of vaporization of 17 esters, including methyl 2,2-dimethylpropanoate, butyl acetate, glyceryl triacetate, diethyl phthalate, methyl 9-octadecenoate, and 12 methyl esters of C3- to C15-fatty acids. Comparison with measurements of ΔHvreported in the literature indicates that the gc–calorimetry method often has smaller uncertainties in measurements (0.25 to 1.00 kJ mol−1) and more consistent methylene increments for the series of fatty acid methyl esters. Two of the experimental ΔHvmeasurements which differ appreciably from recent literature values have been verified by vaporization calorimetry.

ISSN:0008-4042    

DOI:10.1139/v80-447

出版商:NRC Research Press    

年代:1980

数据来源: NRC