摘要:

Electrophilic cyclopropanes 1 bearing an extra aldehyde function are conveniently prepared starting either from the diazoacetal2or from the olefin3.

ISSN:0008-4042    

DOI:10.1139/v83-039

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

A precise analysis of the1H nmr spectrum of 1,2-dimethoxybenzene in benzene solution yields an accurate value for the proximate spin–spin coupling constant,, between theorthoring proton and the methyl protons. The latter also couple to other ring protons and these couplings are assessed. Comparison with some values in other anisole derivatives and with a variety of INDO MO FPT calculations ofstrongly implies the predominance of a planar conformation in solution. This implication disagrees with the interpretation of some other experimental and theoretical data. The mechanism of this proximate coupling is examined by the procedure of Barfield. It seems that the magnitude of the coupling is dominated by interactions involving the orbitals on the carbon atom of the methyl group.

ISSN:0008-4042    

DOI:10.1139/v83-040

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

The Hammett equation has for the first time been applied to the esterification in the gas phase ofm-MeO,p-MeO,m-Me,p-Me, H,m-NO2,m-Cl, andm-Br benzoic acids, catalyzed by AlPO4of the F type. It is shown that the Hammett equation could be applied to the adsorption equilibrium constant,KA, and to the apparent kinetic constant,TheKAandvalues used in this paper have been taken from a study by the same authors. Them-NO2benzoic acid is in disagreement with the general behavior of the other acids in the application of the Hammett equation to the adsorption process. Thep-MeO benzoic acid is in disagreement with the behavior of the acids in the application of the equation to the surface reaction. In these cases, the ρ values were negative. It can be deduced that a positive charge is generated in the adsorption process and in the surface reaction. The AAc2 mechanism is discussed according to the values of ρ, and a more detailed mechanism is proposed. The separation of the enthalpic and entropic contributions to the substituent effect is carried out.andare nearly 50% in the adsorption process. In the surface reaction, the entropie contribution is greater (72.5%) than the enthalpic (27.5%).

ISSN:0008-4042    

DOI:10.1139/v83-041

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

AlkylS-[3]betylates (S,S-dialkyl-S-3[(alkyloxy)sulfonyl]propylsulfonium salts), the first examples ofS-betylates (sulfonioalkanesulfonic esters), have been synthesized by two routes, and their suitability as intermediates in the transformation of alcohols by nucleophilic substitution reactions examined. They have been found to react readily in stoichiometric phase transfer processes, including substrate–reagent ion-pair reactions, like their previously studied nitrogen analogues, with the following particular features: (a) they may be used with basic nucleophiles (unlike [2]betylates), (b) they are more simply made from commercially available starting materials than [3]betylates, and (c) they can be made by a route that avoids a final alkylation step.

ISSN:0008-4042    

DOI:10.1139/v83-042

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

Salting constant measurements have been made on 1-naphthol, 2-naphthol, and 1-NO-2-naphthol using a distribution method at 298 K. In general, the order of the salting effect is similar to that for other acidic nonelectrolytes. However, a net salting-in is observed in the pair 1-NO-2-naphthol – NaF, and such an effect is interpreted by postulating hydrogen bonding. A comparison of results with those found for benzene, naphthalene, phenol, etc …, reveals that salt effects for organic nonelectrolytes depend upon the solute size for a given salt.Experimentalksare compared with those calculated using various salting theories. The agreement is not quantitative.

ISSN:0008-4042    

DOI:10.1139/v83-043

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

The location and the manner of union of theH0andHRacidity functions with −loghave been determined for aqueous HClO4, HCl, and H2SO4(H0only) through particularly careful and extensive indicator measurements in dilute and moderately concentrated solutions of these acids. These data were also used to evaluate and compare a number of different ways of extrapolating measurements made in concentrated acids down to dilute solution; over the limited range of acidity investigated, the traditional acidity function method, as commonly applied in the absence of an appropriate acidity function (i.e. in the form ofmH0), was found to be the least satisfactory of these extrapolative methods, and the Cox–Yates technique was found to be the best.

ISSN:0008-4042    

DOI:10.1139/v83-044

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

The synthesis and crystal and molecular structure of the dinitrato(trimesitylarsine)mercury(II) dimer are reported. The compound [HgAs(mesityl)3(NO3)2]2belongs to the monoclinic space groupP21/cwitha = 20.001(2),b = 17.591(5),c = 16.553(2), β = 99.991(6), andZ = 4; the asymmetric unit contains two independent half dimers. The structure was refined to a finalRof 0.0458 for 2631 observed reflections measured by diffractometer with 2 < θ < 20°. The crystal structure consists of discrete centrosymmetric dimeric molecules of [HgAs(mesityl)3(NO3)2]2separated by normal van der Waals distances. The mercury coordination in both dimersIandIIis characterized by three strong, nearly coplanar bonds (inIHg—As 2.476(3), Hg—O 2.41(2) and 2.20(2), and inIIHg—As 2.482(3), Hg—O 2.28(2) and 2.39(2), and three weaker Hg—O bonds in the range 2.55–2.90 Å. Both independent trimesitylarsine ligands have the same regular propeller conformation (Hg—As—C—C torsion angles of 45 to 50°) and the largest C—As—C angles (mean value 112.5(8)°) yet determined. The As(mesityl)3cone angle is 202°. The two independent dimers differ primarily in the orientation of the non-bridging nitrato groups. Nitrato vibrational and arsine1H nmr data are also presented for [HgAs(mesityl)3(NO3)2]2, which becomes monomeric in dichloroethane solution.

ISSN:0008-4042    

DOI:10.1139/v83-045

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

The redundancy-free internal valence force field of monomeric acetic acid is evaluated using CNDO/force calculations and least-squares refinement. The initial force field is set up by taking the interaction and bending force constants from CNDO force field and transferring the stretching force constants from the force fields of chemically related molecules. Vibrational frequencies of monomeric CH3COOH, CH3COOD, CD3COOH, and CD3COOD are used to refine the force constants. The experimental force field thus obtained is found to be reasonable when compared to the force fields of related molecules as well as on the basis of the frequency fits and potential energy distributions.

ISSN:0008-4042    

DOI:10.1139/v83-046

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

The specific conductivities and pH values of copper sulphate solutions in water were measured in the temperature range from 10 °C to 50 °C. The data, previously corrected by hydrolysis, were analyzed by means of the Lee Wheaton theory.This fit, for the evaluation of Λ0,R, andKAparameters, is quite satisfactory up to a maximum concentration of 25 × 10−4 moldm−3and the agreement between experimental data and the literature value for 25 °C is acceptable.

ISSN:0008-4042    

DOI:10.1139/v83-047

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

Stereospecific total syntheses of (±)-2-desoxystemodinone, (+)-2-desoxystemodinone, and (±)-stemodinol are described. Also described are the isolation of (+)-2-desoxystemodinone fromS.maritimaand its characterization. A strategy for the elaboration of the C/D ring systems of the stemodane diterpenoids, stemarin and aphidicolin, from a common 6-hydroxybicyclo[2.2.2]octan-2-one system is delineated and its efficacy is demonstrated by the synthesis of the stemodane diterpenoids and our previous synthesis of stemarin.

ISSN:0008-4042    

DOI:10.1139/v83-048

出版商:NRC Research Press    

年代:1983

数据来源: NRC