摘要:

Heats of hydrolysis have been measured for the trimethyl orthoesters of isobutyric, propionic, benzoic, methoxyacetic, chloroacetic, and cyanoacetic acids using aqueous acid with an organic cosolvent where necessary, and of the corresponding esters in alkaline solution. Solubilities or free energies of transfer from gas to aqueous solution have been measured, permitting calculation of the free energies of formation of the aqueous orthoesters, and by methods which we have published previously, calculation of the free energies of formation of the covalent hydrates of the esters, and the free energy changes for hydration of these esters.Using estimated pKavalues equilibrium constants were calculated for the addition of hydroxide to the esters. The data are in good agreement with the appropriate Marcus equation relating rate and equilibrium constants with a value forbof 8.99 ± 0.17. This line was used to estimate the equilibrium constant for addition of hydroxide, and thence of water, to some additional esters where only the rate constant was available. Rate constants for hydrolysis of methyl esters in aqueous solution at 25 °C were calculated from literature data, correcting for the effect of other conditions as necessary. From the equilibrium constants for addition of water we could estimate the rate constants for uncatalyzed hydrolysis; for the cases where this rate constant has been measured, the agreement was satisfactory. For acid catalyzed hydrolysis the data permit a test of the two alternative mechanisms considered previously, namely specific acid catalysis and general acid catalysis with hydronium ion acting as a general acid. For esters the mechanism is clearly specific acid catalysis, but for aldehydes and ketones it appears very likely that the mechanism is general acid catalysis.

ISSN:0008-4042    

DOI:10.1139/v80-201

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Natural abundance15N and31P nmr and dynamic13C nmr have been applied to the study of about fifty aminophosphines, in order to generalize the influence of the chemical factors which govern the electronic distribution of the nitrogen–phosphorus III bond. Factor and regression analyses of δ15N, δ31P, and1JP—Nvalues performed on different series of aminophosphines have shown that common factors and various correlations exist between the nmr parameters in the different kinds of derivatives. The statistical results are discussed in terms of topologic, electronic, and steric contributions. The nature of the different substituents of the nitrogen or phosphorus atoms governs the observed changes in screening, coupling constants, and the rotational barriers ΔG≠around the P—N bond, which are explained in considering the type of nitrogen and phosphorus hybridization, thepπ–dπdonation and the electronic states (ΔE−1approximation) of the P—N fragment.

ISSN:0008-4042    

DOI:10.1139/v80-202

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The kinetics of oxidation of benzaldehyde and acetophenone oximes by Tl(III) in aqueous medium has been studied. The reaction occurs in two consecutive steps: formation of a nitroso intermediate and its decomposition. The oxime forms a complex with Tl(III) leading to the rate equation: −d[oxime]/dt = K1/k2[oxime][Tl(III)]/(1 + K1[Tl(III)]). The formation of the final carbonyl product is inhibited by Tl(III), a resuit of the formation of a complex resistant to decomposition. Coordination of Tl(III) by chloride ions affects the rate of the above two steps. The reaction mechanism is discussed. [Journal translation]

ISSN:0008-4042    

DOI:10.1139/v80-203

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The magnitudes of18O-induced isotope shifts in13C nmr spectra of ketones and aldehydes are dependent on structure and range from about 0.05 ppm to 0.03 ppm for the carbon attached to18O. An increase in negative charge density on the carbonyl oxygen or conjugation to an aromatic ring reduces the size of the upfield shift. The shifts in [18O]alcohols are solvent-dependent, range from 0.03 ppm to 0.01 ppm, and tend to decrease in the order tertiary ≥ secondary ≥ primary ≥ phenols.

ISSN:0008-4042    

DOI:10.1139/v80-204

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

In the title ring System, the benzylic nitrogen (N7), whether substituted or not, is abnormally unreactive. Hydrolysis of the di-urethanes3aorboccurs readily at N6to give10aorb, but not at all at N7. In3dPd—H2removes very rapidly the benzyloxycarbonyl group at N6but only very slowly the one at N7. The product7is the first example of a diazetidine unsubstituted on nitrogen which has been fully characterized.N6in7or in10aorbcan be readily acylated (products24,13,14), acyloxylated (23a–c,3a,3b,11,12), or methylated (25). All efforts to induce similar reactions at N7in7or in its monosubstituted derivatives23or24failed.Diazetidine7is thermally very stable, but it is rapidly oxidized by a wide variety of reagents to 2,5-diphenyl-3,4-dimethylcyclopentadienone and nitrogen. There is no evidence for the intermediacy of the cyclic azo compound19, even when the oxidation is carried out at −50 °C.

ISSN:0008-4042    

DOI:10.1139/v80-205

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The diol2was converted by treatment with potassium iodide in polyhydrogen fluoride – pyridine into a mixture of the diiodide and homohypostrophene6. The diol10under the same conditions gave the ether14. Treatment of the mixture of5and6with sodium in boiling tetrahydrofuran gave an easily-separable mixture of6and7.

ISSN:0008-4042    

DOI:10.1139/v80-206

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The ionic addition of molecular bromine to tetracyclo[3.2.0.02,7•04,6]heptane (quadricyclene) has been investigated in a variety of solvent Systems. Depending upon the nature of the solvent, three or more of six dibromo and five solvent-incorporated adducts are isolable. A mechanism involving a series of ion-pairs and competitive edge-on vs. corner (end-on) attack is proposed.

ISSN:0008-4042    

DOI:10.1139/v80-207

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

A pulsed tunable laser Raman spectrometer is described. The relevant characteristics are: tunability in the range of 355–755 nm, peak power of > 100 kW, pulse duration 3.2 ns, spectral line width < 0.1 cm−1. Raman pulses can be studied in real time with a resolution > 10 ns while Raman spectra can be recorded with an experimental slit width > 0.5 cm−1. The overall performance of the instrument may be compared to that of a conventional cw laser Raman spectrometer having typical power levels of 100 mW. Spectroscopic measurements are discussed which demonstrate the capability of the apparatus to probe Raman processes which occur at the pico and microsecond time scale.

ISSN:0008-4042    

DOI:10.1139/v80-208

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The synthesis of a homologous series of new carboxylic acids substituted in the α-position of indan, tetralin, and benzosuberane is accomplished using an efficient general procedure. Cycliacylation of these acids and their corresponding β-isomers produces a complete series of tricyclic aromatic ketones.

ISSN:0008-4042    

DOI:10.1139/v80-209

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

not available

ISSN:0008-4042    

DOI:10.1139/v80-210

出版商:NRC Research Press    

年代:1980

数据来源: NRC