摘要:

The subject of acidity functions is reviewed, with emphasis on modern developments.H0and other scales determined in acid media, using the Hammett cancellation assumption (zero'th order approximation) are discussed briefly. The extension to strongly basic systems is also documented. Literature references to acidity function scales in aqueous acid, aqueous acid/organic solvent, and aqueous base media are tabulated, together with those in aqueous base/organic solvent mixtures at both variable and fixed base concentration. Over 400 acidity functions are referenced, including several electrochemical scales. Various approaches to developing universal functions from the data are discussed. Proton activity scales, based on the Yates–McClelland method ofdetermination, and on electrochemicalHGFscales, are prominent among these. Carpentier's method is mentioned, and the first-order approximation, assumed linearity among log activity coefficient ratios, is used to introduce the Bunnett–Olsen and excess acidity (X-function) methods. A brief critical discussion of which method to use is provided. Future developments anticipate the second-order approximation, with a quadratic dependence of log ionization ratios uponX-functions. The review cites 337 individual references.

ISSN:0008-4042    

DOI:10.1139/v83-388

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

The conformational and dynamic properties of the stereoisomers of 4-methyl-5,6-benzo-2-oxo-1,3,2-dioxathiepin (5) and of the 4,7-dimethyl derivative (6) have been investigated by1H and13C dnmr methods, as well as by ir spectroscopy. Analysis of the nmr spectra at low temperature (−125 °C), together with the conformational interpretation of the stretching vibration bands of the S = O bond in the ir spectra, indicate that the most stable conformations detected for solutions in CHF2Cl areC-a (82%) andTB-t-Mec(18%) for5a,TB-c-Mec, (96%) andTB-c-Mea, (4%) for5b,C-a for6a,TB-t-Mec,c-Mec, for6bandC-e for6c. The substituent effects of a methyl group at the benzylic position on both the conformational and dynamic properties of the seven-membered sulfite are discussed.

ISSN:0008-4042    

DOI:10.1139/v83-389

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

Simmons-Smith cyclopropanation of the trimethylsilyl enol ether of norbornenone has been found to generate the 2-trimethylsilyl ether of homoquadricyclene, homoketonization of which affords the symmetrical tricyclo[3.2.1.02,7]octan-4-one regiospecifically with high stereoselectivity favoring inversion of configuration.

ISSN:0008-4042    

DOI:10.1139/v83-390

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

Racemic and enantiomericp-nitrobenzyl carbapen-2-em-3-carboxylates3,3a, and3bwere prepared starting from inexpensive sorbic acid through the key intermediates, azetidinone esters4, thus establishing a total synthesis of thep-nitrobenzyl ester of a natural product SQ 27,860. Optical resolution was achieved readily on azetidinone menthyl esters,12. The absolute configurations were also established.

ISSN:0008-4042    

DOI:10.1139/v83-391

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

The hydrolysis of phosphoranes Ph2P(pfp)Cl, Ph2P(pfp)OR, PhP(pfp)(OR)2, and (RO)3P(pfp), containing a perfluoropinacolyl (pfp) ring, occurs under neutral, basic, or acidic conditions and leads to the formation of acyclic perfluoropinacolyl products, i.e. R2P(O)OC(CF3)2C(CF3)2OH, as determined by1H,19F,31P,13C nmr and ir studies. In the presence of a base, all trifluoromethyl groups in Ph2P(O)OC(CF3)2C(CF3)2OH are equilibrated, as verified by19F and13C nmr; and from the variable temperature19F nmr line-shape analysis the activation parameters for this exchange process were found to be:Ea = 36.0 ± 3 kJ mol−1, ΔH≠ = 33.5 ± 3 kJ mol−1, ΔS≠ = −86 ± 8 J K−1 mol−1,. The reactions of phosphoranes with HF were briefly investigated.

ISSN:0008-4042    

DOI:10.1139/v83-392

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

The gas phase reactions of S(1D2) and S(3PJ) atoms with alkynes have been studied by photolyzing COS in the presence of CH≡CH, CF3C≡CH, and CF3C≡CCF3. In the reactions with CH≡CH, CS2, benzene, and thiophene were formed; with CF3C≡CH, eight products were found with disubstituted thiophenes and trisubstituted benzenes as the major products. In the case of CF3C≡CCF3, only perfluorotetramethylthiophene was detected at low conversion but at long photolysis several new products were observed. Many of the reaction products characterized here have not been reported before.The formation and distribution of the reaction products could be rationalized by an overall mechanism in which the formation of the highly reactive primary adducts, thiirene and thioformylmethylene, is followed by bimolecular reactions yielding the principal end products. The formation of minor products could be explained by secondary photoisomerizations, secondary photolysis, and by secondary decompositions and the secondary reactions of sulfur atoms with primary products.

ISSN:0008-4042    

DOI:10.1139/v83-393

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

The far infrared and Raman spectra of polyerystalline lithium formate monohydrate and the Rayleigh wing scattering of its aqueous solutions are reported. Three new bands in solid and bands due to librations of HCOO−and the quasi-tetrahedral structure of water in solutions have been identified.

ISSN:0008-4042    

DOI:10.1139/v83-394

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

The fungusPotebniamycesgallicolan. sp. has been isolated from cankered swellings of western hemlock (Tsugaheterophylla(Raf.) Sarg.) produced by the dwarf mistletoe (Arceuthobiumtsugense(Rosendahl) G. N. Jones), and has been implicated in the induction of disease in the infected trees.P.gallicolawas cultured on malt extract, and four isoprenylated pentaketide metabolites were isolated by extraction; these were identified as the known compounds fuscin1and dihydrofuscin2, and two related compounds secofuscin3and dihydrosecofuscin4, not previously reported in nature.

ISSN:0008-4042    

DOI:10.1139/v83-395

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

A new nitration technique, using nitric acid in the presence of stannic chloride in dichloromethane, has been extended to a series of benzofurans. The ease of performing the reaction as well as the diversity of products that can be obtained under various experimental conditions make it a worthwhile technique. [Journal translation]

ISSN:0008-4042    

DOI:10.1139/v83-396

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

The photochemical reaction between benzene and maleic anhydride or benzene and maleimide affords respectively anhydride6aand imide6b. Unequivocal structures6aand6bwere assigned on the basis of an X-ray crystal structure determination of amide5derived from imide6b. Because of pronounced activity (e.g., PS T/C 206 at 50 mg/kg) against several of the U.S. National Cancer Institute's key experimental tumor systems, imide6bhas been designated mitindomide and is being prepared for eventual clinical trial.

ISSN:0008-4042    

DOI:10.1139/v83-397

出版商:NRC Research Press    

年代:1983

数据来源: NRC