摘要:

A kinetic spectrophotometric method for evaluation of pKahas been developed. In the present study this has been utilized towards the pKadetermination, in methanol, of the conjugate acids of 4-picoline, aniline, hydroxylamine, methoxyamine, and hydrazinium ion. For the first two cases the pKavalues determined by the present method could be compared with the potentiometrically measured values, in a methanol solvent, with satisfactory agreement. Our proposed method involves essentially the spectrophotometric determination of the rate of the acid catalyzed conversion ofp-nitrophenyl sulfate top-nitrophenol in methanol in the presence of the acidic species whose pKain this medium is required.

ISSN:0008-4042    

DOI:10.1139/v76-097

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Rate data for the acetolysis ofexo-norbornyl-sulfonates have been correlated with those for the correspondingendoisomers. It is shown that the slopes of the logkexovs. logkendoplots reflect the difference in delocalization between the transition states derived from theexoandendoisomers, respectively. The logkexovs. logkendoplot, which is comprised of the parent norbornyl sufonate and its derivatives substituted at the 5, 6, and 7 positions, has a slope of 1.11 ± 0.08, which establishes that σ bridging is absent in the transition state obtained from theexoisomer. A similar analysis of base-catalyzed hydrogen–deuterium exchange rates of norbornanones reveals thatexoproton exchange is more sensitive to substituent effects than the correspondingendoprocess.

ISSN:0008-4042    

DOI:10.1139/v76-098

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

When heated with a dicobalt octacarbonyl (Co2(CO)8) catalyst under synthesis gas, acetals of aromatic aldehydes (in contrast to aliphatic acetals) gave good yields of the products of reductive cleavage, but no products of hydroformylation. A mechanism is proposed to explain the products of cyclic acetals of benzaldehyde which yielded not only the expected hydroxy-ethers, but also considerable amounts of dibenzyl ethers. The room temperature reductive cleavage of aromatic acetals by pure HCo(CO)4in organic solvents indicates that HCo(CO)4might be the active species in the catalytic reductions. Since acetals of benzaldehydepara-substituted with electron-releasing groups cleaved faster than those substituted with electron-withdrawing groups, the mechanism probably involves a carbonium ion intermediate.The previously observed formation of dibenzyl ether during benzaldehyde reduction with cobalt carbonyl catalysts can now be explained via the reductive cleavage of hemiacetal or acetal intermediates.

ISSN:0008-4042    

DOI:10.1139/v76-099

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

The rate of addition of 2,4-dinitrobenzenesulfenyl chloride tocisandtrans3-NO2, 4-Cl, 4-CH3, 4-OCH3, 4-OC6H5, 4-OCH(CH3)2substituted-1-phenylpropenes has been measured in 1,1,2,2-tetrachloroethane at 25 °C and the product stereochemistry has also been determined. While a plot of logk2vs. either σ or σ+is linear a better correlation is obtained with σ. Such a linear relationship is obtained even though the product stereochemistry changes from stereospecific and nonregiospecific for electron-withdrawing substituents (3-NO2, 4-Cl) to regiospecific and nonstereospecific for electron-donating substituents (4-OCH3, 4-OC6H5, and 4-OCH(CH3)2). These results suggest that the rate determining step for all the additions is bridged and that any open ion is formed after this step.

ISSN:0008-4042    

DOI:10.1139/v76-100

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

The following properties have been investigated: the standard ionic free energy and ionic enthalpy of formation of In3+ion, in water at 25 °C. They are: ΔG0 = −22.9 ± 0.2 kcal mol−1, ΔH0 = −57.8 ± 0.2 kcal mol−1. The entropy of formation of InCl3(aq) has also been determined.In addition, the partially miscible systems indium trichloride – ethyl ether – water, and indium trichloride –n-butyl alcohol – water have been investigated.A solution of indium trichloride causes the inversion of cane sugar. On the assumption that this is due to hydrolysis, the hydrolysis constant has been calculated.

ISSN:0008-4042    

DOI:10.1139/v76-101

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

The rates of nickel(II)–murexide complex formation were studied in dimethylsulfoxide/nitromethane mixed solvents at 25 °C with the latter being an "inert" solvent, to elucidate the mechanism of the reaction. Results do not fit in detail with a D mechanism and the five-coordinated intermediate interpretation. Idmechanisms are able to explain the observations with and without invoking a nitromethane-containing intermediate, Ni(DMSO)5NM2+. Both mechanisms were tested with the aid of nmr data on solvation (second coordinate sphere nitromethane population). Ligand solvation unavoidably plays a major role in the determination of the encounter as well as the complex formation equilibrium. The simplest mechanism assumes an Idprocess in which the probability of encounter between Ni(DMSO)62+and murexide ion is quite sensitive to solvent composition.

ISSN:0008-4042    

DOI:10.1139/v76-102

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Dimethyltin chromate and basic dimethyltin and diphenyltin carbonates have been isolated for the first time. Structural features of these compounds, as well as of the previously known basic dimethyltin chromate, have been investigated by examining their infrared, Raman, and Mössbauer spectra. Infrared, Raman, and Mössbauer spectra of [Me2Sn(NCS)]2O have also been examined, and by comparing its spectroscopic data with those for (Me2Sn)2OCrO4, (Me2Sn)2OCO3, and (Ph2Sn)2O(CO3), possible structures have been suggested for the latter compounds. From the combined infrared and Mössbauer data, a structure is also proposed for Me2SnCrO4. All compounds are indicated to have polymeric structures with bridging CrO42−or CO32−.

ISSN:0008-4042    

DOI:10.1139/v76-103

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

A13C nmr investigation of the protonation in sulfuric acid of the aliphatic ketones MeCOR (R = Me, Et,i-Pr,tert-Bu), 3-pentanone, and the cyclic ketones from cyclobutanone through cyclooctanone is reported. With the exception of cyclobutanone which is considerably less basic, these ketones are all very similar in their basicity, with half-protonation in the region 73–78% H2SO4. The acidity dependence of the protonation is discussed; there appears to be a small dependence on molecular size.13C nmr is shown to be a suitable alternative to1H nmr in the study of the protonation of weak organic bases in strongly acidic solutions.

ISSN:0008-4042    

DOI:10.1139/v76-104

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Haplophytine crystallizes as the methanolate in the orthorhombic space groupP212121witha = 13.874(4),b = 10.628(4),c = 22.890(9) Å,Z = 4. X-Ray structure analysis confirms that the previously assigned structure3is correct and that haplophytine undergoes reversible rearrangement on conversion to its dihydrobromide1. The dimensions of3provide evidence supporting previous interpretations of unusual features of the infrared and proton magnetic resonance spectra of haplophytine.

ISSN:0008-4042    

DOI:10.1139/v76-105

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Fatty acidN-hydroxysuccinimide esters have been prepared from the thallium(I) salt ofN-hydroxysuccinimide and the corresponding acyl chlorides in essentially quantitative yields. These active esters were used for acylation of amino acid esters in organic solvents, or of free amino acids in aqueous medium. The title compounds were found to be selective towards the side chain amino group of lysine. An efficient preparation of ϵ-N-benzyloxycarbonyl-L-lysine using benzyl succinimidyl carbonate is described.

ISSN:0008-4042    

DOI:10.1139/v76-106

出版商:NRC Research Press    

年代:1976

数据来源: NRC