摘要:

Aqueous solutions of 15 acids with pKa < 1 were studied by ir spectroscopy. The ir bands of the acid molecules demonstrate that the proton acceptor strength of the anions increases in the series CF3SO3−, HSO4−, ClO4−, HSeO4−, C6H5SO3−, NO3−. At very high concentrations (number of H2O/acid molecules,n < 1) easily polarizablehydrogen bonds are formed causing continuous absorption in the ir spectra. The deeper well of the double minimum energy surface of these hydrogen bonds at the beginning of the above series is present at the water molecule, and at the end of the series at the anion. The H3O+character of the vibrations of the H+OH2groups increases with increasingn. Forn > 1 the weight of proton limiting structureIIincreases and more and more protons transfer from the acid–water into the water–water hydrogen bonds, i.e., they are present in H5O2+groupings which are embedded in the whole hydrate structure network. H3O+vibrations are no longer found. The easily polarizable hydrogen bond in these groupings causes continuous absorption and the water molecules of these groupings cause broad bands. Of all acids studied, this group is the only cause of continuum in the more diluted solutions. The absorbance of the continuum per H5O2+group atn = 2 increases in the series HClO4, CF3SO3H, H2SO4, H2SeO4, C6H5SO3H. This is because of the increasing polarity of the environment of the H5O2+in this series of acids. The position of the water bands in solutions withn = 6 can be used to characterize the hydrogen bond acceptor strength of the anions. The H2O scissor vibration shows that it increases in the series AuCl4−, PtBr62−, PtCl62−, ClO4−, BF4−, CF3SO3−, J−, HSO4−, HSeO4−, C6H5SO3−, C7H7SO3−, Cl−. Finally molecular quantities which determine the pKavalues of the acids (proton acceptor strength, hydrogen bond acceptor strength, and special interaction properties of the anions) are discussed.

ISSN:0008-4042    

DOI:10.1139/v80-051

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The ionization constant,K, oftrans-crotonic acid, and the first and second ionization constants,K1andK2, of adipic acid have been determined in water at seven different temperatures ranging from 15 to 45 °C with the help of the cells without liquid junction using silver – silver chloride and quinhydrone electrodes. The variations of pK, pK1, and pK2with temperature have been expressed by the equationsandFrom the temperature coefficient of the ionization constants, the standard enthalpy, entropy, Gibbs energy, and heat capacity changes of the corresponding dissociation processes have been calculated. Using the values of ionization constants of adipic acid, the standard potential of the Ag(s)/Ag2Ad(s)/Ad2−electrode, and the related standard thermodynamic quantities for the electrode processhave been calculated in water at those temperatures.

ISSN:0008-4042    

DOI:10.1139/v80-052

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The phytochemical investigation of the root ofSalmaliamalabaricumhas resulted in the isolation and identification ofn-triacontanol, β-sitosterol, and a new glycoside which was characterized as 5,7,3′,4′-tetrahydroxy-6-methoxyflavan-3-O-β-D-glucopyranosyl-α-D-xylopyranoside on the basis of spectral and degradative studies.

ISSN:0008-4042    

DOI:10.1139/v80-053

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Extensiveabinitiomolecular orbital calculations on six sulfonyl radicals (XSO2where X = H, CH3, NH2, OH, F, and Cl), the simplest sulfinic acid HSO2H3and its isomeric sulfone H2SO2, the HSO2−anion of sulfinic acid, the isomeric anion SO2H−, and for completeness, the SO2H radical are presented. By use of the STO-3G* basis set, which includesd-type polarization functions on second-row atoms, all geometrical parameters are varied until the total energy is minimized, subject only to certain symmetry restrictions specified for each system. The inclusion ofdorbitals on S is observed to affect the S—O bond lengths by as much as 0.45 Å. The calculations suggest that the radical site in sulfonyl radicals is significantly delocalized over the entire functional group and that the geometrical parameters of the SO2functional group in sulfonyl radicals are nearly independent of the substituent (r(S—O) = 1.47 ± 0.01 Å, < OSO = 123 ± 2°). Estimates of the X—S bond energy in CH3SO2, NH2SO2, and OHSO2are consistent with the chemistry of alkylsulfonyl and aminosulfonyl radicals and lead to an interesting prediction for alkoxylsulfonyl radicals. Furthermore the calculations yield lower total energies for HSO2H, HSO2−, and SO2H than for the respective isomeric forms H2SO2, SO2H−, and HSO2.

ISSN:0008-4042    

DOI:10.1139/v80-054

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

An nmr study of compounds isolated from the Schiff aldehyde reaction between pararosaniline hydrochloride, sulfur dioxide, and acetaldehyde has demonstrated that these adducts are α-anilinoalkylsulfonic acids. The evidence is incompatible with the other structures most often accepted in the literature,N-phenyl alkylsulfonamides. In combination with nmr spectra obtained from solutions of the Schiff reagent and the Schiff reaction and with literature spectrophotometric data, this result leads to a reasonable proposal for the mechanism of the colour development. The effects of the concentrations of the dye, acetaldehyde, and in particular, sulfur dioxide are explained and suggest that the dominant coloured species is a 2:1 acetaldehyde–dye adduct. The nmr results also reveal a kinetic/thermodynamic competition for acetaldehyde between the aniline of the dye and the aldehyde carbonyl leading to bisulfite addition. The relation of the Schiff test with acetaldehyde and the Feulgen test for aldehydes in biological samples is also discussed.

ISSN:0008-4042    

DOI:10.1139/v80-055

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The rate constants for rearrangement of the 2,2,5,5-tetramethyl-3-hexyn-1-yl radical to the 2,6,6-trimethyl-4-heptyn-2-yl radical have been measured from 45 to 88 °C by kinetic epr spectroscopy. The temperature dependence can be represented bywhere θ = 2.3RT kcal mol−1. This rearrangement, which must involve an intermediate vinyl radical of the methylenecyclopropane type, is much slower than analogous rearrangement of homoallyl radicals but comparable in rate to rearrangement of homobenzyl (neophyl) radicals.

ISSN:0008-4042    

DOI:10.1139/v80-056

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Infrared absorption bands in the OH stretching region of phenol in carbon tetrachloride solution have been recorded for various concentrations and at several temperatures between 25 and 60 °C. Factor analysis of the digitized spectra was carried out and the presence of three absorbing components in the OH stretching band was indicated at all temperatures in the range of 25–60 °C. The three components are assigned to monomer, linear dimer, and a polymeric species. It is suggested that the polymeric species is a cyclic trimer.Band contour resolution was carried out to obtain areas of the component bands. The variation of the monomer and dimer band areas with temperature was used to obtain a value for the enthalpy of dimerization of −15.8 ± 0.6 kJ mol−1.

ISSN:0008-4042    

DOI:10.1139/v80-057

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Carbon-13 nmr chemical shifts of a number ofE-silyl-alkenes containing the silyl substituent at ansp2carbon atom are presented. Assignments of the chemical shifts have been made by noting systematic variations in the spectra with changes in substituents and by comparison of the chemical shifts to those of the corresponding unsubstituted alkenes. The substituent effects observed were explained on the basis of the π-acceptor ability of the silyl substituents and the structure of the molecules. Comparing the13C nmr spectra of theE-silyl-alkenes and those of the corresponding unsubstituted alkenes, differential chemical shifts have been obtained which can be used as empirical substituent parameters for the prediction of the13C nmr spectra of otherE-silyl-alkenes not yet studied. It was also demonstrated that13C nmr spectroscopy can be used without resorting to special techniques (gated decoupling and the addition of paramagnetics) as an alternative method to the1H nmr for the quantitative analysis of mixtures of regio-isomerE-silyl-alkenes.

ISSN:0008-4042    

DOI:10.1139/v80-058

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Photolysis of 2-azido-4-thiochromanone 1,1-dioxide in benzene or dichloromethane leads to the formation of 2H-benzo[f]-1,2-thiazepin-5-one 1,1-dioxide, in very good yield. In contrast, the photolysis of the analogous sulfoxide was much more complex and no ring-expansion product could be isolated, although a small amount of a compound believed to be 2-aminothiochromone 1-oxide was formed. Several attempts to prepare the α-azidosulfide analogue, to compare its photochemical behavior, were unsuccessful and a rationale is proposed for the apparent instability of this member of the series.

ISSN:0008-4042    

DOI:10.1139/v80-059

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Dimethylsulfoxide (DMSO) has been photoionized at 10.0 and 11.7 eV over the pressure range 0.3–210 mTorr. The rate constant for the disappearance of DMSO+is 1.0 × 10−9 cm3 molecule−1 s−1, independent of photon energy. The major products at low pressure are CH3SO(CH3SO)CH3+and CH3SOHCH3+while at high pressure the ion series (DMSO)nH+predominates withn ≤ 5. In experiments with mixtures of DMSO and water or methanol very little mixed solvation of the proton was observed although isotopic D/H exchange between D2O and (DMSO)2H+is facile.

ISSN:0008-4042    

DOI:10.1139/v80-060

出版商:NRC Research Press    

年代:1980

数据来源: NRC