摘要:

We have built a titration calorimeter that is suitable for measurements on colloidal suspensions as well as more conventional chemical reactions in solution. This calorimeter has been used for investigation of a number of ion exchange reactions involving kaolinite and montmorillonite clays. Results of these measurements have led to cation exchange capacities, to enthalpies of ion exchange reactions, and also to equilibrium constants for some of these same reactions. These calorimetrically determined cation exchange capacities and equilibrium constants agree well with corresponding quantities obtained by way of conventional methods based on chemical analyses. It has been demonstrated that titration calorimetry is a useful and convenient method for investigation of ion exchange in clays.

ISSN:0008-4042    

DOI:10.1139/v81-424

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

A new type of luminescent label has been synthesized and a range of carbohydrates has been derivatized with various fluorescent probes. Amine-containing labels were readily transformed with chloroacetylchloride into the corresponding fluorescent chloroacetamide reagents1–4. Suitably blocked monosaccharides containing either a free thio9, hydroxyl11, or carboxyl17functionality have been conjugated with (a) 4-chloroacetamido labels1and2, (b) with 4-aminobenzophenone5, and (c) with 1-dimethyl-1-aminonaphthalene-5-sulfonylchloride21, to form the fluorescent carbohydrate conjugates10,16,18, and20. Direct derivatization of the unblocked disaccharides22and23was achieved by reductive amination with amines5and7and sodium cyanoborohydride affording the 1-deoxyglycit-1-yl derivatives24–26, which were characterized by13C nmr spectroscopy. The synthesis of fluorescent polysaccharides is exemplified by the condensation of 9-anthraldehyde with chitosan either via Schiff 's base formation to afford32, or via reductive alkylation to form33.

ISSN:0008-4042    

DOI:10.1139/v81-425

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The seven hexahaloantimonate anions in the series [SbClnBr6−n]−have been prepared and their antimony-121 nmr spectra show that for [SbCl4Br2]−, [SbCl3Br3]−, and [SbCl2Br4]−, only thecisisomers are present in acetonitrile solution. The pairwise additivity model for central atom shielding has been used for configuration assignments. Models relevant to the higher incidence ofcisovertransisomers are discussed. The nuclear shielding of121Sb is the most sensitive to halogen substitution of all the elements whose halide chemical shifts have been studied. Antimony shieldings exhibit normal halogen dependence, with bromine substitution causingupfieldshifts relative to chlorine substitution.

ISSN:0008-4042    

DOI:10.1139/v81-426

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

A detailed analysis of the high field (400 MHz)1H nmr spectra of the basic antitumor antibiotics saframycin A and C in CDCl3, C6D6, and in aqueous DMSO solutions has been carried out. Selective double irradiation experiments permitted the unambiguous assignment of all the proton chemical shifts and coupling constants. Consideration of the magnitudes of the latter together with specific nOe experiments permits assignment of molecular geometry and average conformations in solution. Selective shifts occurring in DMSO–D2O solutions upon addition of CF3COOD identified the 12-N atom as the site of protonation which result bears directly on the acid promoted binding of these antibiotics to DNA templates as part of their cytotoxic action.

ISSN:0008-4042    

DOI:10.1139/v81-427

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The systems triethylamine–methylethylketone–dimethylsulfoxide and triethylamine–methylethylketone–formamide have been studied by the methods of isothermal equilibrium and thermal analysis. At least in the case of the system triethylamine–methylethylketone–dimethylsulfoxide, the equilibrium conditions have been completely established with respect to concentration and temperature. From these data a solid model can be constructed, as was previously done for the system nicotine–water–methylethylketone. It appears that the miscibility is greater in the system involving dimethylsulfoxide than in the system involving formamide.

ISSN:0008-4042    

DOI:10.1139/v81-428

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The polarographic and voltammetric behaviour of dibiphenylene-ethene (DBPE) has been studied in benzonitrile, acetonitrile, propylene carbonate, acetone,N,N-dimethylformamide,N,N-dimethylacetamide, dimethylsulfoxide,N,N-diethylformamide, pyridine, and ethylenediamine. The two successive reversible electron transfers have been observed in all these solvents. The separation between the formal potentials of DBPE/DBPE−•and DBPE−•/DBPE2−systems was found to vary with the properties of solvents and with the kind of supporting elecrtrolyte cations (tetraethylammonium and sodium perchlorates were used as electrolytes). The variation of redox potentials both with the solvent and the cation is discussed in terms of the donor–acceptor concept for solvent–solute interaction. Numerical analysis using both the values of the donor numbers and the acceptor numbers leads to successful description of experimental results. It has further been observed that DBPE2–dianion is protonized in ethylenediamine solutions.

ISSN:0008-4042    

DOI:10.1139/v81-429

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The formylation of 2-arylpyrroles and methyl 5-arylpyrrole-2-carboxylates (with aryl = benzyl, 2′-thienyl, 3′-thienyl, 2′-furyl, and 3′-furyl) is performed by the Vilsmeier reaction. The orientation of this electrophilic substitution is discussed. The structure of the aldehydes obtained is established by proton nmr data.

ISSN:0008-4042    

DOI:10.1139/v81-430

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Explicit and implicit surface tension equations have been derived using both mole fraction and volume fraction statistics and have been applied to a variety of binary polar–polar, non-polar–non-polar, and non-polar–polar organic systems with good success. Average errors of less than 1% are found for a large variety of such systems with the assumption of ideal chemical potential equations and molar surface areas calculated from bulk density values. These equations are found to be valid for those systems with surface tension differences of 20 ergs/cm2or less. Systems with surface tension differences larger than this value would require the inclusion of activity coefficient effects.

ISSN:0008-4042    

DOI:10.1139/v81-431

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The synthesis of the title compound is described.

ISSN:0008-4042    

DOI:10.1139/v81-432

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The temperature coefficient of cation mobility, dμ/dT, at constant gas densityn, is positive and increases with increasingn. The increase of temperature coefficient is attributed to the clustering of molecules about the ion. However, the temperature coefficient is positive even for the mass-identified, unclustered CO3−ion in N2gas (Eisele, Perkins, and McDaniel. J. Chem. Phys. 1980). The energy dependence of the cross section for the scattering of CO3−by N2was deconvoluted from the (μn,T) data. The cross section decreases with increasing energy in a manner that implies sticky collisions (associative interactions) at energies <0.1 eV, and essentially hard core collisions at higher energies. The scattering of CH5+(?) ions by CH4behaves similarly. The cross section in methane is larger than that predicted by the simple polarization potential at all energies. In the low density gas the ion mobility is controlled by collision with one molecule at a time, and μn ≈ constant. In the dense liquid the mobility is governed mainly by viscosity, and μη ≈ constant. The transition region is, which corresponds toA plot of μη against η for several hydrocarbons ranging from methane ton-hexane is nearly independent of molecular size in both the liquid and gas pha

ISSN:0008-4042    

DOI:10.1139/v81-433

出版商:NRC Research Press    

年代:1981

数据来源: NRC