摘要:

The adsorption isotherms of phenanthrene and its hydrogenated derivatives, of naphthalene, and of tetralin on Raney nickel have been determined by chromatographic studies. The adsorption of these molecules on Raney nickel depends on the number of π electrons and on the position and orientation of hydrogen atoms that can interfere with the interaction of the π electrons with the catalyst.Keywords: adsorption, phenanthrene, chromatographic studies.

ISSN:0008-4042    

DOI:10.1139/v89-059

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Thiochroman-4-one and cyclohexanone have been converted into the corresponding α-oxosulfines and the behaviour of these reactive intermediates with a range of alkenes and alkynes has been examined. In contrast to some earlier work, the major reaction pathway does not involve formation of the initially expected Diels–Alder adducts but instead a series of adducts involving electrophilic addition to the alkene or alkyne, with concomitant deoxygenation and incorporation of chlorine. The structures of these adducts have been determined by the usual spectroscopic means and, in two representative cases, by X-ray crystallographic analysis. The crystal structures, which include unusual features such as relatively short S … O nonbonding contacts, are discussed in detail.Keywords: (α-oxo)sulfines, sulfenic acids, X-ray analysis, electrophilic addition.

ISSN:0008-4042    

DOI:10.1139/v89-060

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Modification of several semiconductors material surfaces with H4SiW12O40•nH2O have been carried out to produce an increase in the open circuit photopotential at the semiconductor/electrolyte interface (Voc) without changing the flat-band potential. The augmentation ofVocis shown to be attributed to a decrease of the minority carriers recombination at the semiconductor/electrolyte interface along with the suppression of Fermi level pinning. The enhancement ofVocand the electrocatalytic activity of the hydrogen evolution reaction in acidic medium of the derivatized electrodes is attributed to the Fermi level unpinning.Keywords: photoelectrodes, photoelectrocatalysis, pinning, modification improvement.

ISSN:0008-4042    

DOI:10.1139/v89-061

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

This study was designed to answer the question whether the chromatographic performance of porous polymers — serving here as a model system for pressure-sensitive separation media of relatively large mass transfer resistance — could be improved (a) by imposing on them a chromatographically favorable, extrinsic macrostructure and (b) by protecting that macrostructure against physical deformation. Packed-column gas chromatography was used as the test system.Protected porous polymers (PPP's) were synthesized from pure divinylbenzene (DVB) inside conventional diatomaceous supports, using various amounts and types of porogens. The non-extractable polymer loads ranged from 10 to 40% and conformed to (i.e. formed layers on) the diatomaceous macrostructures. The best plate numbers were in excess of 4000/m on a 100/120 mesh Chromosorb W base. The mass transfer resistance of these materials was very low and permitted high flow rates. The PPP's could be used up to 280 °C and did not appear to suffer deformation; in fact, the polymer appeared to shield the diatom supports from abrasion. The data indicate that the porous polymer deposits had relatively high specific surface areas, and produced a relatively large value for the free energy of sorption per methylene group, as compared with conventional porous polymer beads. Otherwise, protected and unprotected types of porous polymers had similar chromatographic characteristics.Keywords: porous polymer, poly(divinylbenzene), gas chromatography, protected polymer, diatoms.

ISSN:0008-4042    

DOI:10.1139/v89-062

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

A wide variety of mono-, di-, and tri-substituted tin compounds are transformed to, and transmitted as, chlorides, bromides, or iodides on injection into a gas chromatographic system doped with HCl, HBr, or HI, respectively. This transformation occurs directly from some thirty-odd analytes such as organotin oxides, hydroxides, organic esters, and other halides including fluorides. Three germanium compounds appear to behave similarly. A conventional, packed-column gas chromatographic set-up with flame photometric or flame ionization detector can tolerate the necessary acid doping. Compounds such as bis(tributyltin) oxide will elute, as halides, in subpicogram amounts. If the dopant flow is turned off, the packed column can act as a hydrogen halide reservoir for several days of operation. The transformations of tributyltin species into the halide form are generally fast on the timescale of chromatographic processes, i.e. sharp peaks result from the use of mixed hydrogen halides, and the retention time of mixed-halide peaks can be adjusted by varying the dopant composition.Keywords: organotins, gas chromatography, derivatization, acid doping, photometric detection.

ISSN:0008-4042    

DOI:10.1139/v89-063

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

A new synthesis of monosubstituted tetraarylporphines is described based upon the soluble polymer supported synthesis strategy. Low molecular weight poly(ethylene glycol) is chloromethylated at both ends. These ends are then used to build up the polymer-bound ether of 5-(4′-hydroxymethyl)-10,15,20-tritolylporphine, which, after purification of the polymer, can be cleaved in high yield with TiCl4. While the method offers useful conveniences, such as the ease of separation and purification of the desired material, the overall yield is low: 100 mg from 40 g of polymer. Oligomerization of the polymer during chloromethylation increases the polymer molecular weight and thereby decreases the number of end groups per gram of polymer.Keywords: porphyrin, tetraaryl, monosubstituted poly(ethylene glycol) oligomerization, polymer-supported synthesis.

ISSN:0008-4042    

DOI:10.1139/v89-064

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

The structure of coprinolone (1), an oxygen-bridged protoilludane from the W2 isolate of the fungusCoprinuspsychromorbidus, has been elucidated by chemical transformations and detailed1H and13C magnetic resonance studies, including homo- and heteronuclear correlation spectra. The1H–1H coupling data and nuclear Overhauser difference spectra for1and derived isomers led to the establishment of its stereochemistry. A second metabolite was identified as Δ6-coprinolone (20) by spectroscopic results. Confirmatory evidence in support of the structures was obtained from the labelling patterns of the compounds from cultures supplemented with sodium [1,2-13C2]acetate.Keywords: coprinolone, Δ6-coprinolone, protoilludane, sesquiterpenes, NMR.

ISSN:0008-4042    

DOI:10.1139/v89-065

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Rates and equilibria for the deprotonation of four benzylic ketones containing pyridinium substituents (1,2,5, and6) have been investigated in basic aqueous solution (ionic strength 0.1) over the range 15–45 °C, and thermodynamic and activation parameters have been evaluated. Similar data are also reported for the deprotonation of nitroethane. The kinetic preference for hydroxide ion addition to the carbonyl group in competition with the thermodynamically preferred enolate ion formation, which was previously reported for the 1-methyl-4-phenylacetylpyridinium cation (1) and its 3-phenylacetyl isomer (2), is also found for the 1-(1-methyl-2-oxo-2-phenylethyl)pyridinium cation (6). Rates of equilibration of the 1-(2-oxo-2-phenylethyl)-pyridinium cation (5) with its enolate ion conjugate base are too rapid to allow investigation by stopped-flow spectrophotometry. For the hydroxide ion catalyzed deprotonation of each of1,2,6, and nitroethane,is more negative than ΔS0. This difference, which represents the entropy of activation for protonation of the conjugate base of each of these carbon acids by water, is approximately constant at = −4.9 ± 0.5 cal deg−1 mol−1.Keywords: carbon acids, kinetic studies, deprotonation, activation parameters, pKavalues.

ISSN:0008-4042    

DOI:10.1139/v89-066

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

3-Benzoylpyrroles with a substituent on the pyrrole ring have been synthesized. Both the iodination and chlorination gave only the 2,4 derivatives while isopropylation gave mixtures of the 2,4 and 2,3 compounds. No 3,4 compounds were obtained. Both steric and electronic effects seem to determine the substitution pattern. The Cr(CO)3complexes (Cr on the benzene ring) were prepared and these complexes, together with the uncomplexed pyrroles, were studied by IR,1H-NMR, and ESR of the radical anions from theN-methylpyrrole derivatives. For the 2,4 compounds, the substituent on the pyrrole ring has relatively little effect on the spectral parameters of the benzene ring indicating relatively little electron delocalization between the two rings. 3-Benzoyl-2-isopropylpyrrole, however, gives an ESR spectrum very different from the other compounds.Keywords: benzoylpyrroles, tricarbonylchromium, ESR, chlorination, isopropylpyrroles.

ISSN:0008-4042    

DOI:10.1139/v89-067

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Various statistical and empirical theories of ultrasonic velocity have been applied to a binary liquid mixture (benzene + nitrobenzene) at elevated pressures and their validity have been tested. A pressure-dependent study of ultrasonic velocities has been made at three different temperatures (293.15, 303.15, and 313.15 K). The agreement between the theory and experiment is found to be satisfactory.Keywords: ultrasonic velocity, benzene + nitrobenzene, pressure dependent, theoretical evaluation, binary mixtures at elevated pressures.

ISSN:0008-4042    

DOI:10.1139/v89-068

出版商:NRC Research Press    

年代:1989

数据来源: NRC