摘要:

Condensation of 4-substituted 3-(4,4-dimethyloxazolin-2-yl)-1,4-dihydropyridylacetic acids3with the C-2p-bromophenacyl esters of 6-aminopenicillanic acid salt4andD-α-aminobenzylpenicillin8afforded the respective 1,4-dihydropyridylacetic acid analogs6and10which exhibited moderate antibacterial activity toward Gram-positive strains. The 6-APA derivatives6exhibited dual1H nmr resonances for H2′, H2, H5, and one of the C3-Me groups, suggesting the presence of two rotamers which differ in configuration at the carbonyl-to-nitrogen bond. TheD-aminobenzylpenicillin derivatives9may exist in more than one conformation, one of which may be an intramolecular hydrogen bonded species such as11.

ISSN:0008-4042    

DOI:10.1139/v85-091

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Partial molar volumes of water and ethylammonium nitrate EAN are determined accurately in all water–EAN mixtures, between pure water and pure fused salt at 298 K. It has been found that the partial molar volume of water decreases linearly with molar fraction of salt,x, in concentrated solution of EAN (C > 2 mol L−1,x > 0.04). The main thermodynamic relations are established to describe the volumetric behaviour of salt, water, and solution. It has been shown that the intrinsic volume of salt can be identified roughly with the molar volume of the pure fused salt and the value of apparent molar volume of water with the actual volume of water in solution.

ISSN:0008-4042    

DOI:10.1139/v85-092

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The complexestrans-[RhX(CO)PPh3)2] (1, X = Cl, Br, I) react with CO to form [RhX(CO)2(PPh3)2] (2), and not to formcis-[RhX(CO)(PPh3)2]. Complexes2contain equivalent axial carbonyl ligands. It is proposed that a series of dicarbonyl complexes, including2, is formed during decarbonylation reactions catalyzed by1.

ISSN:0008-4042    

DOI:10.1139/v85-093

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The reaction between 2,2-di(4-nitrophenyl)-1,1,1-trifluoroethane and the alkoxide bases ŌCH3, ŌC2H5, ŌnC4H9, ŌCH(CH3)2, and ŌC(CH3)3in their corresponding alcohol solvents is a multistep reaction with several intermediates: 2,2-di(4-nitrophenyl)-1,1-difluoro-1-alkoxyethane (A), 2,2-di(4-nitrophenyl)-1-fluoro-1-alkoxyethene (B), 2,2-di(4-nitrophenyl)-1,1-dialkoxyethene (C), 2,2-di(4-nitrophenyl)-1,1-difluoroethene (D), and 4,4′-dinitrobenzophene (E). Rate constants and activation parameters have been measured for the appearance of the two stable products B and C. The kinetic deuterium isotope effects for the appearance of B fell in the range ofkH/kD = 1 to 2 at 25 °C for the primary and secondary alkoxides, whereaskH/kD = 5.4 at 30 °C for the appearance of D withtert-butoxide. Exchange experiments showed that H/D exchange took place between the substrate and solvent to the extent of 100% with methoxide, 50% with ethoxide and isopropoxide, and 0% withtert-butoxide. It is concluded the HF elimination from the substrate follows an (ElcB)Rmechanism with methoxide/methanol, changing to (ElcB)Ior E2 withtert-butoxide/tert-but

ISSN:0008-4042    

DOI:10.1139/v85-094

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The crystal structures of the title compounds have been determined from X-ray data collected on a four-circle diffractometer and refined by the full-matrix least-squares method. The former compound crystallizes in the orthorhombic system, space groupPbcn, witha = 14.346(8),b = 7.239(1),c = 17.276(2) Å, and has been refined to a conventionalRfactor of 0.043 for 890 observed reflections. Corresponding results for the latter compound are monoclinic,P21/n,a = 12.222(4),b = 7.482(2),c = 14.170(8) Å, β = 94.06(4)°,R = 0.060 for 2128 observed data. The triazine rings of both compounds exhibit short N(1)—N(2) bonds and tetrahedral geometry at C(4); however, the ring is puckered in the first compound but flat in the second. Molecules in both crystals are linked byhydrogen bonds.

ISSN:0008-4042    

DOI:10.1139/v85-095

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The crystal structures of C(CH2NH3)4Cl4(P42/n,a = 9.503(1) Å,c = 6.549(1) Å,Z = 2) and C(CH2NH3)4(SO4)2(P212121,a = 8.382(2) Å,b = 10.508(3) Å,c = 14.400(3) Å,Z = 4) have been determined. Both crystals contain strongbonds; in the sulfate the hydrogen-bonding network is particularly extensive. The thermal motion of the cation can be described satisfactorily as a rigid-body motion.

ISSN:0008-4042    

DOI:10.1139/v85-096

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The results obtained show that, in a strongly complexing medium, mercury is oxidized to mercury(II) with the concomitant formation of more highly oxidized complexes likeand. When the reactional medium is less strongly complexing, however, the formation of complexes with Hg(1) can be considered. This complicates the exploitation of titration curves resulting from the progressive transformation of the complexes of mercury(II) into complexes of mercury(I) by contact with metallic mercury. Compared to the behavior observed in numerous organic solvents, the behavior of these systems is not fundamentally different.

ISSN:0008-4042    

DOI:10.1139/v85-097

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Cationic micelles of hexadecyltrimethylammonium bromide, chloride, and hydroxide (CTABr, CTACl, and CTAOH) greatly enhance the stability of anionic σ-complex formed by hydroxide ion and 1,3,5-trinitrobenzene (TNB). The counterion binding to the micellar head groups is assumed to vary but is governed by a distribution constant. Different distribution constants are used for different types of counterion. Using this treatment, the rate constant – surfactant concentration profiles for the reactions of TNB with hydroxide ion in CTAOH, CTABr, and CTACl can all be satisfactorily accounted for, yielding consistent results in various conditions. The ion distribution constants,KOH = 55 mol−1 dm3,KBr = 1800 mol−1 dm3, andKCl = 420 mol−1 dm3and the rate constantKM = 3600 s−1are obtained. In view of the success of this treatment, the assumption of a constant β value associated with the pseudophase model at best could only be viewed as an approximation, valid only for micellar systems with tightly bound counterions such as those in the micelles of CTABr.

ISSN:0008-4042    

DOI:10.1139/v85-098

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The synthesis of the linked porphyrin–cyclodextrin3and its zinc complex4is described and their characterization by1H nmr,l3C nmr, circular dichroism, ultraviolet, and infrared spectroscopy is reported. The linked porphyrin–cyclodextrin compounds exhibited perturbed electronic absorption and emission spectra which are consistent with their adopting two conformations, one extended with little interaction between the porphyrin and cyclodextrin, and the other folded with the cyclodextrin weakly complexed to the porphyrin. Quenching of the porphyrin excited state of3by benzoquinone was examined by measurement of the fluorescence lifetime as a function of quinone concentration; the results suggest that the porphyrin excited state can be quenched intermolecularly by benzoquinone and also intramolecularly by quinone complexed within the cyclodextrin cavity.

ISSN:0008-4042    

DOI:10.1139/v85-099

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The proton transfer chemical ionization mass spectra of eleven C5H10O isomers have been obtained using H3+, N2H+, HCO+, and D3+as reagent ions. The chemical ionization mass spectra in combination with isotopic labelling and metastable ion studies have made it possible to elucidate the major fragmentation reaction channels of the C5H11O+ions formed and their dependence on precursor structure. From collision induced dissociation studies nine stable distinct C5H11O+ion structures have been identified; protonated 3-methylbutanone and protonated 2,2-dimethylpropanal readily interconvert by a pinacolic – retro-pinacolic rearrangement.

ISSN:0008-4042    

DOI:10.1139/v85-100

出版商:NRC Research Press    

年代:1985

数据来源: NRC