摘要:

Nickel(II) tetraisopropoxyaluminate undergoes alcoholysis reactions with various alcohols and acetylacetone to yield products with the composition: Ni[Al(OR)4]2(when ROH = methanol, ethanol, 2,2,2-trifluoroethanol, 2,2,2-trichloroethanol,n-butanol, and 1,3-dichloro-2-propanol); Ni[Al(O-i-Pr)(O-t-Bu)3]2(with tertiary butyl alcohol); Ni[Al(O-i-Pr)2(O-t-Am)2]2(with tertiary amyl alcohol); and Ni[Al(O-i-Pr)2(acac)2] (with acetylacetone). On the basis of their visible reflectance and infrared spectra along with molecular weights and magnetic susceptibilities, and octahedral geometry is tentatively suggested for these complexes in the solid state with indications of an equilibrium between tetrahedral and octahedral forms in solution. The alkoxy ligands have also been fitted into the spectrochemical and nephelauxetic series.

ISSN:0008-4042    

DOI:10.1139/v84-166

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

A Picker flow calorimeter has been used to obtain molar excess capacitiesthrough the concentration range at 25 °C for the systemswhere R is the alkyl group CnH2n+1, (n = 1, 2, 3, 4, 8, 12). Excess volumes have also been measured for the mixtures. Two contributions toandvEwere investigated: those associated with disordering the long alkyl chains and with steric hindrance. The steric hindrance contribution has been found to occur for molecules having a highly substituted central atom. The sign of this contribution is negative inhEand positive in, indicative of an ordering or loss of mobility for the molecules going from pure liquid to solution. Theresults confirm the more sterically hindered character of the ethyl and propyl derivatives already found withhE. The separation of the disorder and steric contribution is possible in systems involving long-chain compounds. It is found that the orientational order contribution diminishes more slowly with temperature than the steric hindrance effect. The trend ofvEin the series is reasonably well predicted by the Prigogine–Patterson–Flory theory.

ISSN:0008-4042    

DOI:10.1139/v84-167

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Reactions between Ni(II) and NaBH3CN in the presence of Ph2P(CH2)nPPh2 (n = 1, Dppm;n = 2, Diphos) have been studied. With Dppm, the main products are Ni(I)–CN–Dppm complexes and the nature of the actual product formed depends critically upon the reaction conditions. With Diphos, the products mainly involve coordinated BH3CN−in Ni(II)–Diphos complexes. Evidence from31P nmr and ir spectra are used to support proposed structural assignments.

ISSN:0008-4042    

DOI:10.1139/v84-168

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

PCP was pyrolyzed in air at 400°, 600°, and 800 °C and the yield of HCN produced was barely detectable at 400 °C, 2.3% at 600 °C, and 5.1% at 800 °C. Gas chromatography (gc) and gc/mass spectrometry (gc/ms) showed the only pyrolysis products produced at 400 °C to be phenylcyclohexane and 1-phenylcyclohexene with 60–70% of the PCP recovered. Only trace amounts of PCP survived the 600 °C pyrolysis, the majority of the pyroproducts being polynuclear aromatics (PNAs) with three or fewer rings. The 800 °C pyrolysis yielded minor amounts of four-ring PNAs, the remainder being similar to the 600 °C products but differing in the relative amounts. Minor amounts of aza-arenes were produced in the 600 °C and 800 °C pyrolyses and separation techniques are described.

ISSN:0008-4042    

DOI:10.1139/v84-169

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

The electrochemical reduction of fluoflavine2gives compound9to which we had previously assigned a hexahydroquinoxalino[2,3-b]quinoxaline structure. A crystallographic study of a diacetylated derivative of9shows that9is in fact 2-(o-aminoanilinomethyl)benzimidazole. This result permits us to propose a detailed reduction mechanism for2and its diacetyl derivative25.

ISSN:0008-4042    

DOI:10.1139/v84-170

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Olefins, dienes, and trienes can be hydrogenated in an aqueous–organic two-phase medium using the dimer of chloro(1,5-hexadiene)rhodium as the catalyst. Selective reduction of the double bond of α,β-unsaturated carbonyls occurs in high yields. These reactions occur at room temperatures and atmospheric pressure, and are simple to work-up.

ISSN:0008-4042    

DOI:10.1139/v84-171

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

A comparison of the1H and13C nmr parameters for the disaccharide derivatives βDGal(1→ 4)βDGlcO(CH2)8COOCH3(1), βDGalNAc(1 → 4)βDGalO(CH2)8COOCH3(2), and βDGal(1 → 3)βDGalNAcO(CH2)2CH3(3) allowed assignments of the signals observed for theasialo-GM2- andasialo-GM1-related synthetic haptens, βDGalNAc(1 → 4)βDGal(1→4)βDGlcO(CH2)8COOCH3(4) and βDGal(1 → 3)βDGalNAc(1 → 4)βDGal(1 → 4)βDGlcO(CH2)8COOCH3(5).1H nuclear Overhauser enhancement studies confirmed the conformational preferences for2and3predicted by HSEA calculation. Comparison of the1H and13C spectra indicate that these preferences and that previously known for the lactoside (1) are closely maintained in the haptens4and5. HSEA calculation indicates that the methyl group of methylN-acetyl-α-D-neuraminic acid (10) prefers the orientation wherein the carboxyl group is nearanti-periplanar to the methyl group. However, this orientation was not confirmed by saturation of the methyl group since no enhancement of either Ha-3 or He-3 was observed. On the other hand, saturation of Ha-3cof the αDNeuAc unit of the GM1-related pentasaccharide, βDGal(1 → 3)βDGalNAc(1 → 4)[αDNeuAc(2 → 3)]βDGal(1→4)α,βDGlc, caused strong enhancement of the signal for the aglyconic hydrogen, H-3bof the βDGal(1→4) unit. This observation, along with those of other nuclear Overhauser experiments, established that this pentasaccharide has the carboxyl groupanti-periplanar to C-3b. Furthermore, the C-7cto C-9cchain of the αDNeuAc unit adopts nearly the same conformation for the compound in aqueous solution as exists forN-acetylneuraminic acid in the crystalline state. The HSEA calculation indicates important attractive interaction between this chain and the βDGalNAc unit of the aglycon. These conlcusions were extended to the GM2and GM1gangliosides by the comparison of chemical shift data. In these compounds, the carboxyl group projects over the hydrophobic α-side of the βDGalNAc unit and the polar OH-4c, NAc-5c, OH-7cgroups project over the hydrophobic β-side of the lactose unit. Comments are made on the possible bearing of these topographical features on certain biological properties of gangliosides.

ISSN:0008-4042    

DOI:10.1139/v84-172

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Changes in some of the key intermediates and procedures used in our earlier total synthesis of porphobilinogen from pyrrole that improve the yield to 11% are reported. Ethyl pyrrole-3-acetate was formylated by the Vilsmeier–Haack method and then iodinated. The desired 2,3,4-substituted pyrrole isomer was isolated in moderate yield and, after conversion of iodide to acrylate and aldehyde to aldoxime, reduction and work-up afforded porphobilinogen lactam ethyl ester. Hydrolysis of the latter gave porphobilinogen in ten steps from pyrrole.

ISSN:0008-4042    

DOI:10.1139/v84-173

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Conductance data for the nitrates of sodium, potassium, and ammonium inN,N-dimethylformamide (DMF) – water mixtures (74.39 ≥ D ≥ 36.11) at 25 °C are reported for the concentration range 0.0003–0.06 mol dm−3. Also densities, viscosities, and dielectric constants of the solvent mixture (DMF–water) are reported at the same temperature. The data have been analysed by the Fuoss (1978) equation excluding the term α. The existence of a maximum in the viscosity at a 1:3 mol ratio of DMF and water is attributed to the formation of a solvated complex DMF•3H2O. The Walden products for all the three salts pass through a maximum while the equivalent conductances show a minimum with the change of DMF content in the solvent mixtures. In any given solvent mixture, the limiting equivalent conductances show the trend NaNO3 < KNO3 < NH4NO3. The existence of a maximum in Walden product is attributed to the dehydration of ions due to presence of the cosolvent (DMF). For all the three salts, the association constant was negligible (KA < 10) in all the solvent mixtures studied.

ISSN:0008-4042    

DOI:10.1139/v84-174

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

The synthesis and characterization of the complexes [Me2Gapz2]Rh(LL) (where LL = COD, (CO)2, (PPh3)2, or (PPh3)(CO)), incorporating the bidentate, chelating, dimethylbis(1-pyrazolyl)gallate ligand are described. Non-rigidity in solution has been demonstrated by1H nmr studies for some of the complexes. A crystal structure determination of the COD complex has confirmed the boat conformation for the Ga—(N—N)2—Rh six-membered ring in this complex in the solid state. In addition, the solid state structures of the 3,5-dimethylpyrazolyl bridged dirhodium complexes [Rh(μ-3,5-Me2pz)(CO)2]2and [Rh(μ-3,5-Me2pz)(COD)]2have been determined. Crystals of [Me2Gapz2]Rh(COD) are orthorhombic,a = 22.7447(8),b = 11.9776(5),c = 6.4635(3) Å,Z = 4, space groupPnma; those of [Rh(μ-3,5-Me2pz)(CO)2]2are monoclinic,a = 8.7403(6),b = 16.3594(6),c = 25.434(2) Å, β = 95.286(3)°,Z = 8, space groupP21/c; and those of [Rh(μ-3,5-Me2pz)(COD)]2are triclinic,a = 10.350(2),b = 11.401(2),c = 12.355(2) Å, α = 112.485(7), β = 99.394(9), γ = 105.387(8)°,Z = 2, space group. All three structures were solved by conventional heavy atom techniques and were refined by full-matrix least-squares procedures to final conventionalRvalues of 0.026, 0.024, and 0.037 for 1824, 5135, and 6109 reflections withI ≥ 3σ(I), respectively. In each case the Rh atoms have distorted square planar coordination geometry. Important mean structural parameters are Rh—N = 2.087(2), Rh—C = 2.129(2),for [Me2Gapz2]Rh(COD); Rh—N = 2.063(6), Rh—CO = 1.852(9),for [Rh(μ-3,5-Me2pz)(CO)2]2; and Rh—N = 2.084(1), Rh—C = 2.131(7),for [Rh(μ-3,5-Me2pz)(COD)]2.

ISSN:0008-4042    

DOI:10.1139/v84-175

出版商:NRC Research Press    

年代:1984

数据来源: NRC