摘要:

Bimetallic and cluster rhodium carbonyl complexes catalyze the biphasic reduction of nitro compounds under mild conditions (using CO/5 MNaOH, C6H6or PhCH3). Rate studies indicate the sensitivity of the reaction to the nature of the organic substrate, base concentration, and the temperature. A previously observed bimetallic (Co2(CO)8and (1,5-HDRhCl)2) and phase transfer catalyzed [R4N+X−] reduction of nitro compounds was found to be a consequence of the inhibition and reactivation of the true catalyst by the quaternary ammonium salt and cobalt carbonyl, respectively.

ISSN:0008-4042    

DOI:10.1139/v85-196

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The metabolites produced in liquid culture by the fungusLachnellulafuscosanguinea(Rehm) Dennis have been examined and two antifungal agents, lachnelluloic acid and lachnellulone, have been isolated. The structure of lachnelluloic acid has been established as (−)-4-hydroxy-3-octanoyl-6-pentyl-5,6-dihydro-2-pyrone (1) by chemical and spectroscopic methods. The total synthesis of racemic lachnelluloic acid, starting from 6,8-tridecanedione (6) is reported. Lachnelluloic acid (1) shows strong antifungal activity againstCeratocystisulmi, the causative agent of Dutch elm disease.

ISSN:0008-4042    

DOI:10.1139/v85-197

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The molecular structures ofexo-7-methylbicyclo[3.3.1]nonan-3-one,3, and theendo-7-methyl isomer,4, have been determined using X-ray-diffraction techniques. Compound3crystallizes in the space groupwitha = 15.115(1),c = 7.677(2) Å, andZ = 8 while4crystallizes in the space groupP21witha = 6.446(1),b = 7.831(1),c = 8.414(2) Å, β = 94.42(2)°, andZ = 2. The structures were solved by direct methods and refined to final agreement factors ofR = 0.041 andR = 0.034 for3and4respectively. Compound3exists in a chair–chair conformation and there is no significant flattening of the chair rings. However, in4, the non-ketone ring is forced into a boat conformation. These results are significant in interpreting what conformations may be present in the related sp2-hybridized carbocations.

ISSN:0008-4042    

DOI:10.1139/v85-198

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Cyclic amines are oxidized to the bicyclic compounds by electrochemical oxidation. The presence of halide ions is found necessary for the reaction to proceed and to produce any bicyclic products. It is postulated that a positive halide species, X(+), is produced electrochemically and stabilized under the specific reaction conditions. The X(+)ion forms a complex with the parent cyclic amine which decomposes to the bicyclic product and HX. An analogy between the Hofer–Moest reaction to produce C(+)and this reaction to produce X(+)is postulated

ISSN:0008-4042    

DOI:10.1139/v85-199

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The electronic absorption spectra of coumarin and its derivatives umbelliferone (6-hydroxycoumarin), esculetin (6,7-dihydroxycoumarin), and scopoletin (6-methoxy-7-hydroxycoumarin) were investigated. Then → π* transition was not observed in the spectrum of coumarin but was observed in the spectra of some of its derivatives. Molecular orbital calculations, using the INDO procedures, were carried out on coumarin and some of its derivatives. The activities of the different sites of the molecules are discussed in terms of the coefficients of the atomic orbitals constituting the HOMO and the LUMO. The correspondence between the calculated and experimental transition energy and band intensity is satisfactory.

ISSN:0008-4042    

DOI:10.1139/v85-200

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Partial molar volumepartial molar compressibilityJones–Dole viscosityBcoefficient, and solute activation parameters of adenosine in water–DMSO mixtures in the presence of Ca2+and K+ions have been calculated from ultrasonic, volumetric, and viscometric studies at 25, 30, 35, and 40 °C(± 0.01° C). The results are discussed in terms of the Jones–Dole viscosityBcoefficients and the transition state parameters for viscous flow.

ISSN:0008-4042    

DOI:10.1139/v85-201

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Many methods have been employed for measuring the interactions of trace metals and humic materials but little consideration has been given to the magnitude of error in the resulting titration data. Most common metal-titration methods can be placed into one of three categories based on the chemical species that is most directly measured: free ionic metal, total labile metal, or ligand-bound metal. The propagation of random instrument error into a titration data set is not uniform throughout a titration and the pattern of propagation is shown to be characteristic of the category of method used. Standard deviations are determined for measurements by ion-selective electrodes, fluorescence quenching, and fixed potential amperometry (each representative of a category of methods). Error propagation in resulting titration data is quantified. No single titration method yields uniformly precise data in all concentration ranges and a combination of complementary methods yields the best characterization of metal binding to a humic material.

ISSN:0008-4042    

DOI:10.1139/v85-202

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Rate constants for the β-elimination of HCl from 2,2-di(4-nitrophenyl)-1,1-dichloroethane (I) and 2,2-di(4-nitrophenyl)-1,1,1-trichloroéthane (II) promoted by tetramethylguanidine in the aprotic solvents acetonitrile, tetrahydrofuran, and n-hexane have been measured. The activation parameters are characterized by small enthalpies of activation (4.1 to 7.3 kcal mol−1) and large negative entropies of activation (−35 to −50 cal mol−1 deg−1). The primary deuterium isotope effects at 20° C range fromkH/kD = 4.8 to 10.3. The results are interpreted to indicate an (EcB)1mechanism for both substrates I and II in acetonitrile solvent and an E2H or mixed (ElcB)1–E2H mechanism in the less polar solvents, tetrahydrofuran and n-hexane.

ISSN:0008-4042    

DOI:10.1139/v85-203

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The reactions of the outer-sphere electron transfer reagent, Ni(9-aneN3)23+, (bis(1,4,7-triazacyclononane)nickel(III) ion) with ascorbic acid, hydroquinone, catechol, and resorcinol have been investigated. The absence of any proton related equilibria with the oxidant provides a means of ascribing the observed inverse hydrogen ion dependences to reactions of the dissociated ascorbate or quinolate ions, (HA−). The data are consistent with the rate-determining one-electron transfer reactions:followed by rapid oxidation of the radical ions formed. In the reaction with ascorbic acid,k1~ 0 andk2(T = 25° C) = 5.2 × 106 M−1 s−1(ΔH≠ = 10.1 ± 2.5 kcal mol−1, ΔS≠ = 5.7 ± 5.1 cal mol−1 K−1). For hydroquinone, catechol, and resorcinol,k1 = 2.9 × 103, 2.8 × 102, and ~0 M−1 s−1andk2 = 6.9 × 109, 4.1 × 109, and 2.8 × 108 M−1 s−1, respectively. These data have been combined with those from other similar reactions leading, by use of a Marcus correlation, to self-exchange rate constants for the HAsc−/HAsc•couple of 3.5 × 105 M−1 s−1and for the H2Quin0/+and H2cat0/+systems of 5 × 107and 2 × 107 M−1 s−1, respectively. The importance of the effect of bond-reorganisation on electron transfer is discussed.

ISSN:0008-4042    

DOI:10.1139/v85-204

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

American (Gulf of Mexico), Mexican (Gulf of California), and Japanese (Gulf of Sagami) specimens of the marine bryozoanBugulaneritinawere found to contain in addition to bryostatin 4 (3a) the new bryostatins 5–7 (3b–d) as major antineoplastic components effective against the murine P388 lymphocytic leukemia. A total of 50 kg of wetB.neritinafrom the Northeastern Gulf of Mexico led to bryostatins 5–7 in 14.1, 61.9, and 31.2 mg yields respectively. The structural assignments for each of these potentially important substances were derived from detailed interpretation of the 400 MHz1H nmr and solution phase secondary ion mass spectral measurements, combined with the results of selective acid-catalyzed hydrolyses.

ISSN:0008-4042    

DOI:10.1139/v85-205

出版商:NRC Research Press    

年代:1985

数据来源: NRC