摘要:

Six new nitrogenous sesquiterpenes (1–6), which form two new isocyanide-isothiocyanate-formamide series, have been isolated from the marine spongeAxinellacannabina. The structure elucidation of these compounds is based upon spectral data, including 2D-nmr, and chemical interconversions. The complete assignment of all proton and carbon resonances in nmr spectra of axisonitrile-2 (7), an isonitrile previously isolated from the same source, is also reported, along with its complete relative stereochemistry.

ISSN:0008-4042    

DOI:10.1139/v87-090

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

The aim of this study is to examine hydrodenitrogenation (HDN) of indole on asbestos catalysts (chrysotile and crocidolite) under hydrogen pressure. HDN is carried out according to two competitive pathways, either viaortho-ethylaniline or viaortho-toluidine. This reaction is assisted by increase of temperature and pressure and by pre-reduction of the asbestos. Particles of Fe0on the fibre surface are formed from the original material. Their presence plays a role in the initial breaking of the C—N bond and in the hydrogenation reaction.

ISSN:0008-4042    

DOI:10.1139/v87-091

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

The polarographic study of lead fluoride and of lead chloride complexes has been done in water – hydrogen fluoride solutions. The successive formation of PbF2and of PbF+is in agreement with the reduction of the fluoride ion activity,R0(F), measured with the augmentation of the HF content of the solution. The formation of two crystalline structures of PbF2is in accord with the existence of two complexes in solution. The formation of PbFCl shows the existence of mixed fluoride–chloride complexes in water–HF solutions.

ISSN:0008-4042    

DOI:10.1139/v87-092

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

The2H/1H isotope effect on13C nmr chemical shifts,nΔ,nbeing the number of intervening bonds between2H and13C nuclei, in toluene-α-d3is solvent dependent. For example,1Δ ranges from 817 ppb in CD3OH to 869 ppb in acetone-d6solutions, a positive number indicating increased shielding in the deuterated species.1Δ is linearly dependent on a function of the refractive index,nD, of the solvent, allowing extrapolation tonD = 1. The hyperconjugative model, in which the C—D bond is a poorer electron donor to the aromatic system than is a C—H bond, is tested for the substituents CH2D, CHD2, CD3, CHDCH3, CD2CH3, CD(CH3)2, C6H5CHD, and (C6H5)2CD. For these substituents, the negative5Δ is linearly related to the expectation value of sin2θ; θ is the angle by which the C—D bond twists out of the benzene plane. The model fails quantitatively for C6H5CD2X (X = Cl, COOH, CN, OH). For X = OH, very large negative5Δ and3Δ values are observed.nΔ is also reported for 4-ethyltoluene-α-d3and benzaldehyde-α-d1. For the latter, allnΔ values are positive other than5Δ, which vanishes in acetone-d6solution.

ISSN:0008-4042    

DOI:10.1139/v87-093

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Analysis of the1H nuclear magnetic resonance spectra of the benzyl moieties in phenylacetaldehyde, benzyl methyl ketone, benzyl ethyl ketone, benzyl isopropyl ketone, and 3,5-dichlorobenzyltert-butyl ketone yields the long-range couplings between ring and α protons. These stereospecific couplings change very little upon replacement of the aldehydic hydrogen by various alkyl groups. The couplings for all the molecules studied fall within the ranges4J(CH2, Ho) = −0.566 ± 0.008 Hz,5J(CH2, Hm) = 0.278 ± 0.002 Hz, and6J(CH2, Hp) = −0.409 ± 0.010 Hz, suggesting that in the ketones the alkyl group prefers to betransto the phenyl ring and does not interfere with rotation about the C1—Cαbond. The long-range couplings are consistent with a potential functionV(θ) = 8.4 ± 1.2 sin2θ for two-fold rotation about the C1—Cαbond; θ is the angle between the carbonyl and benzene ring plane.Abinitiomolecular orbital calculations on phenylacetaldehyde at the STO-3G level with the C=O bondcisto the phenyl group yield a potential ofV(θ) = (8.65 ± 0.73) sin2θ + (1.27 ± 0.80) sin22θ, rather close to the experimental potential but with a small fourfold component. The spin–spin coupling constant between the aldehydic and α protons displays a solvent dependence consistent with previously reported values. The insensitivity of4J(CH2, Ho),5J(CH2, Hm), and6J(CH2, Hp) to solvent suggests thatis very weakly dependent on the rotation of the aldehyde group.

ISSN:0008-4042    

DOI:10.1139/v87-094

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Calculations have been made on the enthalpies of the singlet and triplet N2O2species generated from2πNO + 4πNO, and the exciplexes which result from reaction of N2O2with some methyl fluorosilanes. Both the ground-state singlet and the first excited triplet of the latter systems have been studied and are discussed in relation to the mechanism for the decomposition of NO after initial excitation with Hg(63P1) atoms.

ISSN:0008-4042    

DOI:10.1139/v87-095

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

A theoretical study is presented of the relative enthalpies (calculated through heats of atomisation) of complexes of the silanes SiF4, SiF3Me, and SiF2Me2, with ground state2πNO, and exciplexes with excited state4πNO. The calculations favour an increasing relative stability of the complexes and exciplexes with silanes in the order SiF4 < F3SiMe < F2SiMe2with, in each particular case, a geometry favouring theover thearrangement.

ISSN:0008-4042    

DOI:10.1139/v87-096

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

The electrochemical reduction of aromatic or α,β ethylenic aromatic ketones in nonaqueous solvent (DMF) has been performed in the presence of EuCl3•6H2O. Ligand exchange between DMF and water molecules of the europium salt was first studied. A voltammetric study shows that complexation involving electrogenerated Eu(II) and ketone may occur at the electrode interface or in solution, leading respectively toandstoichiometries. The stereochemistry of hydrodimerization products is studied.

ISSN:0008-4042    

DOI:10.1139/v87-097

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

The use of polarographic maximum suppression methods for determining polyacrylamides and polyacrylic acid-based polymers was investigated. Using the oxygen, Co2+, and Hg2+maxima these polymers were determined at the low ppm level. The effectiveness of polymers as maximum suppressors was dependent on the charge of the polymer and that of the electrode at the potential at which the polarographic wave occurred. The maximum suppression of various binary mixtures of polyacrylamides indicated that in some mixtures suppression was additive while in other mixtures, particularly those containing both anionic and cationic polymers, the suppression was greatly reduced. Aqueous extracts of chosen coals contained various interfering substances which could be removed most efficiently using Sephadex G-75, although this resin was only compatible with anionic and neutral polymers.

ISSN:0008-4042    

DOI:10.1139/v87-098

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Using the titration of tertiary aliphatic amines as a model a linear relationship for the log equilibrium constant versus the log dielectric constant over a broad range of dioxane–water mixtures is established. Primary and secondary amines are less responsive to changes in dielectric constant, producing linear data of shallower slope. A study of morpholine andN-alkyl-morpholines produces curves that plateau in high dielectric constant regions and display decreasing slope as water concentrations approach zero. Similar behavior for morpholines is observed in low water mixtures where they form proton transfer complexes withp-nitrophenol. Possible reasons for the behavior are discussed.

ISSN:0008-4042    

DOI:10.1139/v87-099

出版商:NRC Research Press    

年代:1987

数据来源: NRC