摘要:

Attempts to clarify the biosynthetic origin of the eggplant stress metabolite aubergenone (1) by incorporation of label from sodium [2-2H3,1-13C]acetate were frustrated by low yields and enrichment levels. However, the presence of deuterium in the biosynthetically significant 5-position was demonstrated by2Hmr for the closely related auberganol (5) and α-and β-eudesmol (10and11), suggesting that these compounds, and hence also1, are normal eudesmanes and not the products of a possible double rearrangement. Deuterium was also incorporated into the expected positions of 9-oxonerolidol (12), 9-oxynerolidol (13), and lubimin (4). Incorporation of label from [1,2-13C2]acetate could be determined satisfactorily only for13and its allylic isomer14, corresponding with expectations. This is the first report of5as a natural product and of10,11, and the 10-epimer of4as eggplant stress metabolites.

ISSN:0008-4042    

DOI:10.1139/v86-001

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The addition of a metallic nitrate such as Zn(NO3)2, Cu(NO3)2, or UO2(NO3)2to N2O4solutions in aprotic media leads to the reclaiming of the NO+species (which is considered as a catalyst for the nitration of aromatics by N2O4) as follows:. Using linear voltammetry, the study of the N2O4reduction in the presence of metallic nitrates with a platinum electrode has allowed us to derive the equilibrium constant for reaction [1] and that corresponding to the formation of the trinitrato complexes in sulfolane according to:. The strong stability of thecomplexes is due to the weak solvating character of the sulfolane. This hypothesis is also confirmed by the stability constants of zinc[II] chloride complexes:in sulfolane from a potentiometric study by means of a silver chloride – silver electrode.

ISSN:0008-4042    

DOI:10.1139/v86-002

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The electrochemical behaviour of 2,5-dihydroxybenzoic acid (2,5-DHBA) has been studied in the pH range 5.5–12.7 at a hanging mercury drop electrode (HMDE). Voltammograms show the existence of one reversible wave of 2,5-DHBA governed by diffusion conditions. In the oxidation process a two-electron transfer takes place, as shown by the controlled potential electrolysis. From the calculation of the voltammetric parameters (peak widthEp − Ep/2, peak current functionand from the other experimental data, a mechanism for the overall reaction in two different pH ranges, 5.5–9.5 and 9.5–12, is proposed.

ISSN:0008-4042    

DOI:10.1139/v86-003

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The distribution of cobalt(II) between water and an organic extractant (dodecylthioglycolic acid) dissolved in kerosene has been studied using a tracer of60Co. The aqueous media wee always constituted by buffer solutions (acetic acid – sodium acetate) and the ionic strength was adjusted with sodium nitrate to 1 mol dm−3. The main species of cobalt(II) originating in the organic phase has been isolated and characterized on the basis of elemental analysis, thermal gravimetric analysis, and ir spectra.

ISSN:0008-4042    

DOI:10.1139/v86-004

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The kinetics of oxidation of glycolic, malic, tartaric, and citric acids by cerium(IV) ammonium nitrate were investigated in 0.006 mol dm−3nitric acid. The reaction was catalysed by H+in the range 0.006–0.016 mol dm−3at constant(0.02 mol dm−3). The pseudo first-order rate constantkobswas independent of [CeIII] (0.0004–0.002 mol dm−3). The proposed mechanism is based on the assumption that the formation of the precursor Ce(IV) – α-hydroxy acid complex precedes its rate controlling disproportionation, which is assisted by a proton, possibly due to the formation of the activated state [H+—CeIV– HA]≠(where CeIVis the reactive cerium(IV) species and HA is the α-hydroxy acid). The free radical R1R2ĊOH produced in the rate controlling step further reacts with a number of Ce(IV) molecules in the fast step to yield the final oxidation product. The activation parameters for the rate controlling step could be evaluated only in the oxidation of tartaric acid

ISSN:0008-4042    

DOI:10.1139/v86-005

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The interaction between polymeric aluminium hydroxide, Alp, and fluoride has been investigated to optimize the conditions for removal of fluoride from waste waters of aluminium manufacturing plants using Alp. The results of these studies have shown that the nature of products formed between Alpand fluoride depends on the molar concentration ratio of fluoride to aluminium (rF), pH, and initial fluoride concentration. In the absence of interfering ions, fluoride can be effectively precipitated as Al13(OH)29F10with Alp, usingand 4 < pH ≤ 7. At rF > 1, Alpdissociates and fluoride is precipitated as cryolite, and the residual fluoride concentration is controlled by its high solubility.

ISSN:0008-4042    

DOI:10.1139/v86-006

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

HUO2PO4•4H2O (HUP) forms a laminar intercalate with butylamine,c = 29.30(5) Å, which accepts cationic metals in exchange for then-butylammonium ions. Hydrated uranyl metal phosphates M(UO2PO4)2•nH2O (M = Mn, Co, Ni, Cu, Zn, Cd) are obtained by ionic exchange and were studied by thermal analysis and X-ray diffraction. The tetragonal structures of all these product compounds are derived from HUP. The diffuse electronic reflectance spectra of every sample show characteristicabsorption bands. In the spectra of the Co, Ni, and Cu phosphates there are other bands in the 500–800 nm zone compatible with their observed aquocation transitions.

ISSN:0008-4042    

DOI:10.1139/v86-007

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The ion exchange reactions ofn-butylamine intercalates of tin(IV) hydrogen phosphate and hydrogen uranyl phosphate towards carbonatotetraamminecobalt(III), chloropentaamminecobalt(III), and hexaamminecobalt(III) have been investigated. Independent of the complex cation charges, the amounts of Co(III) complex exchanged by then-butylamine intercalate of tin(IV) hydrogen phosphate are practically the same. With then-butylamine intercalate of hydrogen uranyl phosphate, the ionic exchange was completed and the composition was fixed by the exchanged Co(III) complex. The layer charge densities of these phosphates justify the different ionic exchange behaviour observed towards the large complex cations. All the products were characterized by chemical analysis, X-ray diffractometry, infrared spectroscopy, diffuse reflectance spectroscopy, and thermal analysis.

ISSN:0008-4042    

DOI:10.1139/v86-008

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

A sampling device is described which enables the Picker flow heat capacity calorimeter to handle viscous liquids. The necessary constant liquid flow through the calorimetric cell is achieved by an overpressure on the entering liquids, and can be maintained by pressure control. In addition, the device permits automatic measurement of a number of samples. The approach is applied to densities and heat capacities of binary mixtures of dimethylformamide and the viscous liquidsN-ethylacetamide,N-n-propylacetamide, andN-n-butylacetamide. The results appear to be accurate enough to establish excess molar heat capacities as well as apparent molar heat capacities.

ISSN:0008-4042    

DOI:10.1139/v86-009

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Excess volumes and viscosities of binary liquid mixtures ofN-methylpyrrolidinone – tetrahydrofuran and propylene carbonate – acetonitrile are measured and examined in the light of empirical theories such as absolute rate, free volume, and regular solution theories. It is shown that non-ideality arises due to (a) shape factors, (b) molecular interaction, and that the two properties, excess volume and viscosity, illustrate these two aspects of non-ideality.

ISSN:0008-4042    

DOI:10.1139/v86-010

出版商:NRC Research Press    

年代:1986

数据来源: NRC