摘要:

A kinetic method of analysis which distinguishes Fe(II) from Fe(III) and Fe(III) forms of various labilities from each other is based on spectrophotometric monitoring of the reaction of Fe(II) with ferrozine. Reduction of Fe(III) with hydroxylamine hydrochloride allows the single colourimetric reagent to detect all forms of Fe. The method is applied to study of the effects of a well characterized soluble soil organic acid sample, a fulvic acid, on the speciation of Fe(III) under conditions (pH = 6) where Fe(III) forms a colloidal hydrous oxide in the absence of fulvic acid. The effect of fulvic acid is to greatly increase the lability of Fe(III) compared to that in a hydrous oxide colloid. However, ultrafiltration and light scattering experiments indicate that the Fe(III) – fulvic acid species is larger than the hydrous ferric oxide colloid particles. Kinetic studies in the absence of hydroxylamine hydrochloride show that fulvic acid can act as a reducing agent for iron in the presence of an Fe(II) complexing agent like ferrozine but neither kinetic studies with an Fe(III) reagent nor Mössbauer spectra suggest significant initial presence of Fe(II) in the aged Fe(III) – fulvic acid samples.

ISSN:0008-4042    

DOI:10.1139/v81-028

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The crystal structure of S3N2O2has been redetermined and the structure refined to a finalRof 0.057 andRwof 0.076 for 550 reflections withI ≥ 2σ(I). S3N2O2is planar and ofC2vsymmetry, as previously found by Weiss. The central S—N distances and angle are 1.647(3) Å, NŜN 97.3(2)°, with adjacent N—S distances and angles of 1.535(3) Å,, and terminal S—O distances and angles of 1.446(4) Å, NŜO 118.0(2)°. The infrared and Raman spectra are reported and some assignments are mad

ISSN:0008-4042    

DOI:10.1139/v81-029

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Addition of polar solvents to non-polar solutions of crystal violet results in dramatic changes in the visible absorption spectra. The observed changes are explained in terms of crystal violet existing as an ion-pair in non-polar solutions and as a solvated ion in polar solutions.The spectrum of crystal violet in toluene and in acetone solution remains virtually unchanged over a wide temperature range. However in methanol, as was reported for ethanol (1), the short wavelength component of the absorption in the visible region disappears as the temperature is lowered. The spectral behaviour in alcoholic solutions suggests a decreasing solvent–solute interaction around the dye cation due to increased self-association of the solvent molecules as the temperature is decreased. Our observations have a direct application in interpreting some of the results of the photodynamics of crystal violet in solution.

ISSN:0008-4042    

DOI:10.1139/v81-030

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

cis- andtrans-[Pt(pm)2X2] where pm = pyrimidine and X = Cl, Br, have been synthesized. Thecis-compounds were isolated from the reaction of K2PtCl4and pm in water, while thetrans-isomers were obtained by isomerization ofcis-[Pt(pm2X2] in DMF in the presence of pm.The crystal structures of the two compoundstrans-[Pt(pm)2X2] have been determined by X-ray diffraction. The two compounds (X = Br and Cl) are isostructural. The crystals belong to the monoclinicP21/cspace group. The cell parameters area = 4.787(3),b = 14.257(7),c = 8.503(3) Å and β = 99.33(4)° when X = Cl anda = 4.826(3),b = 14.822(5),c = 8.516(5) Å and β = 101.26(4)° when X = Br. The platinum atom is located on a centre of symmetry at the origin andZ = 2. The residual factors areR = 0.029 andRw = 0.036 (X = Cl) andR = 0.036 andRw = 0.035 (X = Br).

ISSN:0008-4042    

DOI:10.1139/v81-031

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The sulfoxides derived from 2,3-dihydro-4H-naphtho[1,2-b]thiopyran and its 4-phenyl and 4-oxo derivatives, as well as the analogous sulfoxides in the 2,3-dihydro-1H-naphtho[2,1-b]thiopyran series, have been synthesized and their structures established by spectroscopic methods, especially1H and13C nmr. On photolysis these sulfoxides have been found to react by a rather inefficient photochemical deoxygenation pathway.

ISSN:0008-4042    

DOI:10.1139/v81-032

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Sweroside tetraacetate (2b) has been converted in high yield by osmylation to the epimeric glycols3and4(R = H) which have been separated. This reaction proceeds with high chemoselectivity for reaction at the vinyl side chain but with low stereoselectivity, leading to a small excess of the 3-Risomer. Secologanin derivatives appear to show a much lower chemoselectivity in this reaction, but the stereoselectivity is considerably higher, and opposite to that in the sweroside example. Conditions have been found for oxidizing the dimethylacetal5bof secologanin tetraacetate in useful yields to the epimeric glycols6and7(R = H); in this reaction a large excess of the 3-Sisomer is formed. The reasons for these differences in selectivity appear to be related to differences between the two series in conformational preference.

ISSN:0008-4042    

DOI:10.1139/v81-033

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

A chemical route from sweroside (2a) to secologanin (1a) has been established. The lactone ring of sweroside tetraacetate (2b) was opened by trimethylsilyl iodide. The unstable iodo carboxylic acid3(R = H; X = I) was then formed and immediately converted to its methyl ester. The iodo function was displaced by formate, and the formate was selectively methanolized under neutral conditions. The resulting alcohol3(R = Me; X = OH) was oxidized by pyridinium chlorochromate to the aldehyde, secologanin tetraacetate (1b). With care, the conversion from the sweroside series to the secologanin series can be carried out in excellent yield. Secologanin can readily be recovered from its tetraacetate.

ISSN:0008-4042    

DOI:10.1139/v81-034

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Certain derivatives of the 1,4-bis(2′-haloethyl)-1,4-diazabicyclo[2.2.1]heptane dication system ranging from dibromide2bto ethanesulfonate2gwere found to be quite stable under essentially neutral conditions. A very convenient synthesis of 1,4-bis(2′-chloroethyl)-1,4-diazabicyclo [2.2.1]heptane dichloride (2d) was developed in order to compare the relative stability of this system with that of dibromide2b. While dichloride2dwas found to be less stable than dibromide2b, it did prove very useful for rapid preparation of other anion derivatives such as dinitrate2e, dihydrogen dimaleate2h, diperiodate2i, tetrachloroplatinate2j, and tetrachloroaurate2k. At temperatures near 150 °C, or upon ignition (in the open) or gentle shock, diperiodate2idetonated violently. The ethanesulfonate2gwas obtained from diperchlorate2aemploying an ion-exchange procedure. Stabilization of dication2provides an unusual heterocyclic system with exceptional anticancer properties.

ISSN:0008-4042    

DOI:10.1139/v81-035

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The adsorption ofN-methylacetamide and ofL-arginine on apatitic phosphates has been studied by infrared spectroscopy. During the initial adsorption, the bands of adsorbedN-methylacetamide indicate the presence of thetransform attached to surface cations via the carbonyl group. The position of the amide I band is found to give a linear correlation withq/rfor apatitic cations (whereqis the charge andrthe radius of a cation). At higher amounts of adsorbed amide, hydrogen bonding arises either from the self-association of amide molecules or from the binding of these to the surface phosphate anions.L-Arginine can be adsorbed through the groups containing NH bonds or through the carboxyl group. Infrared spectra of calcinated samples as well as the Ca/P ratio determinations point out that a substitution ofL-arginine positive ions for surface cations takes place upon adsorption of this amino acid on apatitic calcium phosphate.

ISSN:0008-4042    

DOI:10.1139/v81-036

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Naphtho[2,1-b]thiophene undergoes addition of aromatic hydrocarbons across the 1,2-bond in the presence of aluminum chloride. At 20 °C 1-aryl-1,2-dihydronaphtho[2,1-b]thiophenes are the major products and at higher temperatures 2-arylnaphtho[2,1-b]thiophenes result. 1-Arylnaphtho[2,1-b]thiophenes may be prepared by treatment of the dihydro-addition products with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone thus giving a new synthesis of 1- and 2-arylnaphtho[2,1-b]thiophenes from the parent heterocycle.

ISSN:0008-4042    

DOI:10.1139/v81-037

出版商:NRC Research Press    

年代:1981

数据来源: NRC