A decomposition procedure for the determination of arsenic in marine samples

The use of wet and dry ashing procedures to decompose marine biological tissues and to degrade organoarsenic compounds to inorganic arsenic for analysis by zinc-column arsine generation and atomic-absorption spectrophotometry was investigated. Wet ashing with nitric, sulphuric and perchloric acids (10:2:3 v/v) released the largest percentage of arsenic from fish tissue and quantitatively degraded methylated and other organoarsenic compounds to inorganic arsenic. The arsenic concentrations found when standard reference materials were ashed with this acid mixture were in agreement with the certified values.     

Group IB metal chemistry : V. Some fluxional complexes containing copper or silver

Fluxional poly(pyrazolyl)borate complexes of copper and silver, including the carbonyl Cu(CO)B(pz)₄, contain coordinated and free pyrazolyl groups, which interchange rapidly on the NMR time scale at room temperature; low temperature limiting spectra can be obtained for some copper complexes at ?100°.     

Cyclometallation reactions XII. On the effect of various leaving groups on internal metallation reactions with alkylmanganese complexes

The interaction of azobenzene and MnR(CO)₅ (R  Me, Et, CH₂Ph, CH₂-C₆Me₅, COCF₃, COCH₂C₆F₅, COCH₂OPh, Ph or C₆F₅) affords M$\text{n(C}{}_6\text{H}{}_4\text{NN}$Ph)-(CO)₄, together with a binuclear complex Mn₂(CO)₆(C₁₂H₁₀N₂) in some cases. The metallation reaction is shown to proceed most readily with Mn-(CH₂Ph)(CO)₅; with this reagent, the metallated complexes M$\text{n(C}{}_6\text{H}{}_4\text{CH}{}_2\text{P}$Me₂)-(CO)₃[PMe₂(CH₂Ph)] (two isomers) and M$\text{n(C}{}_6\text{H}{}_4\text{CH}{}_2\text{A}$sMe₂(CO)₄ have been obtained on treatment with EMe₂(CH₂Ph) (E  P and As, respectively).     

Protonation of metal carbonyl complexes : VI. Protonation of manganese π-cyclopentadienylphosphine complexes studied by 13C and 31P NMR techniques

¹³C and ³¹P NMR techniques have been applied to the complexes CpMn(CO)L₂ and CpMn(CO)₂ L (where L₂ is a bidentate tertiary phosphine, L is a monodentate tertiary phosphine, and Cp is cyclopentadienyl). It is shown that the complexes are protonated reversibly, when dissolved in CH₂Cl₂ in the presence of CF₃COOH, with the proton attacking the manganese atom.     

Metall-π-komplexe von benzolderivaten : III. Bis(diphenylphosphino-h6-benzol)-chrom(0)

Rhodium complexes containing poly(pyrazolyl)borate ligands are described, and the fluxional nature of some of them considered.     

Synthesis,structure and reactions of seco-steroids containing a medium-sized ring—IX : Reactions of Δ1(10)-unsaturated 5-oxo-5,10-seco-steroids with hydroxylamine and n-methylhydroxylamine

When treated with hydroxylamine or N-methylhydroxylamine, in the presence of proton donor catalysts, trans-Δ¹⁽¹⁰⁾-unsaturated 5-oxo-5,10-seco-steroids, such as 3 (but not the corresponding diastereomeric cis-compounds), are converted stereospecifically and in good yield to isoxazolidine derivatives (e.g. 4 and 13), resulting from transannular 1,3-dipolar addition of the intermediately formed oximes and nitrones to the trans-double bond in the cyclodecene ring moiety of the seco-steroid system. Reactions are described and physical evidence is presented which establish the constitution and configuration of the isoxazolidine-containing cycloaddition products, and the mechanistic and steric course of this transannular ring closure process is discussed.     

Synthesis of novel rhodanine based functionalized furans from the reaction of tert-butyl isocyanide with acetylenic esters in the presence of rhodanine acetic acid derivatives

The reactive 1:1 intermediate produced from the reaction of tert-butyl isocyanide and dialkyl acetylenedicarboxylates was trapped by rhodanine-N-acetic acid derivatives to generate polyfunctionalized furan rings in fairly good yields.     

Ground state geometry of cinso

The ground state geometry for ClNSO is investigated using ab initio calculations in a moderately large basis set. Variation of the dihedral angle yields a planar syn geometry. The geometry is discussed on the basis of a population analysis.     

An ab initio SCF study of the rotational isomerism in ethyl formate and propargyl formate

SCF computations using STO/3G orbitals have been made for methyl formate, ethyl formate and propargyl formate in order to investigate rotational isomerism in the last two molecules. The results are in good agreement with those of IR and microwave studies.     

Sulfur heterocycles. I. Use of 4,4-dimethyl-1,3-oxathiolane-3,3-dioxide as a carbonyl anion equivalent

The title heterocycle is used as a carbonyl anion equivalent in the preparation of aldehydes and α-silyl ketones; the key step is the thermal demasking of the heterocycle by loss of isobutylene and sulfur dioxide.     

伟大的分析化学家——I．M．Kolthoff

本文简介Ｋｏｌｔｈｏｆ的主要工作并初步探讨了他的学术、教育思想的某些特点     

Organostibines as ligands. Synthesis of dimethyl(α-picolyl)stibine,dimethyl(8-quinolyl)stibine,and (R;S)-methylphenyl(8-quinolyl)stibine and some transition metal derivatives

The unsymmetrical mono-tertiary stibines dimethyl(α-picolyl)stibine (picstib), dimethyl(8-quinolyl)stibine (quinstib), and (R;S)-methylphenyl(8-quinolyl)stibine (R;S-quinstib) have been synthesised and the square-planar complexes [MX₂(picstib)], [MX₂(quinstib)] (where M = Pd or Pt and X = Cl, Br, I or SCN) and [MCl₂(R;S-quinstib)] (where M = Pd or Pt) isolated. The thiocyanato derivatives display linkage isomerism. The octahedral complexes [M(CO)_4-(picstib)] and [M(CO)₄(quinstib)] have also been prepared from the metal hexacarbonyls and the appropriate ligands by UV irradiation in tetrahydrofuran.     

A novel procedure for the aromatization of ring a in 19-nortestosterone

A convenient, 40% overall yield synthesis of 2,3,17β-triacetoxy-1,3,5(10)-estratriene is described, which involves epoxidation of 19-nortestosterone and subsequent acetylation, lead tetra-acetate acetoxylation of the so-formed 17β-acetoxy-4β,5-epoxy-5β-estran-3-one, and aromatization of ring A, by means of acidic alumina, of the resulting 2α and 2β epimers of 2,17β-diacetoxy-4β,5-epoxy-5β-estran-3-one.     

Resolution enhancement of a.c. polarographic peaks by deconvolution using the fast fourier transform

A method for resolution enhancement of a.c. polarograms (voltammograms) is presented. The method is based on deconvolution using fast Fourier transforms. Overlapped a.c. polarograms are mathematically narrowed and sharpened, retaining the peak position and linear proportionality of the sharpened peak height with concentration. The advantages and limitations of the method are demonstrated on simulated and experimental a.c. polarograms. The same approach is applicable to related techniques such as. differential pulse and square-wave polarography.     

Vibrational,NQR and thermogravimetric study of complexes between triphenyl group VB compounds and mercuric halides

The synthesis, identification, vibrational (IR—FIR), NQR and thermal (TGA) study of a series of donor-acceptor complexes (Ph₃E^VB)_n(HgX₂)_m (E^VB = As, Sb, Bi;Ph = phenyl; X = Cl, Br, I; n/m = 2/2, 2/1) is reported. Elemental analysis proved that the aimed stoichiometry is only obtained for the (Ph₃Sb)_n(HgI₂)_m and (Ph₃As)_n(HgX₂)_m complexes, (Ph₃As)₂(HgI₂)₂ excepted. In all other cases a much lower Ph₃E^VB content is found. Assignments for the skeletal vibrational frequencies are based upon a “tetrahedral” C_2v and a “bridge-like” C_2h symmetry for (Ph₃E^VB)₂HgX₂ and (Ph₃E^VB)₂(HgX₂)₂ complexes, respectively. Changes in the electron distribution of the Hg—X bond dominate the halogen NQR frequency. TG curves are characterized by a single step mass loss and the absence of any residue suggests volatilization rather than decomposition.     

The gas phase structures of the isomers of benzene: IV. Hexafluoro-dewar-benzene

Gas phase electron diffraction data for HFDB were analyzed, following conventional procedures, and a structure was deduced for the perfluoro-bicyclo-[2.2.0]hexa-2,5-diene consistent with its C_2v symmetry. A least squares analysis of the molecular scattering function gave the following r_g values: [-C-C-] = 1.597 ± 0.006 Å, [C-C-] = 1.503 ± 0.002 Å, [-C-C-] = 1.356 ± 0.007 Å, [-C-F](bridge) = 1.331 ± 0.008 Å, [-C-F] (terminal) = 1.323 ± 0.004 Å. The flap angle between the rings is 115.3( ± .7)°. The terminal fluorines are in the planes of the corresponding rings.The most notable feature of the structure is the long C-C bridge bond, which was also observed in hexamethyl-Dewar-benzene. The geometrical features of HFDB are compared with corresponding ones in HMDB, and with perfluoro- cyclobutene as well as with theoretical estimates.     

Ring-disk electrode studies of the formation,growth and transformation of iodine films formed during the anodic oxidation of iodide on platinum

The kinetics and mechanism of the formation, growth and dissolution of iodine films on platinum during the electrooxidation of iodide have been investigated using rotating-disk and ring-disk techniques. The dissolution-precipitation mechanism of film formation and a linear growth law for film growth has been confirmed. The iodine film on platinum is believed to be made up of an ionically insulating barrier layer covered by a porous overlayer. The oxidation behavior of iodide and ferrous species shows that the iodine film is predominantly an iodide-ion conductor. Also, a film transformation, responsible for the transient features observed during iodide oxidation has been confirmed. This transformation changes the mechanism of iodide transport through the film from a partly “pore”-type to a Grotthus-type mechanism. The ring current maximum, which occurs at the same instant as the disk current minimum, reveals the mechanism of dissolution of iodine film during the transient period as involving complexation with iodide. Evidence for the mass-transport-controlled component of the potentiostatic transient response has been obtained from the sinusoidal hydrodynamic modulation response.