摘要:

AbstractDimethyl sulphide and other reduced sulphur compounds, produced by marine biogenic activity and other processes, play a significant role in the global biogeochemical cycling of the element. The rates of their reactions with atmospheric oxidants are reviewed and their lifetimes in the troposphere due to the various reactions are computed. Sufficient data are available on the tropospheric abundance of the hydroxyl radical (OH) and on the rates of its reactions with the sulphur compounds for reasonable estimates to be made of the sulphur lifetimes with respect to OH. Summertime lifetimes of 14–87 h for (CH3)2S are computed at different latitudes. In the case of the tropospheric concentrations of the nitrate radical (NO3), few data are available. There is a similar paucity of data on its rates of reactions with the sulphur compounds, and so large uncertainties exist in the computed lifetimes. These are, in any case, much longer than those due to OH. The possibility exists that iodine photochemistry, producing iodoxyl (IO) radicals, may efficiently oxidize the reduced sulphur and other organic compounds in the marine troposphere leading to lifetimes of the order of hours. Few data exist on the rates or mechanisms of these reactions and these are identified as representing the greatest uncertainties in the estimates of organosulphur lifetimes in the tropospher

ISSN:0268-2605    

DOI:10.1002/aoc.590020502

出版商:Longman Group UK Ltd.    

年代:1988

数据来源: WILEY

摘要:

AbstractThein vivoactivity of some R2Sn‐L‐cysteinate complexes (R = Me, Et, n‐Bu) against murine P‐388 leukaemia has been tested. Only the Et2Sn(IV) complex showed a marginal positive effect. Trigonal bipyramidal tin environments with two carbon (R) atoms and the sulfur atom in the equatorial plane and oxygen (carboxylate) and nitrogen (NH2) in apical positions have been proposed for the solid compexes (R = Me, Et, n‐Bu, Ph) on the basis of experimental Mössbauer parameters and infrared (IR) data. Aqueous solutions of the Me2SnL‐cysteinate have been studied by IR,1H NMR and119Sn Mössbauer spectroscopy (in frozen solution) at different pH values to identify the Me2Sn(IV) species present. At pH>2 the dimethyltin aquocation is complexed by the ionized sulfhydryl group ofL‐cysteine to form a five‐coordinated species. With increasing pH values, NH3+is deprotonated and a chelate is proposed with both the sulfhydryl and the amino group bonded to tin, one water molecule or (at still higher pH values) one hydroxyl ion occupying the fifth coordination site of a trigonal bipyramid around tin. Finally at pH>10 the NH2group is substitute

ISSN:0268-2605    

DOI:10.1002/aoc.590020503

出版商:Longman Group UK Ltd.    

年代:1988

数据来源: WILEY

摘要:

AbstractThe bioconcentration of alkyllead compounds from water and from contaminated sediments by freshwater mussels (Elliptio complanata) has been investigated. Higher levels of trimethyllead than triethyllead species are accumulated for the same exposure period.In‐vivotransformation of the trialkyllead species by a series of dealkylation reactions giving dialkyllead and inorganic lead(II) species appears to take place. Rates of accumulation are higher for the more contaminated sediment

ISSN:0268-2605    

DOI:10.1002/aoc.590020504

出版商:Longman Group UK Ltd.    

年代:1988

数据来源: WILEY

摘要:

AbstractThe methylation of tin(II) chloride by methyl iodide in porewater and formation of monomethyltin as the only methyltin product are described. A factorial experiment tested the effects of concentrations of tin(II), methyl iodide, and oxygen on monomethyltin yields. The experiments gave 0.18 to 12.8 % yield. Analysis of variance (ANOVA) calculations showed that all three variables were significant at the 95 % level. Comparison of yields in aqueous 23 g kg−1sodium chloride solutions to those in porewater and to those containing fulvic acid, salicylic acid, and EDTA showed that only fulvic acid significantly reduced yields. Reasons for this observation are discussed and the findings in the model system are related to methylation of tin compounds in sediment

ISSN:0268-2605    

DOI:10.1002/aoc.590020505

出版商:Longman Group UK Ltd.    

年代:1988

数据来源: WILEY

摘要:

AbstractHigh‐performance liquid chromatography coupled with graphite furnace atomic absorption spectroscopy (HPLCGF AA) gives element‐specific detection of environmental samples containing trace amounts of organotin or organolead species. The direct GF AA of organotin and organolead species is subject to errors arising primarily from loss of analyte prior to atomization, probably through the formation of refractory carbides and of compounds or complexes that are volatile at low temperatures. Examples abound in the literature of signal suppression in the GF AA of organometallic species in environmental samples, and several furnace tube modifications have been developed to overcome this suppression. Here, the analyte and a modifier are co‐pipetted into a conventional furnace tube, from either a solution of analyte or an HPLC effluent. Oxides of transition metals (e.g. chromium, manganese, or tungsten) are shown to enhance both tin and lead signals, whereas chlorides do not, suggesting the low‐temperature formation of relatively involatile metal oxides or volatile metal chlorides, respectively. In the absence of modifier, GF AA signal intensities decrease consecutively for equal quantities of mono‐, di‐, tri‐ and tetra‐butyltin species, but are nearly equal for the first three in the presence of complexing dichromate (Cr2O72−). The lesser signal increase for tetrabutyltin indicates a dissimilar low‐temperature complexation chemistry for the fully ligated neutral organometal to that for the ligated ions. similar results are demonstrated in post‐column addition of a matrix modifier to effluent containing either organoti

ISSN:0268-2605    

DOI:10.1002/aoc.590020506

出版商:Longman Group UK Ltd.    

年代:1988

数据来源: WILEY

摘要:

AbstractThe oral acute toxicity for tri‐n‐butyltin glycocholate (TBT‐GA), a newly synthesized organotin steroid, was determined using Long Evans rats. The compound was suspended in corn oil and adminstered by gavage using standard techniques. Unlike tri‐n‐butyltin taurocholate, which exhibited two different toxicities, one for the tri‐n‐butyltin moiety and one for the taurocholic acid moiety, the TBT‐GA exhibited a single toxicity, that of the whole molecule. The LD50value was 213 mg kg−1(0.274 mmol kg), which on a millimolar basis is similar to that observed for other tri‐n‐butyltin compounds. The dead rats exhibited distended stomachs, enlarged ceca, and lesions in the intestinal tract.The actual cause of death could not be positively identified. Animals that survived more than three days also exhibited time‐ and dose‐related atrophy of the thymus gland. With 36% more male than female rats succumbing to TBT‐GA, the chemical appears to be more toxic to

ISSN:0268-2605    

DOI:10.1002/aoc.590020507

出版商:Longman Group UK Ltd.    

年代:1988

数据来源: WILEY

摘要:

AbstractThe configuration of the bonding environment of tin in the complexes [R2Sn(SCH2CH2SO3)2]2−(R = Me, Ph) and [Me3Sn(SCH2CH2SO3)]−has been determined to be tetrahedral both in the solid state and in aqueous solution (for the methyl derivatives). The coordination number of tin increases to five in aqueous solutions for the Me2Sn(IV) complexes in Hepes buffer (N‐2‐hydroxyethylpiperazine‐N′‐2‐ethanesulfonic acid; at least in fivefold excess, at pH 7.4) due to coordination by the tertiary amino nitrogen atom. No effect is detected due to the surfactant 2‐hydroxypropylcellulose concerning both coordination to tin and influence on the Mössbauer parameters. The stoichiometry of mixed complex formation in aqueous solution of Me2Sn(IV), 2‐mercaptoethanesulfonate and Hepes is 1:2:1, according to a procedure of ‘Mössbauer titration’. All complexes in aqueous solution undergo slow lysis of the tin‐sulfur bonds. Structural assignments have been generally effected on the basis of the magnitude of experimental values of Mössbauer nuclear quadrupole splittings, measured at 77 K for both solid and frozen aqueous absorbers, and comparison with data calculated by the

ISSN:0268-2605    

DOI:10.1002/aoc.590020508

出版商:Longman Group UK Ltd.    

年代:1988

数据来源: WILEY

摘要:

AbstractA monomer and polymer of a copper(II) phthalocyanine have been synthesized in order to develop structure‐property relationships. Various electroactive properties such as dielectric constant, resistivity and thermally stimulated depolarization effects were investigated in order to examine the influence of extended conjugatio

ISSN:0268-2605    

DOI:10.1002/aoc.590020509

出版商:Longman Group UK Ltd.    

年代:1988

数据来源: WILEY

摘要:

AbstractThe thermal properties of some organotin complexes of general structure (4‐ZC6H4)2SnCl2.L2(Z=Me, CF3, F, Cl, OMe and H; L2= 2,2′ ‐bipyridyl and 4,4′ ‐dimethyl‐2,2′ ‐bipyridyl) are reported. The thermal data obtained by Differential Thermal Analysis (DTA) for these complexes is reported. Thermal decomposition experiments for some of the complexes are described and indicate a disproportionation of the complexes into the aryltin trichloride complex and the triaryltin chloride. The controlled decomposition provides a possible alternative preparative route to some aryltin trichl

ISSN:0268-2605    

DOI:10.1002/aoc.590020510

出版商:Longman Group UK Ltd.    

年代:1988

数据来源: WILEY

摘要:

AbstractGallium metal readily prompted the allylation of aldehydes and ketones with allyl iodide. α, β‐Unsaturated carbonyl compounds underwent only 1,2‐add

ISSN:0268-2605    

DOI:10.1002/aoc.590020511

出版商:Longman Group UK Ltd.    

年代:1988

数据来源: WILEY