Tetramethylthiuram Disulphide Research Articles

The electrochemical synthesis of O-ethylxanthato and N,N′-dimethyldithiocarbamato complexes of indium(III), tin(IV), lead(II), bismuth(III) and tellurium(IV)

The O-ethylxanthato and N,N′-dimethyldithiocarbamato main group metal complexes were produced by the one-step electrochemical oxidation of the metal (M = In, Sn, Pb, Bi, Te) in the presence of an acetone solution of ethyl dixanthogen or tetramethylthiuram disulphide.

Inactivation of horse liver mitochondrial aldehyde dehydrogenase by disulfiram. Evidence that disulfiram is not an active-site-directed reagent.

The inhibition of mitochondrial (pI 5) horse liver aldehyde dehydrogenase by disulfiram (tetraethylthiuram disulphide) was investigated to determine if the drug was an active-site-directed inhibitor. Stoichiometry of inhibition was determined by using an analogue, [35S]tetramethylthiuram disulphide. A 50% loss of the dehydrogenase activity was observed when only one site per tetrameric enzyme was modified, and complete inactivation was not obtained even after seven sites per tetramer were modified. Modification of only two sites accounted for a loss of 75% of the initial catalytic activity. The number of functioning active sites per tetrameric enzyme, as determined by the magnitude of the pre-steady-state burst of NADH formation, did not decrease until approx. 75% of the catalytic activity was lost. These data indicate that disulfiram does not modify the essential nucleophilic amino acid at the active site of the enzyme. The data support an inactivation mechanism involving the formation of a mixed disulphide with a non-essential cysteine residue, resulting in a lowered specific activity of the enzyme.

The fate of tributyltin toxicants in neoprene‐based elastomeric antifouling coatings: 119mSn Mössbauer, 119Sn NMR and chemical studies

AbstractThe fate of a series of tributyltin toxicants on incorporation into cured neoprene elastomers has been studied by 119mSn Mössbauer and 119Sn NMR spectroscopic techniques, together with supporting chemical derivatization techniques. It is shown that all of the toxicants undergo chemical change during the curing process, being converted into tributyltin chloride, together with (in some cases) tributyltin stearate and a small amount of dibutyltin distearate. Possible interactions between the organotin agents and other components of the elastomer, e.g. carbon black filler, and cure accelerators such as tetramethylthiuram disulphide, have also been investigated.

Modification of polysulphide rubber using butadiene—acrylonitrile copolymer/poly(vinyl chloride) blend

Blending of polymers for property improvement or for economic advantage has gained considerable importance in the field of polymer science in the last decade, Polysulphide rubber is a costly speciality rubber which is well known for its outstanding resistance to solvents such as ketones, alcohols, acids, hydrocarbon solvents, water, etc. However, processing of polysulphide rubber is difficult, its mechanical properties are poor and it has an unpleasant odour [1-3]. Hence it would be worthwhile to attempt to improve the processing and mechanical properties of polysulphide rubber without sacrificing much of its excellent solvent resistance. Attempts have already been made in this direction, by blending polysulphide lattices by other synthetic lattices [4]. One of the commercially important and miscible polymer blends is that of NBR and PVC [5]. Compared to hydrocarbon rubbers, polysuiphide rubber is more polar and hence likely to form successful blends with NBR and PVC. In this study up to 50% by weight of polysulphide rubber is replaced with 50/50 NBR/PVC blend and the properties are compared. MgO/ZnO combination in the presence of stearic acid has recently been shown to be an efficient stabilizer system for PVC, especially in PVC-based blends [6-8]. Hence this combination was used to stabilize the PVC phase in this study. Polysulphide rubber (FA type, Mooney viscosity, ML 1 +4 at 100°C, 82), NBR (33.5% acrylonitrile, Mooney viscosity, ML 1+4 at 100°C, 40.9), PVC (powder, suspension polymer, K = 65), MgO (light magnesia), ZnO (white seal), Stearic acid, dibenzothiazyl disulphide (MBTS), diphenyl guanidene (DPG), tetramethyl thiuram disulphide (TMTD), and sulphur (all rubber grade) were the materials used. 50/50 NBR/PVC blend was made in a Brabender plasticorder model PL3S employing a rotor speed of 30 r.p.m. at the optimum temperature [8]. In addition to the equal weights of NBR and PVC, stabilizers for PVC (MgO 4 parts per 100 parts of PVC resin (p.h.r.), ZnO 4p.h.r. and stearic acid 3p.h.r.) were added at this stage. Blending of the polysulphide rubber and the NBR/PVC blend along with the additives for the rubber was done in a tight warm (about 60°C) laboratory mixing mill. The formulations used for the various mixtures are shown in Table I. The cure characteristics of the mixtures were determined in a Monsanto rheometer model R100 at 150°C. The cure characteristics are shown in Table II. The mixtures were vulcanized up to the respective optimum cure times in an electrically heated press at 150° C in a specially designed mould so that the mould with the sample inside could be cooled immediately after moulding, keeping the sample still under compression. The tensile properties of the vulcanizates were determined as per ASTM D412-80 [9] test method, at 28° C using dumb-bell-shaped test pieces at a crosshead speeed of 500 mm min-' using a Zwick universal testing machine. The ageing characteristics of the samples were determined by keeping them at 100°C for 24 h in an air oven and then measuring the retention in the tensile properties. The hardness of the vulcanizates was determined according to ASTM 2240

Electrochemical synthesis of tetra-alkylthiuram disulphides in emulsions

Sodium dimethyldithiocarbamate, NaDTC, was electrochemically oxidized to tetramethylthiuram disulphide, TMT, in an univided electrolytic cell using a couple of rhutenized titanium electrodes; in earlier work the electrodes were platinum. The reaction was carried out in an emulsion formed by mixing saturated aqueous sodium chloride solution containing the substrate with a suitable organic solvent at constant current density. The product was obtained with a high yield and high degree of purity after the passage of the theoretical amount of charge. It was found that at a high current density and a high reactant concentration the product solubility in the organic solvent used determines the success of the electrochemical reaction. Possible reaction mechanisms are also discussed.

Nobecutane spray as a temporary dressing of skin graft donor sites.

Various methods have been used for managing split-thickness skin graft donor sites. Open and closed techniques have been suggested by various authors with the purpose of achieving smooth and rapid healing of the wound. There is growing evidence to suggest that the site and quality of the healing is improved when the wound is protected from dehydration and further mechanical trauma. A recent method is the spraying of Nobecutane Spray on the donor site. Nobecutane sprayed on a wound forms a plastic film which serves as a dressing material. It contains specially modified acrylic resin in an organic solvent (ethyl acetate) and TMTD (tetramethylthiuram disulphide) which is strongly bactericidal and fungicidal. We employed this method on 50 patients and found it to be effective in achieving rapid and painless healing. The dressing is transparent, permits easy follow-up of healing in the donor site, protects the wound against infection, and does not inconvenience the patient. The treatment is simple, economical, and does not require special skills. The dressing peels off spontaneously after epidermal regeneration of the wound is completed. No complications or allergic reaction were observed with this treatment.

A contribution to the theory of accelerated sulphur vulcanization of natural rubber and polybutadiene BR with tetramethyl thiuram disulphide and bis(2‐benzothiazolyl) disulphide

AbstractA number of simple natural rubber (NR) and polybutadiene (BR) formulations were vulcanized in a differential scanning calorimeter. From the shapes of the exothermal cure curves the interaction of curatives can be examined. It is suggested that polysulphidic‐accelerator‐terminated pendent groups could either crosslink, or be chelated with zinc ions. The latter reaction allows interaction with accelerator molecules to reform the unchelated pendent group, and a zinc accelerator complex, that, in turn, can react with sulphur and rubber molecules to give pendent groups. Differences in the behavior of NR and BR are attributed to the relative rates of these two reactions in the elastomers. Bis(2‐benzothiazolyl) disulphide does not react with zinc, and it is suggested that it coordinates with the zinc dithiolate accelerator complex, increasing its activity.

Effect of thiuram sulphides on the uptake and distribution of nickel in pregnant and non-pregnant mice

Oral administration of 63Ni 2+ together with thiuram sulphides (tetramethylthiuram disulphide, tetraethylthiuram disulphide, tetrabutylthiuram disulphide, dipentamethylenethiuram monosulphide or dipentamethylenethiuram tetrasulphide) or sodium diethyldithiocarbamate resulted in highly increased levels of 63Ni 2+ in several tissues of mice in comparison with animals given 63Ni 2+ alone. Administration of these substances to pregnant animals induced increased levels of 63Ni 2+ in the fetuses. The uptake of 63Ni 2+ in the brains of both adults and fetuses was usually very markedly enhanced by these compounds — dipentamethylenethiuram monosulphide and tetraethylthiuram disulphide being the most efficient compounds in this respect. Determination of the chloroform/water partition coefficients for nickel in the presence of thiuram sulphides or sodium diethyldithiocarbamate showed that these compounds are able to form lipophilic complexes with the metal. A facilitated penetration through the cellular membranes of the lipophilic complexes between nickel and these substances can explain the effects on the fate of the nickel. However, the partition coefficient for nickel in presence of sodium diethyldithiocarbamate was much higher than for the thiuram sulphides, but in spite of that, the effect of sodium diethyldithiocarbamate on the disposition of 63Ni 2+ in the mice was not more marked than for most of the thiuram sulphides. It has been shown that tetraethylthiuram disulphide undergoes a reductive fission in the gut to diethyldithiocarbamate, which is considered to be the active form of tetraethylthiuram disulphide. The marked effects on the disposition of the 63Ni 2+ induced by the other thiuram sulphides examined in the present study suggest that a similar fission to chelating thiocarbamates will take place. However, the formation of lipophilic complexes with the original thiuram sulphides may contribute to the effects on the disposition of the 63Ni 2+.

Application of high-performance liquid chromatography in the trace analysis of some fungicides

A method has been developed for the determination of trace concentrations of iron(III) dimethyldithiocarbamate (ferbam) and its three degradation products (thiram or TMTD, tetramethylthiuram disulphide; TMTM, tetramethylthiuram monosulphide; and TMTU, tetramethylthiourea) in model mixtures and real samples. Quantitative analysis using adsorption and reversed-phase chromatography enables reproducible results to be achieved of in the high-performance liquid chromatographic separation of these compounds in a very short time. All results were verified by mass spectrometry. The limit of detection for thiram in soil was 0.005 mg/kg, which corresponds with the criteria of the FAO (Codex Alimentus) concerning methods for the determination of dithiocarbamate residues in food.

Effect of mineral filler sepiolite on sulphur‐free thiuram vulcanization of natural rubber

AbstractThe effect of sepiolite on the sulphurless vulcanization of NR by tetramethylthiuram disulphide, with and without activator (triethanolamine) was studied. The influence on: a) kinetic vulcanization parameters, b) crosslinking density, c) crosslinking types, d) efficiency factor E and e) zinc sulphide formation was considered. The vulcanization rate increases with increasing sepiolite level but crosslinking density is reduced. Based on these results a vulcanization mechanism is proposed and discussed.

Effect of thiocarbamate derivatives on copper, zinc, and mercury distribution in rats and mice.

Oral treatment of rats with tetramethylthiuram disulphide (TMTDS), 0.1% mixed in the food (corresponding to 20--30 mumol daily) for one week, increased the brain levels of endogenous copper and zinc to 120% and 170%, respectively, of the control levels. Mice injected with HgCl2 (2.5 mumol/kg) were used to study further the effect of DDC (diethyldithiocarbamate), disulfiram, TMTDS or CS2 on heavy metal distribution. The brain levels of Hg were significantly increased in mice given DDC or TMTDS. Disulfiram and CS2 increased the brain levels marginally. Pregnant rats exposed to HgCl2 (0.5 mumol/kg) were also included in the studies. Treatment with DDC (0.5 mmol/kg) immediately after the mercury injection, increased the maternal brain concentration of mercury considerably, as measured after 24 and 78 h. The kidney levels were also increased. In the foetuses, the brain and liver levels were transiently increased after treatment with diethyldithiocarbamate. The observations support the hypothesis that the neurotoxicity of diethyldithiocarbamate and other thiocarbamates may be related to changes in heavy metal metabolism.

Fungicide control ofUstilago bullataseedling and shoot infection ofBromus catharticus

Abstract Fungicide control of Ustilago bullata Berk. seedling and shoot infection of Bromus catharticus Vahl was investigated in glasshouse trials. Seedling infection was controlled adequately with 2,3-dihydro-6-methyl-5-phenylcarbamoyl-l,4-oxathiin (carboxin) and tetramethylthiuram disulphide (thiram) at rates of 3 and 12 g active ingredient (a.i.)/kg seed respectively, without reducing seedling emergence from soil using freshly treated seed, or germination of treated seed after 6 months' storage. Methyl-l-(butyl-carbamoyl)-benzimidazol-2-yl-carbamate (benomyl) at 3 g a.i./kg seed gave good control of seedling infection, but slightly reduced seedling emergence. Shoot infection was controlled with soil drenches of benomyl and carboxin but at rates (40 kg a.i./ha) that were likely to be uneconomic in practice. Five other fungicides, including N-trichloromethyl-thio)-3a,4,7,7a-tetrahydrophthalimide (captan), 2-(4-thiazolyl) benzimidazole (thiabendazole), the 4,4 dioxide of carboxin (oxycarboxin), and two ex...

Effect of vulcanization temperature and synergism of accelerators on the network and technical properties of efficiently vulcanized natural rubber mixes

The effect of an increase in vulcanization temperature from 150° to 180°C on the network structure and technical properties of gum natural rubber vulcanizates has been studied using six different binary combinations of tetramethyl thiuram disulphide (TMTD) and 2-(morpholinodithio)benzothiazole (MDB) at fixed sulphur level (0.6 parts per hundred rubber). On the basis of processing safety, reversion resistance, technical properties, retention of properties after aging and percentage losses in properties on increasing the vulcanization temperature by 30°C, if was found that the combination with MDB (1.2 phr) TMTD (0.6 phr) showed the best synergism of the two accelerators. Results of chemical characterization of vulcanizate networks have been correlated with their technical properties. At higher vulcanization temperature, lower degree of crosslink density and with increasing extent of sulphidic main chain modification, a reduction in strength, modulus, hardness and resilience resulted and brought about a higher compression set and a greater heat build-up during Goodrich flexometer tests. The better cut growth and flex properties of vulcanizates cured at 180°C have been explained on the basis of the distribution of different types of crosslinks and stress relaxation caused by lower crosslink density.

Extraction and spectrophotometric determination of platinum(IV) using tetramethylthiuram disulfide

The extraction and photometric determination of platinum(IV) with tetramethylthiuram disulphide has been studied. Addition of an excess of stannous chloride and maintaining acidity to 2–6 M with HCl is necessary for quantitative extraction. With 10 ml of TMTD in toluene and equilibration for 30 sec, platinum is extracted as a pale yellow complex in the organic phase. It has λ max at 348 nm and obeys Beer's law in the concentration range of 0.2 to 9.0 μg of Pt per ml. The complex is stable for 3 hr. The ratio of Pt:TMTD in the extracted species is found to be 1:1. Most of the anions and cations are tolerated in large ratio. The method can be satisfactorily applied for the determination of platinum in the presence of four- and eightfold excesses of ruthenium and osmium, respectively.

Mechanisms of antioxidant action: A photochemical study of transition metal dibutyl dithiocarbamates (and their photo-stabilizing role in a polyolefin matrix)

Solution photochemistry of some ( N, N-di- n-butyldithiocarbamato) complexes and of the metal-free dithiocarbamate ligands has been used to investigate their role in the photo-oxidation of polyolefins. Transient absorption spectra were recorded for tetramethyl thiuram disulphide at around 600 and 400 nm, and for tetramethyl thiuram monosulphide which also shows an additional band at 350 nm. Kinetic analysis of the decay profiles showed the presence of two different species with first and second order kinetics for the 400 and 600 nm transients respectively. Tentatively, the 400 nm absorption was assigned to a triplet-triplet transition, while the 600 and 350 nm absorption regions were assigned to the dithiocarbamoyl and thiocarbamoyl radicals respectively. Spectrophotometric monitoring has shown that tetramethyl thiuram disulphide is formed during the process of photobleaching of the Fe(III) complex.

Kinetics of photo-oxidation of polydienes

A study was made of photo-oxidation of polyisoprene (SKI) and polybutadiene (SKD) rubbers and SKI rubber vulcanized with tetramethylthiuram disulphide. It was shown that photo-oxidation of SKI takes place as a process with degenerate branching on hydroperoxide and with formally linear chain rupture. Sensitized oxidation of the vulcanizate based on SKI is also a process with linear chain rupture, however, the length of the chain (10–12 units) is considerably shorter than in SKI (≈ 100 units). Photo-oxidation of SKD takes place as a process with quadratic chain rupture. The ratio between rate constants of chain extension and rupture in SKD k ex[PH]/√2 k 0 is (2·7±0·5) × 10 −2 (1./ mole·sec) 1 2 at room temperature.

Extraction and Spectrophotometric Determination of Osmium by Tetramethylthiuram Disulphide in Toluene

Tetramethylthiuram disulphide (TMTD) is used for the extraction and spectrophotometric determination ofμg quantities of osmium. 15 ml of 1.052×10−3 M TMTD in toluene quantitatively extracts osmium from7 M HCl. The complex attains maximum colour intensity in 2 hours. It is red in colour and exhibits two λ max. One at 445 nm and the other at 504 nm. The maximum at 504 nm is more significant. Beer's law was found to hold good over the concentration range of 1.7 to 26.7μg of osmium per ml. The Ringbom plot shows the optimum range of 9.42 to 23.65μg of osmium per ml. The optimum period of equilibration is 30 seconds and the complex is stable up to 5 hours. The extracted species shows the composition to be 1 ∶ 1 (Os ∶ TMTD). It is possible to extract and determine osmium in the presence of other platinum metals with composition corresponding to the ore osmiridium.

Effects of pesticide seed treatments on Rhizobium japonicum and its symbiotic relationship with soybean.

Seventeen Rhizobium japonicum cultures isolated from soybean nodules induced formation of nodules on taproots of soybean plants. All isolates reduced acetylene to ethylene to different extents in vitro. Paper disc assay indicated that two insecticides, lindane (gamma-1,2,3,4,5,6-hexachlorocyclohexane), chlorpyrifos (O,O-diethyl O-3,5,6-trichloro-2-pyridyl phosphorothioate), and a fungicide, thiram (tetramethylthiuram disulphide) individually or in combination caused significant inhibition of the growth of R. japonicum No. 16. The effects of insecticide-fungicide seed treatments on the nitrogenase activity of soybean plants in nitrogen-fixing capacity, weights of leaves, stems, and nodules were determined. Thiram, singly or in combination with lindane and/or chlorpyrifos, significantly delayed growth of the plants and affected the activity of nitrogenase in the fixation of nitrogen 3 weeks after treatments. No drastic effect of any of the pesticide treatments on soybean plant growth was observed after 8 weeks.

Extraction and Photometric Studies of Cu(ll) with Tetramethylthiuram Disulphide

Extraction and Photometric Studies of Cu(ll) with Tetramethylthiuram Disulphide

Chemorheology of irradiation-cured natural rubbers: 2. Stress relaxation mechanisms of sulphur-containing cured systems in air

Stress relaxation mechanisms in air were investigated for irradiation-cured natural rubbers (NR) containing the various levels of sulphur, in relation to the crosslinked structure. All the stress relation curves of these vulcanizates except the sulphur-free sample were the sum of two exponential terms. The relaxation rate in the long time region increased with increasing sulphur contents, in spite of having the same initial chain density. This behaviour could be explained by introducing the assumption, that this system has two independent networks, i.e. one ( N p (O)) based on the polysulphide cross-linkages and another ( N c, m (O)) based on the mono- and di-sulphide linkages and the carbon—carbon bonds. N p (O) increased with increasing sulphur contents and N c, m (O) decreased with increasing sulphur contents. The q m, c ( t) (the number of moles of main chain scission) were in agreement with each other, independent of the sulphur contents. However, this value was larger than that of the sulphur-free sample. This was similar to irradiation-cured tetramethylthiuram disulphide NR, in which the crosslinking sites consisted of mono- and di-sulphides and carbon—carbon bonds.