Crystallization of vulcanizates. I. Low‐temperature crystallization as a function of extent of cure for polyisoprene vulcanized with tetramethylthiuram disulfide/sulfur and 2‐bisbenzothiazole‐2,2′‐disulfide/sulfur

The crystallization of polyisoprene, vulcanized to various degrees of cure with tetramethylthiuram disulfide/sulfur and 2‐bisbenzothiazole‐2,2′‐disulfide (MBTS)/sulfur formulations, was studied in a density column at ?25°C. The densities of vulcanizates before crystallization decrease progressively with cure time, which is ascribed to an increase in free volume occasioned by the formation of accelerator‐terminated pendent groups on the polymer chain. The induction period before the onset of crystallization increases and both the rate of and the degree of crystallization decrease with extent of cure. This is attributed primarily to the presence of residual pendent groups on the polymer chain and secondly to crosslink formation. The changes are more marked with MBTS formulations where pendent groups are more bulky. MBTS compounds fail to crystallize once vulcanized to the point where a gel has formed. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2565–2572, 2001     

Thioether Analogues of Disulfide‐Bridged Cyclic Peptides Targeting Death Receptor 5: Conformational Analysis,Dimerisation and Consequences for Receptor Activation

Cyclic peptides containing redox‐stable thioether bridges might provide a useful alternative to disulfide‐bridged bioactive peptides. We report the effect of replacing the disulfide bridge with a lanthionine linkage in a 16‐mer cyclic peptide that binds to death receptor 5 (DR5, TRAIL‐R2). Upon covalent oligomerisation, the disulfide‐bridged peptide has previously shown similar behaviour to that of TNF‐related apoptosis inducing ligand (TRAIL), by selectively triggering the DR5 cell death pathway. The structural and biological properties of the DR5‐binding peptide and its desulfurised analogue were compared. Surface plasmon resonance (SPR) data suggest that these peptides bind DR5 with comparable affinities. The same holds true for dimeric versions of these peptides: the thioether is able to induce DR5‐mediated apoptosis of BJAB lymphoma and tumorigenic BJELR cells, albeit to a slightly lower extent compared to its disulfide homologue. NMR analysis revealed subtle variation in the conformations of the two peptides and suggests that the thioether peptide is slightly less folded than its disulfide homologue. These observations could account for the different capability of the two dimers to cluster DR5 receptors on the cell surface and to trigger apoptosis. Nevertheless, our results suggest that the thioether peptide is a potential candidate for evaluation in animal models.     

Two-component initiator systems for the ring-opening polymerization of oligomeric cyclic bisphenol-A carbonates: The in situ cleavage of disulfides by triarlyphosphines

A two-component initiator system based on the in situ cleavage of phenyl disulfide by a triarylphosphine has been developed for the ring-opening polymerization of cyclic bisphenol-A (BPA) carbonate oligomers. This development has potential use in composite applications such that the prepolymer can suitably wet the composite material before being converted to high-molecular-weight polymer. The initiator precursors (phenyl disulfide and triphenylphosphine) do not independently initiate significant ring-opening polymerization of the oligomeric cyclic BPA carbonate mixture. A mixture of cyclic BPA carbonate oligomers and one of the initiator components (phenyl disulfide), combined and heated at 300°C with a mixture of the cyclics and the other initiator component (triphenylphosphine), does produce a high-molecular-weight polymer (M_w = ∼ 70,000). The polymerization-initiating species is thought to be thiophenyltriphenylphosphonium thiophenoxide. The effects of concentration of the initiator components, reaction temperature, time, and so forth on polymerization were studied; in general, the degree of polymerization ranged from about 65 to 75%. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 2251–2255, 1997     

甲烷磺酰氯的合成研究

阐述了利用二甲基二硫在相转移催化剂作用下，于盐酸介质中经氯气直接氧化，一步合成甲烷磺酰氯的工艺过程，讨论了几个主要反应因素对产物收率的影响，确定了适宜的工艺条件。表明了产品的检测方法     

GC-FPD测定粗苯中二硫化碳及噻吩含量

建立了气相色谱法测定粗苯中二硫化碳及噻吩含量的分析方法。将粗苯以甲醇为溶剂稀释,采用GC-9A岛津气相色谱分离,FPD检测器检测,指数法分别对粗苯中的二硫化碳、噻吩进行定性定量分析。该方法分离效果好,测定的结果具有良好的准确度和精密度,整个试样分析时间不超过6 min。     

Simple and green method for synthesis of symmetrical dialkyl disulfides and trisulfides from alkyl halides in water; PMOxT as a sulfur donor

An environmentally new, mild and efficient method has been developed for the synthesis of dialkyl disulfides and dialkyl trisulfides in aqueous conditions by a reaction between alkyl halides (and tosylate) and potassium-5-methyl-1,3,4-oxadiazole-2-thiolate (PMOxT) as a sulfur transfer reagent. The advantages of this method are that it occurs under mild reaction conditions, it is base free, it uses water as the solvent and it occurs in high yields. A variety of dialkyl disulfides and dialkyl trisulfides can be obtained in good to excellent yields up to 98%.     

Efficient one-pot preparation of bisalkyl xanthogen disulfides from alcohols

An efficient one-pot synthetic procedure for the preparation of bisalkyl xanthogen disulfides is achieved via oxidation of the in situ generated xanthate salt in an aqueous condition using half an equivalent of molecular iodine in one pot.     

A simple route for the synthesis of symmetrical thiourea derivatives and amidinium cations by reaction between isocyanides,amines and carbon disulfide

Reaction between primary amines and CS₂ promoted by alkyl isocyanides in ethanol as solvent provides a simple and efficient route for the synthesis of symmetrical thiourea derivatives. The reaction of secondary amines with carbon disulfide and alkyl isocyanides afforded new amidinium cations in good yields.     

Oxidative coupling of aromatic thiols to corresponding disulfides using magnetic particle-supported sulfonic acid catalyst and hydrogen peroxide under mild conditions

A green and efficient method for chemoselective oxidation of aromatic thiols to the corresponding disulfides is reported using a recoverable supported iron oxide nanoparticle (γ-Fe₂O₃–SO₃H) catalyst in the presence H₂O₂ as the oxidant and methanol as the solvent at room temperature. This reaction is operationally simple with an easy work-up, utilizes mild reaction conditions, is high-yielding, clean, and exhibits high selectivity toward aromatic disulfides with no side reactions. The supported iron oxide nanoparticles can be easily recovered using an external magnet from the reaction mixture and reused several times. Reaction progress was monitored by potentiometric titration.