F:Flammable;513-53-1Relevant academic research and scientific papers
COPPER PROTECTIVE AGENT
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Paragraph 0039-0040, (2019/05/24)
A copper protective agent is provided. The copper protective agent is represented by a general formula (GI): HS—R (GI); and R is a linear or branched alkyl group having 1 to 20 carbon atoms.
Interrogation of the Substrate Profile and Catalytic Properties of the Phosphotriesterase from Sphingobium sp. Strain TCM1: An Enzyme Capable of Hydrolyzing Organophosphate Flame Retardants and Plasticizers
Xiang, Dao Feng,Bigley, Andrew N.,Ren, Zhongjie,Xue, Haoran,Hull, Kenneth G.,Romo, Daniel,Raushel, Frank M.
, p. 7539 - 7549 (2016/01/09)
The most familiar organophosphorus compounds are the neurotoxic insecticides and nerve agents. A related group of organophosphorus compounds, the phosphotriester plasticizers and flame retardants, has recently become widely used. Unlike the neurotoxic phosphotriesters, the plasticizers and flame retardants lack an easily hydrolyzable bond. While the hydrolysis of the neurotoxic organophosphates by phosphotriesterase enzymes is well-known, the lack of a labile bond in the flame retardants and plasticizers renders them inert to typical phosphotriesterases. A phosphotriesterase from Sphingobium sp. strain TCM1 (Sb-PTE) has recently been reported to catalyze the hydrolysis of organophosphorus flame retardants. This enzyme has now been expressed in Escherichia coli, and the activity with a wide variety of organophosphorus substrates has been characterized and compared to the activity of the well-known phosphotriesterase from Pseudomonas diminuta (Pd-PTE). Structure prediction suggests that Sb-PTE has a β-propeller fold, and homology modeling has identified a potential mononuclear manganese binding site. Sb-PTE exhibits catalytic activity against typical phosphotriesterase substrates such as paraoxon, but unlike Pd-PTE, Sb-PTE is also able to effectively hydrolyze flame retardants, plasticizers, and industrial solvents. Sb-PTE can hydrolyze both phosphorus-oxygen bonds and phosphorus-sulfur bonds, but not phosphorus-nitrogen bonds. The best substrate for Sb-PTE is the flame retardant triphenyl phosphate with a kcat/Km of 1.7 × 106 M-1 s-1. Quite remarkably, Sb-PTE is also able to hydrolyze phosphotriesters with simple alcohol leaving groups such as tributyl phosphate (kcat/Km = 40 M-1 s-1), suggesting that this enzyme could be useful for the bioremediation of a wide variety of organophosphorus compounds.
A general and mild synthesis of thioesters and thiols from halides
Zheng, Tu-Cai,Burkart, Maureen,Richardson, David E.
, p. 603 - 606 (2007/10/03)
The conversion of a wide variety of halides to thioesters by reaction with potassium thiocetate under mild conditions is described, and the generality of the method is demonstrated.
A preparative scale reduction of alkyl disulfides with tributyl phosphine and water
Ayers, Joshua T.,Anderson, Shelby R.
, p. 351 - 358 (2007/10/03)
A series of alkyl disulfides has been shown to be reduced by tributyl phosphine at room temperature. The resulting thiols were then acylated in the same pot and isolated in good yields. This sequence is convenient and is a practical option for the preparation of gram quantities of thiol or thioester from the corresponding disulfide.
Mechanism of the Solution-Phase Reaction of Alkyl Sulfides Atomic Hydrogen. Reduction via a 9-S-3 Radical Intermediate
Tanner, Dennis D.,Koppula, Sudha,Kandanarachchi, Pramod
, p. 4210 - 4215 (2007/10/03)
The low selectivity of benzyl alkyl sulfide fragmentation subsequent to its reaction with atomic hydrogen is indicative of a reaction that proceeds via an early transition state. The competitive reduction of a series of substituted-benzyl alkyl sulfides was insensitive to the substituent on the aromatic ring (ρ = -0.13, r = 0.99). The relative rates of fragmentation of a series of the substituted-benzyl alkyl sulfides gave a V-shaped Hammett plot. Both electron-donating and electron-withdrawing groups destabilized the transition state (ρ = +0.99, r = 0.999; ρ = -0.82, r = 0.992). Since the relative rates of disappearance of the alkyl benzyl sulfides are not substituent dependent, but the relative rates of fragmentation are, a 9-S-3 intermediate is preferred as the structure leading to products.
The Regioselective Reaction of Atomic Hydrogen with Unsymmetric Disulfides and Sulfides
Tanner, Dennis D.,Zhang, Liying,Vigneswaran, Markandu,Kandanarachchi, Pramod
, p. 4481 - 4487 (2007/10/02)
Unsymmetrical disulfides undergo solution phase reduction with atomic hydrogen regioselectively by displacement at the least hindered sulfur atom.The cleavage of the sulfur-sulfur bond forms mixtures of two thiol and two thiyl radicals.At the temperature at which the reactions are carried out, the thiyl radicals form symmetric disulfides by thiyl-thiyl radical coupling and not by thiyl radical displacement on the starting material.The reaction of atomic hydrogen with an unsymmetric sulfide is a cleavage that favors the formation of the most stable radical.The reaction of phenyl cyclohexyl sulfide produces benzene, cyclohexane, cyclohexyl thiol, and thiophenol.Benzene and cyclohexyl thiol produced from the cleavage of the phenyl-sulfur bond are proposed to arise from the α-scission of an intermediate formed by ipso-addition of atomic hydrogen to the benzene ring.
Rate Constants and Equilibrium Constants for Thiol-Disulphide Interchange Reactions Involving Oxidized Glutathione
Szajewski, Richard P.,Whitesides, George M.
, p. 2011 - 2026 (2007/10/02)
The rate of reduction of oxidized glutathione (GSSG) to glutathione (GSH) by thiolate (RS-) follows a Broensted relation in pKas of the conjugate thiols (RSH): βnuc ca. 0.5.This value is similar to that for reduction of Ellman's reagent: βnuc ca. 0.4 - 0.5.Analysis of a number of rate and equilibrium data, taken both from this work and from the literature, indicates that rate constants, k, for a range of thiolate-disulphide interchange reactions are correlated well by equations of the form log k = C + βnucpKanuc + βcpKac + βlgpKalg ( nuc = nucleophile, c = central, and lg = leaving group sulfur): eq 36 - 38 give representative values of the Broensted coefficients.The values of these Bronsted coefficients are not sharply defined by the available experimental data, although eq 36 - 38 provide useful kinetic models for rates of thiolate-disulfide interchange reactions.The uncertainty in these parameters is such that their detailed mechanistic interpretation is not worthwhile, but their qualitative interpretation - that all three sulphur atoms experience a significant effective negative charge in the transition state, but that the charge is concentrated on the terminal sulfurs - is justified.Equilibrium constants for reduction of GSSG using α,ω-dithiols have been measured.The reducing potential of the dithiol is strongly influenced by the size of the cyclic disulfide formed on its oxidation: the most strongly reducing dithiols are those which can form six-membered cyclic disulfides.Separate equilibrium constants for thiolate anion-disulphide interchange (KS-) and for thiol-disufide interchange (KSH) have been estimated from literature data: KS- is roughly proportional to 2ΔpKa is the difference between the pKas of the two thiols involved in the interchange.The contributions of thiol pKa values to the observed equilibrium constants for reduction of GSSG with α,ω-dithiols appear to be much smaller than those ascribable to the influence of structure on intramolecular ring formation.These equilibrium and rate constants are helpful in choosing dithiols for use as antioxidants in solutions containing proteines: dithiothreitol (DTT), 1,3-dimercapto-2-propanol (DMP), and 2-mercaptoethanol have especially useful properties.
