26330-85-8Relevant academic research and scientific papers
Reactions of phosphate and phosphorothiolate diesters with nucleophiles: Comparison of transition state structures
Ye, Jing-Dong,Barth, Christofer D.,Anjaneyulu, Potluri S. R.,Tuschl, Thomas,Piccirilli, Joseph A.
, p. 2491 - 2497 (2008/02/14)
A series of methyl aryl phosphorothiolate esters (SP) were synthesized and their reactions with pyridine derivatives were compared to those for methyl aryl phosphate esters (OP). Results show that SP esters react with pyridine nucleophiles via a concerted SN2(P) mechanism. Bronsted analysis suggests that reactions of both SP and OP esters proceed via transition states with dissociative character. The overall similarity of the transition state structures supports the use of phosphorothiolates as substrate analogues to probe mechanisms of enzyme-catalyzed phosphoryl transfer reactions. This journal is The Royal Society of Chemistry.
Enhanced reactivity in the ammonolysis of phenyl thiolacetates in aqueous medium
Rajarathnam,Babu,Nadar, P. Ananthakrishna
, p. 18 - 26 (2007/10/03)
The ammonolysis of several substituted phenyl thiolacetates is kinetically studied in aqueous medium, 18°C, ionic strength 0.1 M (KCl). By following the leaving groups spectrophotometrically (λmax = 260-410 nm), under excess free ammonia, pseud
Reduction potentials and kinetics of electron transfer reactions of phenylthiyl radicals: Comparisons with phenoxyl radicals
Armstrong,Sun, Qun,Schuler
, p. 9892 - 9899 (2007/10/03)
The reduction potentials relative to the standard hydrogen electrode (SHE) for a number of para-substituted phenylthiyl radicals (Eo(p-XC6H4S./p-XC6H 4S-)) have been derived from pulse radiolytic studies of electron transfer equilibria which compare their values to those of radicals of known reduction potentials. A ladder combining the reduction potentials for both phenylthiyl and phenoxyl radicals has been established. These reduction potentials have been shown to be self-consistent and are intermediate between those of p-benzosemiquinone radical anion at 0.02 V and phenoxyl radical at 0.79 V. The reduction potential decreases as the electron donating power of the para substituent rises. The substituent effect is, however, much weaker for the phenylthiyl radicals than for their oxygen analogs. These observations demonstrate that the electronic interaction between the sulfur atoms and the aromatic ring system is much less than that which occurs with oxygen atoms. Examination of the rates of electron transfer in terms of the Marcus theory indicates that the reorganization energies of both p-XC6H4O. and p-XC6H4S. radicals are similarly affected by H, CH3, and CH3O substitution. However, the reorganization energies increase substantially for H2N and O- para substituents with the effect being much less for the p-XC6H4S. radicals than for the p-XC6H4O. radicals. These observations are in accord with structural information from spectroscopic and theoretical studies of the radicals which show that in the latter system the substituent groups interact strongly with the aromatic π system.
Formation and scission of the sulfur-sulfur bond: a new approach to reactions between sulfur/polysulfide ions and thiolate ions/disulfides in N,N-dimethylacetamide
Bosser, Gerard,Anouti, Meriem,Paris, Jacky
, p. 1993 - 2000 (2007/10/03)
The reactivity of sulfur towaards a series of thiolate ions RS- has been studied by spectroelectrochemistry in N,N-dimethylacetamide.Apparently, sulfur reacts in two parallel ways: (i) oxidation of RS- leading to RS2R and S3 anion radical ions; (ii) preponderant S-nucleophilic process yielding stable RSx- ions (x = 2-5).RSx- species, whose spectrophotometric characteristics have been determined, are successively obtained in the course of sulfur addition with R = alkyl, whereas equilibria between arylpolysulfide ions were observed.At the junction of these two parallel pathways, the slow keyequilibrium 2RS4- RS2R + 2S3 radical anion has been investigated by addition of RS2RR = 1-8 to S3 radical anion solutions.In fact, our study is consistent with a first, a monoelectronic transfer between RS- (or RS2-) ions and the very reactive S2 molecules in equilibrium with S8.The fact and competing couplings of the radicals RS (or RS2 radical), S2 radical anion (or S3 radical anion) agree with the simultaneous formation of RS2R, RSx- and polysulfide ions.More generally, the S2/S2 radical anion redox system is believed to be involved in thiophilic reactions of a number of anions such as RS- towards sulfur rather than the initial opening of the cyclic S8 form.
Lifetimes of iminium ions in aqueous solution
Eldin, Sherif,Jencks, William P.
, p. 4851 - 4857 (2007/10/02)
Iminium cations have been generated in aqueous solution from the solvolysis of anilinothioethers ArN-(CH3)CH2SR at 25 °C. Common ion inhibition of the solvolysis of anilinothioethers was observed when the thiolate anion leaving group
Subsite-differentiated analogues of native [4Fe-4S]2+ clusters: Preparation of clusters with five- and six-coordinate subsites and modulation of redox potentials and charge distributions
Ciurli,Carrié,Weigel,Carney,Stack,Papaefthymiou,Holm
, p. 2654 - 2664 (2007/10/02)
The subsite-differentiated cluster [Fe4S4(LS3)Cl]2- (1, LS3 = 1,3,5-tris((4,6-dimethyl-3-mercaptophenyl)thio)-2,4,6-tris(p-tolylthio) benzene(3-)) in Me2SO solution reacts with a variety of bidentate and tridentate ligands to afford the substituted clusters [Fe4S4(LS3)L′]z-. Some ten clusters of this type were prepared in order to examine the effects of cluster charge and coordination number at the unique subsite on relative stabilities of oxidation states and charge distributions as sensed by 57Fe isomer shifts. This is the first comprehensive study of such effects with Fe4S4 clusters. Clusters prepared include those with L′ = PhS- (4), Me2NCS2- (5), pyridine-2-thiolate (6), 1,4,7-triazacyclononane (8), hydrotris(1-pyrazolyl)borate (9), and 1,2-disubstituted benzenes such as benzene-1,2-dithiolate (11). Cluster formation is detected by 1H NMR isotropic shifts of the LS3 ligand, which are highly sensitive to L′. A tabulation of shifts is presented. All clusters have effective trigonal symmetry in solution. Among the more significant properties of the substituted clusters are the following: (i) chemically reversible [Fe4S4]3+/2+ redox couples at potentials ca. 300-700 mV more negative than that of reference cluster 4; (ii) negative shifts of the potentials of the [Fe4S4]3+/2+ and [Fe4S4]2+/+ couples on mononegative cluster 8 vs 1 and 4; and (iii) skewing of electron distribution at the unique subsites toward "ferric-like" (5, 6, 11) and "ferrous-like" (8, 9) character vs symmetrically delocalized 4. Other matters considered include the source of stability of certain substituted clusters and the effects of cluster charge and core charge density on redox potentials. The data presented approximate the intrinsic effects of various potential ligand sets at a single subsite in native clusters. The possible biological implications of this work are illustrated with the P-clusters of nitrogenase, whose terminal ligation may depart from that of the now-classical native clusters Fe4S4(S·Cys)4.
The E1cB Mechanism for Thiocarbamate Ester Hydrolysis: Equilibrium and Kinetic Studies
Bourne, Nicholas,Williams, Andrew,Douglas, Kenneth T.,Penkava, Thomas R.
, p. 1827 - 1832 (2007/10/02)
The alkaline hydrolyses of a series of S-aryl thiocarbamate esters have been measured and the mechanism confirmed to be dissociative.Equilibrium constant for the synthesis of thiocarbamates from thiol and isocyanic acid have been obtained for aqueous media using both kinetic and analytical techniques.Hammett and Broensted parameters for the equilibrium reaction indicate that there is less positive effective charge on the sulphur in the thiocarbamate compared with that on the oxygen in the oxygen analogue.Theoretical arguments are advanced to show that the dissociative reactions of simple carbamate anions involve a planar geometry of the paticipating atoms.
On Relative Leaving Abilities: Use of Isobasic Plots to Determine the Relative Nucleofugalities of Thiolates and their Oxy-analogues
Douglas, Kenneth T.,Alborz, Manoochehr
, p. 551 - 553 (2007/10/02)
The use of an isobasic plot shows that, when structures are analogous and pKa values identical, RO- departs from acetoacetate ester anions 5 * 103 times faster than RS- and 79 times faster from fluorene-9-carboxylic acid ester anions, a reversal of the apparent order of nucleofugality determined by measured rates of elimination of RS- and RO-.
