20733-13-5Relevant academic research and scientific papers
Fragmentation and Structure of C2H3S(1+) Ions
Cooks, R. G.,Mabud, Md. A.,Horning, S. R.,Jiang, X.-Y.,Paradisi, Cristina,Traldi, Pietro
, p. 859 - 865 (1989)
Daughter spectra for C2H3S(1+) ions, generated from a variety of precursor molecules and activated by different means, are insensitive to the nature of the precursors, but spectra recorded by different methods of activation show unexpectedly large differences.The methyl cation, a fragment characteristic of the thioacylium structure, is the dominant product of collisions at low energy with a gaseous or solid target but is virtually absent for zero scattering angle gas-phase collisions in the kiloelectronvolt range.As the scattering angle is increased, this low-energyfragment increases in abundance, and it is suggested that this is the result of an increased degree of direct vibrational as opposed to electronic excitation.It is shown that (i) the C2H3S(1+) ions sampled by collision-activated dissociation and by surface-induced dissociation have the thioacylium structure, (ii) internal energy differences associated with their formation are not reflected in spectral changes in kiloelectronvolt collision experiments although they do affect the low-energy spectra, (iii) zero-angle, high-energy collisions probably involve fragmentation via excited electronic states, and for this reason they result in different products to those that occur upon low-energy collisions with gaseous or solid targets, and (iv) while activation by collision with a solid surface in the energy range below 100 eV causes very considerable internal excitation, only vibrational and not electronic excitation is involved.Isomerization between the several nascent C2H3S(1+) structures generated from different precursors occurs prior to activation and is favored by the unusually high activation energy required for dissociation.Whenthe highly endothermic charge stripping process is used, it is possible to sample some C2H3S(1+) ions of such low internal energy that they have not completely isomerized.
The Ever-surprising chemistry of boron: Enhanced acidity of phosphine·boranes
Hurtado, Marcela,Yanez, Manuel,Herrero, Rebeca,Guerrero, Andres,Juan Z. Davalos,Jose-Luis, M. Abboud,Khater, Brahim,Guillemin, Jean-Claude
supporting information; experimental part, p. 4622 - 4629 (2009/12/29)
The gas-phase acidity of a series of phosphines and their corresponding phosphine·borane derivatives was measured by FT-ICR techniques. BH 3 attachment leads to a substantial increase of the intrinsic acidity of the system (from 80 to 110 kJ mol-1). This acidity-enhancing effect of BH3 is enormous, between 13 and 18 orders of magnitude in terms of ionization constants. This indicates that the enhancement of the acidity of protic acids by Lewis acids usually observed in solution also occurs in the gas phase. High- level DFT calculations reveal that this acidity enhancement is essentially due to stronger stabilization of the anion with respect to the neutral species on BH3 association, due to a stronger electron donor ability of P in the anion and better dispersion of the negative charge in the system when the BH3 group is present. Our study also shows that deprotonation of ClCH2PH2 and ClCH 2PH2·BH3 is followed by chloride departure. For the latter compound deprotonation at the BH3 group is found to be more favorable than PH2 deprotonation, and the subsequent loss of Cl- is kinetically favored with respect to loss of Cl - in a typical SN2 process. Hence, ClCH2PH 2·BH3 is the only phosphine·borane adduct included in this study which behaves as a boron acid rather than as a phosphorus acid.
Peroxyhydrolysis of nerve agent VX and model compounds and related nucleophilic reactions
Yang, Yu-Chu,Berg, Frederic J.,Szafraniec, Linda L.,Beaudry, William T.,Bunton, Clifford A.,Kumar, Anurag
, p. 607 - 613 (2007/10/03)
The exceedingly toxic agent VX [O-ethyl S-(diisopropylaminoethyl) methylphosphonothioate], 1a, and the midly toxic model compound O,S-diethyl methylphosphonothioate, 1b, react with HO- to give parallel P-S and P-O bond cleavages; the P-O cleavage of VX produces relatively unreactive but very toxic anionic phosphonothioate. Peroxyhydrolysis of 1a,b with HO2- involves quantitative P-S cleavage at rates 30-40 times that with HO giving the corresponding phosphonate and sulfonate ions and disulfide as nontoxic products. In reaction of 1b with HO2- in H218O, oxygen in these final products is not derived from water and HO2- exclusively displaces the thiolate ion at phosphorus. Reaction of 1b with HSO5- gives the same products, but via oxidatively promoted attack of H218O on phosphorus. Kinetic and isotopic labelling results on reactions of 1a,b and a range of related compounds with HO2-, HO- and RO and an oximate ion are interpreted in terms of concerted SN2(P) reactions rather than stepwise reactions with formation of a trigonal bipyramidal (TBP) intermediate. Product selectivity depends on the relative basicities of the anionic nucleophile and the leaving anions.
Synthetic nickel-containing heterometal cubane-type clusters with NiFe3Q4 cores (Q = S, Se)
Ciurli, Stefano,Ross, Paul K.,Scott, Michael J.,Yu, Shi-Bao,Holm
, p. 5415 - 5423 (2007/10/02)
Reaction of the linear trinuclear Fe(III) clusters [Fe3Q4(SEt)4]3- with Ni(PPh3)4 in acetonitrile solution affords the products [NiFe3Q4(PPh3)(SEt)3]2- (Q = S (9). Se (10)) and [NiFe3Q4(SEt)4]3- (Q = S (11) Se (12)) in ca. 30% yield. The reactions involve reductive rearrangement of the initial cluster to a cuboidal fragment and capture of the nickel atom. The compounds (Tt4 N)2 [9/10) are isomorphous and contain cluster anions with the cubane-type [NiFe3Q4]1+ core units and Ni-PPh3 and Fe-SEt terminal ligation. The compound (Et4N)3[12] is isomorphous with (Et4N)3[Fe4Se4(SEt)4] and contains the same cubane unit but with all-thiolate terminal ligation and disordered Ni and Fe subsites. The dimensions of the [NiFe3Q4]1+ cores are closely similar to those of the more familiar [Fe4Q4]2+,1+ cluster cores, rendering separation of the salts of the same cation and cluster charge difficult, Collective structural, magnetic, and spectroscopic results are consistent with the simplified charge distribution [Fe3Q4]1- (S = 5/2) + Ni2+ (S = 1) and an S = 3/2 ground state that arises from antiparallel coupling of the two fragment spins. This mode of spin coupling causes oppositely signed isotropic shifts of the identical ligands at Ni and Fe subsites. Subsite-diffcrentiated cluster 9 undergoes regiospecific substitution reactions to afford products with phosphines, cyanide, and isonitrile at the Ni subsite. These reactions are often accompanied by formation of (Fe4S4(SEt)4]2-,3- minority products. Comparison of properties of the synthetic clusters and of a reconstituted NiFe3S4 species formed with Pyrococcus furiosus ferredoxin (Conover, R. C.; Park, J.-B.; Adams, M. W.; Johnson, M. K. J. Am. Chem. Soc. 1990, 112, 4562) reveals that they are isoelectronic with the same ground state. Consequently, the protein-bound species almost certainly has the cubane-type structure of the synthetic cluster, Some seven types of heterometal cubane clusters MFe3S4 (M = V, Nb, Mo, W, Re, Co. Ni) have now been prepared. Reductive rearrangement reactions are likely to provide routes to additional members of the set. several of which are good structural models fur the immediate hetcrometal coordination environment in enzymes (M = V, Mo), but none of which has as yet been shown to occur naturally.
Kinetics of reactions of thiolate ions with α-nitro β-substituted stilbenes in 50% Me2SO-50% water. Observation of the intermediate in nucleophilic vinylic substitution reactions
Bernasconi, Claude F.,Fassberg, Julianne,Killion Jr., Robert B.,Rappoport, Zvi
, p. 3169 - 3177 (2007/10/02)
The kinetics of reactions of the type Ph(LG)C=CPh(NO2) + RS- →Ph(RS)C=CPh(NO2) + LG- were measured in 50% Me2SO-50% water (v/v) at 20 °C. Results on the following leaving group/nucleophile combination
