Absolute Rate Constants for the Reactions of Sulfur (³P_J) Atoms in Solution

Abstract

The 248-nm laser flash photolysis of methyl isothiocyanate (MeNCS) was used to generate S( 3 P J ) ground state atoms in acetonitrile solution. The reaction of S( 3 P J ) atoms with the MeNCS precursor produces molecular diatomic sulfur S 2 ( 3 Σ g -) in its ground state, which possesses an absorption at ca. 270 nm. The first-order growth of this absorption was used to monitor the decay kinetics of the sulfur ( 3 P J ) atoms and to measure the rate constants for their reactions with additives. The rate constants obtained for a number of olefins, e.g., 9.7 × 10 7 M -1 s -1 for ethyl vinyl ether, hydrogen donors, e.g., 3.1 × 10 9 M -1 s -1 for tributyltin hydride, sulfur atom donors, e.g., 5.0 × 10 7 M -1 s -1 for carbon disulfide, and nucleophiles, e.g., 1.3 × 10 9 M -1 s -1 for chloride ions, demonstrate that S( 3 P J ) atoms behave as reactive, yet very selective, intermediates in solution; the highest reactivity was observed toward nitrogen and phosphorus nucleophiles, e.g., 1.2 and 2.1 × 10 10 M -1 s -1 for hydrazine and triethyl phosphite. The comparison with known nucleophilicity constants, e.g., for methyl iodide as electrophile, suggests further that S( 3 P J ) atoms act as potent but relatively soft electrophiles. The reaction modes between S( 3 P J ) atoms and the additives are assumed to involve abstractions of single atoms or addition to double bonds or lone electron pairs. The reaction rate constants for atomic sulfur S( 3 P J ) in solution are compared with previous gas phase data for S( 3 P J ) atoms and with the data for oxygen ( 3 P J ) atoms in solution.

Gauging the Significance of Atomic Oxygen [O(3P)] in Sulfoxide Photochemistry. A Method for Hydrocarbon Oxidation

“…Am. Chem in solution studies of sulfur, 15 chlorine, 16,17 and fluorine atoms. 18 One would expect that complexation and ionization pathways of O( 3 P) may differ in solution compared to the gas phase.…”

“…Few studies have brought together results on condensed phase O( 3 P) atoms, which address questions about the influence of solvent. Complexes or ions are commonly encountered in solution studies of sulfur, chlorine, , and fluorine atoms . One would expect that complexation and ionization pathways of O( 3 P) may differ in solution compared to the gas phase. , …”

Electrochemical reduction of N,N′-thiobisphthalimide and N,N′-dithiobisphthalimide: ejection of diatomic sulfur through an autocatalytic mechanism

“…Laser flash photolysis studies showed a decay of the S 2 signal in the millisecond range. 28 This indicates that the formation of S 8 from the produced S 2 is feasible under the cyclic voltammetric time scale at the investigated low scan rates. Furthermore, the observation, in all cyclic voltammograms at low scan rates for both compounds 1 and 2, of the second peak, corresponding to the second reduction peak of S 8 , is a clear indication that S 8 is indeed formed at the first reduction peak.…”

Tethered Alkylidenes for REMP from Carbon Disulfide Cleavage

“…The yield of complex 9 in the reaction mixture, based on NMR, is ∼65%. Thioisocyanates are sulfur atom transfer reagents that yield the corresponding isocyanides as byproducts. − However, a 1 H NMR spectrum of the reaction mixture did not reveal PhNC resonances; presumably the PhNC is consumed in side reactions with complex 1 . Confirming the side reactions, in a test reaction, treating 1 with PhNC in C 6 D 6 results in a complicated mixture of products (NMR spectroscopy) (Figure S18).…”