15941-77-2Relevant articles and documents
Gas-phase ion-molecule reactions: a model for the determination of biologically reactive electrophilic contaminants in the environment.
Freeman,Johnson,Yost,Kuehl
, p. 1902 - 1910 (1994)
A promising instrumental technique has been investigated to rapidly screen complex environmental samples for chemical contaminants having the propensity to covalently bond to biomacromolecules such as DNA. Radical molecular ions of pyridine, a model compound for nucleophilic bases of DNA, were mass-selected and allowed to react with electrophilic environmental contaminants in the collision cell of a triple quadrupole mass spectrometer. Analytes were introduced into the collision cell via a gas chromatographic column. Reactive chemicals are then characterized by scanning Q3 to identify associative reaction products. A good qualitative correlation was observed for the gas-phase reactivity of a series of electrophilic reagents with both their alkylating reactivity in solution (4-(4-nitrobenzyl)pyridine) and AMES test mutagenicity which had been previously published. Femtomole limits of detection for specific associative reaction products were demonstrated. Gas-phase reactions of ions of environmental contaminants (introduced into the source) with neutral pyridine (in the collision cell) were also investigated. Reactions of the radical molecular ion of the allyl reagents with neutral pyridine were similar to results from the mass-selected reaction of the pyridine radical molecular ion with neutral allylic reagents.
Flash Photolysis of Transient Radicals. 1. X2(1-) with X = Cl, Br, I, and SCN
Nagarajan, V.,Fessenden, Richard W.
, p. 2330 - 2335 (2007/10/02)
The radicals Cl2(1-), Br2(1-), I2(1-), and (SCN)2(1-) were prepared by photolysis of appropriate chemical systems with one laser and were subsequently photolyzed wuth a second laser.The first three species were photolyzed at 355 nm, and (SCN)2(1-) was photolyzed at 532 nm; I2(1-) was also photolyzed at 700 nm.In each case, dissociation into the fragments X and X(1-) was detected by a bleach in the absorption of X2(1-).The quantum yield for this process is about 0.1 except for Cl2(1-) where the value is 0.2.In no case was electron photodetachment observed.Observation of the recovery of the original absorption allowed the corresponding rate constant to be measured.The values for Cl + Cl(1-) (8E9/M*s) and SCN + SCN(1-) (9E9/M*s) have not previously been measured directly.In the case of Cl2(1-) the bleach in absorption does not completely recover and the loss of absorpion is dose dependent.Because the presence of acid allows a more complete recovery it can be concluded that the product Cl atom is photolyzed by a second photon to procedure OH and Cl(1-).The quantum yield was determined to be about 0.5. this photoreaction is direct experimental evidence that the absorption band of Cl involves charge transfer from solvent.Detailed analysis of the bleaching and recovery behavior at high Cl(1-) concantrations showed no time lag which could be attributed to the 2P1/2Cl atom, implying a short lifetime for this species.
