73787-86-7Relevant academic research and scientific papers
Xenon Matrix Photochemistry of 1,1-Dichloroethene: Matrix-Dependent Surface Crossing and Hydrogen-Bonding Geometries
Laursen, Sandra L.,Pimentel, George C.
, p. 8175 - 8182 (2007/10/02)
The photoproducts of 1,1-dichloroethene (DCE) in Xe matrix at 12 K differ from those observed in Kr.With 239-nm photolysis, chlorine is eliminated from 1,1-DCE in solid Xe, but not in Kr, although HCl elimination and DCE isomerization occur in both matrices.Just as in the 1,2-dichloroethenes, Cl2 elimination proceeds in the heavy Xe matrix via spin-orbit-enhanced intersystem crossing to a triplet reaction surface.At higher photolysis energies, a novel product appears in Xe and is identified with the aid of isotopic substitution as a second HCl*C2HCl isomer, ?-hydrogen-bonded through the acetylenic proton.The product dependence on wavelength, parent, and matrix indicates that it is formed through a triplet-surface process under geometric constraints specific to the 1,1 isomer.Loss of Cl from a dissociative triplett state to form an excited chlorovinyl radical, with further cage reaction of the energetic fragments, is postulated.
Matrix-Induced Intersystem Crossing in the Photochemistry of the 1,2-Dichloroethenes
Laursen, Sandra L.,Pimentel, George C.
, p. 2328 - 2333 (2007/10/02)
The photoproducts of the 1,2-dichloroethenes (DCE) in xenon matrix at 12 K differ from those observed in krypton matrix.In xenon, photolysis at 237 nm of both cis- and trans-dichloroethene results in elimination of both Cl2 and HCl as well as isomerization, whereas only HCl elimination and isomerization are observed in krypton.Longer wavelength irradiation has no effect on either DCE in Kr but produces small, distinct amounts of products in Xe.The results indicate that in xenon, chemistry is occuring through a triplet state as well as from the directly excited singlet state.Enchanced spin-orbit coupling in the heavy-atom environment facilitates intersystem crossing from the initial singlet to a triplet surface, as well as, no doubt enhanced absorption directly into the triplet state.These effects provide access to the normally spin-forbidden chlorine elimination channel.The appearance of products in Xe at the lower photon energies is ascribed to direct T1 0 absorption, assisted by the external heavy atom.
PHOTOSENSITIZED REACTION OF Hg(3P) ATOMS WITH THE DICHLOROETHENES IN KRYPTON MATRIX: TRIPLET SURFACE CHEMISTRY
Cartland, Harry E.,Pimentel, George C.
, p. 5485 - 5491 (2007/10/02)
The reactions between Hg(3P) atoms with the there dichloroethenes in krypton matrix at 12 K have been studied.In the absence of Hg, matrix photolysis with wavelengths longer than 200 nm gives isomerization as well as, for cis-dichloroethene (c-DCE) and 1,1-dichloroethene (1,1-DCE) but not for trans-dichloroethene (t-DCE), HCl elimination to give ClH.C2HCl.In the presence of Hg atoms and with excitation in the range 246-257 nm, HCl elimination is substantially reduced and, for c-DCE and 1,1-DCE, new products appear.These products are identified as Cl2.C2H2 and chlorovinyl mercuric chlorides, the latter the net result of mercury insertion into a carbon-chloride bond.The insertion product from c-DCE is identified as trans-2-chlorovinyl mercuric chloride and that from 1,1-DCE is probably 1-chlorovinyl mercuric chloride.The results indicate that in the krypton matrix, Hg(3P)-initiated chemistry takes place on a triplet surface that is not accessed with higher energy, singlet excitation.Furthermore, the absence of Cl2 elimination or insertion chemistry for t-DCE indicates that the role of Hg(3P) is not merely energy transfer but, instead, one that opens reaction channels not observed without Hg(3P).
Infrared Spectra of Hydrogen-Bonded ? Complexes between Hydrogen Halides and Acetylene
McDonald, Stephen A.,Johnson, Gary L.,Keelan, Brian W.,Andrews, Lester
, p. 2892 - 2896 (2007/10/02)
Hydrogen-bonded ? complexes C2H2--H-X have been formed by codeposition of C2H2 and HX in excess argon at 15 K and by vacuum-UV photolysis of vinyl halides.The strength of the hydrogen bond, as measured by the displacement of the H-X vibrational fundamental below the isolated HX value, decreases in the series HF, HCl, and HBr as expected.Similar complexes made from di- and thichloroethylenes give slightly higher H-Cl vibrations which show minimal interaction between the halide and the acetylene substituent.The H-F fundamentals for C2H4 and C2H2 complexes at 3732 and 3747 cm-1, respectively, show that the ? electrons in double and triple bonds are comparable hydrogen-bond acceptors.
