15729-58-5

The 248 nm photochemistry of methyl iodide thin films was studied using reflection absorption infrared spectroscopy (RAIRS), temperature programmed desorption (TPD), and time-of-flight quadrupole mass spectrometry (TOF-QMS).The formation of predominantly CH2I2 and CH4 and some C2H6, CH3CH2I, CHI3 and I2 photoproducts retained in the film was characterized by RAIRS and TPD.The integrated areas of the IR absorption bands for the two major photoproducts, CH2I2 and CH4, increase to a maximum and then decrease as photolysis of the film proceeds.A cross section for the loss of CH3I by 248 nm photolysis of the film was measured to be (1.0+/-0.1)E-19 cm2, approximately 1 order of magnitude lower than the gas-phase cross section.At all laser fluences used in this study, CH3, I, and CH3I were ejected into the gas phase.The CH3 TOF distribution showed the signature of the gas-phase CH3I photodissociation dynamics-two sharp peaks corresponding to the production of iodine atoms in the I(2P3/2) and I*(2P1/2) states.The TOF distributions of I and CH3I were fit by Maxwell-Boltzmann distributions corresponding to temperatures of 1400 and 1170 K, respectively.Three other species-CH4, I2 and CH2I2-were observed in TOF-QMS, but only at higher laser fluences.It was determined that the I2 and CH2I2 species are most likely fragments of a larger molecule, perhaps a cluster species, that photodesorbs as the film becomes enriched with photoproducts.The mechanism for CH4 photoejection appears to be of a different nature.The photochemistry of methyl iodide thin films can be understood in terms of a combination of photoproceses occuring in the film and at the film surface.

Significant amounts of novel gem-dizinc carbenoids (RZnCHIZnR) are formed when diethylzinc is mixed with iodoform in CH2Cl2 at 0 °C. This reagent was shown to be effective in the cyclopropanation of butenediol derivatives to generate

Unimolecular and collision induced fragmentations of cis- and trans-1-acetyl-2-methylcyclopropanes, complexed to bare Fe+ cations, were examined by means of tandem mass spectrometry. Stereoselective isotopic labeling data as well as comparative studies with acylic isomers reveal that two reaction pathways are in competition with each other. On the one hand, dehydrogenation, loss of ethene, and loss of acetaldehyde proceed via a common intermediate which is formed via ring cleavage of 1-acetyl-2-methylcyclopropane/Fe+ to yield the corresponding 3-hexen-2-one/Fe+ complexes; these undergo subsequently CH- and CC-bond activation via the remote functionalization mechanism. These ring cleavages are associated with a complete loss of stereochemical features for the cis and trans isomers. In contrast, unimolecular decarbonylation occurs stereoselectively and is favored for the trans isomers; this is rationalized via a stereoselective formation of cis- and trans-η3-allyl complexes in the course of the electrocyclic ring-opening process. Furthermore, interconversion reactions, thermodynamic and kinetic aspects, and isotope effects of the CH- and CC-bond activation processes are discussed.

The gas-phase pyrolysis of phenylcyclopropane (5) has been ivestigated in a quartz tubular reactor between 560 and 680 deg C and a contact time of about 1 s.Main reaction is the thermal isomerization to allylbenzene (4) as well as to cis-(1b) and trans--β-methylstyrene (3b).Besides 1, 3, and 4, indene (8) is formed, which is characterized by a statistical distribution of the H atom over the three positions of the five-membered ring.To distinguish between the two possible mechanisms of the isomerization (opening of the cyclopropane ring C-C bond dissociation/ 1,3-diyl formation and 1,2-C,H retro-insertion/ethylcarbene formation), the D distribution in 1 and 3 was carefully determined by 1H-NMR spectroscopy.The results show that the isomerization is initiated by generation of a 1,3-diradical. - Keywords: Isotopic labeling/ Isomerization/ Phenylcyclopropane/ Pyrolysis

Quadropolar splittings in the high resolution deuteron spectra of deuterated haloforms (CX3(2)H, X=Cl, Br, I) and methylene halides (CX2H(2)H) have been measured at 14.35 T (93.5 MHz) and used to determine the anisotropy or asymmetry of their molecular magnetic susceptibility tensors.By combination with the known isotropic susceptibilities, the principal susceptibility tensors have been deduced and decomposed into bond susceptibility tensors.Neither the average susceptibilities nor the principal susceptibility tensor elements of the complete halomethane series follow Pascal's additivity rules.The phenomenon is tentatively attributed to a variable paramagnetic contribution perpendicular to the X-bond.Angular correlation Kirkwood g2 factors have been determined for CHCl3 and CHBr3 and are compared with available literature data.

In the presence of a catalytic amount of bis(acrylonitrile)nickel(0), bicyclopentane suffers from the cleavage of the central ? bond and cycloadds to electron-deficient olefins such as methyl acrylate, acrylonitrile, dimethyl maleate, and dimethyl fumarate to give bicycloheptane derivatives.The stereochemistry and mechanism of the catalyzed cycloadditions have been elucidated by use of deuterated bicyclopentanes.