FTIR/Matrix isolation study of photolysis reactions of allyl halides with oxygen (original) (raw)
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Matrix isolation study of photolysis reactions of allyl halides with ozone
IR/matrix isolation technique has applied to study the photolysis reactions of allyl chloride and allyl bromide with ozone in Ar matrix. The isolated intermediate and products were identified by comparison of new IR frequencies of experimental results with theoretical calculation. The reaction mechanism was first 1,3 dipolar cycloaddition of ozone to double bond of allyl halide to form 4-(halomethyl)-1,2,3-trioxolane (POZ), POZ was then decomposed to carbonyl component and HC(O)CH 2 X which were retro-cycloaddition to carbonyl component to form 3-(halomethyl)-1,2,4-trioxolane (SOZ), and finally the SOZ was decomposed to a stable formic haloacetic anhydride.
Infrared matrix study of reactions of propargyl halides with oxygen
-The reaction of propargyl halide with oxygen in Ar matrix has been conducted. There is no new peak was observed after the codeposition of Ar/propargyl halide. After the photolysis, a peroxide intermediate 3-(halomethyl)-1,2-dioxetene was observed first. Further photolysis led to the breakage of O-O bond of 3-(halomethyl)-1,2-dioxetene and formed final product of 3-halo-2-oxopropanal and/or 2-haloacetaldehyde and CO. The reaction mechanism was similar to that of reaction of chloroacetylene with oxygen, the additional-CH 2-group did not alter the reaction path.
Matrix isolation study of reactions of propargyl halides with ozone
The photolysis reactions of propargyl halide with ozone in Ar matrix have been conducted. After photolysis, the new absorption bands of IR spectra were compared with literature and theoretical calculation frequencies of possible products, indicated the isolated products are 4-(halomethyl)-1,2,3-trioxolene (POZ), 1-(halomethyl)-2,3,5-trioxa-bicyclo[2.1.0]pentane (SOZ), and formic haloacetic anhydride. The reaction mechanism was first 1,3 dipolar cycloaddition of ozone to triple bond of propargyl halide to form POZ and then decomposed to ionic component and rearranged to form SOZ, and finally the SOZ decomposed to stable formic haloacetic anhydride.
Matrix isolation of highly reactive organic intermediates
2017
Das Pentafluorophenylradikal konnte durch Bestrahlung oder Pyrolyse verschiedener Prakursoren erzeugt und in einer Argonmatrix isoliert werden, wo seine Reaktivitat gegenuber O2 sowie CO untersucht wurde. Im Zuge dieser Experimente wurden auch die Radikalkationen des Iodpentafluorbezols sowie des Brompentafluorbenzols gebildet und IR- sowie UV-spektroskopisch charakterisiert. Des Weiteren wurde die Synthese von gespannten Cyclooctinen fur nichtkatalysierte Azid-Alkin-Cycloadditionen erforscht, ebenso wie die Synthese benzannelierter Cycloendiine als Substrate fur mechanochemische Experimente. Schlieslich wurden mit dem p-Tolyl(trifluormethyl)-Carben und dem 2-Fluorenyltrifluormethyl-Carben zwei magnetisch bistabile Carbene beschrieben, die in Edelgasmatrizen im Triplett- sowie im Singulett-Zustand coexistieren und deren Spinzustande photochemisch sowie thermisch reguliert werden konnen.
Kinetic studies of OH and O3 reactions with allyl and isopropenyl acetate
Rate coefficients have been measured for the gas phase reactions of hydroxyl (OH) radicals and ozone with two unsaturated esters, allyl acetate (CH 3 C(O)OCH 2 CH=CH 2 ) and isopropenyl acetate (CH 3 C(O)OC(CH 3 )=CH 2 ). The OH experiments were carried out using the pulsed laser photolysis -laser induced fluorescence technique over the temperature range 243-372 K and the kinetic data used to derive the following Arrhenius expressions (in units of cm 3 molecule −1 s −1 ): allyl acetate, k 1 = (2.33 ± 0.27) × 10 −12 exp[(732 ± 34)/T]; and isopropenyl acetate, k 2 = (4.52 ± 0.62) × 10 −12 exp[(809 ± 39)/T]. At 298 K, the rate coefficients obtained (in units of 10 −12 cm 3 molecule −1 s −1 ) are: k 1 = (27.1 ± 3.0) and k 2 = (69.6 ± 9.4). The relative rate technique has been used to determine rate coefficients for the reaction of ozone with the acetates. Using methyl vinyl ketone as the reference compound and a value of 4.8 × 10 −18 cm 3 molecule −1 s −1 as the rate coefficient for its reaction with O 3 , the following rate coefficients were derived at 298 ± 4 K (in units of 10 −18 cm 3 molecule −1 s −1 ): allyl acetate, (2.4 ± 0.7) and isopropenyl acetate (0.7 ± 0.2). The results are discussed in terms of structure-activity relationships and used to derive atmospheric lifetimes for the acetates.
The Journal of Physical Chemistry B, 2002
In the work presented here, we used photofragment translational spectroscopy and H atom Rydberg timeof-flight (HRTOF) spectroscopy to study the primary photofragmentation channels of allyl iodide excited at 193 nm and the ensuing dissociation of the nascent allyl radicals as a function of their internal energy. Two C-I bond fission channels were found to produce the allyl radical, one channel forming I(2 P 3/2) and the other forming I(2 P 1/2). The nascent allyl radicals are dispersed as a function of the translational energy imparted from the photolysis and therefore by their internal energy. Although all of the I(2 P 3/2) and a portion of the I(2 P 1/2) channel allyl radical products have enough internal energy to overcome the 60 kcal/mol barrier to form allene + H, the data showed that a substantial fraction of the allyl radicals from the I(2 P 1/2) channel that formed with internal energies as high as 15 kcal/mol above the 60 kcal/mol barrier were stable to H atom loss. The stability is due to centrifugal effects caused by significant rotational energy imparted to the allyl radical during photolysis and the small impact parameter and reduced mass characterizing the loss of an H atom from an allyl radical to form allene + H. A photoionization efficiency (PIE) curve identified the major C 3 H 4 secondary dissociation products as allene. Comparison of the mass 40 signal in the TOF spectra at two photoionization energies showed that branching to H + propyne does not occur at near-threshold internal energies, indicating that the experimentally determined allyl f 2-propenyl radical isomerization barrier, which is lower than recent ab initio calculations of the barrier by ∼15 kcal/mol, is far too low.
Chemical Physics Letters, 2001
The rate constants for the reactions of hydroxyl radical (OH) with two unsaturated alcohols (ROH) namely, allyl alcohol H 2 C@CHCH 2 OH and propargyl alcohol HCBCCH 2 OH in the gas phase have been measured. The kinetic measurements were carried out using laser photolysis (LP) combined with laser induced¯uorescence (LIF) technique at room temperature over a pressure range of 10±20 Torr. The bimolecular rate constants for the reactions OH ROH 3 products, are determined at room temperature to be 3:7 AE 0:5 Â 10 À11 , 9:2 AE 1:4 Â 10 À12 cm 3 molecule À1 s À1 , respectively, for allyl alcohol and propargyl alcohol. The measured rate constants in combination with ab initio molecular orbital calculation provide a better understanding of the structure-reactivity rules. Ó 2001 Published by Elsevier Science B.V.
Kinetics and Thermochemistry of the Reaction of 1-Chloroethyl Radical with Molecular Oxygen
The Journal of Physical Chemistry, 1995
The kinetics of the reaction CH3CHC1+ 0 2 F?. CH3CHC102products (1) has been studied at temperatures 296-839 K and He densities of (3-49) x 10l6 molecule cm-3 by laser photolysis/photoionization mass spectrometry. Rate constants were determined in time-resolved experiments as a function of temperature and bath gas density. At low temperatures (298-400 K) the rate constants are in the falloff region under the conditions of the experiments. Relaxation to equilibrium in the addition step of the reaction was monitored within the temperature range 520-590 K. Equilibrium constants were determined as a function of temperature and used to obtain the enthalpy and entropy of the addition step of the reaction (1). At high temperatures (750-839 K) the reaction rate constant is independent of both pressure and temperature within the uncertainty of the experimental data and equal to (1.2 f 0.4) x cm3 molecule-' s-'. Vinyl chloride (C2H3C1) was detected as a major product of reaction 1 at T = 800 K. The rate constant of the reaction CH3CHC1 + C12 products (6) was determined at room temperature and He densities of (9-36) x 10l6 molecule cm-3 using the same technique. The value obtained is k6 = (4.37 f 0.69) x cm3 molecule-' s-'. An estimate of the high-pressure limit for reaction 1 was determined using this measured k6 and the kl/k6 ratio obtained by Kaiser et al.:l k"1 (T=298K) = (1.04 f 0.22) x lo-" cm3 molecule-' s-'. In a theoretical part of the study, structure, vibrational frequencies, and energies of nine conformations of CH3CHC102 were calculated using ab initio UHF/6-31G* and MP2/6-31G** methods. The theoretical results are used to calculate the entropy change of the addition reaction As0298 =-152.3 f 3.3 J mol-' K-'. Th~s entropy change combined with the experimentally determined equilibrium constants resulted in a CH3CHC1-02 bond energy m 2 9 8 =-131.2 f 1.8 kJ mol-l. The rooq-temperature entropy (S O 2 9 8 = 341.0 f 3.3 J mol-' K-') and the heat of formation (A H f o~9 8 =-54.7 f 3.7 kJ mol-') of the CH3CHC102 adduct were obtained.