Merged Jet Deposition Research Articles

Toward a more complete understanding of the reaction mechanism of methyl vinyl ether with ozone: A matrix isolation study

A study of the thermal and photochemical reactions of ozone with methyl vinyl ether (MVE) is described, using both twin jet and merged jet deposition under a variety of conditions. In addition, irradiation experiments were carried out with either a red LED (625 nm) or a Hg pen lamp (254 nm). Products were observed by infrared spectroscopy and identification was aided by 18O and scrambled 16,18O experiments. The experimental work was supported by extensive DFT calculations. Initial thermal products included the primary ozonide (POZ), one of the two possible Criegee intermediates (CI) and H2CO, marking the first observation of the POZ and CI in this system. At longer times using merged jet deposition, observed products include methyl formate, methyl acetate, formic acid and methanol, consistent with an earlier static gas phase study on this system. Photochemical products arose from the addition of a single oxygen atom to MVE, leading to formation of methoxyacetaldehyde and methoxyoxirane, along with minor products.

Matrix isolation study of the red light-induced reaction of triethylborane with ozone

The thermal and red photochemical reaction of triethylborane and ozone has been explored in argon matrices with infrared detection. Using both twin jet and merged jet deposition, no significant thermal reaction was observed. In contrast, red light irradiation of the twin jet-deposited matrix led to the formation of the novel H5C2BO species, ethyloxoborane. A strong, broad absorption was observed at 1963 cm−1 after irradiation and assigned to the 11B = O stretching mode, with a10B counterpart at 2027 cm−1. Two additional bands of lower intensity were also assigned to C2H5BO. Band assignments for this species were supported by 18O isotopic labeling experiments. Computational studies further supported the band assignments and confirmed that H5C2BO plus butane is the thermodynamically favored reaction pathway. Kinetic considerations for this reaction are also presented.

Matrix Isolation Studies of Novel Intermediates in the Reaction of Trimethylaluminum with Ozone.

The thermal reaction of ozone with trimethyl aluminum was explored using twin jet, concentric jet, and merged jet deposition into cryogenic matrixes. Infrared spectroscopy and density functional theory calculations were employed to identify and characterize the products formed in each case. Together, these deposition techniques provide information over the essentially full course of the gas-phase reaction. At short times with twin jet deposition, the primary product is the O atom insertion product (CH3)2AlOCH3. With merged jet deposition and longer gas-phase mixing times, the methyl peroxy radical H3COO· was seen in good yield along with final stable products H2CO, H3COH, and C2H6. Production of Al2O3 and its deposition onto the walls of the reaction tube as a powdery film was noted as well. All of these outcomes were combined to propose a reaction mechanism for this system. Of particular note, the observation of H3COO· provides clear evidence for a free radical component to the overall mechanism.

Infrared matrix isolation study of the thermal and photochemical reactions of ozone with trimethylgallium.

The thermal and photochemical reactions of (CH3)3Ga and O3 have been explored using a combination of matrix isolation, infrared spectroscopy, and theoretical calculations. Experimental data using twin jet deposition and theoretical calculations demonstrate the formation of multiple product species after deposition, annealing to 35 K, and UV irradiation of the matrices. The products were identified as (CH3)2GaOCH3, (CH3)2GaCH2OH, (CH3)(CH3O)Ga(OCH3), (CH3)2GaCHO, and (CH3)Ga(OCH3)(CH2OH). Product identifications were confirmed by annealing and irradiation behavior, (18)O substitution experiments, and high level theoretical calculations. Merged jet deposition led to a number of stable late reaction products, including C2H6, CH3OH, and H2CO. A white solid film was also noted on the walls of the merged (flow reactor) region of the deposition system, likely due to the formation of Ga2O3.

Investigation of the thermal and photochemical reactions of ozone with styrene in argon and krypton matrices

The matrix isolation technique, combined with infrared spectroscopy and twin jet codeposition, has been used to characterize intermediates formed during the ozonolysis of styrene. Absorptions assigned to early intermediates grew in after warming the matrix from 19K to 68K in the twin jet krypton matrix experiments. A number of these absorptions have been assigned to the primary ozonide, formaldehyde-O-oxide Criegee intermediate, and secondary ozonide of styrene, transient species not previously observed for this system. In contrast, the room temperature reaction of ozone with styrene led to the observation of “late,” stable products of this ozonolysis reaction. These product absorptions were observed after merged jet deposition, followed by cryogenic trapping in solid argon. Irradiation with λ⩾220nm of merged and twin jet argon matrices involving ozone led to O atom production and subsequent reaction with styrene. Identification of intermediates formed during the ozonolysis of styrene was further supported by 18O isotopic labeling experiments as well as theoretical density functional calculations at the B3LYP/6-311G++(d,2p) level.

Infrared Matrix Isolation Study of the Thermal and Photochemical Reactions of Ozone with Dimethylcadmium

The matrix isolation technique has been combined with infrared spectroscopy and theoretical calculations to explore the reaction of (CH(3))(2)Cd with O(3) over a range of time scales and upon irradiation. During twin jet deposition, multiple novel product species were observed along with several stable "late" products. Following annealing of these matrices to 35 K, absorptions due to two novel product species increased in intensity. In addition, new bands appeared, indicating the formation of an additional product. Subsequent UV irradiation destroyed several of the initial products and produced a new photoproduct. On the basis of (18)O and (16,18)O spectroscopic data and theoretical calculations, the novel intermediates H(3)COCdCH(3), H(3)CCdCH(2)OH, H(3)COCdOOCH(3), and H(3)CCdCHO were identified. Merged jet deposition led to a number of stable "late" products, including H(2)CO, CH(3)OH, and C(2)H(6), identifications that were confirmed by (18)O substitution. Mechanistic inferences for this reaction are discussed.

Matrix isolation study of the thermal and photochemical reaction of ozone with Trimethyl Indium

The matrix isolation technique has been combined with infrared spectroscopy and theoretical calculations to explore the reaction of (CH 3) 3In with O 3 over a range of time scales. Upon twin jet deposition (short reaction time), formation of the novel H 3COIn(CH 3) 2 species along with a low yield of CH 2O was observed. Subsequent UV irradiation greatly increased the yield of H 3COIn(CH 3) 2 while the intensities of the CH 2O bands were not affected. An extensive set of bands were seen for H 3COIn(CH 3) 2 after irradiation and 18O spectroscopic data was obtained as well. The identification of this species was supported by theoretical calculations at the B3LYP/lanl2dz and B3LYP/dgdzvp levels of theory. Merged jet deposition (longer reaction times) led to high yield of H 2CO, CH 3OH and C 2H 6, identifications that were confirmed by 18O substitution. Mechanistic inferences for the initial steps of this reaction are discussed.

Matrix isolation investigation of the ozonolysis of propene

The matrix isolation technique, combined with infrared spectroscopy and merged jet deposition of ozone with propene led to the observation of “later”, more stable products of this ozonolysis reaction. The observed products, specifically formaldehyde and acetaldehyde, are precisely the products predicted by the Criegee mechanism, formed by the two fragmentation pathways from the initial primary ozonide. Hence, the merged jet results strongly support the Criegee mechanism. In contrast, twin jet codeposition experiments followed by annealing led to no visible changes in the spectra. Subsequent irradiation of these twin jet matrices involving ozone with light of λ ⩾ 220 nm led to O atom production and subsequent reaction with propene. Multiple products were observed in these photochemical experiments. Extensive 18O isotopic labeling experiments, comparisons with literature spectra, and detailed theoretical calculations at the B3LYP/6-311++G(d,2p) level provided important supporting data.

Infrared Matrix Isolation Study of the Thermal and Photochemical Reactions of Ozone with Dimethylzinc

The matrix isolation technique has been combined with infrared spectroscopy and theoretical calculations to explore the reaction of (CH3)2Zn with O3 over a range of time scales. Upon twin jet deposition, an initial cage pair complex was observed, along with formation of the novel H3COZnCH3 species. Subsequent UV irradiation destroyed the complex and greatly increased the yield of H3COZnCH3. An extensive set of bands were seen for this molecule, and (18)O spectroscopic data were obtained as well. The identification of this species was supported by theoretical calculations at the B3LYP/6-311++g(d,2p) level. Merged jet deposition led to a very different set of products, including H2CO, CH3OH and C2H6, identifications that were confirmed by (18)O substitution. In addition, a new variable length concentric deposition technique was developed to permit study of the time scales between twin (relatively short) and merged (relatively longer) reaction times. Mechanistic inferences for this reaction are discussed.

Infrared matrix isolation study of the oxidation of H2S by CrCl2O2

The thermal and photochemical reactions between CrO2Cl2 and H2S have been investigated using matrix isolation infrared spectroscopy. Twin-jet co-deposition of the two reagents into argon matrices at 14 K followed by irradiation with light of lambda > 300 nm led to the growth of a number of new bands. These have been assigned to the HSOH-CrCl2O complex, and to SO2. These assignments were supported by deuterium isotopic substitution and high level density functional calculations. Merged-jet deposition with the reaction zone at temperatures above 125 degrees C led to substantial yields of SO2 and HCl, as well as the complex of HCl with excess parent H2S. The evidence suggests that the thermal and photochemical reactions may follow different pathways.

Infrared Matrix Isolation and Theoretical Study of the Reactions of MoCl4O and MoCl2O2 with CH3OH: Characterization of Cl3Mo(O)OCH3

The matrix isolation technique has been employed to investigate the reactions of Cl4MoO and MoCl2O2 with CH3OH and C2H5OH. Using twin jet deposition, the initial intermediate in the mechanism was identified as a weakly bound molecular complex, characterized by perturbations to the MoO and O−H stretching modes. The complex between Cl4MoO and CH3OH was destroyed by near-UV irradiation, producing the novel Cl3Mo(O)OCH3 species and cage-paired HCl. The complex between CH3OH and MoCl2O2 was not photosensitive. Merged jet deposition of CH3OH and Cl4MoO, with a 70 °C reaction zone, led to complete conversion to Cl3Mo(O)OCH3, the same product observed in after irradiation of the 1:1 complex. This species was identified by use of extensive isotopic labeling, by the observation of HCl (or DCl) as an additional reaction product, and by comparison to density functional calculations. Most of the fundamental vibrational modes of this species that lie above 400 cm-1 were observed, some with very high intensities. C2H5OH...

Matrix isolation and theoretical study of the reaction of HSiCl 3 and CH 3OH: infrared spectroscopic characterization of Cl 2HSiOCH 3

The matrix isolation technique has been employed to investigate the reactions of SiCl 4 and HSiCl 3 with CH 3OH. For the reaction of HSiCl 3 with CH 3OH, twin jet deposition and merged jet deposition led to the same products, although with a much higher yield in the merged jet experiments. This product was identified as HCl 2SiOCH 3, and was conclusively identified by use of extensive isotopic labeling, the observation of HCl (or DCl) as an additional reaction product, and by comparison to density functional calculations. Most of the fundamental vibrational modes of this species that lie above 400 cm −1 were observed, some with very high intensities. Surprisingly, SiCl 4 and CH 3OH did not show similar reactivity.

Infrared matrix isolation study of the reaction of CrCl2O2 with (CH3)2O and (CH3)2CO

Matrix isolation has been combined with infrared spectroscopy to study the reaction chemistry of CrCl2O2 with (CH3)2O and (CH3)2CO. Very similar results were obtained with twin jet and room temperature merged jet deposition, indicating that the initial product forms on the surface of the matrix during deposition, not in the deposition lines prior to matrix condensation. The initial product in both systems was identified as the 1:1 complex between the two reagents, with a structure in which the oxygen atom of the base donates electron density to the Cr center. A number of perturbed vibrational modes of both subunits were observed; for the bases, these modes were vibrations involving the oxygen atom. Hg arc irradiation of the CrCl2O2·O(CH3)2 complex led to growth of a secondary product that is tentatively identified as Cl2CrO(OCH3)2. The CrCl2O2·OC(CH3)2 complex was not photosensitive, and no rearrangements were observed.

Matrix Isolation and Density Functional Study of the Reaction of OVCl3 with CH3OH: Synthesis and Characterization of Cl2V(O)OCH3

The matrix isolation technique has been employed to investigate the reaction of OVCl3 with CH3OH. Using twin jet deposition, the initial intermediate in the mechanism was identified as a weakly bound molecular complex. This species is characterized by perturbations to the C−O, VO, and V−Cl stretching modes. Merged jet deposition, with a room-temperature reaction zone, led to complete conversion to Cl2V(O)OCH3, the second intermediate in the reaction sequence, through HCl elimination from the initial complex. This species was identified by use of extensive isotopic labeling, the observation of HCl as an additional reaction product, and by comparison to density functional calculations. All of the fundamental vibrational modes of this species that lie above 400 cm-1 were observed, some with very high intensities. Heating the reaction zone above 150 °C led to destruction of this intermediate, and production of both CH2O and CH3Cl.

Matrix Isolation Spectroscopic Study of the 1:1 Complexes of TiF4 with NH3 and (CH3)3N

The matrix isolation technique with twin-jet deposition has been coupled with infrared spectroscopy for the isolation, identification, and characterization of the 1:1 complexes of TiF4 with NH3 and (CH3)3N. For each of these complexes, two perturbed Ti−F stretching modes were observed to be red-shifted 40−90 cm-1 from the triply degenerate parent TiF4 mode at 792 cm-1, indicating a reduction of symmetry in the complex to at least C3v. In addition, the symmetric deformation mode of the NH3 subunit shifted 228 cm-1 to higher energy, indicating that TiF4 is a moderate strength Lewis acid. Merged jet deposition of these reagents led to no observed product in the matrix and no parent TiF4, suggesting that a reaction to form a nonvolatile product in the merged or reaction region had occurred, probably forming the very stable 1:2 complex.

Matrix Isolation Study of the Reaction of TiCl4 with CH3OH: Synthesis and Characterization of Cl3TiOCH3

The initial steps of the reaction of TiCl4 with CH3OH and its isotopomers have been investigated using matrix isolation with infrared spectroscopic detection of the reaction intermediates. When twin jet deposition was employed, a substantial yield of a 1:1 adduct was observed. However, when merged jet deposition was employed with a 15 cm merged reaction region, no traces of the precursors or the 1:1 complex were observed. Rather, very intense bands due to previously unreported monomeric Cl3TiOCH3 were observed, as well as bands due to HCl. Band assignments were assisted by extensive isotopic labeling and supported by density functional calculations. In subsequent experiments, heating the merged region to as high as 350 °C led to complete destruction of the bands to Cl3TiOCH3 while bands due to CH3Cl and the complex of CH3Cl with HCl were observed to grow.