scholarly journals Observation of the simplest Criegee intermediate CH2OO in the gas-phase ozonolysis of ethylene

2015 ◽  
Vol 1 (2) ◽  
pp. e1400105 ◽  
Author(s):  
Caroline C. Womack ◽  
Marie-Aline Martin-Drumel ◽  
Gordon G. Brown ◽  
Robert W. Field ◽  
Michael C. McCarthy
Keyword(s):  
Fourier Transform ◽  
Gas Phase ◽  
Rate Constants ◽  
Qualitative Agreement ◽  
High Reactivity ◽  
Microwave Spectroscopy ◽  
Bimolecular Reactions ◽  
Rapid Sampling ◽  
Product Species ◽  
Pulsed Nozzle

Ozonolysis is one of the dominant oxidation pathways for tropospheric alkenes. Although numerous studies have confirmed a 1,3-cycloaddition mechanism that generates a Criegee intermediate (CI) with form R1R2COO, no small CIs have ever been directly observed in the ozonolysis of alkenes because of their high reactivity. We present the first experimental detection of CH2OO in the gas-phase ozonolysis of ethylene, using Fourier transform microwave spectroscopy and a modified pulsed nozzle, which combines high reactant concentrations with rapid sampling and sensitive detection. Nine other product species of the O3+ C2H4reaction were also detected, including formaldehyde, formic acid, dioxirane, and ethylene ozonide. The presence of all these species can be attributed to the unimolecular and bimolecular reactions of CH2OO, and their abundances are in qualitative agreement with published mechanisms and rate constants.

scholarly journals Unveiling epimerization effects: a rotational study of α-d-galactose

2015 ◽  
Vol 51 (50) ◽  
pp. 10115-10118 ◽  
Author(s):  
Isabel Peña ◽  
Carlos Cabezas ◽  
José L. Alonso
Keyword(s):  
Fourier Transform ◽  
Laser Ablation ◽  
Gas Phase ◽  
Microwave Spectroscopy ◽  
Fourier Transform Microwave Spectroscopy

Four conformers of α-d-galactose have been detected in the gas phase by laser ablation coupled with broadband Fourier transform microwave spectroscopy.

Rotational spectrum and properties of the hydrogen-bonded heterodimer H 2 O· · · HCN from pulsed-nozzle, Fourier-transform microwave spectroscopy

1984 ◽  
Vol 396 (1811) ◽  
pp. 405-423 ◽  
Keyword(s):  
Fourier Transform ◽  
Microwave Spectroscopy ◽  
Coupling Constants ◽  
Spectroscopic Constants ◽  
Rotational Spectrum ◽  
Quadrupole Coupling ◽  
Nuclear Quadrupole ◽  
Fourier Transform Microwave Spectroscopy ◽  
Pulsed Nozzle ◽  
Hydrogen Bonded

The ground state rotational spectrum of a hydrogen-bonded heterodimer formed from water and hydrogen cyanide has been detected and measured by using the technique of pulsed-nozzle, Fourier-transform microwave spectroscopy. Rotational constants ( B 0 , C 0 ) centrifugal distortion constants ( ∆ J , ∆ JK ) and, where appropriate, 14 N-, D- or 17 O-nuclear quadrupole coupling constants have been determined for the following isotopic species; H 2 16 O· · · HC 14 N, H 2 18 O· · · HC 14 N, H 2 16 O· · · HC 15 N, HD 16 O· · · HC 15 N, D 2 16 O· · · HC 15 N, H 2 16 O· · · DC 15 N, HD 16 O· · · DC 15 N and H 2 17 O· · · HC 15 N. An analysis of these spectroscopic constants indicates that the heterodimer is effectively planar, with a pair of equivalent protons and the arrangement H 2 O· · · HCN. The intermolecular interaction is through a hydrogen bond between HCN and H 2 O and the distance between the O and C nuclei r (O· · · C) is 3.157 Å (1Å = 10 -10 m). An interpretation of the nuclear quadrupole coupling constants leads to the conclusion that arccos <cos 2 Φ > ½ ≈ 51°, where Φ is the angle between the local C 2 axis of H 2 O and the a -axis of the complex; and that arccos <cos 2 θ > ½ ≈ 10°, where θ is the angle between the HCN axis and the a -axis. The intermolecular stretching force constant k σ = 11 Nm -1 has been determined from ∆ J .

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