Fluoroform (CHF) Production from CFCHO Photolysis and Implications for the Decomposition of Hydrofluoroolefins and Hydrochlorofluoroolefins in the Atmosphere.

Hydrofluoroolefins (HFOs) and hydrochlorofluoroolefins (HCFOs) are the leading synthetic replacements for compounds successively banned by the Montreal Protocol and amendments. HFOs and HCFOs readily decompose in the atmosphere to form fluorinated carbonyls, including CFCHO in yields of up to 100%, which are then photolyzed. A long-standing issue, critical for the transition to safe industrial gases, is whether atmospheric decomposition of CFCHO yields any quantity of CHF (HFC-23), which is one of the most environmentally hazardous greenhouse gases.

The Effect of β-Hydrogens on the Tropospheric Photochemistry of Aldehydes: Norrish Type 1, Triple Fragmentation, and Methylketene Formation from Propanal.

Wavelength and pressure dependent quantum yields (ϕ, QYs) of propanal photolysis have been measured for photolysis wavelengths, λ = 300-330 nm, and buffer gases of 3-10 Torr propanal and 0-757 Torr N. Following laser photolysis, three photochemical pathways were established, using Fourier transform infrared spectroscopy of the stable end-products. Photolysis is dominated by the Norrish Type 1 reaction, which has been reported previously, but with inconsistent quantum yields.

Intramolecular hole-transfer in protonated anthracene.

Excitation spectra of protonated and deuteronated anthracene are obtained by triple-resonance dissociation spectroscopy. Very cold cations, protonated/deuteronated exclusively at the 9-position, are generated from two-colour two-photon threshold ionisation of 9-dihydroanthracenyl radicals (CH). The excitation spectra reveal rich structure, not resolved in previous studies, that is assigned based on anharmonic and Herzberg-Teller coupling calculations.

Photophysical oxidation of HCHO produces HO radicals.

Formaldehyde, HCHO, is the highest-volume carbonyl in the atmosphere. It absorbs sunlight at wavelengths shorter than 330 nm and photolyses to form H and HCO radicals, which then react with O to form HO. Here we show HCHO has an additional HO formation pathway.