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.

Theoretical Investigation of the Atmospheric Photochemistry of Glyoxylic Acid in the Gas Phase.

The photochemistry of glyoxylic acid (HC(O)C(O)OH) is explored in the near UV in both the singlet (/) and triplet () manifolds using density functional theory (M06-2X/aug-cc-pVTZ) to reach an overall mechanistic picture of the atmospherically relevant photochemistry in the gas phase. The calculated energies and structures are also used in RRKM kinetics calculations to compare the relative reaction rates on each of these electronic states. The major photolysis pathways are two possible photodecarboxylation reactions: direct C-C bond cleavage (Norrish Type I reaction) and β-hydrogen transfer followed by CO loss.

Dynamics and quantum yields of H + CHCO as a primary photolysis channel in CHCHO.

The first experimental observation of the primary photochemical channel of acetaldehyde leading to the formation of ketene (CHCO) and hydrogen (H) molecular products is reported. Acetaldehyde (CHCHO) was photolysed in a molecular beam at 305.6 nm and the resulting H product characterized using velocity-map ion (VMI) imaging.

Photo-tautomerization of acetaldehyde as a photochemical source of formic acid in the troposphere.

Organic acids play a key role in the troposphere, contributing to atmospheric aqueous-phase chemistry, aerosol formation, and precipitation acidity. Atmospheric models currently account for less than half the observed, globally averaged formic acid loading. Here we report that acetaldehyde photo-tautomerizes to vinyl alcohol under atmospherically relevant pressures of nitrogen, in the actinic wavelength range, λ = 300-330 nm, with measured quantum yields of 2-25%.

Infrared Spectra of Gas-Phase 1- and 2-Propenol Isomers.

Fourier transform infrared spectra of isolated 1-propenol and 2-propenol in the gas-phase have been collected in the range of 900-3800 cm, and the absolute infrared absorption cross sections reported for the first time. Both cis and trans isomers of 1-propenol were observed with the trans isomer in greater abundance. Syn and anti conformers of both 1- and 2-propenol were also observed, with abundance consistent with thermal population.

Theoretical study of the mechanism for the sequential N-O and N-N bond cleavage within N2O adducts of N-heterocyclic carbenes by a vanadium(iii) complex.

A theoretical study into the reactions of the N2O adducts of N-heterocyclic carbenes (NHCs) and a V((III)) complex was carried out using DFT calculations. Unlike most transition metal reactions with N2O that simply release N2 following O-atom transfer onto the metal centre, this NHC-based system traps the entire N2O molecule and then cleaves both the N-O and N-N bond in two consecutive reactions. The NHC presence increases the reactivity of N2O by altering the distribution of electron density away from the O-atom towards the two N-atoms.

NO2 bond cleavage by MoL3 complexes.

The cleavage of one N-O bond in NO2 by two equivalents of Mo(NRAr)3 has been shown to occur to form molybdenum oxide and nitrosyl complexes. The mechanism and electronic rearrangement of this reaction was investigated using density functional theory, using both a model Mo(NH2)3 system and the full [N((t)Bu)(3,5-dimethylphenyl)] experimental ligand. For the model ligand, several possible modes of coordination for the resulting complex were observed, along with isomerisation and bond breaking pathways.

Synthesis of Ti(IV) complexes of donor-functionalised phenoxy-imine tridentates and their evaluation in ethylene oligomerisation and polymerisation.

A number of analogues of the Mitsui Chemicals ethylene trimerisation system (IV) have been explored, in which one of the donor atoms have been modified. Thus, a series of mono-anionic tridentate phenoxy-imine (3-(t-butyl)-2-(OH)-C6H4C=N(C(CH3)2CH2OMe) 1, 3-(adamantyl)-2-(OH)-C6H4C=N(2'-(2''-(SMe)C6H4)-C6H4) 2, 3-(t-butyl)-2-(OSiMe3)-C6H4C=N(C(CH3)2CH2OMe) 3) or phenoxy-amine (3,5-di(t-butyl)-2-(OH)-C6H4CH2-N(2'-(2''-(OMe)C6H4)-C6H4) 4) ligands have been prepared and reacted with TiCl4 or TiCl4(thf)2 to give the mono-ligand complexes 5-7. The solid state structures of compounds 4-6 have been determined.