On the Reaction Mechanism of Acetaldehyde Decomposition on Mo(110)

Gas-phase detection of oxirene

Oxirenes-highly strained 4π Hückel antiaromatic organics-have been recognized as key reactive intermediates in the Wolff rearrangement and in interstellar environments. Predicting short lifetimes and tendency toward ring opening, oxirenes are one of the most mysterious classes of organic transients, with the isolation of oxirene (c-C₂H₂O) having remained elusive. Here, we report on the preparation of oxirene in low-temperature methanol-acetaldehyde matrices upon energetic processing through isomerization of ketene (H₂CCO) followed by resonant energy transfer of the internal energy of oxirene to the vibrational modes (hydroxyl stretching and bending, methyl deformation) of methanol. Oxirene was detected upon sublimation in the gas phase exploiting soft photoionization coupled with a reflectron time-of-flight mass spectrometry. These findings advance our fundamental understanding of the chemical bonding and stability of cyclic, strained molecules and afford a versatile strategy for the synthesis of highly ring-strained transients in extreme environments.

Mechanistical study on the formation of hydroxyacetone (CH3COCH2OH), methyl acetate (CH3COOCH3), and 3-hydroxypropanal (HCOCH2CH2OH) along with their enol tautomers (prop-1-ene-1,2-diol (CH3C(OH)CHOH), prop-2-ene-1,2-diol (CH2C(OH)CH2OH), 1-methoxyethen-1-ol (CH3OC(OH)CH2) and prop-1-ene-1,3-diol (HOCH2CHCHOH)) in interstellar ice analogs

We unravel, for the very first time, the formation pathways of hydroxyacetone (CH₃COCH₂OH), methyl acetate (CH₃COOCH₃), and 3-hydroxypropanal (HCOCH₂CH₂OH), as well as their enol tautomers within mixed ices of methanol (CH₃OH) and acetaldehyde (CH₃CHO) analogous to interstellar ices in the ISM exposed to ionizing radiation at ultralow temperatures of 5 K. Exploiting photoionization reflectron time-of-flight mass spectrometry (PI-ReToF-MS) and isotopically labeled ices, the reaction products were selectively photoionized allowing for isomer discrimination during the temperature-programmed desorption phase. Based on the distinct mass-to-charge ratios and ionization energies of the identified species, we reveal the formation pathways of hydroxyacetone (CH₃COCH₂OH), methyl acetate (CH₃COOCH₃), and 3-hydroxypropanal (HCOCH₂CH₂OH) via radical-radical recombination reactions and of their enol tautomers (prop-1-ene-1,2-diol (CH₃C(OH)CHOH), prop-2-ene-1,2-diol (CH₂C(OH)CH₂OH), 1-methoxyethen-1-ol (CH₃OC(OH)CH₂) and prop-1-ene-1,3-diol (HOCH₂CHCHOH)) via keto-enol tautomerization. To the best of our knowledge, 1-methoxyethen-1-ol (CH₃OC(OH)CH₂) and prop-1-ene-1,3-diol (HOCH₂CHCHOH) are experimentally identified for the first time. Our findings help to constrain the formation mechanism of hydroxyacetone and methyl acetate detected within star-forming regions and suggest that the hitherto astronomically unobserved isomer 3-hydroxypropanal and its enol tautomers represent promising candidates for future astronomical searches. These enol tautomers may contribute to the molecular synthesis of biologically relevant molecules in deep space due to their nucleophilic character and high reactivity.

Self-supported hydrogenolysis of aromatic ethers to arenes

Arenes are widely used chemicals and essential components in liquid fuels, which are currently produced from fossil feedstocks. Here, we proposed the self-supported hydrogenolysis (SSH) of aromatic ethers to produce arenes using the hydrogen source within the reactants, and it was found that RuW alloy nanoparticles were very efficient catalyst for the reactions. This route is very attractive and distinguished from the reported studies on the cleavage of the C_Ar─O bonds. The unique feature of this methodology is that exogenous hydrogen or other reductant is not required, and hydrogenation of aromatic rings could be avoided completely. The selectivities to arenes could reach >99.9% at complete conversion of the ethers. Moreover, lignin could also be transformed into arenes efficiently over the RuW alloy catalyst. The mechanism studies showed that the neighboring Ru and W species in the RuW alloy nanoparticles worked synergistically to accelerate the SSH reaction.

Differentiation of the C–O and C–C bond scission mechanisms of 1-hexadecanol on Pt(111) and Ru(0001): a first principles analysis

The major product on Pt(111) is hexadecane, whereas it is pentadecane on Ru(0001).