Theoretical study on the thermolysis of methyl-3-hydroxypropanoate in m-xylene solution

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.

FT-IR spectroscopy and DFT calculation study on the solvent effects of benzaldehyde in organic solvents

FT-IR spectra of benzaldehyde in 11 different organic solvents were recorded and analyzed. The density functional theory (DFT) B3LYP/6-31G* method was chosen to calculate the infrared spectrum of benzaldehyde in gaseous state. The electrostatic effects of different solvents in benzaldehyde solutions were calculated using DFT with the self-consistent isodensity polarizable continuum model (SCI-PCM). Two remarkable carbonyl (C=O) peaks of benzaldehyde were observed by FT-IR in alcohol solvents, which were caused by different hydrogen bond species and explained by ab initio calculation. The results showed that the combination of SCI-PCM model and ab initio calculation could give excellent agreements with FT-IR spectra of title compound in solutions.

The catalytic property of 3-hydroxyisobutyrate dehydrogenase from Bacillus cereus on 3-hydroxypropionate

The MmsB gene product from Bacillus cereus ATCC14579 exhibits 3-hydroxypropionate dehydrogenase activity. It encodes the 32-kDa enzyme protein composed of 292 amino acids. Recombinant 3-hydroxyisobutyrate dehydrogenase (3-HIBADH) was purified 100-fold from cell extract by ammonium sulfate fractionation and column chromatography. The enzyme catalyzed oxidation of 3-hydroxypropionate (3-HP) between pH 7.0 and 10.0 with optimal activity between 8.8 and 9.0. A Km of 16.8 mM for 3-HP was calculated from a Lineweaver-Burk plot. The semialdehyde as products has been proven by spectrophotometric determination. The dehydrogenase apparently has no metal ion requirement. Kinetic determinations established that 3-HIBADH was more active with NADP(+) than NAD(+), which did not show similarity with previously reported 3-HIBADH except that from Thermus thermophilus.