811-98-3Relevant articles and documents
Experimental study on the mechanism of gas-phase aromatic nitration by protonated methyl nitrate
Aschi, Massimiliano,Attinà, Marina,Cacace, Fulvio,Ricci, Andreina
, p. 9535 - 9542 (1994)
The mechanism of gas-phase aromatic substitution by (CH3ONO2)H+ ions has been studied by a combination of FT-ICR mass spectrometry and atmospheric pressure radiolytic techniques. Clarifying a long-standing ambiguity, the ICR results characterize the CH3OH-NO2+ complex (1), in essence a nitronium ion solvated by a methanol molecule, as the nitrating agent, whereas the CH3NO2H+ isomer (2) is devoid of nitrating properties and reacts with benzene exclusively as a Br?nsted acid. Indeed, the reaction with benzene has been exploited as an ICR "titration" technique to evaluate the relative abundances of 1 and 2 in mixed populations of (CH3ONO2)H+ ions from different preparative procedures. Radiolytic nitration of p-H-toluene-d7 and p-D-toluene-h7 leads to intraannular hydron migration from the ipso nitrated position, whose rate has been estimated to be ca. 1.6 × 106 s-1 at 315 K. The mutually supporting evidence from the ICR and the radiolytic experiments outlines a reaction mechanism involving preliminary formation of a Wheland intermediate from the attack of 1 on the arene, followed by its isomerization into the more stable O-protonated nitrobenzene structure via a proton shift whose rate is estimated to be ca. 3.6 × 107s-1 at 315 K. The results are compared with those of a recent theoretical analysis of the mechanism of aromatic nitration by isomeric (CH3ONO2)H+ ions, and their correlation with condensed-phase nitration is briefly discussed.
Formation of Glyoxylic Acid in Interstellar Ices: A Key Entry Point for Prebiotic Chemistry
Eckhardt, André K.,Bergantini, Alexandre,Singh, Santosh K.,Schreiner, Peter R.,Kaiser, Ralf I.
supporting information, p. 5663 - 5667 (2019/03/29)
With nearly 200 molecules detected in interstellar and circumstellar environments, the identification of the biologically relevant α-keto carboxylic acid, glyoxylic acid (HCOCOOH), is still elusive. Herein, the formation of glyoxylic acid via cosmic-ray driven, non-equilibrium chemistry in polar interstellar ices of carbon monoxide (CO) and water (H2O) at 5 K via barrierless recombination of formyl (HCO) and hydroxycarbonyl radicals (HOCO) is reported. In temperature-programmed desorption experiments, the subliming neutral molecules were selectively photoionized and identified based on the ionization energy and distinct mass-to-charge ratios in combination with isotopically labeled experiments exploiting reflectron time-of-flight mass spectrometry. These studies unravel a key reaction path to glyoxylic acid, an organic molecule formed in interstellar ices before subliming in star-forming regions like SgrB2(N), thus providing a critical entry point to prebiotic organic synthesis.
Aqueous phase hydrodeoxygenation of polyols over Pd/WO3-ZrO2: Role of Pd-WO3 interaction and hydrodeoxygenation pathway
Liu, Changjun,Sun, Junming,Brown, Heather M.,Marin-Flores, Oscar G.,Bays, J. Timothy,Karim, Ayman M.,Wang, Yong
, p. 103 - 109 (2016/05/11)
Aqueous phase processing of biomass derived sugar alcohols is one of the promising routes to convert biomass into fuels and chemicals. Bifunctional catalysts are critical in the aqueous phase hydrodeoxygenation of sugar alcohol. Understanding the interaction between metal and acidic metal oxides as well as the hydrodeoxygenation pathways will help develop more efficient bifunctional catalysts. Here, tungstated zirconia supported palladium catalysts were prepared and further characterized using nitrogen sorption, X-ray diffraction, FT-IR analysis of adsorbed pyridine, CO chemisorption and diffuse reflectance UV-vis. Strong interaction between palladium and WO3 in addition to a synergetic effect of the acidic and metallic sites were found to promote the aqueous phase hydrodeoxygenation of ethylene glycol. H-D exchange experiments using 13C{1H} NMR spectroscopy confirmed that the aqueous phase hydrodeoxygenation follows a dehydration-hydrogenation pathway. The hydrogenation of the dehydration products shifts the dehydration-hydration equilibrium toward the dehydration pathway and leads to highly selective C-O cleavage.