4712-36-1Relevant articles and documents
Heterogeneous 1H and 13C Parahydrogen-Induced Polarization of Acetate and Pyruvate Esters
Salnikov, Oleg G.,Chukanov, Nikita V.,Kovtunova, Larisa M.,Bukhtiyarov, Valerii I.,Kovtunov, Kirill V.,Shchepin, Roman V.,Koptyug, Igor V.,Chekmenev, Eduard Y.
, p. 1389 - 1396 (2021/05/31)
Magnetic resonance imaging of [1-13C]hyperpolarized carboxylates (most notably, [1-13C]pyruvate) allows one to visualize abnormal metabolism in tumors and other pathologies. Herein, we investigate the efficiency of 1H and 13C hyperpolarization of acetate and pyruvate esters with ethyl, propyl and allyl alcoholic moieties using heterogeneous hydrogenation of corresponding vinyl, allyl and propargyl precursors in isotopically unlabeled and 1-13C-enriched forms with parahydrogen over Rh/TiO2 catalysts in methanol-d4 and in D2O. The maximum obtained 1H polarization was 0.6±0.2 % (for propyl acetate in CD3OD), while the highest 13C polarization was 0.10±0.03 % (for ethyl acetate in CD3OD). Hyperpolarization of acetate esters surpassed that of pyruvates, while esters with a triple carbon-carbon bond in unsaturated alcoholic moiety were less efficient as parahydrogen-induced polarization precursors than esters with a double bond. Among the compounds studied, the maximum 1H and 13C NMR signal intensities were observed for propyl acetate. Ethyl acetate yielded slightly less intense NMR signals which were dramatically greater than those of other esters under study.
Surface-Mediated Isomerization and Oxidation of Allyl Alcohol on Cu(110)
Brainard, Robert L.,Peterson, Cynthia G.,Madix, Robert J.
, p. 4553 - 4561 (2007/10/02)
Allyl alcohol reacts with clean and oxygen-covered Cu(110) surfaces to produce propanal, acrolein, n-propyl alcohol, and hydrogen under ultrahigh-vacuum conditions.Very small amounts of propylene and water are also formed.This pattern of reactivity contrasts sharply to the selective oxidation to acrolein observed on Ag(110).On the clean Cu(110) surface allyl alcohol undergoes O-H cleavage to form the surface alkoxide CH2=CHCH2O(a) and H(a).The results suggest that the olefin in this species undergoes partial hydrogenation to the surface-bound oxametallacycles (-CH2CH2CH2O-)(a) and (-CH-(CH3)CH2O-)(a) and complete hydrogenation to CH3CH2CH2O(a).Propanal forms at 320 K via further reaction of these oxametallacycles.Evidence for a ?-bonded allyl oxide CH2=CHCH2O(a), which is more stable than n-propoxide (CH3CH2CH2O(a)) toward β-hydride elimination, is presented.This allyl oxide decomposes at 370 K to form acrolein.The interaction of the double bond with the surface apparently restricts the interaction of the β-C-H bond with the surface and increases the stability of this species.Propanal, acrolein and H2 are formed at 435 K by a process thought to involve the thermal decomposition of (-CH2CH2CH2O-)(a) by a β-hydride elimination pathway.This dehydrogenation pathway exhibits an activation energy 8 kcal/mol greater than for acyclic alkoxides.The conversion of allyl alcohol to propanal and propyl alcohol obviously involves the hydrogenation of the double bond which, by comparison, does not occur for propylene coadsorbed with hydrogen under similar conditions on this surface.Clearly, the hydroxyl group in allyl alcohol facilitates the hydrogenation of its olefin group by tethering the doublebond to the surface at temperatures higher than the normal desorption temperature of olefins.
