An official website of the United States government
The title compound, C8H18NO2+·Br−·C8H17NO2, crystallizes as the bromide salt of a 50:50 mixture of (triethylazaniumyl)carboxylic acid and the zwitterionic (triethylazaniumyl)carboxylate. The two organic entities are linked by a half-occupied bridging carboxylic acid hydrogen atom that is hydrogen-bonded to the carboxylate group of the second molecule. The tetralkylammonium group adopts a nearly perfect tetrahedral shape around the nitrogen atom with bond lengths that agree with known values. The carboxylic acid/carboxylate group is orientedantito one of the ethyl groups on the ammonium group, and the carbonyl oxygen atom is engaged in intramolecular C—H...O hydrogen bonds.
more »
« less
The Role of Oxygen in the Electrochemical Reduction of Ethyl 2-(2-(Bromomethyl)phenoxy)acetate at Carbon Cathodes in Dimethylformamide
Cyclic voltammetry (CV) and controlled-potential electrolysis (CPE) were employed to examine the direct reduction of ethyl 2-(2-(bromomethyl)phenoxy)acetate at carbon cathodes in dimethylformamide (DMF) containing tetramethylammonium tetrafluoroborate (TMABF4) as the electrolyte. Cyclic voltammogram of the substrate exhibits a single irreversible cathodic wave with a peak potential of –1.75 V vs SCE, which is characteristic for the reduction of organic halides in aprotic solvents. Bulk electrolyses of ethyl 2-(2-(bromomethyl)phenoxy)acetate were carried out in the absence and presence of oxygen. The product distributions were obtained by gas chromatograph (GC) as well as gas chromatograph coupled to a mass spectrometer (GC−MS). Two bicyclic compounds, ethyl 2,3-dihydro-1-benzofuran-2-carboxylate and ethyl benzofuran-2-carboxylate, were found to be formed in a total yield of more than 40% in the presence of oxygen. The reaction mechanism, in which the oxygen plays a significant role, was proposed and discussed on the basis of this study.
more »
« less
- Award ID(s):
- 1757843
- PAR ID:
- 10302741
- Publisher / Repository:
- The Electrochemical Society
- Date Published:
- Journal Name:
- Journal of The Electrochemical Society
- Volume:
- 167
- Issue:
- 4
- ISSN:
- 0013-4651
- Page Range / eLocation ID:
- Article No. 045502
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract The electrochemical conversion of waste CO2into useful fuels and chemical products is a promising approach to reduce CO2emissions; however, several challenges still remain to be addressed. Thus far, most CO2reduction studies use pure CO2as the gas reactant, but CO2emissions typically contain a number of gas impurities, such as nitrogen oxides, oxygen gas, and sulfur oxides. Gas impurities in CO2can pose a significant obstacle for efficient CO2electrolysis because they can influence the reaction and catalyst. This Minireview highlights early examples of CO2reduction studies using mixed‐gas feeds, explores strategies to sustain CO2reduction in the presence of gas impurities, and discusses their implications for future progress in this emerging field.more » « less
-
Abstract 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 of1H and13C 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/TiO2catalysts in methanol‐d4and in D2O. The maximum obtained1H polarization was 0.6±0.2 % (for propyl acetate in CD3OD), while the highest13C 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 maximum1H and13C 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.more » « less
-
ABSTRACT Access to benzofuran‐2(3H)‐one derivatives from readily available substrates under mild conditions is crucial in the pharmaceutical and plastics industries. We identified (Z)‐3‐(2‐phenylhydrazineylidene)benzofuran‐2(3H)‐one (P) during the recrystallization of (E)‐2‐(2,2‐dichloro‐1‐(phenyldiazenyl)vinyl)phenol using a 96% ethanol solution. The mechanism of the unexpected substrate conversion leading toPis investigated using density functional calculations. The computations revealed that ethanol is required to initiate the reaction viaTS1E, which involves a concerted deprotonation of ethanol by the basic diaza group of the substrate and an ethoxy group attacking the electrophilic center (Cl2C), with an energy barrier of 28.3 kcal/mol. The resulting intermediate (I1E) is calculated to be unstable and can yield a cyclic chloroacetal adduct with a lower energy barrier of 2.2 kcal/mol via the ring‐closure transition state (TS2E). In the absence of water, the next steps are impossible because water is required to cleave the ether bond, yieldingP. A small amount of water (4% of the recrystallization solvent) can promote further transformation ofI2Evia the transition statesTS3E(∆G‡ = 11.1 kcal/mol) andTS4E(∆G‡ = 10.5 kcal/mol). A comparison of the ethanol/water‐ and only water‐promoted free energy profiles shows that the presence of ethanol is crucial for lowering the energy barriers (by about 5 kcal/mol) for the initial two steps leading to the cyclic chloroacetal (I2E), whereas water is then required to initiate product formation.more » « less
-
Abstract Oxygen-containing complex organic molecules are key precursors to biorelevant compounds fundamental for the origins of life. However, the untangling of their interstellar formation mechanisms has just scratched the surface, especially for oxygen-containing cyclic molecules. Here, we present the first laboratory simulation experiments featuring the formation of all three C2H4O isomers—ethylene oxide (c–C2H4O), acetaldehyde (CH3CHO), and vinyl alcohol (CH2CHOH)—in low-temperature model interstellar ices composed of carbon monoxide (CO) and ethanol (C2H5OH). Ice mixtures were exposed to galactic cosmic-ray proxies with an irradiation dose equivalent to a cold molecular cloud aged (7 ± 2) × 105yr. These biorelevant species were detected in the gas phase through isomer-selective photoionization reflectron time-of-flight mass spectrometry during temperature-programmed desorption. Isotopic labeling experiments reveal that ethylene oxide is produced from ethanol alone, providing the first experimental evidence to support the hypothesis that ethanol serves as a precursor to the prototype epoxide in interstellar ices. These findings reveal feasible pathways for the formation of all three C2H4O isomers in ethanol-rich interstellar ices, offering valuable constraints on astrochemical models for their formation. Our results suggest that ethanol is a critical precursor to C2H4O isomers in interstellar environments, representing a critical step toward unraveling the formation mechanisms of oxygen-containing cyclic molecules, aldehydes, and their enol tautomers from alcohols in interstellar ices.more » « less
