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Protonated carboxylic acids, (RCOOH)H+, are the initial intermediates in acid-catalyzed (Fischer) esterification reactions. However the identity of the isomeric form is under debate. Surprisingly, no optical spectra have been reported for any isomer of the protonated carboxylic acid monomer, despite it being a fundamental organic cation. Here, we address these issues by using a new approach to prepare cold He-tagged cations of protonated acetic acid (AA), which entails electron ionization of helium nanodroplets containing metastable dimers of AA. The protonated species is subsequently probed using infrared photodissociation spectroscopy and, following a comparison with calculations, we identify the two isomers whose roles are debated in Fischer esterification. These are the carbonyl-protonated E,Z isomer and the metastable hydroxyl-protonated isomer. Our technique provides a novel approach that can be applied to other elusive ionic species.
This article was published in the following journal.
Name: The journal of physical chemistry letters
Raman spectra of acetic acid-water binary solutions with different concentrations have been measured in order to study molecular association of acetic acid. We find that the symmetric and asymmetric O...
The mix of bicarbonate and divalent cations requires a small amount of acid to avoid insoluble precipitation in the dialysate buffer. Small doses of acetic acid (3-7mmol/L) are commonly used. Acetic a...
Charge resonance is a strong attractive intermolecular force in aromatic dimer radical ions. For cations, this stabilization arises from sharing a positive charge between two identical or different mo...
In this study, a novel method based on the determination of 1-naphthalene acetic acid with the usage of magnetite-molecularly imprinted polymer prior to fluorimetric detection has been developed. Magn...
Two new coordination polymers [Pr(PCPA)(HO)]1 and [Pr(PCPA)(HO)]·nHO 2(PCPA = p-chlorophenoxyacetic acid) have been synthesized under similar conditions by the hydrothermal method and characteriz...
The main objective of this study is to evaluate the ability of infrared spectroscopy to discriminate simple hepatic steatosis from NASH
The aim of this study is to demonstrate that infrared spectroscopy is able to detect pressure injuries at a very early stage
RATIONALE: Drugs used in chemotherapy such as gossypol acetic acid, work in different ways to stop the growth of tumor cells, either by killing the cells or by stopping them from dividing....
Investigators aim to study efficiency of systemic thrombolytic therapy on acute ischemic stroke patients with near infrared spectroscopy.
Intraduodenal acetic acid can stimulate secretion of water and bicarbonate from pancreatic ductal cells. In this study, acetic acid spraying to duodenal bulb was compared with saline solut...
ACETIC ACID or acetic acid esters substituted with one or more CHLORINE atoms.
A noninvasive technique that uses the differential absorption properties of hemoglobin and myoglobin to evaluate tissue oxygenation and indirectly can measure regional hemodynamics and blood flow. Near-infrared light (NIR) can propagate through tissues and at particular wavelengths is differentially absorbed by oxygenated vs. deoxygenated forms of hemoglobin and myoglobin. Illumination of intact tissue with NIR allows qualitative assessment of changes in the tissue concentration of these molecules. The analysis is also used to determine body composition.
A spectroscopic technique in which a range of wavelengths is presented simultaneously with an interferometer and the spectrum is mathematically derived from the pattern thus obtained.
Acetic acid and its derivatives which may be formed by substitution reactions. Mono- and di-substituted, as well as halogenated compounds have been synthesized.
Measurement of the regional temperature of the body or an organ by infrared sensing devices, based on self-emanating infrared radiation.