Formation of isomers of anionic hemiesters of sugars and carbonic acid in aqueous medium

Santos, Vagner Bezerra dos; Vidal, Denis Tadeu Rajh; Francisco, Kelliton José Mendonça; Ducati, Lucas C.; Lago, Claudimir Lúcio do

doi:10.1016/j.carres.2016.04.007

Cited by 9 publications

(12 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Although variation of the solvent in step (1) has an impact on the reaction product, the variation of the solvent in step (2) has no impact. In Figure 4, spectra of b-H 2 CO 3 and CAME are shown, which were recorded after acidification and solvent evaporation.…”

Section: Variation Of Solvents In Step (2)mentioning

confidence: 99%

“…Starting from the basic formation studies by Hempel and Seidel at the end of the 19th century, [1] nowadays the interest is more focused towards, for example, its importance in biochemistry [2] or food chemistry. [3] Singly esterified carbonic acids are known as hemiesters of carbonic acid (HECAs), [2] and their salts are known as monoalkyl carbonates (MACs). [4] The molecule investigated in this work is the methyl hemiester of carbonic acid, which we will refer to as CAME (carbonic acid monomethyl ester) in the following.…”

Section: Introductionmentioning

confidence: 99%

“…[4] The molecule investigated in this work is the methyl hemiester of carbonic acid, which we will refer to as CAME (carbonic acid monomethyl ester) in the following. In biochemistry, [2] and in food chemistry, that is, carbonated alcoholic beverages, [3] the focus is on detection and reaction of very low concentrations of carbonic ester derivatives in aqueous solution. [5] MACs or HECAs are studied from small alkyl esters to quite complex esters, for example, with sugars.…”

Section: Introductionmentioning

confidence: 99%

“…In the present study, the re-evaluation of a-H 2 CO 3 as CAME is built on four pillars: (i) variation of solvents during both preparation steps; (ii) isotopic shifts in the solid-state spectra by substitution of the CH 3 with a CD 3 group and matching with calculated spectra of species connected by hydrogen bonds; (iii) complete assignment of practically all bands between 4000 and 600 cm À1 of matrix isolation IR spectra by considering different CAME conformers, but also CAME dimers and water complexes; and (iv) forced conversion of conformers by irradiation experiments of the molecules trapped in the matrix. The assignment for the single molecules trapped in matrix (item (iii)) is guided by harmonic frequency calculations at the MP2/aug-cc-pVTZ level of electronic structure theory and isotopic labeling, leading to the following CAME isotopomers: HO 2 COCD 3 (CD 3 -CAME), DO 2 COCH 3 (OD-CAME), and HO 2 13 COCH 3 ( 13 C-CAME). This strategy puts us in a position to identify minor species present in the matrix besides the two CAME conformers identified by Reisenauer et al [16] To learn more about the chemistry of the methyl group in the process leading to the pure solid, the cryo-technique as employed by HHM [9][10] was adapted.…”

Section: Introductionmentioning

confidence: 99%

“…The reactivity of carbonic acid (H 2 CO 3 , CA) towards its ester derivatives has been of interest for more than a century. Starting from the basic formation studies by Hempel and Seidel at the end of the 19th century, nowadays the interest is more focused towards, for example, its importance in biochemistry or food chemistry . Singly esterified carbonic acids are known as hemiesters of carbonic acid (HECAs), and their salts are known as monoalkyl carbonates (MACs) .…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Alpha‐Carbonic Acid Revisited: Carbonic Acid Monomethyl Ester as a Solid and its Conformational Isomerism in the Gas Phase

Köck

Bernard

Podewitz

et al. 2019

Chemistry A European J

View full text Add to dashboard Cite

In this work, earlier studies reporting α‐H2CO3 are revised. The cryo‐technique pioneered by Hage, Hallbrucker, and Mayer (HHM) is adapted to supposedly prepare carbonic acid from KHCO3. In methanolic solution, methylation of the salt is found, which upon acidification transforms to the monomethyl ester of carbonic acid (CAME, HO‐CO‐OCH3). Infrared spectroscopy data both of the solid at 210 K and of the evaporated molecules trapped and isolated in argon matrix at 10 K are presented. The interpretation of the observed bands on the basis of carbonic acid [as suggested originally by HHM in their publications from 1993–1997 and taken over by Winkel et al., J. Am. Chem. Soc. 2007 and Bernard et al., Angew. Chem. Int. Ed. 2011] is inferior compared with the interpretation on the basis of CAME. The assignment relies on isotope substitution experiments, including deuteration of the OH‐ and CH3‐ groups as well as 12C and 13C isotope exchange and on variation of the solvents in both preparation steps. The interpretation of the single molecule spectroscopy experiments is aided by a comprehensive calculation of high‐level ab initio frequencies for gas‐phase molecules and clusters in the harmonic approximation. This analysis provides evidence for the existence of not only single CAME molecules but also CAME dimers and water complexes in the argon matrix. Furthermore, different conformational CAME isomers are identified, where conformational isomerism is triggered in experiments through UV irradiation. In contrast to earlier studies, this analysis allows explanation of almost every single band of the complex spectra in the range between 4000 and 600 cm−1.

show abstract

Section: Variation Of Solvents In Step (2)mentioning

confidence: 99%