Methyl Hydrogen Carbonate

On the Existence of the Elusive Monomethyl Ester of Carbonic Acid [CH3OC(O)OH] at 300 K: 1H‐ and 13C NMR Measurements and DFT Calculations

“…Accordingly, 4 has been reported to be a labile species and has only been characterized so far by IR spectroscopy at low temperature. [3] Therefore, it is not likely that it will exist for a long time at temperatures above 273 K. These results suggest that the direct insertion of CO 2 into the O-H bond of methanol is quite unlikely to occur under reaction conditions such as those used for the synthesis of organic carbonates, [7] and CH 3 OC(O)OH is unlikely to be an intermediate in such a reaction.…”

“…It is worthwhile mentioning that previous theoretical studies [8][9][10][11] on the mechanism of carbonic acid formation from H 2 O and CO 2 , a reaction that is analogous to Equation (4), have excluded the possibility of a direct bimolecular insertion because the activation energy predicted for this step is about 50 kcal mol -1 , [8][9][10] while the energy barrier decreases substantially (to about 15 kcal mol -1 ) [8] if an additional water molecule is assumed to participate in the hydration process. Our calculations carried out at the B3LYP/ 6-311++G** level of density functional theory for CH 3 OC(O)OH formation involving two CH 3 OH molecules (see Figure 1) predict a relatively high energy barrier for this process (∆G ‡ gas = 28.9 and ∆G ‡ solv = 22.7 kcal mol -1 if solvent effects due to the methanol environment are included), indicating that reaction 4 is likely to be kinetically hindered. Furthermore, CH 3 OC(O)OH is found to be thermodynamically unstable with respect to its dissociation products, since the calculations give ∆G gas = +9.9 kcal mol -1 for the gas-phase reaction shown in Figure 1, which decreases to ∆G solv = +4.4 kcal mol -1 in the solvated model [for the isolated CH 3 OC(O)OH molecule the calculated dissociation free-energy values are ∆G gas = +15.1 and ∆G solv = +11.6 kcal mol -1 ].…”

“…The X-ray structure shows the existence of H-bonding through the carboxylic moieties [R = C 6 H 5 CH 2 , RЈ = H; or R,RЈ = PhP(OCH 2 CH 2 ) 2 ]. [1,2] For 3 only a report of its low-temperature IR spectrum can be found in the literature; [3] no report of its existence at room temperature or information tions are examined on the basis of density functional calculations. For kinetic and thermodynamic reasons CH 3 OC(O)OH is unlikely to be formed by insertion of CO 2 Despite their instability, compounds 1-3 are often proposed to be intermediates in reactions in which carbon dioxide is implied.…”

“…Their isolation as pure compounds is not trivial as they easily decompose to afford CO 2 plus water [Equation (1)], amine [Equation (2)], or alcohol [Equation (3)]. …”

Fundamentos, produção e aplicações de marcas térmicas em eletroforese capilar

“…Assim, ocorre uma limitação em O primeiro relato da determinação de pK a de um MAC surgiu com Gattow e Beherendt, que determinaram o pK a do monometilcarbonato de sódio através de hidrólise, obtendo o valor de 5,6 a 25 ºC [101]. Entretanto, esse é apenas um valor aparente, devido à decomposição do ácido.…”