- Manifesto for the routine use of NMR for the liquid product analysis of aqueous CO2 reduction: From comprehensive chemical shift data to formaldehyde quantification in water
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CO2 reduction research is at a critical turnaround since it has the potential to partially or even substantially fulfil future clean energy needs. CO2-to-CO electrochemical conversion is getting closer from industrial implementation requirements. Efforts are now more and more directed to obtain highly reduced products such as methanol, methane, ethylene, ethanol, etc., most of them being liquids. Gas-phase products (e.g., CO, CH4) are typically detected and quantified by well-defined gas chromatography (GC and GC/MS) protocols. On the other hand, NMR, GC-MS, HPLC have been used for the liquid phase characterization, but no routine technique has yet been established, mainly due to lack of versatility of a single technique. Additionally, except NMR and GC-MS, classical techniques cannot distinguish 13C from 12C products, although it is a mandatory step to assess products origin. Herein, we show the efficiency and applicability of 1H NMR as routine technique for liquid phase products analysis and we address two previous shortcomings. We first established a comprehensive 1H and 13C NMR chemical shifts list for all 12CO2 and 13CO2 reduction products in water ranging from C1 to C3. Then we overcame the difficulty of identifying aqueous formaldehyde intermediate by 1H NMR through an efficient chemical trapping step, along with isotopic signature study. Formaldehyde can be reliably quantified in water with a concentration as low as 50 μM.
- Boutin, Etienne,Chatterjee, Tamal,Robert, Marc
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supporting information
p. 4257 - 4265
(2020/04/17)
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- A mechanistic study of the reactions of formaldehyde with aniline in the presence of sulfite
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1H NMR results are reported for the reactions of hydroxymethanesulfonate, 1, with aniline and its derivatives to produce anilinomethanesulfonates, 3. The mechanism of the reaction involves dissociation of 1 to produce formaldehyde, as a steady state intermediate, which reacts with aniline to give a carbinolamine;? subsequent dehydration and reaction with sulfite produces the product. The kinetics of individual steps have been investigated. The release of sulfite from 1, measured by reaction with iodine, is shown to involve the ionised, dianionic form when pH >3. Rate constants, k2, and equilibrium constants, K2, are reported for carbinolamine formation; the values of k2, but not K2, are affected significantly by substituents in the aniline. It is deduced that the rate-limiting step in the overall formation of products 3 changes in the pH range 6-8 from carbinolamine formation to carbinolamine dehydration.
- Atherton, John H.,Brown, Kathryn H.,Crampton, Michael R.
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p. 941 - 946
(2007/10/03)
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- Synthese d'α-Hydroxysulfinates
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α-hydroxysulfinates 1 (table 1) are synthesized (path b, Fig. 1), by slowly adding aldehydes 3 to the mixture sodium dithionite 4 - sodium hydroxide.Owing to their limited stability the products 1 are readily separated from sodium sulfite 5 and isolated.They are easily distinguished (table 2) from their oxydation counterparts 2.
- Mulliez, Michel,Naudy, Carole
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p. 2469 - 2476
(2007/10/02)
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- TRIMETHYLAMMONIOMETHANESULFINATE AND TRIMETHYLAMMONIOMETHANESULFONATE, THE SIMPLEST SULFINIC AND SULFONIC ACID BETAINES. REVISION OF THE STRUCTURE OF THE TRIMETHYLAMINE OXIDE-SULFUR DIOXIDE PRODUCT
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Bromomethanesulfinic acid (1) reacted with eccess trimethylamine to give trimethylammoniomethanesulfinate (3) which was converted by aqueous chlorine into trimethylammoniomethanesulfonate (4).Compounds 3 and 4 are (a) the first examples of sulfino- and sulfo-betaines in which the sulfur and quaternary nitrogen are bound to the same carbon, and, at the same time, are (b) the parent compounds of the respective classes of the sulfinic and sulfonic acid betaines.Reaction of 1 with dimethylamine followed by aqueous chlorine yielded a compound which (a) proved to be identical to the product of the reaction of trimethylamine oxide with sulfur dioxide, and also to the formaldehyde-bisulfite-dimethylamine adduct, and (b) gave 4 on methylation with dimethyl sulfate.We conclude that the sulfur dioxide-trimethylamine oxide product, contrary to an earlier proposal, is dimethylammoniomethanesulfonate (8).The pK'a of 8 and the equilibrium constant for the reaction Me2NCH2SO3- + H2O Me2NH + HOCH2SO3- (in H2O, ionic stength 0.5 M with NaCl), were found from 1Hmr spectra to be 6.05 (at 19.2 deg C) and 1.20*10-4 M (at 20.8 deg C), respectively.
- King, J. F.,Skonieczny, S.
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- PREPARATION AND REACTIONS OF MONOSULPHOMETHYLMELAMINE
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Melamine, formalin and sodium sulphite in aqueous solution gives monosulphonylmethylmelamine and its sodium salt.The properties of the compound and its salts were studied.
- Kunka, I.,Wirpsza, Z.
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p. 1855 - 1856
(2007/10/02)
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- MECHANISM OF AMINOMETHANESULFONATE FORMATION AND HYDROLYSIS REACTIONS
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Based on kinetic, structural and synthetic evidence, a mechanism is proposed fro the synthesis of aminomethanesulfonates (R*NH*CHR'*SO3(1-)).The mechanism involves the initial protonation of the amine, proton transfer to the hydroxymethanesulfonate via a six-membered cyclic intermediate followed by a nucleophilic attack of the free amine on the carbon atom.The transition state is assumed to correspond to a structure with practically all the positive charge on the nitrogen atom.For the hydrolysis reaction, the initial protonation of the aminomethanesulfonate is followed by the nucleophilic attack of a water molecule.This mechanism is in agreement with the experimentally determined Hammett reaction constants ρ, i.e. -3.5 for the formation reaction and -2.3 for the hydrolysis.
- Groote, R. A. M. C. De,Neumann, M. G.,Frollini, E.
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p. 295 - 302
(2007/10/02)
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