Kinetic investigation on carbamate formation from the reaction of carbon dioxide with amino acids in homogeneous aqueous solution

Abstract

The kinetics of carbamate formation from the reaction of carbon dioxide with a-amino acids in D 2 O was first investigated by means of nuclear magnetic resonance spectroscopy. Potassium carbonate was used as the CO 2 source. For each amino acid, the maximum carbamate yield, the apparent rate constant for the carbamate formation k app , and the rate constants for the formation k 1 and the breakdown k À1 of the carbamate were estimated. Plots of log k 1 or log k À1 versus pK a of amino acids indicated that the formation rate k 1 increased with the basicity (pK a ) of amino acid, while the decomposition rate k À1 decreased. A Brfnsted b value of 0.39 was obtained from the former plot, being in good agreement with the previously reported ones (0.26-0.43). The observed negative pK a dependence of log k À1 (Brfnsted a = 0.34) is reasonable, because the carbamate decomposition is acid-catalyzed and the steady-state concentration of H + should be higher for weaker basic amines. The charge (s) and the lone-pair energy (E N ) at the nitrogen atom of the amino group were calculated. Although log k 1 correlated with s and E N , log k À1 was unrelated with both of these parameters. Considering that the carbamate formation (k 1 ) is not only base-catalyzed but should also be promoted by the nucleophilicity of the amino nitrogen, its correlation with s and E N in addition to pK a is rational. The irrelevance of log k À1 to s and E N is not surprising, because s and E N are not a direct measure of [H + ] of the solution.

CO2-sensitive tRNA modification associated with human mitochondrial disease

“…For TC-AMP formation catalyzed by YrdC, L -Thr needs to form a carbamate ( N -carboxy- L -Thr), followed by adenylation 32 . It is known that amino acids form carbamates at high concentration of bicarbonate or CO 2 at alkaline pH non-enzymatically 56 . The high Km value of bicarbonate for TC-AMP and t 6 A37 formation can be explained by the carbamate formation of L -Thr at the initial step of the reaction.…”

Efficient CO2 Sequestration by a Solid–Gas Reaction Enabled by Mechanochemistry: The Case of l-Lysine

“…[52][53][54] The latter mechanism is commonly used to explain CO2 reaction with amino acids. 20,22,23 In this proposed reaction pathway In solution-based reactions, it has been reported that carbamic acids of amines and lysine peptide are selectively generated in polar aprotic solvents. 44,20 For our experiments, using LAG conditions of solvents such as DMSO and DCM led only to the formation of ammonium carbamates of L-lysine as indicated by 13 C NMR spectra ( Figure S6).…”

“…20,22,23 In this proposed reaction pathway In solution-based reactions, it has been reported that carbamic acids of amines and lysine peptide are selectively generated in polar aprotic solvents. 44,20 For our experiments, using LAG conditions of solvents such as DMSO and DCM led only to the formation of ammonium carbamates of L-lysine as indicated by 13 C NMR spectra ( Figure S6). The latter result can be rationalized by the poor solubility of L-lysine in the organic solvents taking into account that the previously reported experiments were performed on -amino acids completely solubilized in organic solvents.…”

“…[11][12][13][14][15][16][17] While the predominant processes capturing CO2 rely on the use of toxic alkanolamines as chemical sorbents, some research groups have studied the reactivity of CO2 with amino groups of innocuous -amino acids and derivatives to form carbamates. [18][19][20][21][22][23] Of note, vast majority of these reactions are performed in a liquid phase, mostly using water as a solvent. Using a solvent is the standard approach to homogenize reaction mixtures and to facilitate agitation by traditional stirring systems, yet lowering the theoretical maximum speed of reactions by moving the reactants away from each other.…”

Chemistry and Chemical Equilibrium Dynamics of BMAA and Its Carbamate Adducts

“…4e). However, due to the steric hindrance of the additional methyl group (Yamamoto et al 2012), the β-amine is unfavorable; instead, the α-carbamate is favored due to the presence of the electron-withdrawing group (α-carboxylic group), promoting the formation of the C-N bond with either CO 2 or HCO 3 − .…”