Experimental determination of dissociation constants (pK_a) for N‐(2‐aminoethyl)‐1,3‐propanediamine, 2‐methylpentamethylene diamine, N,N‐dimethyldipropylenetriamine, 3,3′‐diamino‐N‐methyldipropyl‐amine, Bis[2‐(N,N‐dimethylamino)ethyl]ether, 2‐[2‐(dimethyl‐amino) ethoxy] ethanol, 2‐(dibutylamino) ethanol, and N‐propylethanol‐amine and modeling with artificial neural network

Abstract

The dissociation constants (pK a ) of the eight amines, namely, N-(2-aminoethyl)-1,-3-propanediamine, 2-methylpentamethylene diamine, N,N-dimethyldipropylenetriamine, 3,3 0 -diamino-N-methyl-dipropylamine, Bis[2-(N,N-dimethylamino) ethyl] ether, 2-[2-(dimethyl-amino)ethoxy] ethanol, 2-(dibutylamino) ethanol, and N-propylethanolamine were measured between 298.15 and 313.15 K with 5 K increment. Based on the experimental values and using the van't Hoff equation, thermodynamic properties such as the standard state changes of enthalpy, entropy, and Gibbs free energy were calculated. Using computational chemistry calculations, the amine that is protonated first was predicted. Furthermore, computer-free group contribution methods such as the original Perrin-Dempsey-Serjeant (PDS), the modified PDS, and the Qian-Sun-Sun-Gao (QSSG) model were used to estimate the dissociation constants of the studied amines at 298.15 K. The QSSG provided the most accurate results. Finally, this work utilized an artificial neural network for estimating the pK a values, which were in excellent agreement with the experimental data.

Kinetic study on the reaction between CO2 and tertiary amine catalyzed by zinc(II) aza‐macrocyclic complexes

“…In this work, the calculated p K a values of MDEA, DMEA, and DEEA at 298 K were 8.58, 9.31, and 9.84, respectively, which were in good agreement with the data in reference (more information about the experimental setup and results of the p K a measurement were found in the Supporting Information Section S5). 61 First, the higher p K a contributes to raising the pH range of the reaction, thus increasing the CO 2 hydration. Second, tertiary amine with higher p K a is more likely to bind protons released from the carbonic acids, and LZnH 2 O is formed in an aqueous solution and promotes CO 2 conversion via hydration reaction.…”