Molecular Mobility in Aqueous Systems of Primary Aliphatic Amino Alcohols

• Published in: Russian Journal of Physical Chemistry A Vol. 97; no. 5; pp. 921 - 927
• Main Authors: Arkhipov, R. V., Rodnikova, M. N., Solonina, I. A., Razumova, A. B.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 01-05-2023; Springer Nature B.V
• Subjects: Activation energy; Alcohol; Alcohols; Aqueous solutions; Chemical bonds; Chemistry; Chemistry and Materials Science; Hydrogen bonds; Liquid phases; Mathematical analysis; Monoethanolamine (MEA); NMR; Nuclear magnetic resonance; Physical Chemistry; Physical Chemistry of Solutions; Self diffusion; Water chemistry; aqueous solutions; self-diffusion coefficients; H NMR; amino alcohols
• ISSN: 0036-0244; 1531-863X
• DOI: 10.1134/S0036024423050047

Self-diffusion coefficients (SDCs) of 3-amino-1-propanol (3AP), monoethanolamine (MEA), and water molecules are measured via
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H NMR using a pulsed magnetic field gradient and a stimulated echo sequence throughout a range of concentrations at temperatures of 293–333 K. It is found that the studied amino alcohols and water form a nearly tetrahedral three-dimensional network of hydrogen bonds between the molecules of the system. It is shown that this network is stable in the liquid phase, despite the mobility of the molecules that constitute the network. The mechanism of molecular mobility is studied. It is shown that the SDC of the molecules of the above amino alcohols and their aqueous solutions depends linearly on temperature. It is concluded that the molecular mobility mechanism has a pattern of activation. To verify this hypothesis and interpret the mechanism, the energies of activation are calculated for the self-diffusion of all the studied molecules in water–amino alcohol systems. The determined energies of activation for the mobility of amino alcohol molecules in aqueous systems have similar values, suggesting they undergo interactions that produce either mixed water–amino alcohol spatial networks or amino alcohol–water molecule associations in the liquid phase.