Date of Submission

5-26-2021

Document Type

Thesis

Department

Chemistry and Chemical Engineering

Advisor

Chong Qiu, Ph. D.

Keywords

Aminium Dicarboxylates, Thermal Decomposition, Polyacids, Aminium Salts, Decomposition Mechanisms

MeSH

Amines, Carboxylic Acids, Oxalic Acid, Dicarboxylic Acids, Succinic Acid, Oxalates

LCSH

Amines, Carboxylic acids, Oxalic acid, Succinic acid, Adipic acid, Thermal properties, Oxalates, Acids

Abstract

This proposed research project will investigate the thermal decomposition profiles and mechanisms of aminium dicarboxylates, the salts from the neutralization reactions between amines and dicarboxylic acids. Information on this research is currently missing from literature and will contribute to our knowledge on ambient amines and their transformation in the atmosphere.

Amines can be found in various forms in the environment. They are differentiated by the functional groups that replace one or more of the hydrogens from ammonia (NH3). One amine that will be studied is methylamine. Methylamine is the simplest amine: It has a methyl group (- CH3) that is the replacement of one of the hydrogens of ammonia. Dimethylamine is the second amine being studied, which has two methyl groups that replace two of the hydrogens of ammonia. Lastly, trimethylamine is the third amine being studied, which contains three methyl groups that replace all three hydrogens of ammonia.

One class of carboxylic acids is polyacids which are defined as acid molecules containing more than one carboxyl group on them. Since each carboxyl group can react with one amine molecule, polyacids can react with more than one amine. By controlling the amount of a polyacid and an amine added to a reaction system, fully or partially neutralized aminium carboxylates can be synthesized. Different numbers of hydrogens of a carboxylic acid can react with an amine and the thermal properties of the partially and fully neutralized carboxylates could differ as well. For example, the dibasic product has the potential to have more hydrogen bonding that makes the thermal profile different from the monobasic one.

This research project used oxalic acid as a polyacid to react with the amines mentioned above. Oxalic acid is a polyacid because it is a dicarboxylic acid, which means there are two carboxyl groups in its structure. Two other dicarboxylic acids, succinic acid and adipic acid, will 4 also be used to react with the different amines. The thermal properties of various aminium salts were analyzed and compared to each other. Based on the preliminary results in this project, several conclusions were made. Amine oxalates seem to be as thermally stable as ammonium oxalates in the particle phase in the ambient environment. There seems to be no dependency on intermolecular forces for the stability of methylamine acids. Intermolecular forces (dipole-dipole attraction) can be the major contribution to the stability of dimethylamine acids. There are different decomposition mechanisms between the fully neutralized salts and partially neutralized hydrogen salts. The aqueous phase of dimethylamine adipate sample was a supersaturated aqueous solution of dimethylamine adipate with a solid precipitation.

Available for download on Monday, May 11, 2026

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