XYLARIC ACID, D–ARABINARIC ACID (D-LYXARIC ACID), L-ARABINARIC ACID (L-LYXARIC ACID), AND RIBARIC ACID-1,4-LACTONE; SYNTHESIS AND ISOLATION – SYNTHESIS OF POLYHYDROXYPOLYAMIDES THEREFROM
This dissertation describes the nitric acid oxidation of the pentoses D-xylose, L-arabinose, D-arabinose, and D-ribose to produce xylaric acid, L-arabinaric acid (L-lyxaric acid), D-arabinaric acid (D-lyxaric acid), and ribaric acid, respectively, or salts therefrom. Isolation of the aldaric acids from nitric acid has proven difficult in prior reports and an improved nitric acid oxidation and isolation method for each aldaric acid is described. Aldaric acids are the starting monomers for a class of polymers known as polyhydroxypolyamides (PHPAs) or “hydroxylated nylons,” produced through condensation polymerization of the esterified aldaric acid and a diamine of choice. In an effort to obtain larger polymers synthetic routes were varied to initially produce smaller polyamides labeled as “prepolymers.” Of these prepolymers, poly (hexamethylene xylaramide) was subjected to three post production treatments to further increase their size. Additionally, in an effort to better predict physical and chemical properties and potential applications of PHPAs, the conformation of the aldaryl monomer units in solution were investigated using 1H NMR, and molecular mechanics modeling. Limitations inherent to 1H NMR and MM3(96) computational modeling required the use of glutaramides and pentaramides as small molecule mimics of the PHPA’s aldaryl monomer unit. A converging Monte Carlo Metropolis search coupled to MM3(96) was employed to search the conformational space afforded the diamides. A Boltzmann distribution was applied to the resultant conformational ensemble which was analyzed for structural detail. Theoretical average 1H vicinal coupling constants were compared to experimental 1H NMR coupling constants. Dependence of experimental 1H NMR coupling constants on solvent composition was investigated. MM3(96) lowest energy conformations of the diamides had structural detail consistent with their corresponding 1H NMR and x-ray crystal data.
© Copyright 2008 Michael Raymond Hinton