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Synthesis, characterization, reaction mechanism and kinetics of 3,4-dihydro-2H-1,3-benzoxazine and its polymer

Liu, Jingping

Abstract Details

1995, Doctor of Philosophy, Case Western Reserve University, Macromolecular Science.
A method for the synthesis of 3,4-dihydro-3-pentafluorophenyl-2H-1,3-benzoxazine in a high yield derived from pentafluoroaniline is described. The synthesized compounds are characterized by Fourier-Transfer Infrared spectroscopy (FTIR), proton nuclear magnetic resonance spectroscopy (1H NMR), size exclusion chromatography (SEC) and normal-phase high performance liquid chromatography (HPLC), The synthesis of 3,4-dihydro-2H-3-pentafluorophenyl-1,3-benzoxazine by the condensation of pentafluoroaniline with formaldehyde and bisphenol-A is monitored in 1,4-dioxane solution at 75°C by attenuated total reflection Fourier transform infrared (ATR-FTIR) technique using a liquid cell. It is found that the pH value of the reaction medium is the controlling factor in term of the yield. A strongly acidic condition is necessary for the synthesis of similar compounds from other very weak amines having a pK a lower than 3. In the presence of trace amount of HCl, the synthesis of benzoxazine includes a two step reaction. The formation of 1,3,5-tripentafluorophenylperhydro-1,3,5-triazine are involved in the first step of the reaction, which can be completed almost immediately after the addition of acid. The reaction between the acid-promoted cleavage of the perhydrotriazine and derivative of b isphenol-A and formaldehyde is the rate limiting reaction. The methods to synthesize 3,4-dihydro-1,3-benzoxazine by thermal reaction of paraformaldehyde, phenol and amine in the absence of solvent are developed. The reaction of solventless synthesis of 3,4-dihydro-2H-3-(4-methyl)phenyl-1,3-benzoxazine has been monitored by means of normal phase HPLC, FTIR and proton NMR at different reaction temperature in a closed and an open system respectively. The thermal transitions involved in this heterogeneous system resulted from both physical phase changes and chemical reactions are described in detail by differential thermal analysis (DTA). The role of the decomposition of paraformaldehyde in the whole reaction has been emphasized. The pressure, temperature and stoichiometric effects are also discussed. It has been found that the reaction kinetics and mechanism strongly depend on the reaction temperature. Within 50-75°C, the overall reaction rate is controlled by the decomposition rate of paraformaldehyde. Pseudo-stoichiometric effect plays an important role in this temperature range. At 100°C, the overall reaction rate is a function of the concentrations of paraformaldehyde, toluidine and bisphenol-A. Reaction mechanisms in both cases are proposed. A new type of polymer, the repeat unit of which is composed by 3,4-dihydro-2H-1,3-benzoxazine, has been synthesized by reaction between methylene-bis-(2,6-dimethylaniline), formaldehyde and bisphenol-A in the organic solvent contained certain amount of triethylamine and water. The polymer structure is characterized by means of FTIR, NMR. Molecular weight and its distribution is measured by SEC. Several factors affecting on molecular weight of the polymer such as solvent, catalyst, cocatalyst, temperature and reactant ratio have been discussed in detail. It has been found Lewis base, water and temperature have great effect on the molecular weight and molecular weight distribution, and solvent and reactant ratio have certain influence on the benzoxazine ring content on the polymer backbon
Hatsuo Ishida (Advisor)
220 p.

Recommended Citations

Citations

  • Liu, J. (1995). Synthesis, characterization, reaction mechanism and kinetics of 3,4-dihydro-2H-1,3-benzoxazine and its polymer [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1062775094

    APA Style (7th edition)

  • Liu, Jingping. Synthesis, characterization, reaction mechanism and kinetics of 3,4-dihydro-2H-1,3-benzoxazine and its polymer. 1995. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1062775094.

    MLA Style (8th edition)

  • Liu, Jingping. "Synthesis, characterization, reaction mechanism and kinetics of 3,4-dihydro-2H-1,3-benzoxazine and its polymer." Doctoral dissertation, Case Western Reserve University, 1995. http://rave.ohiolink.edu/etdc/view?acc_num=case1062775094

    Chicago Manual of Style (17th edition)