Starch may be derived from any of a number of seed plants (primarily corn in the US). Hydrolysis of starch provides glucose (this will come from cellulose in the future). Hydrogenation followed by double dehydration converts glucose to isosorbide, a diether diol. Castor oil is obtained from the castor bean and is available in large quantities. It is a non-edible oil and its use in a chemical process does not impact the world food supply. Pyrolysis of castor oil or a major constituent generates 10-undecanoic (undecylenic) acid. The ester derived from isosorbide and undecanoic acid contains two terminal unsaturations. This compound undergoes smooth thiol-ene reaction with 2-hydroxyethan-ethiol to afford a diol. Treatment of the diol with a variety of phosphorous reagents generates phosphorous esters. These compounds display good thermal stability. Thermal decomposition begins at approximately 230 °C and reflects elimination of a phosphorous acid. This process may be conveniently monitored using infrared spectroscopy. These compounds are, in the main, good char formers.
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