Synthesis of amino acids by ultraviolet light



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The synthesis of amino acids was accomplished by irradiation of simple carbon and nitrogen precursors with ultraviolet rays. The reaction mixtures used were aqueous solutions of formaldehyde and ammonium nitrate and aqueous solutions of paraformaldehyde, ammonium nitrate, and potassium thiocyanate. These solutions were irradiated for various lengths of time, ranging from 0.5 hours to 10.0 hours. Four of the experiments were carried out at pH 1.0, and one experiment at pH 2.5. The amino acids synthesized were separated from other compounds by ion-exchange resins. Analysis of the synthesized amino acids was carried out by paper chromatographic and ion-exchange chromatographic methods. Also, thin-layer chromatography was used in identification of the dinitrophenyl derivatives of the amino acids. Gas chromatography of the N-trifluoroacetyl-methyl esters of the amino acids was also carried out. The analysis by ion-exchange chromatography allowed for fairly accurate calculation of the amino acid yields. Maximum yields were obtained upon irradiation of the paraformaldehyde-ammonium nitratepotassium thiocyanate solution for ten hours. The yields were in the range of 2-80 milligrams of amino acid per mole of paraformaldehyde. Mechanisms for several of the amino acids synthesized are postulated based on known photochemical reactions and Oro's mechanisms for the thermal synthesis of amino acids.