Organic Lab Reactions 283

Organic Lab Reactions 283 - 278 THE AROMATIC PRIMARY AMINO...

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278 THE AROMATIC PRIMARY AMINO GROUP phorous acid in deaminations. Only recently has it been demonstrated that the reduction of diazonium compounds by hypophosphorous acid is an excellent and general method for replacing the diazo group by hydrogen. 13 ' 80 ' 81 - 82 ' M The yield depends upon the molar ratio of hypophosphorous acid to diazonium salt. 81 - 82 If it is assumed that hypophosphorous acid under- goes oxidation to phosphorous acid, then one molecule of hypophos- phorous acid will be required for the reduction of each diazo group. ArN 2 +X- + H3PO2 + H 2 O -» ArH + H 3 PO 3 + HX + N 2 . In practice, however, it is advisable to use 5 moles of hypophosphorous acid per mole of diazonium compound, and with the more difficultly reduced diazo salts this ratio should be 15 to 1. Treatment of o-toluenediazonium chloride with only 2.75 moles t>f hypophosphorous acid per mole of diazonium chloride gives some o-cresol, much tar, and no toluene. 13
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This note was uploaded on 11/20/2011 for the course CHM 2210 taught by Professor Reynolds during the Fall '01 term at University of Florida.

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