<span style="font-size:16.0pt;mso-bidi-font-size:12.0pt" lang="EN-IN">Studies on reactions of organic bases and nucleophiles with bis-(<i style="mso-bidi-font-style: normal">p</i>-nitrophenyl) methylphosphonothionate </span>

Abstract

<span style="font-size:16.0pt;mso-bidi-font-size:12.0pt" lang="EN-IN">Bis-(<i style="mso-bidi-font-style:normal">p</i>-nitrophenyl) methylphosphonothionate (b-<i style="mso-bidi-font-style:normal">p</i>-NPMPT) (<b style="mso-bidi-font-weight: normal">I</b>) reacts with amines in aqueous medium via general base catalysis of water attack. The rate is first order each in [substrate] and [amine]. Solvent deuterium isotope effect, <i style="mso-bidi-font-style:normal">k</i>₂(H₂O)<i> </i>/ <i style="mso-bidi-font-style:normal">k</i>₂(D₂O), is greater than 2 for amine reactions. Different classes of amines follow Bronsted relation with a slope of <span style="mso-bidi-font-style:italic">0.40<i>. </i>Fluoride and phosphate ions react with (<b style="mso-bidi-font-weight: normal">I</b>) by nucleophilic mechanism. At higher fluoride ion concentration, 2 mol of <i style="mso-bidi-font-style:normal">p</i>-nitrophenol (<i style="mso-bidi-font-style:normal">p</i>-NP) is released by a first order process. At lower fluoride ion concentration less than 2 mol of <i style="mso-bidi-font-style:normal">p</i>-NP is produced. <i style="mso-bidi-font-style: normal">k</i>₂(H₂O)<i> </i>/ <i style="mso-bidi-font-style: normal">k</i>₂(D₂O)<i> </i>for the reaction of fluoride and phosphate ions with b-<i style="mso-bidi-font-style:normal">p</i>-NPMPT≡ 1. It is believed that steric crowding in the transition state causes reaction of (<b style="mso-bidi-font-weight:normal">I</b>) with amine to proceed via general base mechanism and that of fluoride ion, oxyanions and phosphate anions through a nucleophilic mechanism.

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