• 제목/요약/키워드: O-Cyclization and N-cyclization of N-methylphthalamic acid

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Unexpected Rate Retardation in the Formation of Phthalic Anhydride from N-Methylphthalamic Acid in Acidic H2O-CH3CN Medium

  • Ariffin, Azhar;Khan, M. Niyaz
    • Bulletin of the Korean Chemical Society
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    • 제26권7호
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    • pp.1037-1043
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    • 2005
  • Kinetic study on the cleavage of N-methylphthalamic acid (NMPA) in mixed acidic aqueous-acetonitrile solvent reveals the formation of both phthalic anhydride (PAn) (through O-cyclization) and N-methylphthalimide (NMPT) (through N-cyclization). The formation of NMPT varies from $\sim$20% to $\sim$3% with the increase in the content of acetonitrile from 2 to 70% v/v. Pseudo first-order rate constants for the formation of PAn are more than 4-fold larger than those for the formation of NMPT at 2% v/v $CH_3CN$ in mixed aqueous solvents. Pseudo first-order rate constants for alkaline hydrolysis of NMPT reveal a nonlinear decrease with increase in the content of $CH_3CN$ in mixed aqueous solvents.