• Title/Summary/Keyword: cyclization

Search Result 391, Processing Time 0.026 seconds

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
    • /
    • v.26 no.7
    • /
    • pp.1037-1043
    • /
    • 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.

  • https://doi.org/10.5012/bkcs.2005.26.7.1037 인용 PDF KSCI

Hydroxy-Substituted Polyenaminonitrile as a Soluble Precursor for Rigid-Rod Polybenzoxazole

  • Kim, Ji Heung;Lee, Jae Gwan
    • Bulletin of the Korean Chemical Society
    • /
    • v.22 no.9
    • /
    • pp.999-1004
    • /
    • 2001

  • (1-Chloro-2,2-dicyanovinyl)benzene or 1,4-bis(1-chloro-2,2-dicyanovinyl)benzene was reacted with 2-amino-phenol to give the model compound, hydroxy enaminonitrile, which was found to undergo thermal cyclization reaction to form the corresponding benzoxazole. This intramolecular cyclization reaction is expected to occur through nucleophilic attack to electropositive enamine carbon by ortho-hydroxy group on the phenyl ring, which is accompanied by the release of neutral malononitrile through rearrangement. From each bifunctional monomer, o-hydroxy substituted polyenaminonitrile was prepared and characterized as a new precursor polymer for well-known aromatic polybenzoxazole. Also the unusual macrocyclic dimer formation from the 1,4-bis(1-chloro-2,2-dicyanovinyl)benzene and 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane polymerization reaction system was discussed. The thermal cyclization reactions and the properties of polymers were investigated using FT-IR and thermal analysis (DSC & TGA).

  • https://doi.org/10.5012/bkcs.2001.22.9.999 인용 PDF