Comparison of solution chemistries of orthophthalaldehyde and 2,3-naphthalenedicarboxaldehyde.
Polarography was used to obtain the concentrations of the dialdehydic (10%), monohydrated acyclic (5%), and cyclic hemiacetal form (85%) of orthophthalaldehyde (OPA). For 2,3-naphthalenedicarboxaldehyde (NDA) these values were estimated to be 15, 7, and 78%. Addition of water in unbuffered solutions followed first-order kinetics with rate constants 0.0018 s-1 for OPA and 0.0012 s-1 for NDA. Dehydration to form both the dialdehyde and the monohydrate is both acid- and base-catalyzed. Both dialdehydes yield on reaction with OH- ions geminal diol anion, which is electro-oxidized to a carboxylic acid. In the most frequently used pH range for the determination of amino acids, NDA can undergo reaction with OH- ions, but OPA does not. In aqueous solutions, NDA is less strongly hydrated than OPA.
Salem
N
N
Department of Chemistry, Clarkson University, Potsdam, New York 13699-5810, USA.
Zuman
P
P
D000596:Amino Acids / Q000032:analysis; D002021:Buffers; D002384:Catalysis; D006863:Hydrogen-Ion Concentration; D006878:Hydroxides / Q000737:chemistry; D007700:Kinetics; D009281:Naphthalenes / Q000737:chemistry*; D010084:Oxidation-Reduction; D012996:Solutions / Q000737:chemistry*; D014867:Water / Q000737:chemistry; D009764:o-Phthalaldehyde / Q000737:chemistry*
D000596:Amino Acids; D002021:Buffers; D006878:Hydroxides; D009281:Naphthalenes; D012996:Solutions; D014867:Water; D009764:o-Phthalaldehyde; C027717:2,3-naphthalenedicarboxaldehyde; C031356:hydroxide ion