Investigations of intramolecular hydrogen bonding in three types of Schiff bases by 2H and 3H NMR isotope effects.
Hydrogen bonding within the structures of three Schiff bases (1-3), obtained by condensation of 4-methoxy-, 5-methoxy- and 4,6-dimethoxysalicylaldehyde with methylamine, was investigated by measuring deuterium and tritium NMR isotope effects. The primary deuterium and tritium isotope effects (delta(XH)-delta(XD/T)) and secondary one-bond nitrogen deuterium effect appear to be very useful parameters for defining the character of intramolecular hydrogen bonds. The tritium isotope effects were also determined for nitrogen-hydrogen one-bond coupling constants for both 4-methoxy and 4,6-dimethoxy derivatives. These parameters are seen to be highly sensitive to hydrogen bond characteristics and can be used to distinguish localized and tautomeric hydrogen bonds.
Schilf
Wojciech
W
Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland. schilf@icho.edu.pl
Bloxsidge
James P
JP
Jones
John R
JR
Lu
Shui-Yu
SY
D003903:Deuterium; D006860:Hydrogen Bonding; D007554:Isotopes / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D012545:Schiff Bases / Q000032:analysis* / Q000737:chemistry*; D014316:Tritium
D007554:Isotopes; D012545:Schiff Bases; D014316:Tritium; D003903:Deuterium