Ph-Metric Study on Determination of Proton- Ligand Stability Constants of Some Substituted Pyrazolines

P. J. Parmar

Department of Chemistry, Rashtriya Arts, Science and Commerce College, Chalsigaon - 424 101 (India).

Proton - ligand stability constant ( pK) of 1-H-3 - ( 2’’ - hydroxy-3’’ -nitro -5’’ -methylphenyl ) -5- phenyl - D2 - pyrazonlines ( L1), 1-H-3 ( 2’’ - hydroxy - 3’’ -nitro -5’’ - methylphenyl) -5 - ( 4’- methoxyphenyl) - D2 - pyrazonline ( L2), 1-H-3 - ( 2’’ - hydroxy-3’’ -nitro -5’’ -methylphenyl ) -5 - ( 3’ nitrophenyl) D2 - pyrazonline and 1-H-3- ( 2’’ - Hydroxy - 3’’ - nitro - 5’’ - methylphenyl -5 - (3’,4’ - methylenedioxyphenyl) - D2 - pyrazonline ( L4) have been investigated pH- metricaly in 70% dioxane - water mixture as a solvent by Calvin- Bjerrum titration technique at 0.1 M ionic strength and at ( 27± o.1o C ) temperature. The Proton - ligand stability constantrs for above ligands are found to be more than pH = 8.0. This showed dissociation of phenolic - OH group. The data obtained were used to determine the standard deviation (s) by using diferent values of A of same ligand except the difference in concentration of alkali NaOH.

Synthesis; pyrazolines; pH-metric study