US EPA

8493088 

Journal Article 

Effect of aqueous solutions of various alcohols on kinetics of aromatic nucleophilic substitution reaction of 1-fluoro-2,4-dinitrobenzene with piperidine 

Habibi, YA; Gholami, MR 

2003 

1 

Indian Journal of Chemistry. Section B
ISSN: 0376-4699
EISSN: 0975-0983 

42 

4 

895-899 

English 

WOS:000182588500007 

Reaction kinetics of 1-fluoro-2, 4-dinitrobenzene with piperidine has been studied spectrophotometrically in aqueous solutions of methanol, ethanol, propan-2-ol and 2-methylpropan-2-ol at 10°C. The reaction in the aqueous solutions is not catalyzed by nucleophile(piperidine). Second-order rate constants of the reaction decrease with increasing mole fraction of water and ETN (normalized polarity parameter). Therefore, polarity of the reactants of the reaction is higher than that of the activated complex. Single-parameter correlations of log kA vs ETN give satisfactory results (regression coefficients in aqueous solutions of methanol, ethanol, propan-2-ol and 2-methylpropan-2-ol are 0.988, 0.994, 0.995 and 0.996, respectively). Single-parameter correlations of logkA vs π* dipolarity/polarizability) and α (hydrogen-bond donor acidity) do not give acceptable results(fore example, in the all aqueous solutions regression coefficients are 0.893 and 0.789, respectively), hence π* and α are not individually major factors in determining the reaction rate. Dual-parameter correlations of log kA vs π* and α in the all solutions represent significant improvement in statistical factors with regard to the single parameter models. Dipolarity/polarizability and hydrogen-bond donor acidity (HBD) of media have parallel and approximately equal effects on the reaction rate. Increasing of hydrogen-bond donor acidity of media stabilizes piperidine via hydrogen bonding interactions (one of the reactants) and hence the reaction rate decreases. A dual-parameter equation of logkA vs π* and α is obtained in the all aqueous solutions (n=41, r=0.990, s.e=0.070, F2.38=968.10) in which π* and α have parallel and approximately equal effects on the reaction rate.