Kinetics of the reaction of methyl 4‐nitrobenzenesul‐fonate + Br⁻ in ethanol amine based surfactants

Abstract

The kinetics of the reaction of methyl 4-nitrobenzenesulfonate + Br − ions has been studied in ethanol amine based (alkyldimethylethanolammonium bromide and alkyldiethylethanolammonium bromide) surfactant solutions. The observed first-order rate constants increase monotonically with surfactant concentration, with hydrophobic chain length and with head group bulk in a manner similar to other quaternary ammonium surfactants. The results were analyzed using the pseudophase model of micellar rate effects in conjunction with a Langmuir form to describe micellar binding of bromide ion. An attempt to estimate activation parameters of the reaction from temperature variance of micellar pseudophase rate constants has also been made.

Counterion‐Induced Cationic Flexible Nanoparticle Catalytic of Piperidinolysis of Phenyl Salicylate

“…These results may be compared with experimental observations of the larger micellar binding constant of PSa -, (K S ) in CTABr (K S = 7000 M -1 ) than that in TTABr (K S = 3660 M -1 ) obtained under the same experimental conditions. Several studies have reported that for the surfactants of the same headgroups, decrease in hydrophobic chain length will decrease the values of micellar binding constant of substrate, K S [57][58][59]. Shorter hydrophobic chain length will cause a smaller aggregation number of micelles [60], which reflects the decrease in micellar size for the surfactant of the same head group [61].…”

Effects of Surfactants on the Rate of Chemical Reactions

“…In the latter case, the interaction of anionic surfactants with neutral substrates increases the electronic repulsion between the resulted complex and hydroxide ions. On the other hand, the reaction rates of a number of nucleophiles (other than hydroxide ion) with neutral [71][72][73] and anionic [74][75][76][77][78][79] substrates are increased in the presence of cationic surfactants. It was observed that the increase in the chain length of cationic surfactants [75] and adding TX-100 [79] to the reaction media decreases the reaction rate.…”

“…On the other hand, the reaction rates of a number of nucleophiles (other than hydroxide ion) with neutral [71][72][73] and anionic [74][75][76][77][78][79] substrates are increased in the presence of cationic surfactants. It was observed that the increase in the chain length of cationic surfactants [75] and adding TX-100 [79] to the reaction media decreases the reaction rate. Also, results show that adding organic cosolvents [76][77][78] to the surfactant-contained media further decreases the reaction rate compared to that in the presence of surfactant only.…”