Quantitative Correlation of Counterion (X) Affinity to Ionic Micelles and X- and Temperature-Induced Micellar Growth (Spherical – Wormlike Micelles – Vesicles) for X = 5-Methyl- and 5-Methoxysalicylate Ions

Abstract

The semiempirical kinetic method has been used to determine the ratio of cetyltrimethylammonium bromide, CTABr, micellar binding constants of counterions X (K(X)) and Br (K(Br)), i.e., K(X)/K(Br) (= R(X)(Br)) for X = dianionic 5-methyl- and 5-methoxysalicylate ions. The values of K(X) and K(Br) have been derived from the kinetic parameters obtained in the presence of spherical/nonspherical and spherical micelles, respectively. The values of R(X)(Br) remain essentially independent of [CTABr] within its range 0.005-0.015 M for both dianionic 5-methyl- and 5-methoxysalicylate ions. The increase in temperature from 35 to 55 °C decreases the values of R(X)(Br) from 796 to 53 for 5-methylsalicylate ions and from 89 to 7.0 for 5-methoxysalicylate ions. Rheological properties of 0.015 M CTABr solutions containing ≥0.01 M counterionic salt, M(2)X, show indirectly the presence of unilamellar vesicles, ULV, and long linear, entangled, and branched wormlike micelles, WM, at, respectively, 35 and 55 °C for X = dianionic 5-methylsalicylate ion. However, such studies show WM and probable spherical micelles, SM, at, respectively, 35 and 55 °C for X = dianionic 5-methoxysalicylate ions. It has been shown that, at a constant [CTABr], the micellar structural transitions from SM-to-WM-to-vesicles may be correlated quantitatively with the values of R(X)(Br) regardless of whether such micellar structural transitions occur due to variation in the values of [M(2)X] at a constant temperature or due to variation in temperature at a constant [M(2)X].

Kinetics and Mechanism of Nanoparticles-Catalyzed Piperidinolysis of Anionic Phenyl Salicylate

“…The value of R X Br (=68) for X = 1 − may be compared with the R X Br (=89) obtained at [NaOH]/[ X H] = 2.1 for X representing 5-methoxysalicylate dianion [ 20 ]. The reported values of R X Br for X = salicylate dianion, benzoate ion, and 4-methoxybenzoate ion are 44, 5.6, and 5.2, respectively [ 20 ].…”

“…The value of R X Br (=68) for X = 1 − may be compared with the R X Br (=89) obtained at [NaOH]/[ X H] = 2.1 for X representing 5-methoxysalicylate dianion [ 20 ]. The reported values of R X Br for X = salicylate dianion, benzoate ion, and 4-methoxybenzoate ion are 44, 5.6, and 5.2, respectively [ 20 ]. It is evident from the literature that the aqueous solutions of CTABr/ M v X containing ≤15 mM CTABr and 12 mM ≤ [ M v X ] ≤ 22 mM exhibited the presence of SM for M v X = sodium benzoate [ 21 ] and WM for M v X = sodium salicylate [ 22 ], sodium 3-, 4-, and 5-methyl salicylate [ 23 ], and Na v 1 , Na v 2 where v = 1,2.…”

A Semi-Empirical Spectrophotometric (SESp) Method for the Indirect Determination of the Ratio of Cationic Micellar Binding Constants of Counterions X^|^ndash; and Br^|^ndash; (KX/KBr)

“…Once such decreasing effects of Na v X on HO M is saturated 32 at the optimum value of Na v X Na v X OH op , a further increase in Na v X at Na v X Na v X OH op , has no effect on ion exchange X /HO . estimated by an iterative technique described elsewhere 14,19 .…”

Kinetics and Mechanism of Counterionic Salt-Catalysed Piperidinolysis of Anionic Phenyl Salicylate in the Presence of Cationic–Nonionic Mixed Micelles

“…Commercially available reagent-grade chemicals such as piperidine (pip), phenyl salicylate (PheSH), HDAB, C 16 E 20 and sodium bromide (NaBr) were used as received. [19,27]. Pseudo first-order rate constants, k obs , for the piperidinolysis of PheSare affected by the amount of counterion, X -.…”

“…This effect has been investigated in the absence and presence of a C 16 E 20 surfactant and used as a kinetic probe for the use of the SEK method. Details of the method and the probe are described elsewhere [19,21,27]. Table 2.…”