Effects of Polymer and Salt Concentrations on Ketal Acid Hydrolysis in Solutions of Sodium Dodecyl Sulfate and Poly(vinyl pyrrolidone) or Poly(ethylene oxide)

Abstract

The acid-catalyzed hydrolysis of 2-(methoxyphenyl)-1,3-dioxolane (p-MPD) and di-n-butyl benzaldehyde acetal (BBA) has been studied in solutions containing poly(ethylene oxide) (PEO) or poly(vinyl pyrrolidone) (PVP) and sodium dodecyl sulfate (SDS). First-order rate constant−[SDS] profiles were obtained at 0.010 and 0.105 M PEO or PVP, and both polymers strongly inhibit the reaction, to an extent depending on the polymer and SDS concentrations. Added NaCl also decreases the rate, and the behavior is similar to that with SDS micelles. The inhibition induced by increasing polymer concentration was interpreted by assuming decreases in the interfacial H+ concentration. This conclusion is supported by values of pH apparent obtained with the pH indicator pyridine-2-azo-p-dimethylaniline (PADA) at the same experimental kinetic conditions. Qualitatively, the results are interpreted in terms of the pseudophase ion exchange (PPIE) model applied to bimolecular reactions.

Effects of Nonionic Micelles on the Rate of Mononuclear Heterocyclic Rearrangement of (Z)-Phenylhydrazones of 5-Substituted 3-Benzoyl-1,2,4-oxadiazoles

“…The k obs vs [Triton X-100] profiles are analogous to those reported previously for micelle-catalyzed bimolecular reactions (6,26,27). Therefore, the effect of the surfactant on the observed rates in the presence of the substrates 1b and 1d can be depicted (6) according to Scheme 2.…”

“…It is expected that the anionic base species present in the micellar pseudophase are located in the outer hydrophilic poly(ethoxy) sheath of the micelle by electrostatic interactions with the dipoles of the head groups of the surfactant (28). It is likely that these interactions are of the same type of those involved in the electrostatic association of the surfactant sodium dodecyl sulfate with the polymer polyethylene oxide (PEO) (27).…”

Autoassociação de misturas dos Surfactantes Dodecanoato de Sódio (SDoD) e Decanoato de Sódio (SDeC) com o Polímero Hidrofobicamente Modificado Etil(Hidroxietil)Celulose (EHEC)

“…Vol. 34,No. 6 Misturas SDoD-SDeC em ausência de EHEC A condutividade é uma propriedade largamente empregada no estudo sobre interação entre polímeros e surfactantes iônicos.…”

“…[1][2][3][4][5][6][7][8] Surfactantes aniônicos associam-se, fortemente, com polímeros e, geralmente, o fenômeno inicia em concentrações menores do que quando na ausência do polímero. A associação é vista como sendo um fenômeno induzido pelo polímero.…”

“…17 Um sistema bastante estudado é a interação PEO-SDS, onde tem sido mostrado que a cadeia polimérica se envolve ao redor da micela, e que as interações variam de acordo com o tamanho da cadeia do polímero. 5,6,10,13,[18][19][20][21][22][23] Comumente, sistemas formados por polímeros não iônicos e surfactantes iônicos são governados por forças de interação entre grupos hidrofílicos, hidrofóbicos e iônicos. Soluções aquosas de etil(hidroxietil)celulose (EHEC) com adição de um surfactante aniônico constituem um sistema típico desta classe.…”