Spectrophotometric and Thermodynamic Studies of Micellar Interaction of Surfactants with p-Nitrophenol

Abstract

Interaction of p-nitrophenol (NPH) with various surfactants, viz., cetylpyridinium chloride (cationic), sodium dodecylsulphate (anionic) and Triton X-100 (nonionic) are studied spectrophotometrically, in aqueous-micellar medium. The interactions are of electrostatic as well as hydrophobic nature. The strength of interaction is represented in terms of the equilibrium constants and other thermodynamic quantities of formation of the p-nitrophenol-micelle donor-acceptor complexes in addition to a shift in the acid-base equilibrium of NPH. The interaction between NPH and CPC is much stronger that with Triton X-100 whereas the interaction with SDS is very weak. Formation of 1:1 charge transfer (or electron donor-acceptor) complex is evidenced from the results. The interaction of NPH is enthalpy driven with CPC and entropy driven with Triton X-100.

Keywords:

• Electron donor-acceptor complexes
• ionic and nonionic surfactants
• micellar interaction
• p-nitrophenol
• spectrophotometric study

Notes

Error limits: *(±2.5%); ^β(±1.6%); ^γ(±2.4%); ^@(±70 dm³ mol⁻¹ m⁻¹); ^#(±75 dm³ mol⁻¹ m⁻¹).