Proton magnetic resonance investigations of the formation of alkylammonium propionate micelles in benzene and in carbon tetrachloride

Abstract

Changes in the chemical shifts for butyl (BAP), hexyl (HAP), octyl (OAP), decyl (DeAP), and dodecyl (DAP) ammonium propionates in benzene and in carbon tetrachloride as functions of their concentrations have established the formation of micelles. Treatment of the ¹H n.m.r. data afforded values for the critical micelle concentration, the aggregation number and the equilibrium constant for the formation of micelles in benzene listed in sequence as follows: BAP, (4.5–5.5)× 10^–2 M, 4, 1 × 10⁴ M^1–n; HAP, (2.2–3.2)× 10^–2 M, 7, 5 × 10² M^1–n; OAP, (1.5–1.7)× 10^–2 M, 5, 1 × 10⁸ M^1–n;; DeAP, (8–10)× 10^–3 M; DAP, (3–7)× 10^–3 M, and those in carbon tetrachloride: BAP, (2.3–2.6)× 10^–2 M, 3, 9 × 10² M^1–n; HAP, (2.1–2.4)× 10^–2 M, 7, 7 × 10¹¹ M^1–n; OAP, (2.6–3.1)× 10^–2 M, 5, 5 × 10⁷ M^1–n; DeAP, (2.2–2.7)× 10^–2 M, 5, 1 × 10⁷ M^1–n; DAP, (2.1–2.5)× 10^–2 M, 4, 5 × 10⁴ M^1–n. These micelles have their polar head groups in the interior of the aggregate while the hydrophobic carbon chain is in contact with the non-polar solvent.