Soap-based detergent formulations: XVIII. Effect of structure variations on surface-active properties of sulfur containing amphoteric surfactants

Abstract

Quaternary ammonium amphoteric surfactants have been found in the past to be excellent lime soap dispersing agents and detergents but exhibit unusual solubility behavior. In search of a relationship between chemical structure and surface-active properties, compounds having the following general formula were synthesized: ZN⁺(CH₃)₂(CH₂)_nX⁻, where Z is C₁₂H₂₅-, C₁₄H₂₉-, C₁₆H₃₃-, or C₁₅H₃₁CONHC₃H₆-, n is 2, 3, or 4 and X is SO₃- or OSO₃-. Tertiary amines were converted to sulfobetaines (X=SO₃-) by reaction with (a) butanesultone (n=4), (b) propanesultone (n=3), or (c) sodium 2-bromoethanesulfonate (n=2). An alternate synthesis for the sulfoethylbetaines (n=2) involved the reaction of the tertiary amines with ethylene bromide, followed by treatment with sodium sulfite. All sulfated quaternary ammonium compounds (X=OSO₃-) were synthesized by treatment of the tertiary amine with the appropriate chloroalcohol, followed by sulfation with chlorosulfonic acid. The sulfated quaternary ammonium amphoterics are stable to acid hydrolysis, and alkaline stability improves with increasing bridge chain length. Sulfoethyl amphoterics are less water soluble than sulfobutyl, which in turn are less soluble than sulfopropyl derivatives of the same alkyl chain length. For the most part, the sulfated amphoterics are insoluble but are solubilized by soap. The lime soap dispersing properties improve as the carbon chain bridge length increases for both the sulfates and sulfonates. Formulations of tallow soap, amphoteric surfactant, and sodium silicates gave good detergency in most cases.