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Chemical structure/property relationships in surfactants. 17. N ‐substituted‐ N ‐acyl glycinates in pure and synthetic hard river water
Author(s) -
Zhu YunPeng,
Rosen Milton J.,
Morrall Stephen W.
Publication year - 1998
Publication title -
journal of surfactants and detergents
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.349
H-Index - 48
eISSN - 1558-9293
pISSN - 1097-3958
DOI - 10.1007/s11743-998-0001-y
Subject(s) - chemistry , alkyl , critical micelle concentration , surface tension , distilled water , aqueous solution , substituent , adsorption , thermodynamics of micellization , gibbs isotherm , micelle , molecule , medicinal chemistry , stereochemistry , organic chemistry , chromatography , thermodynamics , physics
The surface properties [effectiveness of surface tension reduction (γ CMC ), critical micelle concentration (CMC), efficiency of surface tension reduction (p C 20 ), maximum surface excess concentration (Γ CMC ), minimum area/molecule at the interface ( A min ), and the CMC/ C 20 ) ratio] of well‐purified N ‐substituted glycine derivatives, having the structural formula RC(O)N(R′)CH 2 COONa, where RC(O)=lauroyl, myristoyl, or oleoyl, and R′=Et, Pr, Bu, CH 2 CH 2 OH or CH 2 CH 2 CH 2 OCH 3 , were investigated at 25°C in hard river water and distilled water. These surfactants show greater surface activity in hard river water than in distilled water. The effect of both the main alkyl chain R and the N ‐substituent R′ on surface properties was elucidated, the oleoyl group showing properties equivalent to that of a C 16 saturated acyl group. A linear relationship was observed between the p C 20 or CMC values and the number of carbon atoms in the alkyl chain R or in R′ when it was alkyl. With increase in the number of carbon atoms in either R or the N ‐substituent R′ when it is alkyl, both p C 20 and micelle‐forming ability increase, although the effect of R′ on the foregoing two surface properties is lower than that of R. When R′ is (CH 2 ) 3 OCH 3 , however, the results suggest that R′ is only partly removed from contact with the aqueous phase either upon adsorption at the water/air interface or upon micellization. It increases A min , is equivalent only to an ethyl group in its effect on p C 20 and to a methyl group in its effect on CMC, and, in contrast to the effect of R′ when it is alkyl, produces no increase in the CMC/ C 20 ratio. As a result, γ CMC increases with R when R′ is alkyl and decreases with R when R′ is (CH 2 ) 3 OCH 3 .