2-Tetracosanyl acetate

The force-area curves for racemic and (5)-(+)-2-tetracosanyl acetate recorded with a barrier speed of 5 cm/min are shown in Figures 17 and 18, respectively. Again, both enantiomers showed identical monolayer behavior. The film balance behavior of the racemic acetate was indistinguishable from that of the pure enantiomers at temperatures above about 27°C however, below this temperature the force-area curves differed markedly even at low surface pressures, which indicates that racemic compound formation occurs at relatively large areas per molecule. 

Figure 17. -A curves for racemic 2-tetracosanyl acetate at different temperatures. From Lundquist (77). Permission of Stockholm University Library.

Figure 28. tt-T diagram of quasi-enantiomeric 1 1 mixture of (iS)-(+)-2-tetracosanyl acetate and methyl ester of (5 )-(+)-2-methyl-hexacosanoic acid. From Lundquist (7 9). Permission of Stockholm University Library. 

The force-area curves for racemic and (5 )-(+>2-tetracosanyl acetate were shown in Figures 17 and 18, respectively, while those of methyl esters of racemic and (5 )-(+)-2-methylhexacosanoic acid are found in Figs. 21 and 22, respectively. All these curves were obtained under identical experimental conditions at thevarious temperatures indicated in the figures. Simple inspection shows that the force-area curves of the two racemic samples are very similar, as are those for both optically pure samples. Lundquist suggested that this is merely a result of the very similar shapes and molecular structures of these chiral surfactants. Apart from the chain length, the only structural difference is limited to a reversal of the positions of the carbonyl group and ester oxygen. 

Figure 20 shows the force-area curves obtained from an equimolar mixture of (S)-(+)-2-tetracosanyl acetate and the methyl ester of (5)-(+)-2-methylhexacosanoic acid. Comparison with either Figure 18 or Figure 22 demonstrates that the force-area curve of the mixed mono-layer has the same general appearance as those of the individual pure enantiomers. 

---