The mixtures were heated on a hot plate at 100°C-150°C to dissolve the compounds and then left at room temperature for 12 h to form gels. The bottles were inverted; if the content did not flow, it was considered gelated. The gel hardness and relative turbidity were then measured (Figure , Table ). Scheme 2. Selective introduction of palmitic acid. At 1 wt%, only C16GL (4) and C18GL (5) formed gels, while the others did not. At 5 wt%, all 137 compounds except C12GL (2) formed gels. In particular, C18GL (5) showed a high gel hardness of 138 207 mN and relatively low turbidity. Although its hardness was lower than that of C16AG (8), an 139 existing gelator, its transparency was higher. 5-OH-C16GL (7), which has a free 5-position hydroxy 140 group, had lower gel hardness than the fully palmitoylated C16GL (4). ), (c) C16GL ( ), (d) C18GL ( ), (e) C22GL ( ), (f) 5-OH-C16GL (7), and (g) C16AG ( ). These results indicate an optimal fatty acid chain length for gelation, with 16 and 18 carbons being optimal. The difference between C16GL (4) and C16AG ( ) is the presence or the absence of a carbonyl group at the 1-position and the difference between a five-and six-membered ring. A fivemembered ring allows the 5-and 6-position carbons to rotate freely, increasing molecular freedom.