Structure and Crystallization Behavior of the β Phase of Oleic Acid, страница 10

Another important point is probably the structure of the growing crystal ends. For usual polymorphs of long-chain compounds, a growth unit (in the case of fatty acids, a dimer) newly attached at the growing crystal ends can be stabilized largely with dispersion forces from the lateral side of the crystal, as shown in Figure 9a. In particular, the contributions from the lamellae in the same level are quite large. A growth unit can be attached at almost any position of the growing lateral face. However, the situation of the β phase is quite different from that of other long-chain compounds, as shown in Figure 9b. In the β phase where the neighboring dimers are different in height by one molecular length, the number of potential sites suitable for the attachment of a new dimer decreases significantly. It seems that a flat site consisting of more than two lamellar layers (Figure 9, top; at least this site needs four dimers, in contrast with two dimers in the γ phase) is required for the adsorption and stabilization of a dimer; the whole part of the dimer can be incorporated into a crystal face in register and can get dispersion forces from the crystal wall. However, a flat site consisting of one lamellar layer cannot stabilize fully a newly attached dimer; only a half portion of the dimer can be stabilized, and the other one cannot attach steadily on the crystal face (this is a structure similar to the overhang that appears in crystallization under high supersaturation³⁷). We inferred that these limited possibilities of positioning of molecular attachment would suppress the crystal growth rate.

Figure 9 Schematic representation of the growing lateral face in the γ phase and the β phase.

· 

Supporting Information Available

Tables of F data, anisotropic thermal factors, and coordinates of hydrogen atoms (13 pages). Ordering information is given on any current masthead page.

 Abstract published in Advance ACS Abstracts, February 15, 1997.

This article references 37 other publications.

1.  (1) Applegate, K. R.; Glomset, J. A. J. Lipid Res. 1991, 32, 1635, 1645.

[PubMed], [ChemPort]

2.  (2) Pearce, L. L.; Harvey, S. C. Biophys. J. 1993, 65, 1084.

[PubMed]

3.  (3) Di. L.; Small, D. M. J. Lipid Res.1993, 34, 1611.

[PubMed], [ChemPort]

4.  (4) Di, L.; Small, D. M. Biochemistry1995, 34, 16672.

[ACS Full Text ], [PubMed], [ChemPort]

5.  (5) Suzuki, M.; Ogaki, T.; Sato, K. J. Am. Oil Chem. Soc.1985, 62, 1600.

[CrossRef], [ChemPort]

6.  (6) Lutton, E. S. Oil Soap (Chicago) 1946, 23, 265.

7.  (7) Abrahamsson, S.; Ryderstedt-Nahringbauer, I. Acta Crystallogr. 1962, 15, 1261.

[CrossRef], [ChemPort]

8.  (8) Kobayashi, M.; Kaneko, F.; Sato, K.; Suzuki, M. J. Phys. Chem.1986, 90, 6371.

[ACS Full Text ], [ChemPort]

9.  (9) Kobayashi, M. In Crystallization and Polymorphism of Fats and Fatty Acids; Garti, N., Sato, K., Eds.; Marcel Dekker:  New York, 1988.

10.  Sato, K. In Advance in Applied Lipid Research; Padley, F., Ed.; JAI Press:  New York, 1996; Vol. 2.

11.  (11) Kaneko, F.; Yamazaki, K.; Kobayashi, M.; Sato, K.; Suzuki, M. Spectrochim. Acta1994, 94, 3180.

12.  (12) Kaneko, F.; Yamazaki, K.; Kobayashi, M.; Sato, K.; Suzuki, M. J. Phys. Chem.1996, 100, 9138.