2- Methyloctadecanoic acid

Vaccenic acid, c/j-CH3(CH2)5CH=CH(CH2)9COOH. 8. Corynomycolenic acid, c/J-/ C 3H27CH2CH(COOHX HOH(CH2)7CH=CHC6HIrff. 9. Tuberculostearic acid, 10 methyloctadecanoic acid. 10, Qrpl thienoic acid, CH3(CH2)7CH(CH3>CH2CH (CH3)CH==C(CH3)C00H. 11. CC, octadecanoic acid DD, 2-methyloctadecanoic acid. 12. Juvenile hormone,... 

C19H38O2 10-Mel8 0 10-Mel8 0 10-Methyloctadecanoic acid Tuberculostearic acid 1929... 

Wallace, P.A., D.E. Minnikin, K. McCrudden, and A. Pizzarello, Synthesis of (R,5)-10-Methyloctadecanoic Acid (Tuberculostearic Acid) and Key Chiral 2-Methyl Branched Intermediates, Chem. Phys. Lipids 71 145-162 (1994). 

Figure 12. Electron ionization mass spectrum of the picolinyl derivative of I4-methyloctadecanoic acid extracted from the gui nea pig Harderian gland, illustrating the determination of branching position. Reproduced from reference [I58J with permission.

An alternative simple orthorhombic chain packing, O l, which is closely related to Oi, has been observed in three lipids, two of which are branched fatty acids (Abrahamsson, 1959). The space group is the same (Pbnm) the main difference is a kind of inversion of the a and b axes. In the unusual chain packing, O i, a is about 7.4 A and b is about 5.0 A. In 2D-methyloctadecanoic acid (Abrahamsson, 1959) the dimensions are a = 7.43 A, b — 5.01 A, c = 2.50 A, with a cross-section area of 18.61 A ... 

Figure 8.33 Crystal structure of 16 DL-methyloctadecanoic acid viewed along the shortest unit cell axis (Abrahamsson, 1958).

The optically active methyl-branched octadecanoic acids, although less studied, show similar structures. The 2D-methyloctadecanoic acid has a high-melting r-form where the molecules are arranged head-to-tail in monolayer units. The methyl branch is located in the gap between the end group planes and the hydrogen bond system is of the infinite helical type (Abrahamsson, 1959c). 

Methanogenic bacteria, 158 Methanoic acid, 1,351 Methanolysis, 477, 478 Methods, lUPAC, 249 Methoxystearic acids, 467 Methyl esters, physical properties, 349,350, 351, 353,477 Methyl glucosides, 280 Methyl group, van der Waals radius, 346 a-Methylene group, 484 Methyloctadecanoic acids, crystal structures, 15, 347, 348 Methylsterols in fats, 105 Metridiidae, 147 Micellar solutions, 357 Micrococcus lysodeikticus, 35, 46, 47 Microemulsions, 329-32 Migratory grasshopper, 145 Milk fat, 23,51, 60,113-18,167-69,397, 556-57... 

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