PHYSICAL PROPERTIES OF FATTY ACIDS 55 



Table 17. Effect of Introduction of Methyl Group on Melting Point 

 OF Saturated Fatty Acids 



Melting point, °C. 



Systematic 10- 2- Comparable 



name of Methyl- Methyl- nonmethyl- 



acid I'oruuila ated ated ated 



^-Octadecanoic'' CH3(CH2)i6COOH — — 69. 6"-* 



10 Methylocta- 



decanoic^ CH3(CH2)7CH(CH3)(CH2)sCOOII 10-11'' — — 



2-]Methylocta- 



decanoic Cn:,(CH,),5Cn(Cn;0C()()H — 54.5' — 



«-Eicosanoic CH3(CH2)i8COOH — — 75.4 



2-Methyleico- 



sanoic CH3(CH2)i7CH(CH3)COOH — 61.5-G2.0 — 



n-Docosanoic CH3(CH2)2oCOOH — — 79.95" 



10-Methyldoco- 



sanoic CHsCCH.OaCHCCHsXCHOsCOOH 45.5-46.0" — — 



2-lVIethyldoco- 



sanoic CH3(CH2)i9CH(CH3)COOH — 67.0-67.5 — 



n-Tetracosanoic CH3(CH2)22COOH — — 84.15" 



10-Methyltetra- 



cosanoic CH3(CH2)i3CH(CH3)(CH2)8COOH 51' — — 



2-Methyltetra- 



cosanoic CH3(CHo)2iCH(CH3)COOH — 72.0-72.5 — 



n-Hexacosanoic CH3(CH2)24COOH — — 87.7"-^ 



10-Methylhexa- 



cosanoic CH3(CH2),5CH(CH3)(CH2)8COOH 54.0-55.0' — — 



2-Methylhexa- 



cosanoic CH3(CH2)23CH(CH3)COOH — 75.5-76.0" — 



" F. Francis and S. H. Piper, ./. Am. Chem. Soc, 61, 577-581 (1939). 

 * A. Gascard, Ann. chini. [9], 15, 332-382 (1921). 

 ' Tuberculostearic acid. 



-* Isolated bv R. J. Anderson and E. Chargaff, /. Biol. Chem., 85, 77-88 (1929). M. A. 

 Spielman, J. Biol. Chem., 106, 87-96 (1934). 



« A. K. Schneider and M. A. Spielman, J. Biol. Chem., H2, 345-354 (1942). 

 i W. Bleyberg and H. Ulrich, Ber. 64, 2504-2513 (1931). 



Table 18 

 Effect of Number of Methyl Groups on Melting Point of Saturated Acids" 



Melting point, °C. 



Systematic 2,2- Non- 



name of acid Formula 2-Me diMe methylated 



n-Dodecanoic CH3(CH2)ioCOOH — — 44. 2"^ 



2,2-Dimethyldodecanoic CH3(CH2)9C(CH3)2COOH — 4* — 



n-Octadecanoic CH3(CH2)i6COOH — — 69.6' 



2-Methyloctadecanoic CH3(CH2)i5CH(CH3)COOH 54.5" — — 



2,2-Dimethyloctadecanoic CH3(CHo),5C(CH3)2COOH — 42* — 



" K. S. Markley, Fattii Acids, Interscience, New York, 1947, p. 114. 



* A. J. Birch and R. Robinson, J. Chem. Soc, 1942, 488-497. 



' F. Francis and S. H. Piper, ./. .4m. Chem. Soc., 61, 577-581 (1939). 



"* A. Gascard, Ann. chim. [9], 15, 332-382 (1921). 



' A. K. Schneider and M. A. Spielman, /. Biol. Chem., U2, 345-354 (1942). 



