Fatty acid are hydrocarbon chains with carboxylic acid at the end. Unsaturated fatty acid contain one or more double bonds, usually in cis conformation. There are two methods of naming the unsaturated double bonds, delta and omega.
Delta naming system:
1. Count carbons starting from the carboxylic end. The total number of carbons in the fatty acid is the first number in the name.
2. The second number represents the number of double bonds. For example 14:2 means there are 14 carbons total in the fatty acid and there are two double bonds.
3. After the delta sign, we put numbers signifying the location of the double bonds. Now putting it all together, lets look at a name and understand it. 18:2 ∆ 3, 6. This name means there are 18 total carbons and two double bonds.The first double bond begins on carbon 3 and the second double bond begins on carbon 6.
Omega naming system
1. Count carbons starting from the methyl end. The total number of carbons in the fatty acid is the first number in the name.
2. The second number represents the number of double bonds just like the delta naming system.
3. After the omega sign, we put -number signifying where the first double bond begins from the methyl end. If there are more than one double bonds, we assume that each subsequent double bond is three carbons away from the last double bond. Thus lets look at a name 18:3 Ω-3, means there are 18 total carbons and 3 double bonds. The first double bond is 3 carbons away from the methyl end, on carbon 3, the next one is 3 carbons away and should be on carbon 6, and the third double bond is on carbon 9.
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