Fatty acid reaction and derivatives (Unit 5 b)

It prepared for Undergraduate students teaching purpose

1. Fatty acid clusters and reaction and derivatives 5.3 Methylene-interrupted polyunsaturated acids 5.4 Branched fatty acids 5.5 Reaction with 5.5.1 Methylene group, 5.5.2 Double bond 5.6 Derivatives 5.6.1 higher aliphatic 5.6.2 Polycarboxylic acid 5.6.3 Fatty aldehydes 11/3/2020 Dr. Mohammed Danish/CPB30303 Oil & Fat Technology 1

2. Methylene interrupted polyunsaturated fatty acids In polyunsaturated fatty acids, when two or more double bonds are separated by one –CH2- groups are called methylene interrupted polyunsaturated fatty acids This pattern results from the operation of a few specific desaturates and chain-elongation enzymes. 11/3/2020 Dr. Mohammed Danish/CPB30303 Oil & Fat Technology 2

3. Conjugated fatty acid Fatty acids with two or more conjugated double bonds are found in some plants and animals. Alternate single and doubles are called conjugated double bonds. Example of conjugated fatty acids 11/3/2020 Dr. Mohammed Danish/CPB30303 Oil & Fat Technology 3

4. Branched fatty acids There are many branched-chain acids, but branched chain fatty acids are seldom occur at a significant levels. Examples include the iso fatty acids (mainly with an even number of carbon atoms), anteiso fatty acid (mainly with an even number of carbon atoms) found in wool wax and other animal fats. Phytol-based fatty acids present at low level in fish oils. 11/3/2020 Dr. Mohammed Danish/CPB30303 Oil & Fat Technology 4

5. Reactions with methylene group The methylene groups flanked by doubly bonded atoms present in highly unsaturated faty acids very reactive. The –CH 2 – group present in linoleic acid component of the unsaturated glyceride is readily attacked by oxygen of the air to form hydroperoxyl group (-O-O-H) at these sites. These hydroperoxyl groups then react with unchanged –CH 2 – groups in other fatty acid molecules to form peroxide bridges. The hydroperoxide formation accompanied by polymerization converts polyunsaturated fatty acids into vast network of interlinked units. Such a network forms a dry, tough and durable film when exposed to air. 11/3/2020 Dr. Mohammed Danish/CPB30303 Oil & Fat Technology 5

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7. Reaction with double bonds Hydrogenation is an addition reaction at double sites. Unsaturated fatty acids can be converted into saturated fatty acids. Hydrogenation is used in the food industry. 11/3/2020 Dr. Mohammed Danish/CPB30303 Oil & Fat Technology 7

8. Higher Aliphatic Higher aliphatic compounds can be prepared by reducing the acid group in fatty acid into alcohol with lithium aluminium hydride (LiAlH 4 ) & diethylether reagents. Then Alcohols further reduced into aliphatic compound using tosyle chloride ( p - toluenesulfonyl chloride) and LiAlH 4 . 11/3/2020 Dr. Mohammed Danish/CPB30303 Oil & Fat Technology 8

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10. Polycarboxylic acid Unsaturated fatty acid can be converted into polycarboxylic acids with conc. KMnO 4 , the reaction takes place at unsaturated bonds. 11/3/2020 Dr. Mohammed Danish/CPB30303 Oil & Fat Technology 10 Transition Phase

11. Fatty Aldehydes Fatty aldehydes can be prepared from fatty acid in two stages. In first stage fatty acids converted into acid chlorides with SOCl 2 reagent. In second stage acid chlorides converted in aldehydes using LiAlH (O-t-Bu) catalyst. 11/3/2020 Dr. Mohammed Danish/CPB30303 Oil & Fat Technology 11

12. Slides end here! Thanks for your attention! 11/3/2020 Dr. Mohammed Danish/CPB30303 Oil & Fat Technology 12 Dr. Mohammed Danish Senior Lecturer, Food Technology Section, UniKL -MICET, Alor Gajah 78000, Melaka, Malaysia