Triglycerides are triesters of glycerol, propane−1,2,3−triol, and three fatty acids. Complete hydrolysis produces glycerol and three acid-derived species. Acidic conditions give fatty acids; alkaline conditions give carboxylate salts, which can act as soaps. Triglycerides may contain different fatty-acid chains within one molecule.
Carbon–carbon double bonds react by addition with bromine or hydrogen. Each isolated C=C consumes one Br2 or H2 under the stated complete-addition assumptions. Cis double bonds bend chains, usually weakening packing and lowering melting point compared with similar saturated chains. Hydrogenation can raise melting point. Soap ions have non-polar tails and ionic heads; micelles enclose grease in a non-polar region while presenting hydrated heads to water.
Example 1
How much NaOH completely hydrolyses 0.0100 mol triglyceride?
There are three ester links per triglyceride. Complete alkaline hydrolysis requires 3×0.0100=0.0300 mol NaOH and produces glycerol plus three carboxylate equivalents.
Example 2
A triglyceride has four C=C bonds. Find H2 needed for complete hydrogenation of 0.020 mol.
Each C=C consumes one H2. Required amount =4×0.020=0.080 mol H2, assuming only those double bonds react.
Watch out: Its non-polar tail associates with grease, while its ionic head interacts with water; both regions are necessary.