Transcript Oils and fats

Most oils and fats are esters of propane-1,2,3-triol and carboxylic acids with long
chains.
Palmitic acid is one such long chain carboxylic acid.
An ester link involves the hydrogen atom in the hydroxyl group of the alcohol, and
the hydroxyl group in the carboxylic acid.
This is the triester or triglyceride formed in the reaction.
It contains three ester links.
It contains three ester links.
It contains three ester links.
Esterification is a condensation reaction, with water formed in addition to the
organic product.
This is the general structure of a triester.
The acid groups, shown here as R, are often not all the same. A triglyceride where
the acid groups are different is called a mixed ester.
The carboxylic acids in triglycerides are often called fatty acids. They can have
quite complex systematic names, so their traditional names are often used instead.
These two fatty acids are saturated.
These three fatty acids are unsaturated.
Triglycerides formed from saturated fatty acids like this can pack closely together.
Their intermolecular forces are relatively strong and they tend to have high melting
points.
Triglycerides formed from trans-unsaturated fatty acids like this can also pack closely
together. Saturated fats and trans-unsaturated fats tend to be solids at room
temperature.
Triglycerides formed from cis-unsaturated fatty acids like this cannot pack so
closely together. Their intermolecular forces are weaker, so they tend to be liquids
at room temperature.
Unsaturated fats and oils are often hydrogenated to make margarine.
This is an electrophilic addition reaction with hydrogen.
A heated nickel catalyst is used.
The addition of hydrogen to unsaturated fats and oils reduces the number of double
bonds, making the molecules more saturated.
As a result, the treated fats and oils have a higher melting point than before.
Oils and fats can be hydrolysed.
This is usually achieved using hot sodium hydroxide solution.
One of the products is glycerol, propane-1,2,3-triol. This is useful as a solvent.
The other products are sodium salts of the fatty acids, in this example sodium
stearate. These are used as soaps.