Both stearic acid and oleic acid are C18 fatty acids but differ in their unsaturation. Stearic is a saturation C18 fatty mountain whereas oleic mountain is one unsaturated C18 fat acid.

Saturated fat acids will show different physical properties contrasted with unsaturated fatty acids of similar chain length. Among the important property is melt point.

You are watching: What is the melting point of stearic acid

Two components mainly influence melting suggest of fat acids. One is molecular weight and another is unsaturation.

For example, stearic has actually a melting allude of 69oC conversely, palmitic acid has 63oC.


Stearic mountain is a C18 fat acid and also palmitic acid is C16 fat acid. Both space saturated fat acids yet stearic mountain (C18) has more molecular weight 보다 palmitic mountain (C16) hence much more melting point.

Molecular weight increases with variety of carbons and also hence chain length of the fat acid. Because of this C18 fat acids will have much more molecular weight 보다 C16 fatty acids.

As the chain size increases, the valve der Waals forces in between fatty mountain molecules increases thereby intermolecular pressures increase. This results in boost in the melt point.

2. Unsaturation

Now let’s consider second factor, unsaturation.

Again typical with every hydrocarbons, melting allude decreases with unsaturation.

greater the unsaturation, reduced the melt point.

For example, oleic acid, linoleic acid and also linolenic acid all space unsaturated C18 fat acids. Oleic mountain melts at 13oC, linoleic acid at -5oC and linolenic acid at -11oC.

Here the number of double bonds play crucial role.

Oleic acid has one dual bond,


linoleic acid has actually two


and linolenic acid has actually three twin bonds.

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As the number of double bonds (unsaturation) increases, the molecule has tendency to lie in non-linear fashion and attains more spherical structure. Due to spherical, structure poly unsaturated fat acids show less call with various other molecules for this reason less intermolecular interaction.


As the intermolecular communication decreases, van der Waals forces between molecules decrease and also melting point decreases.

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