Physical Properties of Alcohols

Physical Appearance

Most simple alcohols are liquid at room temperature. Alcohols with more than twelve carbon atoms are waxy solid at room temperature.

Melting and boiling point

Like the parent hydrocarbon, the boiling points among the alcohols increase steadily with increase in the number of carbon atoms. The boiling point of alcohols are very high compared with that of the corresponding alkane because of their ability to form hydrogen bond between the hydrogen atom of the hydroxyl group and the oxygen atom of another molecule

 

The influence of the —OH group however becomes less significant as the carbon skeleton increases.

 

The order of boiling points of isomeric alcohols is 1° alcohol >2° alcohols >3° alcohols.

Density

The density of alcohols increases with increasing relative molecular mass, however, branching can reduce this effect.

 

All simple alcohols are less dense than water, but the aromatic homologues are slightly denser than water.

Solubility

Hydrogen bonding in alcohols influences their solubility in water. Alcohols with a relatively short carbon skeleton are soluble in water. For example methane, ethanol, propan-1-o1 and propan-2-o1 are completely miscible with water in all chains increases, the solubility of alcohols drop drastically.

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All alcohols are miscible with most organic solvents such as hexane, benzene and ethanol; the smaller ones are useful organic solvents.