Isomers
The unmodified term butanol usually refers to the straight chain isomer with the alcohol functional group at the terminal carbon, which is also known as n-butanol or 1-butanol. The straight chain isomer with the alcohol at an internal carbon is sec-butanol or 2-butanol. The branched isomer with the alcohol at a terminal carbon is isobutanol; 2-methyl-1-propanol, and the branched isomer with the alcohol at the internal carbon is tert-butanol; 2-methyl-2-propanol.
| n-butanol | sec-butanol | isobutanol | tert-butanol |
Butanol isomers, due to their different structures, have somewhat different melting and boiling points. n-Butanol and isobutanol have limited solubility, while the other two isomers are fully miscible with water. This is because all alcohols have a hydroxyl group which makes them polar which in turn tends to promote solubility in water. At the same time, the carbon chain of the alcohol resists solubility in water. Methanol, ethanol, and propanol are fully miscible with water, while n-butanol is only moderately miscible because of the balance between the two opposing solubility trends.
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