Physical Properties
The boiling points of the pentane isomers range from about 9 to 36 °C. As is the case for other alkanes, the more branched isomers tend to have lower boiling points.
The same trend normally holds for the melting points of alkane isomers, and indeed that of isopentane is 30 °C lower than that of n-pentane. However, the melting point of neopentane, the most heavily branched of the three, is 100 °C higher that of isopentane. The anomalously high melting point of neopentane has been attributed to the better solid-state packing assumed to be possible with its tetrahedral molecule; but this explanation has been challenged on account of it having a lower density than the other two isomers.
The branched isomers are more stable (have lower heat of formation and heat of combustion) than normal pentane. The difference is 1.8 kcal/mol for isopentane, and 5 kcal/mol for neopentane.
Rotation about two central single C-C bonds of n-pentane produces four different conformations.
Read more about this topic: Pentane
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