Three structural isomers having the empirical formula C6H14 are listed below with their experimentally determined normal boiling points:
• n-hexane: 68.7 °C
• 2-methylpentane: 60.3 °C
• 2,2-dimethylbutane: 49.7 °C
All three molecules are non-polar and experience only London dispersion forces between molecules.
(a) Describe the trend in boiling point across the series of isomers.
(b) Explain the observed trend in terms of the strength of intermolecular forces, making explicit reference to both polarizability and molecular surface (contact) area.
(c) Predict whether the normal boiling point of n-heptane (C7H16) is likely to be higher than, lower than, or between the boiling points of the three C6H14 isomers. Justify your prediction.
(d) A sample containing an equimolar mixture of n-hexane and 2,2-dimethylbutane is distilled. Explain which component will vaporize preferentially at any given temperature below 68 °C and relate your reasoning to London dispersion forces.