Chapter 2, Problem 51P

Interpretation Introduction

Interpretation: The alkane molecules octane, $3-\text{methylheptane}$ , $\text{2,2,4- trimethylpentane}$ and $\text{2,4- dimethylhexane}$ should be ranked in order of increasing boiling point.

Concept introduction: A liquid only bolls once its vapor pressure equals atmospheric pressure. This is directly dependent upon intermolecular forces. If the latter are large in magnitude the temperature is attained at high values. Thus, higher order alkanes particularly after pentane exhibit higher boiling points.

In general the alkanes that are branched appear to be spherical, as a result of less surface area show smaller boiling points. For higher alkanes, the greeter size amounts to greeter surface are4s and thus high values of boiling points. For example $\text{2,2,3,3-tetramethylbutane}$ has boiling point of $106.8°\text{C}$ relative to octane that has value of $\text{126 }°\text{C}$ .