Physical Properties of Alcohols and Alkyl Halides Intermolecular Forces

5 PHYSICAL PROPERTIES OF ALCOHOLS AND ALKYL HALIDES INTERMOLECULAR FORCES 

Boiling Point. When describing the effect of alkane structure on boiling point in Section 2.14, we pointed out that the forces of attraction between neutral molecules are of three types listed here. The first two of these involve induced dipoles and are often referred to as dispersion forces, or London forces. 

Because so many factors contribute to the net intermolecular attractive force, it is not always possible to predict which of two compounds will have the higher boiling point. We can, however, use the boiling point behavior of selected molecules to inform us of the relative importance of various intermolecular forces and the structural features that influence them. 

Consider three compounds similar in size and shape the alkane propane, the alcohol ethanol, and the alkyl halide fluoroethane. 

FIGURE 4.3 A dipole-dipole attractive force. Two molecules of a polar substance are oriented so that the positively polarized region of one and the negatively polarized region of the other attract each other. 

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Physical Properties of Alcohols and Alkyl Halides Intermolecular Forces... 

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