STRUCTURE AND PROPERTIES OF HALOALKANES

We recall that the halogens are more electronegative than carbon. As a result, the carbon atom of a carbon-halogen bond bears a partial positive charge. The halogen atom has an equal and opposite partial negative charge. 

The atomic radii of the halogens increase going from top to bottom in the periodic table. This trend is reflected in the bond lengths of the carbon—halogen bond. 

The polarizability of an atom (Section 2.8) is a measure of the ease with which its electrons can be distorted in an electric field. The polarizabihty of the halogen atoms increases as we move down the periodic table F Cl Br I. Highly polarizable atoms interact more strongly by van der Waals forces than less polarizable atoms. Therefore, intermolecular forces for haloalkanes increase in the order RF RCI RBr RJ. The effect of intermolecular forces is reflected in the boiling points of haloalkanes, which increase in the same order as the polarizability of their halogen components. 

Fluoroalkanes and chloroalkanes that contain a single halogen atom are less dense than water. Compounds with two or more chlorine atoms are more dense than water. AU bromoalkanes and iodoalkanes have greater densities than water (Table 9.1). 

Boiling Points and Densities of Haloalkanes Boiling Points and Solubilities of Alcohols  

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