The presence of the ester linkage functional group determines the unique physical and chemical properties of this family.

1. Physical Properties
   
   
   1. Boiling Point
      
      

      Unlike the alcohols and carboxylic acids, esters cannot hydrogen bond with themselves. In general, boiling points of esters increase as CH₂ groups are added to the parent chain. This occurs because the number of electrons increases, strengthening the London forces. However, note that the smaller esters demonstrate higher boiling points than similarly sized alkanes. This is because esters are polar and, therefore, exhibit a small additional dipole-dipole force. In large esters, however, the non-polar portion of the molecule becomes predominant and dipole-dipole forces contribute much less to the total intermolecular forces present.

   2. Solubility
      
      

      Small esters are fairly soluble in water. While small esters cannot form hydrogen bonds between themselves, they can hydrogen-bond to water molecules. This occurs when one of the slightly positive hydrogen atoms in a water molecule becomes attracted to one of the ester.s oxygen atoms. As chain length increases, however, the hydrocarbon portion of the ester molecule begins to interfere with hydrogen bonding. This decreases solubility.

2. Chemical Properties
   

   
   The presence of the ester linkage determines the chemical properties of the esters. What reactions involve esters? You will explore this question in Lesson 2.