Physical properties of aldehydes and ketones

Exercise

Compare the boiling temperatures and the solubilities of the following substances: Dimethylether, ethanol and ethanal $t_{b}$(ethanol)= $78^oC$ > $t_{b}$(ethanal) = $ 20^o C$ > $t_{b}$(dimethylether) =$-20^oC$ Solubility(ethanol) > Solubility(ethanal) > Solubility(dimethylether)

Explanation: 1) The strength of van der Waals forces are almost identical between the hydrocarbon chains. 2) Ethanol has many intermolecular hydrogen bonds, acetaldehyde still has a strong polarity due to its carboxyl group, dimethylether has a very low polarity because the dipoles are canceled partly by symmetry: