There is hydrogen bond form between the molecules of alcohol and in the water molecules. In a mixture, both the molecules joined together by forming a hydrogen bond between H atom of COOH group and H atom of H₂O. However, the size of the alkyl group plays a major role in forming this H-bond between two molecules. Large the alkyl group prevents this bond formation, therefore solubility decreases and vice versa. As a result, alcohol and water molecule produces the heterogeneous solution in nature due to weak bond formation between the molecules. In addition, it increases the vapour pressure and leads to lower the boiling point of the solution mixture.