Aliphatic carboxylic acids with up to four carbon atoms are miscible in water due to hydrogen bond formation. However, solubility decreases with an increasing number of carbon atoms. Higher carboxylic acids become practically insoluble in water due to increased hydrophobic interactions of the hydrocarbon portion.
Describe the solubility of simple aliphatic carboxylic acids in water and how it varies with the number of carbon atoms. Why are higher carboxylic acids practically insoluble in water?
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The solubility of simple aliphatic carboxylic acids in water decreases with an increase in the number of carbon atoms. Short-chain carboxylic acids (1-4 carbons) are generally soluble due to the formation of hydrogen bonds with water molecules. However, as the carbon chain lengthens, the hydrophobic alkyl portion dominates, diminishing the ability to form hydrogen bonds. Carboxylic acids with higher carbon atoms, like those with more than 10 carbons, become practically insoluble in water. The hydrophobic effect outweighs the limited hydrogen bonding ability, leading to decreased solubility and forming a separate, immiscible layer in aqueous solutions.