Question

Which one of the following compounds will be least soluble in water?

Answer 1

Water is a polar solvent. Since, 'Like dissolves like' a polar compound will be most soluble in water whereas a non-polar compound will be the least soluble.

The increasing order of polarity for the given organic compounds is:-

CH3OCH3 < CH3NH2 < CH3CHO < CH3CH2OH

Ether is the least polar and hence least soluble in water.

Answer 2

Answer: The correct answer is (A).

Explanation :

$CH_3OCH_3$ that is dimethyl ether will be least soluble in water because extent of hydrogen bonding interaction with water molecules are weakest in comparison to other listed options.

Where as :

• In $CH_3CH_2OH$ that is ethanol,in which extent of inter-molecular hydrogen bonding with water molecules will be highest due to the presence of polar (-OH) group.Where as ($-NH_2$) group is less polar than that of the (-OH) group.
• in $CH_3NH_2$ that is methyl amine in which extent of hydrogen bonding will higher than than that of the $CH_3CHO$ that is ethanal. This is due to presence of two hydrogen atoms in primary amine which are available for inter-molecular hydrogen bonding with water molecules.

So, the order  of solubility from least soluble to highly soluble compound in water will be:

$CH_3OCH_3$