Question

How do functional groups influence solubility?

Answer 1

Functional group is defined as the substituents which are attached to a molecule and are responsible for the characteristics of the molecule. They provide specific chemical and physical properties to a molecule.

Complete step by step answer:
The atoms or group of atoms bonded to a molecule is referred to as the functional group. The functional group imparts changes in physical properties of a molecule as solubility, boiling point, melting point etc. It also affects the chemical properties of the molecules which it is attached to.
The functional group attached to the molecule is of two types one is polar and the other is non-polar. The polar functional group interacts with the molecules coming nearby by dipole-dipole interactions, hydrogen bonding, ion dipole interactions and Vander Waal forces.
The non polar functional groups only interact with the other molecules by weak Vander Waals forces. Due to this they affect the solubility of the whole molecule in different solvents or mediums.
There is a rule which governs the solubility of compounds and the rule is mostly true and is reliable. The rule is stated as dissolves like. This means that a polar compound is dissolved in polar solvents and the non-polar compounds are dissolved in non-polar solvents.
The polar character of organic molecules is assigned by the presence of polar substituents like electronegative atoms (e.g. $N$ ,$O$) in polar functional groups like amines ($- N{H_2}$) and alcohols ($- OH$). The overall polarity is the summation of the nonpolar parts and polar parts within a molecule.
If a large nonpolar hydrocarbon part is present in a molecule which makes the molecule non-polar then it is more soluble in nonpolar solvents.

Note: The solubility of a molecule is dependent on the functional groups attached with the molecule. As for example the organic ethers or organic acids are more soluble in alcohol than the pentane or hexane. Further benzene or toluene is more soluble in hexanes.