How do functional groups affect organic molecules?

Sep 24, 2015

Functional groups determine the identity of organic molecules

Explanation:

Functional groups are very important in organic chemistry since they determine the identity of these molecules and therefore, depict the chemical and physical properties of them.

For example, hydroxy groups $O H$ is specific for alcohols. the general structure for alcohols is $R - O H$.

In a similar way, $C O O H$ is the functional group for carboxylic acids of a general structure $R - C O O H$.

For esters, the functional group is $C O O R '$, where esters have the general structure $R - C O O R '$.

And so on.

with different functional groups, alcohols, carboxylic acids, and esters have different chemical and physical properties and therefore, different identity.

Let us take a specific example; Propane $C {H}_{3} C {H}_{2} C {H}_{3}$. Propane is a gaseous molecule at room temperature. Adding a hydroxy group to its structure we get $C {H}_{3} C {H}_{2} C {H}_{2} - O H$ which is the propanol. Propanol is liquid at room temperature ( change on physical property ). Propanol can react thanks to the presence of the oxygen atom in its backbone, however, propane has very limited reactivity ( change on chemical property ).

There are many other functional groups such as:
Sulfides: $R - S - R '$
Thiols: $R - S H$
Ethers: $R - O - R '$
Anhydrides: $R - C O - O - C O - R '$
Ketones: $R - C O - R '$
Aldehydes: $R - C O - H$
Amides: $R - C O - N {\left(R '\right)}_{2}$ or $R - C O - N {H}_{2}$ or $R - C O - N H R '$
Amines: $R - N {H}_{2}$ or $R - N H R '$ or $R - N {\left(R '\right)}_{2}$
Nitriles: $R - C N$
Alkyl halides: $R - X$ where $X$ is an element from group 17.
Alkenes: $R - C H = C H - R '$
Alkynes: $R - C \equiv C - R '$
etc.