Aromatic vs Aliphatic
Organic molecules are molecules consist of carbons. Organic molecules are the most abundant molecule in living things on this planet. Therefore, organic molecules are associated with nearly every aspect of our lives. Therefore, a separate subject as organic chemistry has evolved to learn about these compounds. In the eighteenth and nineteenth century, important advances were made in the development of qualitative and quantitative methods for analyzing organic compounds. Organic chemists divide all the organic compounds into two groups as aliphatic and aromatic compounds. This separation is based on the way carbon atoms are arranged in the molecule.
Aliphatic compounds in organic chemistry are the non aromatic compounds. They can be either cyclic or acyclic. Alkanes, alkenes, alkynes and their derivatives are mainly considered as aliphatic compounds. These can have branched or linear structures and can be either saturate (alkanes) or unsaturated (alkenes and alkynes).
Studies about this class of compounds were started with the discovery of a new hydrocarbon by Michael faraday in 1825. This new hydrocarbon compound was named as “bicarburet of hydrogen” which is now known as benzene. Further studies about this compound had shown that it has different characteristics than the other organic compounds. The molecular formula of benzene is C6H6, and it is surprising because it has the same number of carbon atoms and hydrogen atoms. Most of the initially identified aromatic compounds were resins and essential oils, which had a fragrance. This gave them the name “aromatic.” Kekule was the first to recognize these aromatic compounds. He also proposed the structure of benzene which eventually became the parent compound of all the aromatic compounds. Though the formula shows a highly unsaturated nature in benzene, its reactions are contradictory. Normally, unsaturated compounds like alkene decolorize bromine; change the color of potassium permanganate by being oxidized, etc. But benzene doesn’t show any of these. So they show different relativities than unsaturated aliphatic compounds. By saying a compound is aromatic, we mean that its π electrons are delocalized over the entire ring and that it is stabilized by the π electron delocalization. When naming monosubstituted benzene, we can adopt two methods. In some compounds benzene is used as the parent name and the substituent is indicated by a prefix (ex: bromobenzene). In other compounds, the compound takes a new name (ex: toluene). Other than the simple benzene and benzene derivatives, there are other aromatic compounds. Polycyclic benzenoid aromatic hydrocarbons are one of them. This class has molecules with two or more fused benzene rings (ex: naphthalene). Further there are nonbenzenoid aromatic compounds like azulene and cyclopentadienyl anion. Other than the rings composed only on carbon atoms there are some other aromatic molecules which are heterocyclic. Pyridine, furan, and pyrrole are some examples for heterocyclic aromatic compounds.
What is the difference between Aliphatic and Aromatic?
• Aliphatic means compounds react like an alkane, alkene, alkyne or one their derivatives. Aromatic compounds are benzene, benzene derivatives or sometime heterocyclic aromatic compounds.
• Aliphatic compounds have straight, branched or cyclic structures whereas aromatic compounds contain a cyclic structure.
Th• ough the formula shows a highly unsaturated nature in aromatic compounds, their reactions are contradictory to the unsaturated aliphatic molecules.