Conjugation In Organic Chemistry

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An aromatic compound can be defined as a cyclic compound, containing a certain number of conjugated double bonds, and being especially stable due to resonance. Many people define conjugation as the presence of alternating single and double bonds. However, this definition is too specific and not general enough. Consider the example of the compound furan: In Section 3.1 Organic Chemistry- Introductory Topics, it was mentioned briefly that hybridization associated with aromaticity follows a different set of rules. The hybridization state of the oxygen atom in furan is sp2. It is sp2 hybridized because: 1) the oxygen atom has at least 1 lone pair of electrons and 2) it is attached to another sp2 hybridized atom. The oxygen atom in furan possesses two lone pairs of electrons. One pair resides in a sp2 hybrid orbital while the other pair resides in a p-orbital. Electrons found in p-orbitals are known as electrons. Since all the five atoms have lone pairs in their p-orbitals, conjugation can…show more content…
In 1931, a German chemist and physicist Erich Hückel proposed a theory to help determine if a cyclic molecule possesses aromatic properties. According to him, if a cyclic planar molecule contains (4n+2) electrons, then it is considered aromatic. This rule would come to be known as the Hückel’s rule. On paper, it is almost impossible to determine whether a molecule is flat or planar by looking at its displayed structure. However, an aromatic compound must possess (4n+2) electrons. Using furan as an example, it has 2 C=C bonds which is equivalent to 4 electrons. Since the oxygen atom is sp2 hybridized, it has 1 lone pair residing in the p-orbitals and this is equivalent to 2 electrons. As furan has a total of 6 electrons, it fulfils the Hückel’s rule of 4n+2 (where n = 0, 1, 2, 3 …) and it is aromatic. Only aromatic compounds can undergo electrophilic

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