how we will calculate the aromaticiy of the aromatic compound
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They are cyclic.
They are conjugated all around the ring. The easiest way to put it is this: every atom in the ring must be able to participate in resonance. So atoms that have pi-bonds, carbocations, or lone pairs are OK; but atoms with four single bonds are out.
the molecule must have (4n+2) Pi electrons. This is just a different way of expressing the series (2,6,10,14, 18, etc. )**. Huckel’s Rule states that all aromatic molecules must satisfy this condition. Now, Pi electrons can either come from double bonds, or from lone pairs that can align themselves with the pi system. [What does 4n+2 mean?]
The molecule must be flat. This is generally assumed to be true for most molecules that meet the previous 3 conditions, except in cases where steric hindrance prevents it. An example is
Note how pyridine (the third example) has a lone pair but it doesn’t “count” for purposes of aromaticity! More on that next time.
They are conjugated all around the ring. The easiest way to put it is this: every atom in the ring must be able to participate in resonance. So atoms that have pi-bonds, carbocations, or lone pairs are OK; but atoms with four single bonds are out.
the molecule must have (4n+2) Pi electrons. This is just a different way of expressing the series (2,6,10,14, 18, etc. )**. Huckel’s Rule states that all aromatic molecules must satisfy this condition. Now, Pi electrons can either come from double bonds, or from lone pairs that can align themselves with the pi system. [What does 4n+2 mean?]
The molecule must be flat. This is generally assumed to be true for most molecules that meet the previous 3 conditions, except in cases where steric hindrance prevents it. An example is
Note how pyridine (the third example) has a lone pair but it doesn’t “count” for purposes of aromaticity! More on that next time.
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