how Huckel's rule is applied to a molecule? and how it is related with the aromaticity?

Question

please explain with an ex. that how to apply Huckel's (4n+2II) rule to any molecule

Answer 1

There are some conditions for application of Huckel's rule.One of the most important among them is that the molecule must have a planar structure. It must not contain any sp3 or dsp2 & other hybidised C atom which correspond to a three dimensinal structure. If the molecules do not obey this condition, then even if they have 4n+2 pi electrons, they will not looked upon as an aromatic compound.

the next speculum is that they must have a cyclic structure.

If the concerned molecule satisfies the above said conditions, we may apply the Huckel's rule that is it must contain 4n+2 pi electrons.(n=an integer, ie 0,1,2,3.....) .Each single bond correspond to 0 pi electrons ,each double bond correspond to 2 pi electrons,& each triple bond corresponds to 2*2=4 pi electrons.

If the concerned compound follows all these said conditions, it may be looked upon as an aromatic organic compound.

eg- Benzene(C6H6)
1)All carbon atoms in Benzeze is sp3 hybridised. So it has a planar structure.( 1st condition fulfilled)

2) it has a cyclis ring structure,(2nd condition fulfilled)

3) A benzene molecule contains 3 single & 3 double bond. Hence the total no. of pi electrons= 3*0+3*2=6
putting n=1,
hence 4n+2=6
Hence benzene follows 4n+2 rule.(3rd condition fulfilled)

all the conditions being fulfilled Benzene may be looked upon as an aromatic compound.

Answer 2

Ignore the sigma bonding electrons and look at the electrons available for pi bonding. If the total number of electrons available for pi bonding fits the formula 4n+2 where n is an integer (thus the number is 2, 6, 10, 14, etc.) in a cyclic system, the system will be aromatic, which means those electrons will be delocalized throughout the system.

Answer 3

Remember an umpire giving out a player Shoulder Before the Wicket. If that could be given out, then Hand before the Wicket is next or Arm Before the Wicket. But if the ball has made contact with the glove or bat, then obviously, it can't be given out LBW but that is also given out, when umpire fails to register that contact. I think its umpire's discretion to give out, if he deems the ball was on its way to hit the wicket, if the ball hasn't touched bat or glove, it would be interesting to see, if it hits the box & umpires gives it out & then the entry should be WBW or BoxBW but its always LBW otherwise :D :D