Benzene and Alkyl Benzene - Result Question 25

####29. Which of the following molecules, in pure form, is/are unstable at room temperature?

(2012) (a)

(c)

(b)

(d)

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Solution:

  1. According to Huckel rule, the compounds which have 4n(n=0,1,2,3) delocalised π-electrons in a close-loop are anti-aromatic and characteristically unstable. Compound B satisfy the criteria of anti-aromaticity as :

Compound C is anti-aromatic in its resonance form :

Compound A has 4π-electrons which are also delocalised but do not constitute close loop, hence non-aromatic.

Compound D is aromatic, characteristically stable.

Order of stability Aromatic > Non-aromatic > Anti-aromatic



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