Question

For each of the species below, identify any cyclic conjugated system, then:

Determine the number of electrons in a system of cyclic conjugation (zero if no cyclic conjugation). B. Specify whether the species is "a"-aromatic, "aa"-anti-aromatic, or "na"-non-aromatic (neither aromatic nor anti-aromatic). A. Electrons in a cyclic conjugated system. B. The compound is (a, aa, or na) A. Electrons in a cyclic conjugated system. B. The compound is (a, aa, or na)

My answer is 10, a; 6, a. why it's not correct??

Answer 1

Aromaticity in a compound is determined by following some rules which are as follows: (1) The compound must be cyclic. The cydlic compound must have conjugated pielectrons. (3) The compound must be planar which means each atom must be sp hybridized. (4) The compound must follow Huckel rule of aromaticity also called 4n+2 rule. According to this rule, 4nt2 is equal to the number of pi-electrons in the cyclic system and n is whole number. In an aromatic system, the number of conjugated pi-electrons must be 2,6, 10, 14 and so on having corresponding n values as 0, 1, 2, 3 and so on. When all the mentioned conditions are followed, then the compound is said to be aromatic. The compounds which follows all the above rules from (1) to (3) except the Huckel rule are said to be anti-aromatic. H3 A. There are ten electrons in the cyclic conjugated system. B. The given compound follows all the rules of aromaticity, but it is non-aromatic. This is because the two methyl groups present causes steric hinderance. So, to ease out the steric repulsion the molecule is forced out of planarity, making it a non-planar molecule. O: CH A. There are six electrons in the cyclic conjugated system. B. This compound has 6 pi electrons, so, it is satisfying the Huckel rule. Moreover, the compound is planar, so it is aromatic