Why is benzene extra ordinarily stable though it contains three double bonds?

A gas which contains double bond is :

Gas containing double bond.

In the following questions, a statement of assertion (A) is following by a statement of reason (R ) A : The number of optically active isomers of tartaric acid is three though it contains two asymmetric carbons. R: One of the optical isomers has a centre of symmetry..

Degree of unsaturation of A = 2, it contains no double or triple bonds.

Give reasons for the following: (i) tert-buty lbenzene does not give benzonic acid on treatment with acidic KMnO_(4) . (ii)Normally, benzene gives electrophilic substitution reaction rather than electrophilic addition reaction although it has double bond.

Give an example of the following: A carbon compound containing two double bonds.

The C -C bond length is 1.54 Å C =C bond length is 1.33 Å What is the circumference of benzene ring ? Bond length between single and double bonds = 1.4 Å .

Explain the following observation : a. When pent -1 en -4- yneistrested with HBr in molar proportion, the addition takes place on the double bond and not on the triple bond, thereby, yielding the porduct , b. The (C=-C) bond length in propene is shorter than expected. c. Whey benzyl carbocation is more stable than ethyl carbocation ? d. Why does but -2- ene exhibit cis - trans isomerism but but -2- yne does not ? e. CI_(2)C=C C I_(2) does not add CI_(2) under usual conditions but adds in the presence of AICI_(3) .

Fill in the blanks with the correct word from the brackets: The covalent molecule containing three single covalent bonds is ____________________ [water / methane / ammonia].

Which of the following reactions of benzene does not account for the three C=C bonds in the molecule- (a) Benzene +Br_(2)underset("conc". H_(2)SO_(4))overset(FeBr_(3))rarr"bromobenzene"+HBr (b) Benzene +HNO_(3)rarr"nitrobenzen.e+H_(2)O (c) Benzene +3O_(3)rarr Triozonide (d) Benzene +3H_(2)overset(Ni)rarr cyclohexane