Which one of the following reactions does not give benzene as the product? [2025]
(2)
Consider the following compounds/species:
The number of compounds/species which obey Huckel’s rule is _______. [2023]
2
5
4
6
(3)
These compounds obey Huckel's rule as these contain electrons.
Which compound amongst the following is not an aromatic compound? [2022]
(4)
Compound (4) is not an aromatic compound as reflected by the non-planarity of the methylene bridge (——) with respect to other atoms. However, tropylium cation is aromatic due to planarity.
Among the following the reaction that proceeds through an electrophilic substitution is [2019]
(3)
The attacking species in the reaction given in option (3) is an electrophile i.e., Therefore, it is an electrophilic substitution reaction.
Which of the following can be used as the halide component for Friedel–Crafts reaction? [2016]
Chlorobenzene
Bromobenzene
Chloroethene
Isopropyl chloride
(4)
Friedel–Crafts reaction:
Chlorobenzene, bromobenzene and chloroethene are not suitable halide components as C–X bond acquires some double bond character due to resonance of lone pair of electrons with -bond.
In which of the following molecules, all atoms are coplanar? [2016]
(1)
Biphenyl is coplanar as all C-atoms are hybridised.
In pyrrole the electron density is maximum on [2016]
2 and 3
3 and 4
2 and 4
2 and 5
(4)
Pyrrole has maximum electron density on 2 and 5. It generally reacts with electrophiles at the C-2 or C-5 due to the highest degree of stability of the protonated intermediate.
Attack at position 3 or 4 yields a carbocation that is a hybrid of structures (I) and (II). Attack at position 2 or 5 yields a carbocation that is a hybrid not only of structures (III) and (IV) (analogous to I and II) but also of structure (V). The extra stabilization conferred by (V) makes this ion the more stable one. Also, attack at position 2 or 5 is faster because the developing positive charge is accommodated by three atoms of the ring instead of only two.
In the given reaction, 
the product P is [2016]
(3)
Consider the nitration of benzene using mixed conc. and . If a large amount of is added to the mixture, the rate of nitration will be [2016]
unchanged
doubled
faster
slower
(4)
Mechanism of nitration is:
If a large amount of is added, then conc. of ions increases and the reaction will be shifted in backward direction. Hence, the rate of nitration will be slower.
The oxidation of benzene by in the presence of air produces [2015]
maleic anhydride
benzoic acid
benzaldehyde
benzoic anhydride
(1)
