Question

How do amino groups and nitro groups affect the properties of (a) aliphatic, and (b) aromatic compounds?

Answer 1

Aliphatic compounds:

Amino group present in aliphatic compounds shows the basic nature because of presencs of localized lone pair of electrons over N-atom.

Where as aliphatic nitro group containing compounds are non basic due to absence of lone pair electron over N-atom.

Aromatic compounds:

In amino group say -NR₂, the N atom have lone pair of electron which take part in various chemical activity. For example if this group is attached directly with aromatic ring then it activates the ring with its lone pair of electrons (ie. delocalization of electron) and increase the elecrton density perticularly at ortho and para positions (that is why these are ortho-para directing groups for electrophilic aromatic substitution reactios) and facilitate the electrophilic substitution reactions. But these are less basic in nature as compared to aliphatic amino compounds because their lone pair of electrons are engaged some what with the aromatic ring.

On the other hand nitro groups are having just opposite in behavior of amino group because of presence of 2-oxygen atoms causing the defficiency of electron over N-atom. So, if this group is attached with aromatic ring. They are often highly explosive, especially when the compound contains more than one nitro group and is impure. The nitro group is one of the most common explosophores (functional group that makes a compound explosive).