Devise sequences for preparing the following compounds from benzene

1.	Devise sequences for preparing the following compounds from benzene
Answer» Solution :(a) The process can be started if we can do the nitration of benzene ring two times and then can reduce one of the group selectively. AMMONIUM sulphide allows selective reduction of one NITRO group in the presence of anothe. The mechanism of this reaction is complex. It is the transformation itself which you need to know. (b) The target can be achieved if wee can form phenol from benzene. Formation of phenol from benzene is not straightforward. The route shown below involves the nitration, reduction to aniline and diazotisation. "Hydrolysis" of the diazonium ion gives phenol. The subsequent steps involve temporary introduction of a `-SO_(3)` group as a protecting group of the para-position. This allows selective bromination of the ortho-position.(Note : Which products would you get without the `-SO_(3)` group?) (c) Alkylation are carried out using Friedel-Crafts method. As carbocations are involved the potential of rearrangements has to be taken into account. In this case, the primary propyl cation obtained from chloropropane could easily rearrange into the more stable SECONDARY carbonication. This can be avoided using a Friedel-Crafts acylation. The CARBONYL group is easily reduced , using the Clemmensen reduction as shown below: (d) Iodine and fluorine are halogens which cannot be introduced using conventional Friedel-Crafts halogenation chemistry(why?). Since aniline is very electron rich,it undergoes electrophilic substitution even with relatively poor electrophiles such as iodine.