The reagent A is FeCl2
2 moles of cyclopentadine reacts with one mole of ferrous chloride to form one mole of ferrocene.
Phenyl magnesium bromid reacts with oxygen to form phenol.
2PhMgBr(i)ReagentA−−−−−−−−−→(ii)H3O+2PbOH
Thus, the reagent A is oxygen, O2
Phenyl magnesium bromide reacts with oxygen at low temperature followed by acidification to form benzoic acid.
pHMgBr(i)ReagentAat−70oC−−−−−−−−−−−−−−−−−−−→(ii)H3O⊕PbCOOH
Thus, the reagent A is oxygen, O2.
When tert butyl bromide is heated with neopentane, neopentane is obtained.
Thus, the reagent A is dimethyl zinc.
Me2Zn
When ethyl magnesium bromide is heated with a mixture of CoCl2 and ethyl tosylate, butane is obtained.
C2H5MgBrΔ−−−−−−−−→ReagentAButane
Thus, the reagent A is a mixture of CoCl2 and Et−OTs.