Question

(a) Write the structures of main products when benzene diazonium chloride reacts with the following reagents :
(i) `H_(3)PO_(2)+H_(2)O`
(ii) `CuCN//KCN`
(iii) `H_(2)O`
(b) Arrange the following in the increasing order of their basic character in an aqueous solution :
`C_(2)H_(5)NH_(2),(C_(2)H_(5))_(2)NH,(C_(2)H_(5))_(3)N`
(c) Give a simple chemical test to distinguish between the following pair of compounds :
`C_(6)H_(5)-NH_(2) and C_(6)H_(5)-NH-CH_(3)`

Answer 1

(a) (i) `C_(6)H_(5)N_(2)Cl+H_(3)PO_(2)+H_(2)Ooverset(Cu^(+))underset("reduction")rarrC_(6)H_(6)+N_(2)+H_(3)PO_(3)+HCl`
`C_(6)H_(5)N_(2)Cloverset(CuCN)underset(KCN)rarrC_(6)H_(5)CN`
(iii) `underset("Unstable")(C_(6)H_(5)CH_(2))-overset(+)Nequiv NCl^(-)overset(H_(2)O)rarrunderset("Benzylalcohol")(C_(6)H_(5)CH_(2)OH)+N_(2)uarr+HCl`
(b) In gaseous phase, basic character of amines increases with increase in number of electron releasing group, due to + 1 effect, so trend of basic character is `3^(@)gt2^(@)gt1^(@).`
But in aqueous phase, solvations of ammonium cation occurs by water molecules, greater the size of ion, lesser will be the solvation, and lesser will be the stability of ion, so on combining + 1 effect and solvation effect, in aqueous phase trend changes to `2^(@)gt3^(@)gt1^(@),`