Explain:
a. Oxime are more acidic than hydroxylamine.
b. when 1 mol of and 1 mol of `(PhCH=O)`, after standing for a few hours, the only procut formed is benzaldehyde semicarbazone.
c. In the conversion of

by using Grignard reagent of
(I), why `(C=O)` group is protected?

Explanation

a. i.
Loss of `H^(o+)` from `NH_(2)OH` gives cojugate base `NH_(2)O^(Θ)` is not stabilised, so the reaction is reversible.
ii.
The negative charge on the conjugate base if oxime is resonance stabilised by the delocalisation of negative charge by extended `pi-` bond, as shown above. So the reaction is irreversible. Hence, `R_(2)C=N-O^(Θ)` is a weaker base and its conjugate acid, the oxime `(R_(2)C=N-OH)` is more acidic.
Thus, oximes are more acidic than hydroxylamine.
b. i.
ii.
In cyclohexanone `(A), (C=O)` group is not sterically hindered because its `R` groups are tied back into a ring, so kinetically controlled product `(I)` is formed first.
Formation of `(II)` takes place slowly because `(C=O)` group is deactivated by `bar(e)-`donating (+R effect) of `(Ph)` group. But `(II)` is more stable product due to the conjugation of double of `(Ph)` group with the double bond of `(CH=N)`

So the formation of product `(II)` is thermodynamically controlled. In such competitive reversible reaction, the equilibrium shifts with time to the more stable product `(II)`.
c. If `(C=O)` group in the compound `(I)` is not protected, the G.R. of `(I)` will react with the `(C=O)` group in other molecule as it forms. So, before making G.R. of `(I)`,`(C=O)` group is protected by cyclic acetal formation.