(a) (i) Acetaldehyde (CH3‌CHO) reacts with hydrogen cyanide HCN to give
2-hydroxypropapanenitrile as product.

CH3‌CHO+HCN

Acetaldehyde

→

CN3−CH(OH)−CN

2‌hydroxypropapanenitrile

(ii) Acetaldehyde (CH3‌CHO) reacts with Hydroxylamine (NH2‌OH) to give acetaldoxime as a product.

CH3‌CHO

Acetaldehyde

+

NH2‌OH

Hydroxylamine

→CH3−CH =NOH‌‌+H2O
(iii) Reaction of acetaldehyde in the presence of dilute NaOH, this is the kind of Aldol reaction by which obtained 3-hydroxybutanal as product. Further proceed reaction when using heat in the reaction, its gives aldol condensation product which is But-2-enal.
2

CH3−CHO

Acetaldehyde

NaOH

────▸

CH3−CH(OH)−CH2−CHO

3−hydroxybutanal

Heat,−H2O

──────▸

CH2−CH

But−2−en−al

=CH−CHO
(b) Chemical tests to distinguish the following compounds:
(i) Ferric chloride test: When phenol react with Ferric chloride, it form an Iron phenol complex which give violet colour to the solution, while Benzoic acid do not give any colour.
(ii) Propanal and propanone: These two are distinguished by the iodoform when it reacts with I2 in the presence of NaOH while propanone give iodoform test when reacts with I2 in the presence of NaOH.
CH3COCH3+3‌NaOI→CHI3 +CH3‌COONa‌CHI3+2‌NaOH‌ (Yellow ppt) ‌
CH3CH2‌CHO+NaOl →‌ No ppt of ‌CHI3‌ formed ‌
OR
OR
(a) (i) Chloroacetic acid is stronger acid than Acetic acid because −Cl is an electron withdrawing group which increase the acidic character by dispersing electron due to presence of inductive effect. Cl, as a result of the −I effect, removes electrons from the O−H bond and reduces its electron density. Weakening the O−H bond makes it easier for H+to be released. CH3 group has a positive impact. It makes the release of H+from acetic acid more challenging than from chloroacetic acid by increasing the electron density in the O−H bond. Consequently, ClCH2‌COOH is a more potent acid than CH3‌COOH.
(ii) Carboxylic acid contains carbonyl group and do not undergo nucleophilic addition reaction because oxygen atom in - OH contain lone pair of electrons. That's why, electrophilic character decreases because of resonance and it gives stability to the structure (b) (i) From acid chloride (Rosenmund's reduction):

R− O ∥ C −Cl+H2

Acid‌chloride

Pb‌−BaSO4,S

──────────▸

Rosenmund‌Reduction

R− O ∥ C −H

Aldehyde

+HCl
Formaldehyde cannot be prepared by this method as HOCl is highly unstable.
(ii) Cannizzaro Reaction: Aldehydes undergo self -oxidation and reduction on heating with conc. alkali. The aldehydes which do not have alpha-hydrogen undergo this reaction.
(C) Both give positive Iodoform test as they contain CO−CH3 group in their structure.