(i) Compound (A) does not reduce Fehling's solution, so it is benzaldehyde.
(ii) Benzaldehyde (A) reacts with acetone in the presence of NaOH to give on a, p unsaturated compound (B).
\(\\ \\ \\ \underset { (A) }{ { C }_{ 6 }{ H }_{ 5 }CHO } +{ CH }_{ 3 }-{ COCH }_{ 3 }\overset { NaoH }{ \longrightarrow } \underset { (B) }{ { C }_{ 6 }{ H }_{ 5 } } -\underset { Acetone }{ CH=CH-{ COCH }_{ 3 } } \) 
(iii) (A) reacts with dimethyl aniline in the presence of conc. H₂SO₄ to give compound (C).

Compound	Compound Name	Formula
A	Benzaldehyde	C6H5CHO
B	Benzal acetone	C6H5CH = CH-COCH3
C	Triphenyl methane dye

(i) Organic Compound (A) is Acetone. Acetone (A) on iodoform test.
\({ CH }_{ 3 }CO{ CH }_{ 3 }\overset { { I }_{ 2 } }{ \underset { NaOH }{ \longrightarrow } } \underset { Iodoform }{ { CHI }_{ 3 } } +{ CH }_{ 3 }COONa\)
(ii) Compound (B) is Benzaldehyde. It is called oil of bitter almonds.
(iii) Acetone (A) reacts with (B) Benzaldehyde to from Benzal acetone (C). This reaction is known Claisen Schmidt reaction.
\(\underset{(B)}{{ C }_{ 6 }{ H }_{ 5 }CHO}+{ CH }_{ 3 }COC{ H }_{ 3 }\overset { NaOH }{ \longrightarrow } { C }_{ 6 }{ H }_{ 5 }\underset{(C)}CH=CHCOC{ H }_{ 3 }\) 
(iv) Benzaldehyde reacts with malonic acid in the presence of pyridine gives compound (D) Cinnamic acid
\(\underset{(B)}{{ C }_{ 6 }{ H }_{ 5 }CHO}+ \underset{Malonicaid}{{ H }_{ 2 }C}\left( COOH \right) _{ 2 }\longrightarrow { C }_{ 6 }{ H }_{ 5 }CH=C \left( COOH \right) _{ 2 }\longrightarrow \underset{(D)}{{ C }_{ 6 }{ H }_{ 5 }CH=CHCOOH}\) This reaction is called Knoevenagal reaction.

(i) An organic compound (A) is identified as C₆H₅CHO benzaldehyde. Benzaldehyde reduces Tollen'sreagent and also undergoes. Cannizaro reaction.
\(\underset { (A) }{ C_{ 6 }{ H }_{ 5 }CHO } +{ Ag }_{ 2 }O\longrightarrow 2Ag+\underset { (B) }{ { C }_{ 6 }{ H }_{ 5 }COOH } \) 
(ii) Benzaldehyde reacts with acetic anhydride in the presence of sodium acetate gives cinnamic acid and it is (B) an unsaturated acid
\(\underset { (A) }{ { C }_{ 6 }{ H }_{ 5 }CHO } +\left( { CH }_{ 3 }CO \right) _{ 2 }O\overset { { CH }_{ 3 }COONa }{ \longrightarrow } \underset { (B) }{ { C }_{ 6 }{ H }_{ 5 }CH } { =CHCOOH }+{ CH }_{ 3 }COOH\) 
(iii) Compound A reacts with acetone to form compound (C) benzal acetone.
\(\underset {(A)}{{ C }_{ 6 }{ H }_{ 5 }CHO}+{ CH }_{ 3 }COC{ H }_{ 3 }\overset { NaOH }{ \longrightarrow } { C }_{ 6 }{ H }_{ 5 }CH=\underset { (C) }{ CH } -CO{ CH }_{ 3 }\) 

(i) From the molecular formula, (A) is identified as benzaldehyde and it is called as oil of bitter almonds.
(ii) Benzaldehyde is oxidised to benzoic acid by alkaline permanganate which gives brisk effervescence with NaHCO₃.
 \(\underset { (A) }{ { C }_{ 6 }{ H }_{ 5 }CHO } \overset { (O) }{ \longrightarrow } \underset { (B) }{ { C }_{ 6 }{ H }_{ 5 } } -COOH\)
(iii) When benzaldehyde is refluxed with aqueous alcoholic KCN, benzoin (C) is formed.
\({ C }_{ 6 }{ H }_{ 5 }CH=O+H-\overset { \underset { || }{ O } }{ C } -{ C }_{ 6 }{ H }_{ 5 }\overset { alc }{\underset{KCN} \longrightarrow } { C }_{ 6 }{ H }_{ 5 }-\underset { \overset { | }{ OH\\ (C) } }{ CH } -\overset { \underset { || }{ O } }{ C } -{ C }_{ 6 }{ H }_{ 5 }\)

(i) Compound (A) with molecular formula C₂H₄O reduces Tollen'sreagent.
(ii) (A) on treatment with HCN gives compound (B).
\(\underset { (A) }{ { CH }_{ 3 }-CHO } +HCN\longrightarrow { CH }_{ 3 }-\underset { \overset { | }{ OH\\ (B) } }{ CH } -CN\) 
(iii) Compound (B) on hydrolysis with an acid gives compound (C) with molecular formula C₃H₆O₃ which is an optically active compound.
\({ CH }_{ 3 }-\underset { \overset { | }{ OH\\ (B) } }{ CH } -CN\overset { { H }^{ + }{ H }_{ 2 }O }{ \underset { \Delta }{ \longrightarrow } } CH_{ 3 }-\underset { \overset { | }{ OH\\ (C) } }{ CH } -COOH\) 
(iv) Compound (A) on reduction with N₂H/C₂H₅ONa gives a hydrocarbon (D) of molecular formula C₂H_6.
\(\underset { (A) }{ { CH }_{ 3 }CHO } \overset { [H] }{ \underset { { N }_{ 2 }{ H }_{ 4 }/{ C }_{ 2 }{ H }_{ 5 }ONa }{ \longrightarrow } } \underset { (D) }{ CH_{ 3 }{ CH }_{ 3 } } \)