The product obtained is ethanol

Benzaldehyde condenses with tertiary aromatic amines like N, N - dimethyl aniline in the presence of strong acids to from triphenyl methane dye or malachite green dye.

Two possible isomers of C₃H₆O are
\(\underset { \overset { (A) }{ Acetone } }{ { CH }_{ 3 }CO{ CH }_{ 3 } } \quad \underset { \overset { (B) }{ Propanal } }{ { CH }_{ 3 }{ CH }_{ 2 }CHO } \) 
\(\\ \underset { \quad \quad (A)\\ Proponal }{ { CH }_{ 3 }CO{ CH }_{ 3 } } \overset { { I }_{ 2 }/NaOH\Delta }{ \underset { Iodo\ form\ \\ reaction }{ \longrightarrow } } \underset { Sodium\\ acetate }{ { CH }_{ 3 }COONa } +\underset { Iodoform\\ Yellow\ ppt }{ { CHI }_{ 3 } } \) 
\(\underset { \quad \quad \quad (B)\\ Propanal }{ { CH }_{ 3 }{ CH }_{ 2 }CHO } \overset { { I }_{ 2 }/NaOH }{ \underset { \Delta }{ \longrightarrow } } No\quad ppt\quad of\quad { CHI }_{ 3 }\) 
Acetone answers Iodo form test whereas proponal does not.

(i) It is oxidised to benzoic acid by alkaline permanganate.
\({ C }_{ 6 }{ H }_{ 5 }CHO\overset { [O] }{ \longrightarrow } { C }_{ 6 }{ H }_{ 5 }COOH\) 
(ii) It is reduced to benzyl alcohol by NaBH₄ or LiAlH₄
\({ C }_{ 6 }{ H }_{ 5 }CHO\overset { \left[ { H }^{ - } \right] }{ \longrightarrow } { C }_{ 6 }{ H }_{ 5 }{ CH }_{ 2 }OH\)
(iii) It can be reduced to toluene by Clemmenson or Wolff Kishner procedure.
\({ C }_{ 6 }{ H }_{ 5 }CHO\overset { Zn/Hg/HCl }{ \underset { \overset { or }{ { N }_{ 2 }{ H }_{ 4 }/KoH } }{ \longrightarrow } } { C }_{ 6 }{ H }_{ 5 }{ CH }_{ 3 }\) 

During oxidation of unsymmetric ketones with oxidising agent which brings about the cleavage of C-C bond, the smaller alkyl group goes preferentially with the carbonyl group resulting in the carboxylic acids.
\({ CH }_{ 3 }-{ CH }_{ 2 }-{ CH }_{ 2 }-\underset { \overset { || }{ O } }{ C } -{ CH }_{ 3 }\overset { (O) }{ \underset { Con.HNO_{ 3 } }{ \longrightarrow } } \underset { Propanoic\ acid }{ { CH }_{ 3 }{ CH }_{ 2 }-COOH } +\underset { acetic\ acid }{ { CH }_{ 3 }COOH } \)

(i) \(\underset { Propanal }{ { 2CH }_{ 3 }-{ CH }_{ 2 }-CHO } \overset { Dil\quad NaOH }{ \underset { \quad Aldol\\ Condensation }{ \longrightarrow } } \underset { 3-hydroxy-2-methyl \ pentanal }{ { CH }_{ 3 }-{ CH }_{ 2 }-\underset { \overset { | }{ OH } }{ CH } -\underset { \overset { | }{ { CH }_{ 3 } } }{ CH } -CHO } \)
(ii) (CH₃)C-CHO:
\({ CH }_{ 3 }-\overset { \underset { | }{ { CH }_{ 3 } } }{ \underset { \overset { | }{ { CH }_{ 3 } } }{ C } - } CHO\overset { dil.NaOH }{ \underset { Cannizzao\\ reaction }{ \longrightarrow } } \underset { 2,2diemthy-l-propanol }{ { CH }_{ 3 }-\overset { \underset { | }{ { CH }_{ 3 } } }{ \underset { \overset { | }{ { CH }_{ 3 } } }{ C } } -{ CH }_{ 2 }OH+ } \underset { 2,2-dimethyl \ sodium \ propionate }{ CH_{ 3 }-\overset { \underset { | }{ { CH }_{ 3 } } }{ \underset { \overset { | }{ { CH }_{ 3 } } }{ C } } -COONa } \) 

(i) Ethanal
(ii) sp²
(iii) CH₃CHO + 2Cu₂⁺ + 3OH^- ⟶CH₃COO^- + 2Cu⁺ + 2H₂O
\({ CH }_{ 3 }CHO+{ CH }_{ 3 }CHO\overset { NaOH }{ \longrightarrow } { H }_{ 3 }C-\overset { \underset { | }{ H } }{ \underset { \overset { | }{ OH\\ Aldol } }{ C } } -{ CH }_{ 2 }-CHO\)

(i) Perkin's Reactions:
When an aromatic aldehyde is heated with an aliphatic acid anhydride in the presence of the sodium salt of the acid corresponding to the anhydride, condensation takes place and an α, β unsaturated acid is obtained
This reaction is known as Perkin's reaction.

(ii) Knoevengal Reaction:
(a) Benzaldehyde condenses with malonic acid in the presence of pyridine forming cinnamic acid
(b) Catalyst - Pyridine
(c) Carbanion formed from malonic acid.

(i) Benzaldehyde from Toluene: Side chain chlorination of toluene gives benzal chloride, which on hydrolysis gives benzaldehyde.

(ii) Benzoin from benzaldehyde: Benzaldehyde reacts with alcoholic KCN to form benzoin.
\({ C }_{ 6 }{ H }_{ 5 }-\overset { \underset { | }{ H } }{ \underset { \overset { || }{ O } }{ C } } +H-\underset { \overset { || }{ O } }{ C } { -C }_{ 6 }{ H }_{ 6 }\overset { alc \ KCN }{ \underset { \Delta }{ \longrightarrow } } { C }_{ 6 }{ H }_{ 5 }-\underset { \overset { | }{ OH } }{ CH } -\underset { \overset { || }{ O } }{ C } -{ C }_{ 6 }{ H }_{ 5 }\)

Primary alcohols and aldehydes can easily be oxidised to the corresponding carboxylic acids with oxidising agents such as potassium permanganate (in acidic or alkaline medium), potassium dichromate (in acidic medium)
Example:
\(\underset{Ethyl \ alcohol}{ { CH }_{ 3 }{ CH }_{ 2 }OH}\overset { { H }^{ + }/{ K }_{ 2 }{ Cr }_{ 2 }{ O }_{ 7 } }{ \underset { (O) }{ \longrightarrow } } \underset{Acetaldehyde}{{ CH }_{ 3 }CHO}\underset { (O) }{ \longrightarrow } \underset{Acetic \ acid}{{ CH }_{ 3 }COOH}\)

(i) Chain isomerism: This arises due to the difference in the carbon chain of alkyl group attached to carboxyl group. C₅H₁₀O₂.
\({ CH }_{ 3 }-\underset { Pentanoic\ acid }{ { CH }_{ 2 }-{ CH }_{ 2 }-{ CH }_{ 2 } } -COOH\quad \underset { 3-mrthyl\ butanoic\ acid }{ { CH }_{ 3 }-\overset { \underset { | }{ { CH }_{ 3 } } }{ CH } -{ CH }_{ 2 }-COOH } \) 
(ii) Functional isomerism: Carboxylic acids are functional isomers of ester . C₃H₆O₂ 
\(\underset { Propanic \ acid }{ { CH }_{ 3 }-{ CH }_{ 2 }-COOH } \) and \(\underset { Methyl\ acetate }{ { CH }_{ 3 }COO{ H }_{ 5 } } \)  \(\underset { Ethyl\ formate }{ HCOO{ C }_{ 2 }{ H }_{ 5 } } \)

(i) Cannizzaro reaction is a redox reaction which takes place only in aldehydes which do not have α- hydrogen atom.
(ii) Formaldehyde (HCHO) and benzaldehyde (C₆H₅CHO) do not have a-hydrogen atom and so they undergo Cannizzaro reaction.
(iii) But acetaldehyde CH₃CHO contains 3 α-H atoms and it does not undergo Cannizzaro reaction.

(i) When reduced with hydrogen in the presence of 'poisoned' palladium catalyst, they form aldehydes. This reaction is called Rosenmund reduction.
\(\underset { acetyl\ chloride }{ { CH }_{ 3 }-\underset { \overset { || }{ O } }{ C } -Cl } +H-H\overset { Pd }{ \underset { Ba{ SO }_{ 4 } }{ \longrightarrow } } \underset { acetaldehyde }{ CH_{ 3 }-\underset { \overset { || }{ O } }{ C } -H+HCl } \) 
(ii) BaSO₄ is used as a catalytic poi on to stop the reduction at the stage of aldehyde.
(iii) Otherwise, the aldehyde formed will be further reduced to primary alcohol.

When alkylcyanides are reduced using SnCl₂ HCl, imines are formed, which on hydrolysis gives corresponding aldehyde.
\({ CH }_{ 3 }-C\equiv N\overset { { SnCl }_{ 2 }/HCl }{ \longrightarrow } { CH }_{ 3 }-CH={ NH }\overset { { H }_{ 3 }{ O }^{ + } }{ \longrightarrow } { CH }_{ 3 }-CHO\)

Ozone forms addition product with olefin called I ozonide, which on reductive cleavage gives aldehyde.