- I etiect increases the acidity. If electronegativity is high, - I effect is also high.

(i) An organic compound A (C₂H₃N) on reduction with SnCl₂/HCI gives B (C₂H₄O) which reduces Tollens reagent.
\({ CH }_{ 3 }-C\overset { | }{ \underset { \underset { H-H\\ \quad (A) }{ | } }{ = } } N\overset { sn{ Cl }_{ 2 } }{ \underset { HCl }{ \longrightarrow } } { CH }_{ 3 }CH=NH-HCl\overset { Hydrolysis }{ \longrightarrow }\underset{(B)} {{ CH }_{ 3 }CHO}+{ NH }_{ 4 }Cl\) 
(ii) Compound B on reduction with N₂H₄/C₂H₅ONa gives C (C₂H₆).

(i) From the molecular formula compound (A) is identified as Benzaldehyde I C₆H₅CHO and it reduces Tollen's reagent.
\(\underset { Tollen's\ regant\ silver\ mirror }{ { C }_{ 6 }{ H }_{ 5 }CHO+{ Ag }_{ 2 }O\longrightarrow 2Ag+{ C }_{ 6 }{ H }_{ 5 }COOH } \) 
(ii) Benzaldehyde on treatment with alkali undergoes Cannizzaro reaction to give benzoic acid (B) and benzyl alcohol (C).
\(\underset { (A) }{ { C }_{ 6 }{ H }_{ 5 }CHO+{ C }_{ 6 }{ H }_{ 5 }CHO } \overset { NaOH }{ \longrightarrow } \underset { (B) }{ { C }_{ 6 }{ H }_{ 5 }COOH } +\underset { (C) }{ { C }_{ 6 }{ H }_{ 5 }{ CH }_{ 2 }OH } \) 
(iii) Benzoic acid on treatment with sodalime gives benzene.
\(\underset { (B) }{ { C }_{ 6 }{ H }_{ 5 }COOH } \overset { NaOH }{ \underset { CaO }{ \longrightarrow } } \underset { Benzene }{ { C }_{ 6 }{ H }_{ 5 }+{ CO }_{ 2 } } \)
(iv) Benzyl alcohol acts as an antiseptic.

(i) Tollens Reagent Test: Tollens reagent is an ammoniacal silver nitrate solution. When an aldehyde is warmed with Tollens reagent a bright silver mirror is produced due to the formation of silver metal. This reaction is also called silver mirror test for aldehydes.
\({ CH }_{ 3 }CHO+2\left[ Ag\left( { NH }_{ 3 } \right) _{ 2 } \right] ^{ + }+3{ OH }^{ - }\longrightarrow { CH }_{ 3 }CO{ O }^{ - }+\underset { Silver\ mirror }{ 4{ NH }_{ 3 }+2Ag+2{ H }_{ 2 }O } \) 
(ii) Fehlings solution Test:
(a) Fehling's solution is prepared by mixing equal volumes of Fehlings solution A containing aqueous copper sulphate and Fehlings solution 'B' containing alkaline solution of sodium potassium tartarate (Rochelle salt).
(b) When aldehyde is warmed with Fehlings solution deep blue colour solution is changed to red precipitate of cuprous oxide.
\(\\ \\ { CH }_{ 3 }CHO+\underset { blue }{ 2{ Cu }^{ 2 } } +5{ OH }^{ - }\longrightarrow { CH }_{ 3 }{ COO }^{ - }+\underset { red }{ { Cu }_{ 2 }O\downarrow } +3{ H }_{ 2 }O\)
(iii) Schiffs' reagent Test: Dilute solution of aldehydes when added to Schiff's reagent (Rosaniline hydrochloride dissolved in water and its red colour decolourised by passing SO₂) yields its red colour. This is known as Schiff's test for aldehydes. Ketones do not give this test. Acetone however gives a positive test but slowly.

\(\underset { Acetaldehyde }{ { CH }_{ 3 }-\underset { \overset { || }{ O } }{ C } -H+4(H) } \overset { { NH }_{ 2 }{ NH }_{ 2 } }{ \underset { { C }_{ 2 }{ H }_{ 5 }ONa }{ \longrightarrow } } \underset { Ethane }{ { CH }_{ 3 }-{ CH }_{ 3 }+{ H }_{ 2 }O+{ N }_{ 2 } } \)
(i) Clemmensen reduction: Aldehydes and Ketones when heated with zinc amalgam and concentrated hydrochloric acid gives hydrocarbons. 
Example:
\(\underset { Acetald4ehyde }{ { CH }_{ 3 }-\underset { \overset { || }{ O } }{ C } -{ H }^{ + }4(H) } \overset { Zn^{ - }Hg }{ \underset { Conc.HCl }{ \longrightarrow } } \underset {Ethane}{{ CH }_{ 3 }-{ CH }_{ 3 }\pm { H }_{ 2 }O}\) 
\(\underset { Acetone }{ { CH }_{ 3 }-\underset { \overset { || }{ O } }{ C } -{ CH }_{ 3 }+4\left( H \right) } \overset { { Zn }^{ - }Hg }{ \underset { Conc.HCl }{ \longrightarrow } } { CH }_{ 3 }{ CH }_{ 2 }{ CH }_{ 3 }+{ H }_{ 2 }O\)
(ii) Wolff-Kishner Reduction: Aldehydes and Ketones when heated with hydrazine (NH₂NH₂) and sodium ethoxide, hydrocarbons are formed Hydrazine acts as a reducing agent and sodium ethoxide as a catalyst.
Example :
\(\underset { Acetaldehyde }{ { CH }_{ 3 }-\underset { \overset { || }{ O } }{ C } -H+4(H) } \overset { { NH }_{ 2 }{ NH }_{ 2 } }{ \underset { { C }_{ 2 }{ H }_{ 5 }ONa }{ \longrightarrow } } \underset { Ethane }{ { CH }_{ 3 }-{ CH }_{ 3 }+{ H }_{ 2 }O+{ N }_{ 2 } } \) 
\(\underset { Acetone }{ { CH }_{ 3 }-\underset { \overset { || }{ O } }{ C } -{ CH }_{ 3 }+4(H) } \overset { { NH }_{ 2 }{ NH }_{ 2 } }{ \underset { { C }_{ 2 }{ H }_{ 5 }ONa }{ \longrightarrow } } { CH }_{ 3 }{ CH }_{ 2 }{ CH }_{ 3 }+{ H }_{ 2 }O+{ N }_{ 2 }\)
Aldehyde (or) ketones is first converted to its hydrazone which on heating with strong base gives hydrocarbons.
(iii) Reduction to pinacols: Ketones, on reduction with magnesium amalgam and water, are reduced to symmetrical diols known as pinacol.

(i) With NH₃ :
Formaldehyde forms hexa m ethylenetetramine with NH₃
\(\underset { Formaldehyde }{ 6{ CH }_{ 2 }O+4N{ H }_{ 3 } } \longrightarrow \underset { Hexamethylene\quad tetramine }{ \left( { CH }_{ 2 } \right) _{ 6 }{ N }_{ 4 }+6{ H }_{ 2 }O } \) 

(ii) With CH₃MgI
Formaldehyde gives primary alcohol

(iii) With NaOH :
Cannizaro Reaction
\(\underset { Formaldehyde }{ HCHO } +HCHO\overset { NaOH }{ \longrightarrow } \underset { Sodiumformate }{ HCOONa } +\underset { Methnol }{ { CH }_{ 3 }OH } \) 

Vinegar is 6 to 8% solution of acetic acid in water.

(i) \({ CH }_{ 3 }-\underset { \overset { | }{ { C }_{ 6 }{ H }_{ 5 } } }{ C } =\underset { \overset { | }{ Br } }{ C } -{ CH }_{ 2 }-COOH\) 
(ii)  \({ CH }_{ 3 }-{ CH }_{ 2 }-\overset { \underset { | }{ { CH }_{ 3 } } }{ CH } -COOH\)

(i) Benzoic acid is used as an urinary antiseptic.
(ii) Sodium benzoate is used as food preservative.
(iii) Benzoic acid vapours are used to disinfect bronchial tube.

(i) Decarboxylation: When anhydrous: sodium salt of carboxylic acids are heated with soda lime, carboxyl group is removed with the· formation of hydrocarbon containing one carbon atom less.
\(\underset { Sodium \ acetate }{ { CH }_{ 3 }COONa } \overset { NaOH/CaO }{ \longrightarrow } \underset { Methane }{ { CH }_{ 4 } } +{ Na }_{ 2 }{ CO }_{ 3 }\) 
(ii) Heating benzoic acid with soda lime gives benzene.
\({ C }_{ 6 }{ { H }_{ 5 }COOH }\underset { Sodalime }{ \overset { NaOH }{ \underset { CaO\Delta }{ \longrightarrow } } } { C }_{ 6 }{ H }_{ 6 }+{ CO }_{ 2 }\) 

(i) Aqueous solution of carboxylic acids turn blue litmus into red colour.
(ii) Carboxylic acids give brisk effervescence with sodium bicarbonate due to the I evolution of CO₂,

Aldehydes that do not have a-hydrogen atom undergo Cannizaro reaction.
Eg: HCHO, C₆H₅CHO.

(i) \(H-\underset { \overset { || }{ O } }{ C } -H\) - Formaldehyde
(ii) \({ CH }_{ 3 }-\underset { \overset { || }{ O } }{ C } -H\) - Acetaldehyde
(iii) \({ CH }_{ 3 }-\underset { \overset { || }{ O } }{ C } -{ { CH }_{ 3 } }\) - Acetone
(iv) \(\\ { C }_{ 6 }{ H }_{ 5 }-\underset { \overset { || }{ O } }{ C } -{ CH }_{ 5 }\) - Aceopenone

An carbonyl compound having molecular formula C₅H₁₀O giving positive iodoform test. It does not reduce Fehling solution.So it is 2- pentanone.

∴ (A) is 2-pentanone.

(ii) 2,4-dichlorobenzaldehyde.

(iii) ethanal

(ii) benzoic acid

(iii) α - hydroxyphenylaceticacid.

\(\underset { Phenyl\ magnesium\\ bromide }{ { C }_{ 6 }{ H }_{ 5 }MgBr } +{ CO_{ 2 }\longrightarrow \quad }{ C }_{ 6 }{ H }_{ 5 }\overset { \underset { || }{ O } }{ C } OMgBr\underset { { H }_{ 2 }O/{ H }^{ + } }{ \longrightarrow } \underset { \quad \quad \quad \quad (A)\\ Benzoic\ acid }{ { C }_{ 6 }{ H }_{ 5 }COOH } \)

(A) C₆H₅COOH-Benzoic acid
(B)

(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) 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.
\({ C }_{ 6 }{ H }_{ 5 }-\overset { \underset { | }{ H } }{ \underset { \overset { || }{ O } }{ C } } +H-\underset { \overset { || }{ O } }{ C } { -C }_{ 6 }{ H }_{ 6 }\overset { alc \ KCN }{ \underset { \Delta }{ \longrightarrow } } { C }_{ 6 }{ H }_{ 5 }-\underset { \overset { | }{ OH } }{ CH } -\underset { \overset { || }{ O } }{ C } -{ C }_{ 6 }{ H }_{ 5 }\)

(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.

Phenyl Acetic acid
Benzyl Magnesium bromide

Propanal into butanone:

(b) Hex-3-yne into hexan-3-one.
Hydration of alkynes in 42% sulphuric acid containg H₂SO₄ as catalyst
\(\underset {Hex-3-yne}{\mathrm{CH}_{3}-\mathrm{CH}_{2}}-\mathrm{C} \equiv \mathrm{C}-\mathrm{CH}_{2}-\mathrm{CH}_{3} \frac{\mathrm{HgSO}_{4}}{\mathrm{H}_{2} \mathrm{SO}_{4} / \mathrm{H}_{2} \mathrm{O}} \)

(c) phenylmethanal into benzoic acid

(d) phenylmethanal into benzoin