Nitro compounds — preparation, reduction to amines (Sn - HCl, Fe - HCl, H₂ - Pt)

4.4.3 · Chemistry › Nitrogen-Containing Compounds

1. Nitro compound kya hota hai?

$N + O^{-} = O ⟷ N + = O O^{-}$

3. Main event: Reduction to amines

Figure — Nitro compounds — preparation, reduction to amines (Sn - HCl, Fe - HCl, H₂ - Pt)

3.1 Intermediates (selectivity ke peeche WHY)

Acidic conditions mein reduction in se guzarta hai: $A r - N O_{2} \to A r - N O (nitroso) \to A r - N H O H (hydroxylamine) \to A r - N H_{2}$

3.2 Apna reagent choose karo (80/20)

Reagent	Product	Key point / WHY
Sn/HCl	$A r - N H_{2}$	Classic, complete, lab-friendly
Fe/HCl	$A r - N H_{2}$	Sasta; HCl catalytic hai (Fe ise regenerate karta hai) → industrial favourite
H₂/Pt (Pd/Ni)	$A r - N H_{2}$	Clean, lekin $C = C$ , $C \equiv N$ , $C = O$ bhi reduce karta hai — chemoselective nahi
$S n / H C l$ + di-nitro	dono $N O_{2}$ reduce karta hai	strong, unselective
== $(N H_{4})_{2} S$ / $N a_{2} S$ ==	do mein se EK $N O_{2}$ reduce karta hai	selective mild reductant
== $L i A l H_{4}$ == (aliphatic)	$R - N H_{2}$	aliphatic nitro ke liye great; aromatic ke saath azo compounds deta hai!

4. Common Mistakes (Steel-man)

5. Active Recall

Recall Self-test (hide & answer)

$A r - N O_{2} \to A r - N H_{2}$ ke liye kitne $[H]$ chahiye? Kyun?
$A g N O_{2}$ kyun, $N a N O_{2}$ kyun nahi?
Nitrobenzene ki acidic reduction mein 3 intermediates order mein batao.
Kaunsa reagent do nitro groups mein se sirf ek reduce karta hai?
Aromatic nitro ke liye $L i A l H_{4}$ kyun bura hai?

Recall Feynman: 12-saal ke bachche ko samjhao

Ek nitro group aise hai jaise nitrogen ne do oxygens ka bhaari backpack pehna hua ho — yeh "loaded up" hai. Ise reduce karna matlab hai nitrogen ko chhe hydrogen helpers dena taaki woh oxygens drop kar sake (jo paani banke nikal jaate hain) aur do friendly H arms ugaa sake ( $- N H_{2}$ ). Tin ya iron acid mein chhoti machines hain jo woh hydrogen helpers banate hain; ya tum pure hydrogen gas ko ek metal sponge (Pt) par blow kar sakte ho jo tumhare liye $H_{2}$ split karta hai. Same kaam, teen alag delivery trucks.

6. Connections

Amines — basicity and reactions
Diazonium salts — synthesis from aniline
Electrophilic aromatic substitution (nitration mechanism)
Ambident nucleophiles ( $N O_{2}^{-}$ , $C N^{-}$ )
Oxidation states of nitrogen
Reducing agents in organic chemistry ( $L i A l H_{4}$ , $H_{2}$ /metal, dissolving-metal)

ArNO₂ ko ArNH₂ reduce karne ke liye kitne [H] chahiye aur kyun?

6[H]; N +3→−3 jaata hai (6 electrons), 2 O nikal jaate hain 2H₂O ke roop mein (4H) aur 2H N par add hote hain.

6[H] ka molecular hydrogen mein equivalent kya hai?

3H₂ (Pt/Pd/Ni catalyst ke saath).

Nitroalkane banane ke liye AgNO₂ kyun use karte hain NaNO₂ ki jagah?

NO₂⁻ ambident hai; Ag salt N-bonded nitroalkane deta hai, Na salt O-bonded nitrite ester deta hai.

Nitrobenzene ki acidic reduction mein teen intermediates order mein?

Nitroso (Ar-NO) → hydroxylamine (Ar-NHOH) → amine (Ar-NH₂).

Dinitro compound mein sirf EK nitro group selectively reduce karne ke liye kaunsa reagent?

Ammonium sulfide / Na₂S ((NH₄)₂S) — mild partial reductant.

LiAlH₄ aromatic nitro compound ke saath kya deta hai?

Azobenzene (Ph-N=N-Ph), aniline NAHI.

H₂/Pt hamesha best nitro reducer kyun nahi hai?

Yeh chemoselective nahi hai; yeh C=C, C=O, aur –CN bhi reduce karta hai.

Nitration mein conc. H₂SO₄ kyun chahiye?

HNO₃ se electrophilic nitronium ion NO₂⁺ generate karne ke liye.

Fe/HCl reduction mein HCl ka role (industrial advantage)?

HCl catalytically kaam karta hai (regenerate hota hai), Fe/HCl ko Sn/HCl se sasta banata hai.

m-Dinitrobenzene + (NH₄)₂S ka product?

m-Nitroaniline (sirf ek NO₂ reduce hota hai).

Nitro compounds — preparation, reduction to amines (Sn - HCl, Fe - HCl, H₂ - Pt)

1. Nitro compound kya hota hai?

2. Preparation

2.1 Aromatic — nitration (easy route)

2.2 Aliphatic — do routes