4.4.4
Dono groups mein same do atoms hain — carbon aur nitrogen ek triple bond se jude hue — phir bhi ye door ke rishtedaar ki tarah behave karte hain. Poora raaz yeh hai: kaunsa atom baaki molecule (R) se bonded hai .
Ek cyanide (nitrile) mein, R carbon se bonded hota hai: R − C ≡ N
Ek isocyanide (isonitrile) mein, R nitrogen se bonded hota hai: R − N + ≡ C −
Connectivity ka yeh ek hi difference smell, hydrolysis products, reduction products, aur bonding picture sab decide karta hai. Connectivity samajh lo aur baaki sab apne aap nikal aayega.
Definition Cyanide (Nitrile)Ek organic compound jisme functional group − C ≡ N carbon atom R se attached hai.
General formula: R − C N alkanenitrile (CN ka C count karo). Common name = alkyl cyanide .
Example: C H 3 C N
Definition Isocyanide (Isonitrile / Carbylamine)Ek organic compound jisme group − N ≡ C nitrogen R se attached hai.
General formula: R − N C alkyl isocyanide ya alkyl carbylamine kehte hain.
Example: C H 3 N C
Note karo carbon count trick: C H 3 − C N ethane nitrile hai (2 C). Lekin wahi C H 3 methyl cyanide (common name) mein sirf alkyl part ko name karta hai.
Intuition Isocyanide carbon kyun special haiElectrons draw karo. R − C ≡ N R − N + ≡ C : − ⟷ R − N + = C 2 − ? .. R − N + ≡ C − : terminal carbon ek lone pair aur ek formal negative charge carry karta hai aur yeh divalent (bivalent carbon, ek carbene-jaisa centre) hai. Woh lone-pair carbon ek isocyanide ka reactive, nucleophilic, aur badbodar dil hai.
H 3 C − N ≡ C
N: 5 valence − 0 − 2 1 ( 8 bonding ) = 5 − 4 = + 1
C (terminal): 4 valence − 2 − 2 1 ( 6 ) = 4 − 2 − 3 = − 1
Common mistake Steel-man: "KCN aur AgCN dono same product dene chahiye, dono cyanides hain!"Kyun sahi lagta hai: dono salts mein C N − Fix: yeh donor atom ki availability ke baare mein hai. KCN mein ion essentially free hai → softer carbon end R–X ke soft carbon ko attack karta hai (HSAB) → R–CN. AgCN mein, silver covalently carbon se bonded hai, C lone pair ko cage kar deta hai , isliye sirf nitrogen ka lone pair free hai → R–NC. Same ion, lekin alag kaunsa end available hai .
C H 3 C H 2 C N Step 1: Identify karo: yeh nitrile hai (C ethyl se bonded hai). Kyun? Connectivity C 2 H 5 − C ≡ N Step 2: Nitrile rule apply karo: R, C pe rehta hai, N N H 3 Kyun? R–C bond hydrolysis mein nahi tuta.
Step 3: Product = C H 3 C H 2 C O O H + N H 3 Propanoic kyun? Nitrile C samet kul teen carbons hain.
C H 3 N C Step 1: Isocyanide (R = methyl on N). Kyun? Likha hai R–NC.
Step 2: 4 H add karo. N pe R rehta hai; baahri C, N pe C H 3 Kyun? N–R bond bachta hai; carbon sirf H gain karta hai.
Step 3: Product = C H 3 − N H − C H 3 2° kyun? Nitrogen ab do carbon groups carry karta hai.
Worked example Worked — smell + carbylamine se do unlabeled bottles distinguish karoBottle A halki fruity smell deta hai → likely ek nitrile hai. Bottle B bahut zyada badbu/unbearable smell deta hai → isocyanide hai.
Kyun? Isocyanides badnaam roop se, bahut offensive smell dete hain — yeh carbylamine test ka basis hai jo primary amines ke liye use hota hai (sirf 1° amines + CHCl₃ + KOH foul isocyanide dete hain).
Common mistake Steel-man: "Dono ke reduction se primary amine milna chahiye kyunki dono mein ek N hai."Kyun sahi lagta hai: reduction se usually amines bante hain, aur ek nitrogen hai. Fix: amine ki degree is baat pe depend karti hai ki N pe kitne R groups aate hain. Nitrile N ko sirf naya C H 2 aur ek C H 3
Property
Cyanide R − C ≡ N
Isocyanide R − N ≡ C
R attached to
Carbon
Nitrogen
R–X se reagent
KCN AgCN
Hydrolysis
R − C O O H + N H 3 R − N H 2 + H C O O H
Reduction
R − C H 2 N H 2 R − N H − C H 3
Smell
mild/pleasant
foul, characteristic
Terminal C
normal
lone pair, − 1
Recall Feynman: ek 12-saal ke bachche ko explain karoSocho ek do-bachon wala see-saw (carbon aur nitrogen hath pakad ke tight = triple bond). Tum, bada group R, kisi bhi bachche ke saath hath pakad sakte ho. Agar tum carbon bachche ka free hath pakdo, woh cyanide hai. Agar tum nitrogen bachche ka hath pakdo, woh isocyanide hai. Jab baad mein unhe paani mein dubao (hydrolysis) ya snacks do (hydrogen), jo bhi tumhara hath pakde hua tha woh tumse attached rehta hai — isliye bilkul alag final dost milte hain. Aur, nitrogen-wala version bahut badbu deta hai!
Mnemonic Reagents aur products yaad karo"sil-V-er isocyanide deta hai, K cyanide deta hai" — AgCN → iso (silver = sneaky N attack), KCN → cyanide (K = Carbon-Kind).
Hydrolysis: "NitR ile → caRboxylic acid" (dono mein R, C pe hai, COOH ending). Iso → amine (R, N pe → amine).
Reduction degree: C → CH₂ → 1° , iso mein N pe extra group → 2° .
Structurally cyanide aur isocyanide mein kya fark hai? Cyanide mein R carbon se bonded hai (R − C ≡ N R − N ≡ C
Kaun sa reagent R–X ko cyanide banata hai, aur kaun sa isocyanide? KCN → cyanide (C-attack); AgCN → isocyanide (N-attack).
AgCN isocyanide kyun deta hai? Ag covalently carbon se bonded hai, C lone pair block ho jaata hai, isliye nitrogen ka lone pair attack karta hai.
R − C ≡ N R − C O O H + N H 3
R − N ≡ C R − N H 2 + H C O O H
Nitrile R − C N Primary amine R − C H 2 − N H 2
Isocyanide R − N C Secondary amine R − N H − C H 3
Isocyanide ke terminal carbon pe formal charge kya hai? − 1
Woh test kaun sa hai jo primary amines detect karne ke liye isocyanide formation use karta hai? Carbylamine (isocyanide) test: 1° amine + CHCl₃ + alc. KOH → foul-smelling isocyanide.
C H 3 C N Ethanenitrile (acetonitrile / methyl cyanide).
C N − Yeh carbon ya nitrogen dono se donate kar sakta hai, cyanides ya isocyanides deta hai.
Alkyl halides and SN2 substitution — ambident nucleophile attackAmines preparation and properties — reduction productsCarboxylic acids — nitrile hydrolysis routeCarbylamine reaction — test for primary aminesHSAB principle — why soft C vs hard N attacksAmides and dehydration — alternative nitrile synthesis
Charge-separated divalent carbon
