Functional groups and homologous series — Hinglish notes

4.1.3 · Chemistry › General Organic Chemistry (GOC)

1. Functional Groups

Ek chhota sa group reactivity kyun control karta hai? C–C aur C–H bond strong, nonpolar, aur chemically lazy hoti hai. Reactivity ke liye ek electron imbalance chahiye: ek $π$ -bond (extra reactive electron cloud), ek lone pair, ya ek polar bond (electronegativity difference, jaise C–O, C=O, C–X). Yeh features functional group mein hote hain, isliye reactions wahan hoti hain.

Common ones kaun se hain?

Group	Structure	Class name	Suffix / Prefix
C=C	alkene	-ene
C≡C	alkyne	-yne
–OH	hydroxyl	alcohol	-ol
–O–	ether	alkoxy-
–CHO	aldehyde	-al
>C=O	ketone	-one
–COOH	carboxylic acid	-oic acid
–COOR	ester	-oate
–X (F,Cl,Br,I)	haloalkane	halo-
–NH₂	amine	-amine
–C≡N	nitrile	-nitrile
–NO₂	nitro	nitro-

2. Homologous Series

Hum ise kaise pehchaante hain? Char signatures:

Same general formula. Jaise alkanes $C_{n} H_{2 n + 2}$ , alcohols $C_{n} H_{2 n + 1} O H$ .
Consecutive members ke beech $- C H_{2} -$ (mass $14$ ) ka constant difference.
Physical properties mein gradation (smooth trend) — boiling point, density dheere-dheere badhti hai jab $n$ badhta hai (zyada surface area → stronger van der Waals forces).
Same chemical properties — kyunki functional group identical hai.

Figure — Functional groups and homologous series

3. Yeh kyun matter karta hai (the 80/20)

Jab ek baar tumhe pata ho ki –COOH acidic hai, –OH H-bonds deta hai aur Na se react karta hai,

C=O electrophilic hai, etc., toh tum ek nayi molecule ka behaviour sirf uska group dekh ke predict kar sakte ho. Tumhe har molecule ke liye dobara nahi seekhna — tum family ke hisaab se seekhte ho.

Recall Feynman: ek 12-saal ke bachche ko explain karo

Socho ek lamba boring stick (carbon chain) hai jis par ek chhota sa magic button laga hai (functional group). Stick zyada kuch nahi karta — lekin button dabane par hamesha same trick hoti hai, chahe stick chhoti ho ya lambi. Homologous series bas "badhti hui lambaai ki sticks par same button" hai. Lambi sticks bhaari aur chipchipahati hain (higher boiling point), lekin woh abhi bhi same button-trick karte hain.

Flashcards

Functional group kya hota hai?

Ek specific atom/group of atoms jo molecule ki characteristic chemical reactions ke liye responsible hota hai.

Functional group reactivity control kyun karta hai (chain nahi)?

C–C/C–H bonds strong aur nonpolar (lazy) hoti hain; reactivity ke liye π-bonds, lone pairs, ya polar bonds chahiye, jo functional group mein hote hain.

Homologous series define karo.

Same functional group wale compounds ki ek family jisme har member agle se –CH₂– (mass 14) se different hota hai.

Alkanes / alkenes / alcohols ka general formula.

CₙH₂ₙ₊₂ / CₙH₂ₙ / CₙH₂ₙ₊₁OH.

Homologous series ke consecutive members ke beech constant mass difference kya hota hai?

14 (ek CH₂ unit).

Homologous series mein boiling points dheere-dheere kyun badhte hain?

Lambi chains → bada polarizable surface → stronger London (van der Waals) forces → alag karne ke liye zyada energy.

Suffix for: aldehyde, ketone, carboxylic acid, alcohol.

-al, -one, -oic acid, -ol.

Ethanol vs dimethyl ether (dono C₂H₆O) Na ke saath — same?

Nahi; ethanol (–OH) H₂ release karta hai, ether (–O–) nahi karta. Different functional groups (functional isomers).

Homologous series mein kya CONSTANT rehta hai vs kya CHANGE hota hai?

Same chemical properties (same group); physical properties n ke saath dheere-dheere change hoti hain.

Connections

Hydrocarbons — inert skeleton jo functional groups carry karta hai
IUPAC Nomenclature — suffixes/prefixes inhi groups se aate hain
Isomerism — functional isomers (same formula, different group)
Inductive and Mesomeric Effects — chain length group reactivity ko kaise tune karti hai
Intermolecular Forces — boiling-point gradation explain karta hai
Oxidation of Alcohols — alcohol→aldehyde→acid ladder