IUPAC nomenclature — alkanes, alkenes, alkynes, aromatics, alcohols, ethers, aldehydes, ketones, acids, esters, amines,
1. The Skeleton: Root Words (chain length)
| C | Root | C | Root |
|---|---|---|---|
| 1 | meth | 6 | hex |
| 2 | eth | 7 | hept |
| 3 | prop | 8 | oct |
| 4 | but | 9 | non |
| 5 | pent | 10 | dec |
2. The Bonds: Suffix for unsaturation
The position of the multiple bond is given by the lower-numbered carbon it starts on.
3. The Functional Group: The Principal Characteristic Group
Seniority (high → low). The one highest on this list = suffix:
| Rank | Group | Suffix | Prefix (if not senior) |
|---|---|---|---|
| 1 | Carboxylic acid –COOH | -oic acid | carboxy |
| 2 | Ester –COOR | -oate | alkoxycarbonyl |
| 3 | Amide –CONH₂ | -amide | carbamoyl |
| 4 | Nitrile –C≡N | -nitrile | cyano |
| 5 | Aldehyde –CHO | -al | oxo / formyl |
| 6 | Ketone >C=O | -one | oxo |
| 7 | Alcohol –OH | -ol | hydroxy |
| 8 | Amine –NH₂ | -amine | amino |
| — | Ether –O– | (never suffix) | alkoxy |
| — | Halide –X | (never suffix) | fluoro/chloro/bromo/iodo |
4. The Master Algorithm (HOW to name anything)
5. Worked Examples (each step justified)
6. Common Mistakes (Steel-manned)
7. Active Recall
Recall Q: In
but-3-en-1-ol, why does the OH get C1 instead of the C=C getting low numbers? Because –OH is the principal characteristic group (senior to a C=C), so it must receive the lowest locant; numbering direction is decided by the suffix group first.
Recall Q: Which two groups can NEVER be a suffix?
Ethers (alkoxy-) and halides (halo-) — they are always cited as prefixes.
Recall Q: Name
. 4-oxobutanoic acid (COOH senior → C1; CHO → 4-oxo prefix).
Recall Feynman: explain to a 12-year-old.
Imagine a train. The engine is the most important wagon (the strongest functional group — like the acid). You always count seats starting from the engine so it's seat #1. The middle name tells you how many wagons (carbons). Stickers on the wagons (chlorine, methyl bits) are listed in alphabetical order at the front of the name. Bumps where wagons are joined tightly (double/triple bonds) get a number too. Follow the same rule every time, and everyone in the world builds the exact same train from your description.
Flashcards
Root word for 5 carbons
Suffix for a ketone
Suffix for carboxylic acid
Prefix for an ether group –OR
Prefix for –Cl
Highest priority functional group for suffix selection
Two groups that are only ever prefixes
Retained IUPAC name for C6H5OH
Retained IUPAC name for C6H5NH2
IUPAC name of CH3OCH2CH3
IUPAC name of CH3CHClCH3
IUPAC name of CH3CH(OH)CH2CH3
IUPAC name of CH2=CHCH2CH2OH
Do "di/tri" count when alphabetizing substituents?
The three name slots in order
Suffix for an aldehyde
What locant does the COOH/CHO carbon always get?
Numbering rule when a senior suffix group is present
Benzene + CHO retained name
Suffix for an amine
Connections
- Degree of Unsaturation — counting C=C, C≡C, rings before naming
- Functional Groups Overview — what each suffix/prefix represents
- Isomerism — different names ⇒ different structures, the uniqueness guarantee
- Priority and Seniority Rules (CIP vs IUPAC)
- Aromatic Compounds — Benzene Derivatives
- Reaction Mechanisms in GOC — naming products correctly
Concept Map
Hinglish (regional understanding)
Intuition Hinglish mein samjho
Dekho yaar, IUPAC nomenclature basically ek grammar hai molecules ke liye. Pehle har compound ke 10-10 trivial naam hote the (acetic acid, vinegar...) — confusion hi confusion. IUPAC ne ek fixed rule bana diya: ek structure ka sirf ek hi sahi naam, aur ek naam se sirf ek hi structure banega. Naam ke teen parts hote hain: Prefix (substituents jaise chloro, methyl), Root (longest chain me kitne carbon — meth, eth, prop, but, pent...), aur Suffix (sabse important functional group — -ol, -al, -one, -oic acid).
Sabse bada concept yeh hai: agar molecule me kai functional groups hain, to sirf sabse senior wala suffix banta hai, baaki sab prefix ban jaate hain. Priority order yaad rakho: Acid > Ester > Amide > Nitrile > Aldehyde > Ketone > Alcohol > Amine. Aur ether/halide kabhi bhi suffix nahi bante — woh hamesha prefix (alkoxy, chloro). Yeh seniority isliye chahiye taki naam unique rahe.
Numbering ka golden rule: chain ko aise number karo ki senior group ko sabse chhota locant mile. Bahut log galti karte hain — woh double bond ko low number dene lagte hain. Galat! Jaise CH2=CH-CH2-CH2-OH me OH senior hai, isliye OH wale end se C1 start karenge → but-3-en-1-ol, na ki but-1-en-4-ol. Acid aur aldehyde ka carbon to hamesha C1 hi hota hai automatically.
Practice ka 80/20 funda: bas algorithm rato — (1) senior group dhoondo, (2) longest chain jisme woh group ho, (3) low locant ke liye number karo, (4) substituents alphabetical, (5) jod do. Di/tri ko alphabet me mat ginna. Yeh 6 steps har question solve kar denge, chahe alkane ho ya complex acid.