Nomenclature of Organic Compounds — Revision Notes

⚡ 30-Second Revision

Word Root: — Number of carbons (meth-, eth-, prop-, but-, pent-, hex-).
Primary Suffix: — Bond type (-ane, -ene, -yne).
Secondary Suffix: — Principal functional group (-ol, -al, -one, -oic acid, -oate, -amide, -amine, -nitrile).
Prefixes: — Substituents (methyl, ethyl, chloro, bromo, nitro, hydroxy, oxo, amino).
Locants: — Numbers for positions.
Priority Order (Highest to Lowest): — $ext{COOH} > \text{SO}_3\text{H} > \text{COOR} > \text{COX} > \text{CONH}_2 > \text{CN} > \text{CHO} > \text{C}=\text{O} > \text{OH} > \text{SH} > \text{NH}_2 > \text{C}=\text{C} > \text{C}equiv\text{C} > \text{R} > \text{X} > \text{NO}_2$.
Numbering Rule: — Lowest locant to principal functional group $ightarrow$ multiple bond $ightarrow$ substituents.

2-Minute Revision

IUPAC nomenclature provides a systematic way to name organic compounds. Start by identifying the longest continuous carbon chain that contains the principal functional group and any multiple bonds; this is your parent chain.

Assign a 'word root' based on its length (e.g., 'pent-' for 5 carbons). Determine the 'primary suffix' based on carbon-carbon bonds: '-ane' for single, '-ene' for double, '-yne' for triple. Next, identify the highest priority functional group, which dictates the 'secondary suffix' (e.

g., '-ol' for alcohol, '-oic acid' for carboxylic acid). All other functional groups or alkyl groups are treated as 'prefixes' (e.g., 'hydroxy-', 'methyl-'). Number the parent chain to give the principal functional group the lowest possible 'locant' (position number).

If there's a tie, prioritize multiple bonds, then substituents. List prefixes alphabetically before the parent name, each with its locant. Remember to use 'di-', 'tri-' for multiple identical substituents, but ignore them for alphabetization.

For ethers, name as 'alkoxyalkanes', with the smaller alkyl group forming the 'alkoxy' part.

5-Minute Revision

Mastering IUPAC nomenclature involves a step-by-step approach. First, always identify the parent chain or ring. This is the longest continuous carbon chain that *must* include the principal functional group (if any) and the maximum number of multiple bonds.

For cyclic compounds, the ring is usually the parent. Once the parent chain is identified, determine the word root (e.g., 'hex-' for 6 carbons). Next, identify the primary suffix based on saturation: '-ane' for single bonds, '-ene' for double bonds, and '-yne' for triple bonds.

If both double and triple bonds are present, '-ene' comes before '-yne' in the suffix, and numbering prioritizes the first multiple bond encountered. The most crucial step for functionalized compounds is identifying the principal functional group using the IUPAC priority order (Carboxylic acids > Esters > Amides > Nitriles > Aldehydes > Ketones > Alcohols > Amines > Alkenes > Alkynes > Alkanes > Ethers > Halogens > Nitro groups).

This group determines the secondary suffix (e.g., '-oic acid', '-al', '-one', '-ol'). All other functional groups or alkyl groups are treated as prefixes (e.g., 'hydroxy-', 'oxo-', 'amino-', 'methyl-', 'chloro-').

Numbering the parent chain is critical: assign numbers to give the principal functional group the lowest possible locant. If there's no principal functional group, prioritize multiple bonds, then substituents.

For cyclic systems, numbering starts from the carbon bearing the principal functional group or a substituent to achieve the lowest sum of locants. Finally, assemble the name: prefixes (with locants, in alphabetical order, ignoring di/tri/tetra) $ightarrow$ word root $ightarrow$ primary suffix (with locant) $ightarrow$ secondary suffix (with locant).

For example, $ext{CH}_3\text{CH}(\text{OH})\text{CH}_2\text{COOH}$ has a carboxylic acid (higher priority) and an alcohol. The parent chain is 4 carbons (butane), suffix '-oic acid'. The -COOH is C-1, so -OH is at C-3.

Name: 3-hydroxybutanoic acid. For ethers like $ext{CH}_3\text{OCH}_2\text{CH}_3$, name as 'alkoxyalkane', where the smaller alkyl group is the alkoxy part: methoxyethane. Practice with diverse structures, especially polyfunctional and cyclic ones, to solidify these rules.

Prelims Revision Notes

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IUPAC System: — Systematic, unambiguous, universal naming. Preferred over common names.
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Components of IUPAC Name:

* Word Root: Number of carbons in parent chain (meth-1, eth-2, prop-3, but-4, pent-5, hex-6, hept-7, oct-8, non-9, dec-10). * Primary Suffix: Nature of C-C bonds (-ane for single, -ene for double, -yne for triple).

* Secondary Suffix: Principal functional group (e.g., -ol for -OH, -al for -CHO, -one for $>\text{C}=\text{O}$, -oic acid for -COOH, -oate for -COOR, -amide for -CONH$_2$, -amine for -NH$_2$, -nitrile for -CN).

* Prefixes: Substituents (e.g., methyl, ethyl, chloro, bromo, nitro, hydroxy, oxo, amino). * Locants: Numbers indicating positions.

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Steps for Naming:

* 1. Parent Chain Selection: Longest continuous C-chain containing principal functional group $ightarrow$ max multiple bonds $ightarrow$ max substituents. * 2. Principal Functional Group: Identify highest priority functional group (determines secondary suffix).

* 3. Numbering: Assign lowest possible locant to: Principal functional group $ightarrow$ multiple bonds $ightarrow$ substituents. * For -CHO, -COOH, -CN, -COOR, -CONH$_2$: Carbon of functional group is C-1.

* For alkenes/alkynes: Number from end giving first carbon of multiple bond lowest locant. * For cyclic compounds: Start numbering from carbon with principal functional group or substituent to give lowest locants.

* 4. Substituents: Name and list alphabetically (ignoring di, tri, etc.) before parent name. Use prefixes (e.g., di-, tri-) for identical substituents. * 5. Assemble: Prefixes (locants) - Word Root - Primary Suffix (locant) - Secondary Suffix (locant).

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Functional Group Priority Order (Highest to Lowest):

* Carboxylic acids (-COOH) > Sulfonic acids (-SO$_3$H) > Esters (-COOR) > Acid halides (-COX) > Amides (-CONH$_2$) > Nitriles (-CN) > Aldehydes (-CHO) > Ketones ($>\text{C}=\text{O}$) > Alcohols (-OH) > Phenols > Thiols (-SH) > Amines (-NH$_2$) > Ethers (-OR) > Alkenes ($>\text{C}=\text{C}<$) > Alkynes ($-\text{C}equiv\text{C}-$) > Halogens (-X) > Nitro (-NO$_2$) > Alkyl (-R).

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Special Cases:

* Ethers: Alkoxyalkanes (smaller alkyl as alkoxy, larger as alkane). E.g., $ext{CH}_3\text{OCH}_2\text{CH}_3$ is Methoxyethane. * Aromatic Compounds: Substituted benzenes (e.g., Toluene, Phenol, Aniline, Benzoic acid, Benzaldehyde). Ortho-, meta-, para- for disubstituted benzenes.

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Common Mistakes: — Incorrect parent chain selection, wrong numbering, ignoring alphabetical order, misapplying functional group priority.

Vyyuha Quick Recall

To remember the functional group priority order for IUPAC naming (highest to lowest for common NEET groups):

Can Some Elephants Always Name All Kind Animals And Always Have Xylophones?

Carboxylic acids
Sulfonic acids
Esters
Amides
Nitriles
Aldehydes
Ketones
Alcohols
Amines
Alkenes
Halogens (and Hydrocarbons/Alkanes)
Xylophones (just a filler for 'X' or 'eXtra' to complete the sentence, but reminds you of the lower priority groups like halogens and alkyls).