IUPAC Nomenclature Notes

IUPAC Nomenclature

Introduction

  • IUPAC nomenclature involves a systematic way of naming organic compounds.

  • The general structure for IUPAC names is: 2° Prefix + 1° Prefix + Word Root + 1° Suffix + 2° Suffix.

Types of Compounds

  • Saturated Compounds

  • Unsaturated Compounds

  • Cyclic Compounds

  • Bicyclo Compounds

  • Spiro Compounds

  • Monofunctional Group Compounds

  • Polyfunctional Group Compounds

  • Ethers

  • Benzene Derivatives

Components of IUPAC Nomenclature

  1. 2° Prefix:

  • Tells about side chains, branching, or substituents in an organic compound.

  • Common substituents:

    • -X (halo): -F (fluoro), -Cl (chloro), -Br (bromo), -I (iodo)

    • -NO_2 (nitro)

    • -N=O (nitroso)

    • -O-N=O (nitrite)

    • -R (alkyl):

      • -CH_3 (methyl)

      • -CH2CH3 (ethyl)

      • -CH2CH2CH_3 (propyl)

      • -CH(CH3)2 (isopropyl)

      • -CH2CH2CH2CH3 (butyl or n-butyl)

      • -CH3CHCH2CH_3 (secondary butyl or sec-butyl)

      • -CH2CH(CH3)_2 (isobutyl)

      • -C(CH3)3 (tertiary butyl or tert-butyl)

      • -CH2CH2CH2CH2CH_3 (n-pentyl)

      • -CH3CH2CH2CH(CH3)_2 (sec-pentyl)

      • -CH3CH2C(CH3)2CH_3 (neo-pentyl)

      • -CH3CHCH2CH2CH3 (isopentyl)

    • Phenyl (C6H5)

    • Benzyl (C6H5CH_2)

    • Vinyl (CH_2=CH)

    • Allyl (CH2=CH-CH2)

    • Ethynyl (CH≡C)

  1. 1° Prefix:

  • Indicates whether the compound is a closed chain or ring.

  • Cyclo

  • Bicyclo: Two cycles are fused into one another, having more than one common carbon.

  • Spiro: Two cycles are fused into one another, having one common carbon.

  1. Word Root:

  • Indicates the number of carbon atoms in the main chain.

    • 1: meth

    • 2: eth

    • 3: prop

    • 4: but

    • 5: pent

    • 6: hex

    • 7: hept

    • 8: oct

    • 9: non

    • 10: dec

  1. 1° Suffix:

  • Indicates saturation or unsaturation in the compound.

    • Single bond: -ane

    • Double bond: -ene (two double bonds: -diene; three: -triene)

    • Triple bond: -yne (two triple bonds: -diyne)

    • Combination: -eneyne, -dienyne, -enediyne

    • Vowel Rules: Two vowels can't come together, or one vowel and one 'y' can't come together; the former vowel is canceled.

  1. 2° Suffix:

  • Tells about the functional group in the compound (discussed later).

Nomenclature of Saturated Compounds

  • Only 3 Steps:

    1. Selection of Parent Chain

    2. Numbering of Parent Chain

    3. Naming of Compound

Selection of Parent Chain

  • Rule 1: The carbon chain having the maximum number of carbon atoms will be taken as the parent chain.

  • Rule 2: When more than one parent chain is present, select the carbon chain with more substituents.

Numbering of Parent Chain (PC)

  • Rule 1: Numbering is done in such a way that substituents get the lowest locant number.

  • Rule 2: In the case of more than one substituent, follow the first point principle.

  • Rule 3: If the first point difference rule fails, then numbering is done alphabetically.

Naming of Compound

  1. The locant number of the substituent must be before the name of the substituent.

  2. A hyphen is used to separate numbers and letters.

  3. A comma is used to separate numbers.

  4. No gap between letters.

  • Example: 2-methyl

  • Example: 2,2-dimethylpentane

  • Rule 3: Always follow alphabetical order in naming substituents.

  • Example: 3-ethyl-2-methylpentane

  • Rule 4: Use di, tri, tetra, penta, etc., in the case of more than one identical substituent.

Note on di, tri, tetra

  • When di, tri, tetra are used for normal substituents, they are not considered for alphabetical order. However, when used for complex substituents, they are considered.

  • Example: 4-ethyl-2,3-dimethylhexane

Complex Substituents

  • 4-(1-methylethyl)heptane

  • 4-(1-methylpropyl)heptane

  • IUPAC name of Isopropyl =(1-methylethyl).

  • 2-Bromo-5-(1-methylethyl)octane

  • 2-Bromo-5-ethyl-3-methyl-6-(1-methylpropyl)nonane

  • 4-(1,1-dimethylethyl)-5-ethyl-3-methyloctane

Nomenclature of Unsaturated Compounds

Selection of Parent Chain

  • Rule 1: The parent chain contains the maximum number of multiple bonds, irrespective of the longest carbon chain.

  • Rule 2: If the number of multiple bonds is the same, then select the chain that has the maximum number of carbon atoms.

  • Rule 3: If the above two rules fail, then select the carbon chain as the parent chain that contains more double bonds than triple bonds.

  • Rule 4: If the above three rules fail, then select the carbon chain as the parent chain that contains the maximum number of substituents.

Numbering of Parent Chain

  • Rule 1: Multiple bonds should get the lowest locant number.

  • Rule 2: When the locant number is the same from both ends, the numbering should be done from the end that gives the lowest locant number to the double bond.

  • Rule 3: If the above two rules fail, then select the numbering which gives the lowest locant to the substituent.

  • Rule 4: If the above three rules fail, then follow alphabetical order.

  • 3-butylpent-1-ene-4-yne

  • 3-methylhepta-1,5-diene

  • Penta-1,3-diene

  • Hepta-1,3,5-triene

  • 3-ethyl-4-methylhexa-1,5-diene

  • Pent-2-yne

  • 3-propylhexa-1,5-diyne

  • Hepta-2,4-diyne

  • 3-ethyl-5-methylhepta-1,6-diyne

  • 2-Bromo-2-ethyl-4-methylpenta-1,3-diyne

  • Hepta-1,3-diene-6-yne

Nomenclature of Cyclic Compounds

  • Cyclopropane

  • Cyclobutane

  • Cyclopentane

  • Cyclohexane

  • 1-methylcyclopropane

  • 1,2-dimethylcyclobutane

  • 1,1-dimethylcyclobutane

  • 1,1,2-trimethylcyclobutane

  • If more than one substituent, follow alphabetical order.

  • 1-bromo-2-chlorocyclobutane

  • 1-bromo-3-chlorocyclopentane

  • 1-ethyl-2-methylcyclobutane

  • 1-Bromo-2-chloro-3-fluorocyclohexane

  • Rule 3: If more than two substituents are present, then follow the lowest locant rule.

  • 4-Bromo-2-ethyl-1-methylcyclohexane

  • 2-Bromo-1-chloro-4-methylcyclohexane

  • 2-Bromo-1-Chloro-3-Fluoro-4-iodocyclohexane

  • Rule 4: In the case of a cyclic compound, the parent chain is the chain (cyclic or open) containing more carbon atoms.

  • 2-Chloropentylhexane

  • 1-(1-methylpropyl)cyclopentane

  • 1-(1-methylbutyl)cyclopentane

  • 4-cyclobutyl-2-cyclopentylhexane

  • Cycloprop-1-ene

  • Cyclobut-1-ene

  • Cyclobuta-1,3-diene

  • Cyclopenta-1,3-diene

  • Rule 5: If a multiple bond is present, then the parent chain must contain the maximum number of multiple bonds.

  • 1-cyclopentyleth-1-ene

  • 6-ethyl-3,3-dimethylcyclohex-1-ene

  • 1,2,3-trimethylcyclopent-1-ene

  • 1,2-dimethylcycloprop-1-ene

  • 2-cyclobutylpentane

  • 1,2-dimethylcyclohex-1-ene

  • 1-Cyclopropylcyclohexane

Bicyclo Compounds

  • Bicyclo[4.4.0]decane

  • Bicyclo[4.2.0]octane

  • Bicyclo[1.1.0]butane

  • Bicyclo[2.2.2]octane

  • Bicyclo[3.2.1]octane

  • Bicyclo[2.2.1]heptane

  • Bicyclo[2.1.0]pentane

Spiro Compounds

  • Spiro[3.3]heptane

  • Spiro[2.4]heptane

  • Spiro[3.4]octane

  • Spiro[3.4]oct-6-ene

  • 5, 6-dimethylspiro[3.4]octane

  • 1,2-dimethylspiro[3.3]heptane

Seniority Table - Functional Groups

Functional Group

Prefix

Suffix

-COOH

Carboxy

-oic acid

-SO_3H

Sulfo

-sulfonic acid

Anhydride

N/A

-oic anhydride

-COOR (Ester)

Alkoxycarbonyl

alkyl-oate

-COX (Acid Halide)

Haloformyl

-oyl halide

-CONH_2 (Amide)

Carbamoyl

-amide

-CN (Nitrile)

Cyano

-nitrile

-NC (Isocyanide)

Isocyano

-carbylamine

-CHO (Aldehyde)

Formyl/Oxo

-al

>C=O (Ketone)

Oxo/Keto

-one

-OH (Alcohol)

Hydroxy

-ol

-SH (Thiol)

Mercapto

-thiol

-NH_2 (Amine)

Amino

-amine

Examples

  • Butane-1-oic acid

  • 2,2-dimethylbutane-1-oic acid

  • Butane-1,4-dioic acid

  • Propane-1,2,3-tricarboxylic acid

  • Cyclohexane-1,2,3-tricarboxylic acid

  • Cyclohexane-1,2,3,4-tetracarboxylic acid

  • 2-propylhexane-1-oic acid

  • Butane-4-sulfonic acid

  • Cyclohexane-1,3-disulfonic acid

  • 2-methylpropane-1-nitrile

  • 3,3-dimethylbutane-1-nitrile

  • Cyclohexane-1,2-dicarbonitrile

  • 2-Bromocyclohexa-1,5-diene-1,3-dicarbonitrile

  • Propane-1,3-dial

  • Cyclohexane-1,2-dicarbaldehyde

  • Cyclohexa-1,5-diene-1-carbaldehyde

  • 3-methylbut-2-ene-1-amide

  • Propane-1,3-diamide

  • Cyclohexane-1-carbamide

  • Cyclohexane-1,4-dicarbamide

  • 3-propylpent-4-ene-1-amide

  • N-ethylprop-2-ene-1-amide

  • N-ethyl-N,3-dimethylbutane-1-amide

  • Butane-1-oyl chloride

  • Pentane-1,5-dioyl chloride

  • Cyclohexane-1,3-dicarbonyl chloride

  • Cyclohex-3-ene-1-oyl chloride

  • Carbonyl chloride

  • 5-Bromohex-2-ene-1,6-dioyl bromide

  • Ethane-1-oic anhydride

  • Ethanoic propanoic anhydride

  • Methylpropane-1-oate

  • Ethylbutan-1-oate

  • Cyclohexylbutane-1-oate

  • Ethyl-2-methylbutane-1-oate

  • 2-methylcyclohexane-1-carbylamine

  • Cyclopropane-1,2-dicarbylamine

  • Cyclohexane-1-one

  • Cyclohexane-1,4-dione

  • Pentane-2,4-dione

  • Pent-1-ene-3-one

  • Cyclohexan-1-ol

  • Cyclohexane-1,2-diol

  • 3,5-dimethylcyclohexan-1-ol

  • Cyclohex-3-ene-1-ol

  • Cyclohexane-1-thiol

  • Pentane-1-thiol

  • Hex-4-ene-2,3-dithiol

  • Ethane-1-amine

  • Pentane-2-amine

  • Hexa-3,5-diene-1-amine

  • N-ethylpropane-1-amine

  • N-ethyl-N-methylbutane-1-amine

  • 3-Chloroformylcyclopropane-1,2-dicarboxylic acid

  • 3-Carbamoylcyclohexane-1-carboxylic acid

  • 3-Cyanopropane-1-oic acid

  • 5-Oxopentane-1-oic acid

  • 2-Formylpentane-1,5-dioic acid

  • 2,3-dihydroxypropane-1-al

  • 2-Hydroxypropane-1,2,3-tricarboxylic acid

  • 5-Oxohexa-1,3-dial

  • 5-Oxohex-3-ene-1-al

  • 3,5-Dioxopentane-1-oic acid

  • 3-Formyl-6-oxo-4-sulfohexane-1-oic acid

  • 7-Oxohept-4-ene-1-amide

  • 4-Cyanobutane-1-amide

Ether Nomenclature

Functional Group

Prefix

Suffix

-OR

Alkoxy

None

  • Methoxyethane

  • 1-methoxypropane

  • 2-methoxypropane

  • 1-ethoxyethane

  • 3-Bromo-6-chloro-2-propoxycyclohexane-1-ol

  • 3-ethoxybut-1-ene

Benzene Derivatives

  • Benzene Carboxylic acid

  • Common name - Benzoic acid

  • Benzene carbaldehyde

  • Common name - Benzaldehyde

  • Benzene Carbonitrile

  • Benzonitrile

  • Benzenol (Phenol)

  • Benzene amine (Aniline)

  • Methyl Benzene (Toluene)

  • Benzene carboxamide (Benzamide)

  • Benzene Carbonyl chloride (Benzoyl chloride)

Introduction

  • IUPAC nomenclature is a systematic way of naming organic compounds.

  • General structure: 2° Prefix + 1° Prefix + Word Root + 1° Suffix + 2° Suffix.

Types of Compounds

  • Saturated, Unsaturated, Cyclic, Bicyclo, Spiro, Monofunctional, Polyfunctional, Ethers, Benzene Derivatives

Components

  1. 2° Prefix: Substituents (halo, nitro, alkyl, etc.)

  2. 1° Prefix: Ring structures (cyclo, bicyclo, spiro)

  3. Word Root: Number of carbons (meth, eth, prop, etc.)

  4. 1° Suffix: Saturation (-ane, -ene, -yne)

  5. 2° Suffix: Functional group

Saturated Compounds

  1. Parent chain selection (longest chain, more substituents)

  2. Numbering (lowest locant, first point principle, alphabetical)

  3. Naming (locant-substituent, hyphen, comma, alphabetical order)

Unsaturated Compounds

  1. Parent chain (max multiple bonds, max carbons, more double bonds)

  2. Numbering (lowest locant for multiple bonds, then double bond, then substituent, then alphabetical)

Cyclic Compounds

  • Follow alphabetical order and lowest locant rule for substituents.

  • Parent chain is the chain (cyclic or open) with more carbon atoms.

Bicyclo Compounds

  • Naming: Bicyclo[x.y.z]alkane

Spiro Compounds

  • Naming: Spiro[x.y]alkane

Functional Groups

  • Use a Seniority Table to determine prefixes and suffixes (Carboxylic acid, Sulfonic acid, Ester, etc.)

Ether Nomenclature

  • Use "Alkoxy" as a prefix.

Benzene Derivatives

  • Common names for basic structures (Benzoic acid, Benzaldehyde, Phenol, Aniline, Toluene, etc.).