Organic Formulation

Determination of the Main Chain

• The longest one containing the principal functional group. If repeated, the one with the highest number of them.
• The longest one containing the highest number of secondary functional groups, in priority order.
• The one with the highest number of double and triple bonds.
• The one with the highest number of double bonds.

Determination of Locants

Numbering is chosen to assign the lowest locants to the following elements in order:

Numerical Prefixes for the Carbon Main Chain

General Nomenclature Rules

Functional Groups

• The suffix indicates the principal functional group, chosen by preference order.
• Secondary functional groups are named as substituents in alphabetical order.
• If there are multiple identical groups, numeral prefixes di, tri, tetra, etc. are used, separated by commas from each other and a hyphen from the name.
• The numbering direction must assign the lowest locant to the principal functional group.

Branches or Radicals (Substituents)

• Side chains are named before the main chain, preceded by their locant with a hyphen and ending in "-yl", or their own functional group prefix ("hydroxy-, carboxy-, alkoxy... etc").
• Multiple identical side chains use prefixes di-, tri-, tetra-, etc.
• Substituents are listed alphabetically, ignoring the multiplier prefix.

Example:

CHO - CH₂ - C(OH)(CH₃) - CH = CH₂

3-hydroxy-3-methylpent-4-enal (Numbering from left to right)

Alkanes (C-C) Suffix -ane

Chains of C and H linked by single bonds. Examples:
CH₃—CH₂—CH₂—CH₃ Butane
CH₃—(CH₂)₇—CH₃ Nonane

Alkenes (C=C) Suffix -ene

Chains with at least one double bond. Examples:
CH₃—CH=CH—CH₃ But-2-ene
CH₃—CH=CH—CH=CH—CH₂—CH₃ Hepta-2,4-diene
CH₂=CH—CH₃ Propene

Alkynes (C≡C) Suffix -yne

Chains with at least one triple bond. Examples:
CH≡C—CH₂—CH₃ But-1-yne
If there are both double and triple bonds, choose the locants that give the lowest numbers for both. If numeration matches from both sides, the double bonds get the lower numbers.
CH≡C—C≡C—CH=CH₂ Hexa-1-en-3,5-diyne

Alicyclic Hydrocarbons

They form closed rings. Represented simply as polygons.

• Cyclopentene (5-sided polygon with one double bond).
• Cyclohexa-1,3-diene (6-sided polygon with two double bonds).

Branches (Radicals)

Chains that lose a hydrogen act as radicals with suffix -yl.
Ex.: CH₄ methane → —CH₃ methyl
Ex.: CH₂=CH₂ ethene → —CH=CH₂ ethenyl (vinyl)

If a radical itself has branches, it is named in parentheses and its numbering starts at the carbon attached to the main chain.
Ex.: —CH(CH₃)—C(CH₃)=CH₂ (1,2-dimethylpropenyl)

Common names for branches:

• —CH(CH₃)₂ Isopropyl
• —CH₂—CH(CH₃)₂ Isobutyl
• —CH=CH₂ Vinyl

Aromatics

Derivatives of benzene. Locants ortho o-(1,2), meta m-(1,3), para p-(1,4) are used.
When benzene acts as a radical, it is named -phenyl.

• o-dimethylbenzene (1,2-dimethylbenzene)
• m-dimethylbenzene (1,3-dimethylbenzene)
• p-ethylmethylbenzene (1-ethyl-4-methylbenzene)

Halides

Halogens are named as substituents (fluoro, chloro, bromo, iodo).
Cl—CH₂—CH₃ Chloroethane
BrCH₂—CHBr—CH₂—CH₃ 1,2-dibromobutane

Alcohols and Phenols (-OH) Suffix -ol

As a substituent, it is named -hydroxy.
CH₃—OH Methanol
CH₃—CH=CH—CH(OH)—CH₂OH Pent-3-en-1,2-diol

Phenol is a derivative of benzene. Examples:
m-hydroxyphenol (benzene-1,3-diol)
3,5-dihydroxy-2-methylphenol
2-phenylphenol

Ethers (-O-) Suffix -ether / -oxy

1) Name the radicals in alphabetical order + -ether.
2) Name the simplest radical as a substituent with the suffix -oxy and the other as the main chain.

• CH₃—O—CH=CH₂ Ethenyl methyl ether / Methoxyethene
• CH₃—CH(OCH₃)—CH₂—CH₃ 2-methoxybutane
• 2-methoxyphenol (Benzene ring with -OH at C1 and -OCH₃ at C2)

Aldehydes (-CHO) Suffix -al

Terminal group. When it is the principal group, numbering starts there. As substituent: formyl-.
CHO—CH₂—CH=CH₂ But-3-enal
CHO—CH(CH₂OH)—CH=CH₂ 2-(hydroxymethyl)but-3-enal
Benzene ring—CHO Benzaldehyde

Ketones (-CO-) Suffix -one

Main chain ends in -one with the lowest possible locant for C=O. As substituent: oxo-.
CH₃—CO—CH₃ Propanone (Dimethyl ketone)
CH₃—CO—CO—C≡C—CH₃ Pent-4-yne-2,3-dione

Carboxylic Acids (-COOH) Suffix -oic acid

Numbering starts at the -COOH group. As substituent: carboxy-.
HCOOH Methanoic acid
CH₃—COOH Ethanoic acid
CH₂=CH—COOH Prop-2-enoic acid
HOOC—CH₂—CH₂—COOH Butanedioic acid

Esters (-COO-) Suffix -oate

The -ic acid suffix is replaced by -oate, followed by the alkyl radical name. As substituent: -oxycarbonyl.
HCOO—CH₂—CH₃ Ethyl methanoate
CH₃—COO—CH₃ Methyl ethanoate

Amines (-NH₂) Suffix -amine

Derivatives of ammonia that lose hydrogens. As substituent: amino-

• Primary: CH₃—CH₂—NH₂ Ethylamine (Ethanamine)
• Secondary and Tertiary: The largest radical ends in -amine and the others are prefixed with "N-".
  CH₃—CH₂—NH—CH₃ N-methylethylamine
• Chains with multiple N (-aza rule):
  CH₃—NH—NH—CH₂—NH—CH₃ 2,3,5-triazahexane

Amides (-CONH₂) Suffix -amide

Derived from acids by substituting -OH with -NH₂. As substituent: carbamoyl-

• Primary: CH₃—CONH₂ Ethanamide
• Secondary and Tertiary: CH₃—CONH—CH₃ N-methylethanamide

Nitriles (-CN) Suffix -nitrile

1) Named as cyanide followed by the radical: CH₃—CN Methyl cyanide
2) Suffix -nitrile added to the main chain: CH₃—CN Ethanenitrile

Nitro Compounds (-NO₂) Prefix nitro-

ALWAYS named as a substituent with the prefix nitro-.
NO₂—CH₂—CH(NO₂)—CH₂—NO₂ 1,2,3-trinitropropane