Alkenes and Alkynes Nomenclature

Naming Alkenes

• The longest continuous chain must include BOTH alkene carbons.
• Even if a longer chain exists, the chain with the alkene carbons is prioritized.
• The longest carbon chain is only 5 carbons long when it contains BOTH alkene carbons.
• To name an alkene, indicate where the double bond is, with the double bond receiving the lowest possible number.
• Example: 2-propyl-1-pentene or 2-propylpent-1-ene.
• When dealing with more than one alkene group, the substance is named accordingly, for example: 2-methyl-1,3-butadiene

Cis and Trans Alkenes

• Cis alkenes have hydrogens on the same sides of the double bond.
• Trans alkenes have hydrogens on opposite sides of the double bond.
• Cis and Trans alkenes have different properties.

Naming Alkynes

• The longest continuous carbon chain should contain both alkyne carbons.
• Example: 3-propyl-1-heptyne
• Combination molecules of alkenes and alkynes are named as an "enyne".
• 5-methyl-1-hepten-6-yne is an example, where the 1st double bond and 2nd triple bond are numbered.

Naming Alkyl Halides

• Halogen atoms, when naming, are treated as regular branches
• For example: 3-chloro-2-methylpentane.

Naming Benzene Compounds

• Monosubstituted benzenes have common names like chlorobenzene, nitrobenzene, and cyanobenzene.
• Trivial names also exist, such as phenol, aniline, benzoic acid, and toluene.
• Systematic (IUPAC) names exist, such as hydroxybenzene, aminobenzene, carboxybenzene, and methylbenzene.
• Disubstituted benzenes include 1,2-dimethylbenzene, 1,3-dimethylbenzene, and 1,4-dimethylbenzene.
• These can also be named ortho-xylene, meta-xylene, and para-xylene, o-xylene, m-xylene, and p-xylene, respectively.
• Polysubstituted benzenes are named with numbers indicating the positions of the substituents.
• Examples include 4-bromo-2-methylnitrobenzene, 5-bromo-2-nitrotoluene, and 3-methyl-4-nitrobromobenzene.
• Further examples include 1,4-dimethyl-2-propylbenzene, 4-methyl-2-propyltoluene, and 2,5-dimethylpropylbenzene.
• Another example is 2-methyl-1,3,5-trinitrobenzene or 2,4,6-trinitrotoluene.

Naming Alcohols

• The longest continuous chain containing the -OH group is used to name alcohols.
• Propan-1-ol is a primary alcohol.
• Propan-2-ol is a secondary alcohol.
• Examples of complex alcohols include 4-methyl-1,2,4-pentanetriol and 4-methylpentane-1,2,4-triol.

Naming Aldehydes

• The aldehyde group is always in a terminal position.
• Examples of aldehydes include methanal, ethanal, and benzaldehyde.
• Also examples include methylpropanal, 2,2-dimethylbutanal, and butanal.
• The -CHO group is always where numbering starts.

Naming Ketones

• The aldehyde group is always in a terminal position.
• The ketone group is always in an internal position.
• An example is 2,6-dimethyl-4-heptanone or 2,6-dimethylheptan-4-one

Naming Carboxylic Acids

• Carboxylic acid group is always in a terminal position.
• Examples include butanoic acid (butyric acid) and propanoic acid (propionic acid).
• Additional examples include 2-Methylpentanoic acid (B-Methylvaleric acid), and 3-Chloropropanoic acid (y-Chloropropionic acid).

Naming Nitriles

• Nitriles contain the cyano group, -C≡N
• Examples for Nitriles:
  • Ethyl cyanide or Propiononitrile, IUPAC name: Propane nitrile
  • Vinyl cyanide or Acryl nitrile, IUPAC name: Prop-2-ene nitrile
  • Isopropyl cyanide or Isobutyl r o nitrile, IUPAC name: 2-Methyl popane nitrile
  • Tolyl cyanide p-toluonitrile, IUPAC name: p-toluenenitrile

Naming Esters

• Esters are involved in the Fischer esterification reaction: alcohol + carboxylic acid → ester + H2O
• Some examples include Methyl ethanoate and Ethyl propanoate.