How would you name the following compounds? (i) CH3 - CH2 - Br (ii) H - CHO (ii) CH3 - (CH2) 3 - CH = CH2 (1) (i) Bromomethane (ii) Methanol (iii) Hexene (2) (i) Bromoethane (ii) Ethanol (iii) Hexene (3) (i) Bromopropane (ii) Methanol (iii) Hexene (4) (i) Bromoethane (ii) Methanal (iii) Hexene

Answer: (4)

A single chemical compound can have several acceptable systematic names and the systematic method of naming organic chemical compounds is called IUPAC Nomenclature but no two compounds can have the same.

Rules underlying IUPAC nomenclature of alkanes, alkenes, and alkynes are discussed below

  • The longest hydrocarbon chain is selected and is termed as parent chain in case of alkanes.
  • For alkanes suffix ‘-ane’ is used, for alkenes, suffix ‘-ene’ is used and suffix ‘yne’ is used for alkynes.
  • The parent chain is numbered such that we reach to the double-bonded or triple bonded carbon atom earliest. The position of the carbon atom with the double bond is mentioned in numerals.
  • In the case of multiple double bonds in the carbon chain, Greek numerical prefixes such as di, tri are used to denote their number.
  • Number the longest carbon chain such that the carbon atom to which the halogen is attached get the lowest number.
  • According to the IUPAC nomenclature -al is attached as a suffix to parent alkane for the naming of aldehydes.

Given chemical compounds

(i) CH3 – CH2 – Br

Ethyl bromide or broom ethane

  • Longest carbon chain has two carbon atoms and it is an example of haloalkane.

(ii) H−CHO

Formaldehyde or methanal

  • The compound has 1 carbon atom and an aldehyde is present.

(iii) CH3− (CH2)3 − CH = CH2

1- Hexene

  • Longest carbon chain has six carbon atoms, so suffix end is used and double bond present at the first carbon atom.

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