Question

What is the I.U.P.A.C. name of acetylene?
A.Propane
B.Propyne
C.Ethene
D.Ethyne

Answer 1

Hint:
The term nomenclature is used for naming a compound. In the earlier days of the development of organic chemistry, the compounds were named after the source from which it is obtained. Formic acid was named from the word formicus as it was obtained from red ants. The liquid obtained by the destructive distillation of wood was named as methyl alcohol because in Greek methu stands for spirit and hule stands for wood. So, this system of naming was known as the trivial system of nomenclature.


Complete answer:
Step 1
With the advancement of organic chemistry, the number of organic compounds increased to a great extent, so in 1892 the International Congress of Chemists adopted a new system of nomenclature called the Geneva system. Though this system made the study of organic compounds much easier, it could not successfully be applied to the complicated compounds. In 1931, the Council of International Union of Chemistry modified this system to I.U.C. System. It was further revised by the International Union of Pure and Applied Chemistry which was known as the I.U.P.A.C. system.
Step 2
According to the IUPAC system, the name of an organic compound, in general, consists of the following three parts:
Word root – represents the number of carbon atoms present in the parent chain of the molecule. The parent chain is the longest possible continuous chain of carbon atoms containing maximum possible functional groups and multiple bonds present in the molecule.
The suffix – The main functional group and the multiple bonds present in the given compounds are indicated by adding a specific suffix to the word root.
Prefix – The alkyl groups and functional groups other than the principal functional group are regarded as substituents or side chains which is indicated by writing suitable prefixes before the word root.
Step 3
Acetylene is the trivial name for the compound \[CH \equiv CH\]. Here the longest chain consists of two carbon atoms therefore the word root is ‘eth’.
As the compound contains \[ - C \equiv C - \] a carbon-carbon triple bond, so the suffix is ‘yne’.

Hence the IUPAC name for acetylene is ethyne and the correct answer to the given question is option d).


Note:
A functional group is defined as an atom or a group of atoms that largely decides the activity of a given compound. A homologous series is a list of the organic compounds having the same functional group where there is an increase in the number of carbon atoms. Each of the carbon atoms gets added to the series by a \[ - C{H_2}\]group.