Question

The first member of alkyne, homologous series is:
A.ethyne
B.ethene
C.Propyne
D.Methane

Answer 1

Hint: The first member of alkyne series is ethyne with two carbon atoms bonded by a triple bond; \[HC \equiv CH\] .

Complete step by step answer:
Homologous series of compounds is referred to as the series of compounds that have the same general formula but differ from adjacent members by $C{H_2}$ - group. The homologous group of compounds are alkanes, alkenes, alkynes etc.
Hydrocarbons having triple bonds between carbon atoms are alkynes. Its general formula is, $C_nH_{2n-2}$ where n is the number of carbon atoms. They are unsaturated hydrocarbons. The first member of the alkyne family is Ethyne $({C_2}{H_2})$ , with two carbon atoms bonded by a triple bond. It is a hydrocarbon and the simplest alkyne Its molecular weight is 26.04g/mol.
Ethyne or Acetylene is used for arc welding purposes in the form of oxyacetylene flame obtained by mixing ethyne with oxygen gas. It is also widely used as a fuel and a chemical building block. It is usually unstable in its pure form and therefore is mostly handled as a solution. Pure ethyne is always odourless. It is a reactive material that poses a fire and explosion hazard. Its lower and upper explosive limits in air are \[2.5\% \] and \[93\% \] , respectively.
Ethyne shows acidic nature because the removal of a proton results in a stabilised anion, the negative charge on carbon generated after the removal of proton is stabilised because of the high electronegativity of SP hybridised Carbon atom.

Therefore, the correct answer is option (a).

Note: Ethyne is most commonly known as Acetylene. It’s IUPAC name Ethyne is derived from ethane and is an extremely important starting material in commercial chemical synthesis.