structures of different isomers corresponding to the th member of alkyne series. Also write IUPAC names of all the isomers. What type of isomerism is exhibited by different pairs of isomers? th member of alkyne has the molecular formula C H .
The possible isomers are: Table . Common and IUPAC Names of Alkynes (C n H 2n– ) Value of n Formula Structure Common name IUPAC name C H H-C ≡ CH Acetylene Ethyne C H CH -C ≡ CH Methylacetylene Propyne C H CH CH -C ≡ CH Ethylacetylene But- -yne C H CH -C ≡ C-CH Dimethylacetylene But- -yne (a) HC ≡ C – CH – CH – CH – CH Hex- -yne (b) CH – C ≡ C – CH – CH – CH Hex- -yne (c) CH – CH – C ≡ C – CH – CH Hex- -yne -Methylpent- -yne -Methylpent- -yne -Methylpent- -yne , -Dimethylbut- -yne Position and chain isomerism shown by different pairs. . .
Structure of Triple Bond Ethyne is the simplest molecule of alkyne series. Structure of ethyne is shown in Fig. . .
Each carbon atom of ethyne has two sp hybridised orbitals. Carbon-carbon sigma ( σ ) bond is obtained by the head-on overlapping of the two sp hybridised orbitals of the two carbon atoms. The remaining sp hybridised orbital of each carbon atom undergoes overlapping along the internuclear axis with the s orbital of each of the two hydrogen atoms forming two C-H sigma bonds. H-C-C bond angle is of °.
Each carbon has two unhybridised p orbitals which are perpendicular to each other as well as to the plane of the C-C sigma bond. The p orbitals of one carbon atom are parallel to the p orbitals of the other carbon atom, which undergo lateral or sideways overlapping to form two pi ( π ) bonds between two carbon atoms. Thus ethyne molecule consists of one C–C σ bond, two C–H σ