Choose the best description for the indicated bond H-CEC-CH3 A) This is a triple bond between two carbons in which three pi bonds hold the atoms together. B) This is a single bond between two carbons formed by the overlap of an sp orbital on each carbon. Extra electrons on each carbon exist as lone pairs in p orbitals. C) This is a triple bond between two carbons in which a sigma bond arises from sp- sp overlap and two pi bonds are formed by side-to-side overlap of unhybridized p orbitals on each carbon. D) This is a triple bond between two carbons in which there are three sigma bonds between the atoms, which are each spa hybridized

C) This is a triple bond between two carbons in which a sigma bond arises from sp- sp overlap and two pi bonds are formed by side-to-side overlap of unhybridized p orbitals on each carbon.

Explanation:

Alkynes are hydrocarbons that contain carbon-carbon triple bonds. Each carbon atom is bound to the other two atoms, and there are no free valence electrons. Each carbon atom needs two hybrid orbitals to form the skeleton of sigma bonds. The hybridization of the s orbital with a p orbital generates two hybrid orbitals, oriented at 180º of separation for each carbon atom. The overlap of these hybrid orbitals sp with the s orbitals from the hydrogen produces the skeleton of sigma bonds.

The result of the overlap of the two remaining unhybridized p orbitals of each atom of carbon is the formation of two pi bonds. These orbitals overlap in right angles with each other, forming a pi bond with electronic density above and below the sigma bond and the other with electronic density in front of and behind the sigma bond. The form of these pi bonds is such that they combine to form a cylinder of electron density that "wraps" the sigma bond between the two carbon atoms.