The compound C₃H₄ has two double bonds. Describe its bonding and geometry, using a valence bond approach.

Verified step by step guidance

1. Identify the molecular formula and structure: The compound C3H4 is known as propyne, which has a linear structure with two double bonds.
2. Determine the hybridization of each carbon atom: The central carbon atom is sp hybridized due to its linear geometry, while the terminal carbon atoms are sp2 hybridized because they form double bonds.
3. Describe the sigma bonds: Each carbon-carbon bond involves the overlap of sp or sp2 hybrid orbitals, forming sigma bonds. The carbon-hydrogen bonds are formed by the overlap of sp2 or sp hybrid orbitals with the s orbitals of hydrogen.
4. Explain the pi bonds: The double bonds consist of one sigma bond and one pi bond. The pi bonds are formed by the sideways overlap of unhybridized p orbitals on adjacent carbon atoms.
5. Discuss the geometry: The sp hybridized carbon atom has a linear geometry with a bond angle of 180°, while the sp2 hybridized carbon atoms have a trigonal planar geometry with bond angles of approximately 120°.

Key Concepts

Valence Bond Theory

Valence Bond Theory explains how atoms bond by overlapping their atomic orbitals to form covalent bonds. In the case of C3H4, the carbon atoms utilize sp2 hybridization to form sigma bonds with hydrogen and other carbon atoms, while the remaining p orbitals can participate in forming pi bonds, which are characteristic of double bonds.

Hybridization

Hybridization is the process of mixing atomic orbitals to create new hybrid orbitals that can form bonds. For C3H4, the carbon atoms undergo sp2 hybridization, resulting in three equivalent sp2 hybrid orbitals that lie in a plane, allowing for the formation of two double bonds and maintaining a trigonal planar geometry around each carbon atom involved in the double bonds.

Molecular Geometry

Molecular geometry refers to the three-dimensional arrangement of atoms in a molecule. In C3H4, the presence of two double bonds leads to a planar structure, with bond angles of approximately 120 degrees around the sp2 hybridized carbon atoms, resulting in a geometry that is consistent with trigonal planar arrangements.