Bond Angle of C-C Bonds in Benzene Explained

Benzene is a highly stable organic molecule with the chemical formula C$_6$H$_6$. It has a unique structure consisting of a six-membered ring of carbon atoms, with one hydrogen atom attached to each carbon atom.

Let's understand the structure and bonding in Benzene to determine the C-C bond angles:

• Benzene has a planar, hexagonal structure.
• Each carbon atom in the Benzene ring is bonded to two other carbon atoms and one hydrogen atom.
• Due to resonance, the bonds between carbon atoms are neither pure single nor pure double bonds; they are intermediate in character, often depicted as a ring inside the hexagon.
• Each carbon atom in Benzene is sp$^2$ hybridized.
• sp$^2$ hybridization leads to a trigonal planar geometry around the central atom, with ideal bond angles of 120°.

In the Benzene ring, the carbon atoms form C-C-C bonds. Since each carbon atom is sp$^2$ hybridized and the structure is a regular hexagon, the bond angle between any two adjacent C-C bonds (i.e., the C-C-C angle) is determined by the geometry of the sp$^2$ hybridized carbon atom within the hexagonal ring.

For a perfect hexagon, the internal angle is 120°. Since Benzene is a planar hexagon with sp$^2$ hybridized carbons, all the C-C-C bond angles are 120°.

Therefore, the bond angle of C-C bonds in Benzene (referring to the angle between adjacent C-C bonds, i.e., the C-C-C angle) is 120° for all such angles in the ring.

Let's consider the given options:

• All 120°: This aligns with the structural analysis of Benzene.
• Three are 180° and three are 120°: 180° implies a linear geometry, which is not present in the cyclic Benzene structure.
• All are 60°: A 60° angle in a six-membered ring would introduce significant ring strain (like in cyclopropane, which has 60° bond angles and is highly strained). Benzene is known for its stability and absence of significant ring strain.
• Three are 60° and three are 120°: This mix does not fit the symmetrical, regular hexagonal structure of Benzene.

Based on the sp$^2$ hybridization and the planar hexagonal geometry of Benzene, all the C-C-C bond angles are 120°.