Question

what is the different between C-C-C bond angles, C-C-H bond angles and X-C-C-X torsion angles

Answer 1

Angle between two bisecting planes are called torsional angle or dihedral angle. The torsion angle, χ, which ranges from -180° to 180°

The torsion angle between X-C(1)-C(2)-X is defined by the angle between the planes formed by atoms X-C(1) and X-C(2).Angle can be 0⁰ or 180⁰, it depends whether structure is cis or trans. or when the atoms are eclipsed, the dihedral angle is 0⁰ and when the atoms are opposite, the angle is 180⁰.

In case of C-C-C and C-C-H bond angle, it genrates due to shape of bond instead of planes. The C atoms in alkanes are tetrahedral so their H-C-H, C-C-H, and C-C-C bond angles are all near to 109.5°.  this value occurs only when the four other atoms attached to the carbon atom are identical to each other. When they are not all identical, the bond angles differs from109.5°.