Here's why:
* Hybridization: The carbon atom in methanol is sp3 hybridized. This means it has four electron domains (one for the C-O bond, three for the C-H bonds), which arrange themselves tetrahedrally.
* Ideal angle: In an ideal tetrahedral arrangement, the bond angle is 109.5 degrees.
* Slight deviation: The lone pairs of electrons on the oxygen atom exert a slightly greater repulsive force than bonding pairs, causing a slight compression of the HCH bond angle in methanol, resulting in a value slightly less than the ideal 109.5 degrees.
Therefore, the HCH bond angle in methanol is approximately 108.9 degrees.
