methane which is composed of carbon and hydrogen, lacks fuctional groups and is a gas at room temperature.upon replacing one of the hydrogen atoms with a hydroxyl group, methane is converted to a liquid called methanol at room temperature. please explain to me the reason behind this difference in physical properties.
The difference in physical properties between methane and methanol can be attributed to the change in molecular structure caused by the replacement of a hydrogen atom with a hydroxyl group (OH).
Methane (CH4) is a simple hydrocarbon, consisting of one carbon atom bonded to four hydrogen atoms. It is a gas at room temperature because its molecules are not very polar, meaning there is no significant difference in electron distribution within the molecule. This lack of polarity results in weak intermolecular forces known as dispersion forces, which are relatively weak and can be easily overcome, allowing methane to exist as a gas.
When one of the hydrogen atoms in methane is replaced with a hydroxyl group to form methanol (CH3OH), the molecular structure changes significantly. The addition of the hydroxyl group introduces a highly polar bond between carbon and oxygen and enhances the overall polarity of the molecule.
The oxygen atom in the hydroxyl group is more electronegative than carbon, causing the electrons to spend more time around the oxygen atom. This creates a partial negative charge on the oxygen atom and a partial positive charge on the carbon atom. As a result, methanol molecules have a dipole moment, meaning they have a positive and a negative end.
The presence of dipole moments in methanol allows for stronger intermolecular forces, particularly hydrogen bonding between methanol molecules. Hydrogen bonding occurs when the hydrogen atom in a hydroxyl group forms a weak bond with an electronegative atom, such as oxygen or nitrogen, in a neighboring molecule.
These hydrogen bonds are stronger than the dispersion forces in methane, resulting in a higher boiling point and greater intermolecular cohesion. As a result, methanol remains a liquid at room temperature due to the stronger forces holding the molecules together.
In summary, the change in physical properties between methane and methanol is due to the introduction of a hydroxyl group, increasing the polarity and enabling the formation of stronger intermolecular forces, such as hydrogen bonding, in methanol. This results in methanol being a liquid at room temperature while methane remains a gas.