Ethanol has boiling of 78.5 while dimethyl ether has boiling point of -24.9;so account for this diffrence in boiling points since they both have the same molecular weight.how can this be explained using diagrams?
Hydrogen bonding
The boiling points of compounds can be influenced by various factors, including intermolecular forces and molecular shape. In order to explain the difference in boiling points between ethanol and dimethyl ether, we can examine their molecular structures using diagrams.
Ethanol (C2H5OH) has a hydroxyl (-OH) group attached to a two-carbon chain. On the other hand, dimethyl ether (CH3OCH3) has two methyl (-CH3) groups attached to an oxygen atom. Both compounds have the same molecular weight, but their boiling points differ significantly.
To analyze the difference in boiling points, we can consider the intermolecular forces present in each compound. In the case of ethanol, the hydroxyl group allows for hydrogen bonding to occur. Hydrogen bonding is a strong intermolecular force in which hydrogen is partially positive and attracted to highly electronegative atoms, such as oxygen. This extra intermolecular force leads to stronger attractions between ethanol molecules, requiring more energy to break these bonds and reach its boiling point of 78.5 °C.
However, dimethyl ether lacks a hydrogen attached to an oxygen atom and, therefore, cannot form hydrogen bonds. Instead, it experiences weaker London dispersion forces. These forces arise due to temporary shifts in electron density, creating temporary dipoles that attract neighboring molecules. Since London dispersion forces are generally weaker than hydrogen bonding, less energy is required to overcome these forces in dimethyl ether, resulting in a lower boiling point of -24.9 °C.
Therefore, the difference in boiling points between ethanol and dimethyl ether can be explained by the presence of hydrogen bonding in ethanol, which is absent in dimethyl ether. The formation of stronger intermolecular hydrogen bonds in ethanol requires more energy to break, leading to a higher boiling point.