Which one is least soluble in water? a. CH3CH2OH b. CH3OCH3 c. CH3CH2CH2CH2CH2OH d. CH3OH e. CH3CH2CH2OH
The Correct Answer and Explanation is:
The least soluble compound in water is CH3OCH3 (dimethyl ether).
Here’s why:
Water solubility is mainly determined by the ability of a compound to form hydrogen bonds with water molecules. Compounds that are capable of hydrogen bonding tend to dissolve better in water, which is a highly polar solvent. Now, let’s analyze each compound:
- CH3CH2OH (Ethanol): Ethanol has both a polar -OH group and a non-polar ethyl group (-CH2CH3). The -OH group can form hydrogen bonds with water molecules, making ethanol quite soluble in water.
- CH3OCH3 (Dimethyl ether): This compound has an oxygen atom that can potentially form hydrogen bonds. However, the -OCH3 group is less effective in hydrogen bonding compared to alcohols, which have an -OH group. Furthermore, dimethyl ether is a smaller molecule with no additional polar groups like ethanol, making it less soluble in water.
- CH3CH2CH2CH2CH2OH (Pentanol): Pentanol, like ethanol, contains an -OH group, which can form hydrogen bonds with water. However, because it has a longer non-polar hydrocarbon chain, it is slightly less soluble than ethanol but still quite soluble due to the hydrogen bonding.
- CH3OH (Methanol): Methanol is highly soluble in water. The -OH group can readily form hydrogen bonds with water, making it very soluble.
- CH3CH2CH2OH (Propanol): Propanol, like ethanol and methanol, has an -OH group that can hydrogen bond with water molecules. It’s also quite soluble, though less than methanol or ethanol.
In conclusion, dimethyl ether (CH3OCH3) is the least soluble because it lacks the -OH group, which is essential for forming strong hydrogen bonds with water molecules. The other compounds all have hydroxyl groups (-OH), which enable them to form hydrogen bonds and dissolve more easily in water
