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Problems related to the trends in physical properties
Description:
You will be given specific properties of alcohol, phenols and ethers and asked to arrange them in increasing or decreasing order. Questions may be related to boiling points and solubility.
How to Approach:
Pay attention to the type of compounds mentioned in the question and arrange them according to the following trend.
Boiling point:-
- Alcohols and phenols have higher boiling points than ethers and other hydrocarbons of comparable molecular mass because of presence of intermolecular hydrogen bonding.
- The boiling point of isomeric alcohols decreases with branching due to decrease in surface area.
- The boiling point of alcohols increases with molecular mass.
- Ethers have weak polarity and no inter molecular hydrogen bonding, hence their melting and boiling point is comparable to that of hydrocarbons.
Solubility:-
- Solubility of alcohols in water is due to their ability to form hydrogen bonding with water.
- Only lower members of alcohols are completely soluble in water.
- Ethers can also form hydrogen bond with water and hence their solubility is similar to that of alcohols of similar molecular mass.
