Question

Which compound in each of the following pairs would be more soluble in water explain.

a.

or

b. acetone or 2-pentanone

c. propanal or pentanal

Short answer

a.

is more soluble.

b. Acetone is more soluble in water than 2-pentanone.

c. Propanal is more soluble in water than pentanal.

Step-by-step solution

Part (a) Given information

The given compounds are

and

Part (a) Explanation

Out of the given compounds,

is more soluble due to hydrogen bonding. Hydrogen bonding is the interaction that involves a hydrogen atom and pair of other atoms.

Part (b) Given information

The given compound is acetone or 2-pentanone.

Part (b) Explanation

The given compounds are ketones.

• Aldehydes and ketones are soluble in water.
• The solubility depends upon the length of an alkyl chain.
• More the length of an alkyl chain, the lesser will be the solubility in water.
• Since acetone is a ketone having three carbon atoms chains while 2-pentanone is the one with five carbon atoms chains.

Therefore, acetone is more soluble than 2-pentanone in water as the solubility decreases with the increase in the length of the alkyl chain.

Part (c) Given information

The given compounds are propanal or pentanal.

Part (c) Explanation

The given compounds are aldehydes.

• In the case of aldehyde,less or less than five carbon atoms are soluble in water; while carbon atoms above five, make the aldehyde insoluble due to the large hydrocarbon part.
• Since, propanal is an aldehyde having three carbon atoms while pentanal is an aldehyde having five carbon atoms.

As the solubility will decrease with the length of the alkyl chain. Thus, in this case, propanal is more soluble in water than pentanal.