Assertion: Tetrahydrofuran is aliphatic compoundsReason: Sometimes atoms other than carbon are also present in the ring known as heterocyclic.

The assertion and the reason given are not directly related.

Assertion: Tetrahydrofuran is an aliphatic compound. This statement is incorrect. Tetrahydrofuran is not an aliphatic compound, but rather a heterocyclic compound. Aliphatic compounds are organic compounds where carbon atoms form open chains, not rings. In tetrahydrofuran, the carbon atoms form a ring structure, which classifies it as a cyclic compound.

Reason: Sometimes atoms other than carbon are also present in the ring known as heterocyclic. This statement is correct. Heterocyclic compounds are cyclic compounds where at least one of the atoms in the ring is not a carbon atom. In the case of tetrahydrofuran, there is an oxygen atom in the ring, making it a heterocyclic compound.

So, the assertion is incorrect but the reason is correct.