Question

The aliphatic compounds having cyclic structures are known as:
A.Heterocyclic compounds
B.Alicyclic compounds
C.Arenes
D.Polycyclic compounds

Answer 1

Aliphatic compounds are non- aromatic hydrocarbons. The constituent carbon atoms in an aliphatic compound can be linear chained, branched chain, cyclic, saturated and unsaturated. Cyclic compounds consist of rings of carbon atoms in their molecules.

Complete answer:
The cyclic compounds can be classified as alicyclic compounds, heterocyclic compounds, aromatic compounds and polycyclic compounds.
The cyclic compounds that have hetero atoms present at the corners of the ring apart from the carbon atoms are known as heterocyclic compounds. The hetero atoms are generally nitrogen, oxygen or Sulphur atoms. Furan and thiophene are some examples of heterocyclic compounds. Option A is incorrect.
Alicyclic compounds are those ring compounds that contain a carbon atom at each corner of the ring. Their properties are similar to those of the corresponding open chain compounds and they do not show aromatic properties. Thus, alicyclic compounds can be said as aliphatic compounds with a cyclic structure.
Arenes are aromatic organic compounds. Aromatic compounds differ in properties from aliphatic compounds. The smallest aromatic hydrocarbon is benzene. All the compounds that resemble benzene in chemical behaviour are arenes.
Polycyclic organic compounds are those compounds which contain several rings. Generally, they refer to polycyclic aromatic hydrocarbons.

Thus, the correct option is option (B).
Note:
On the basis of the structure of the carbon skeleton. Organic compounds can be classified in two classes namely open chain and cyclic. Open chain compounds are also known as aliphatic or acyclic compounds. In aliphatic compounds, the carbon atoms are linked in such a way so as to form linear or branched chains. The first and last carbon atoms of the chain do not have a direct bond between them.