Question

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

Answer 1

Hint: The aliphatic compounds in terms of organic chemistry are non – aromatic hydrocarbons. The constituent carbon atoms in aliphatic compounds can be straight chain, branched chain, cyclic, saturated or unsaturated. The cyclic organic compounds contain chains or rings of carbon atoms in their molecules.

Complete step by step answer:
On the basis of structure or carbon skeleton, the organic compounds have been classified into two classes- open chain and cyclic. The open chain compounds are also called acyclic or aliphatic compounds. In these compounds, the carbon atoms are linked so as to form straight chains or branched chains. The first and the last carbon are not directly joined to each other in these compounds.
Now, the cyclic compounds are further classified into alicyclic compounds, aromatic compounds and heterocyclic compounds.
The alicyclic compounds are ring compounds that contain a carbon atom at each corner of the ring. These are also called carbocyclic compounds. They have properties similar to their corresponding open chain compounds and do not contain aromatic properties. They may be saturated or unsaturated. Thus, alicyclic compounds are those organic compounds which have cyclic structure combined with aliphatic properties. Therefore, option B is correct.

The aromatic organic compounds are also called arenes. The term aromatic is applied to those of closed chain compounds which differ in properties from the aliphatic compounds. These compounds obey the Huckel’s rule for aromaticity. The parent aromatic hydrocarbon is benzene. All the hydrocarbons which resemble benzene in their chemical behavior are known as arenes. They may contain more than one benzene ring also. Thus, option C is wrong.

Heterocyclic compounds are those cyclic compounds which have hetero atoms at the corners in addition to the carbon atoms. For example, furan, thiophene etc. Thus, option A is wrong.

Polycyclic organic compounds are those organic compounds which contain several rings of atoms, primarily carbon. Generally, the term polycyclic refers to polycyclic aromatic compounds including polycyclic aromatic hydrocarbons. Thus, option D is wrong.

Hence, option B is correct.

Note: The saturated open chain organic compounds or hydrocarbons are called alkanes. They contain carbon – carbon single bonds in their molecules. For example, methane, ethane etc.
The first four alkanes are colourless, odourless gases. The next thirteen members are colourless, odourless liquids.
Alkanes have very low densities and are non-polar due to which they are soluble in non-polar solvents.