Question

The structure of spiro $\left[ {3,3} \right]$ heptane is:
A.

B.

C.

D.

Answer 1

Hint: Spiro compounds are the bi- or polycyclic organic compounds with rings connected through just one atom. The rings can be different in nature or identical. The connecting atom is also called the spiro atom or spiro carbon, most often a quaternary carbon.

Complete step by step solution:
There are two types of spiro compounds. They are mono and poly spiro compounds. Mono spiro compounds are the compounds having two rings. Poly spiro compounds are the compounds having three or more spiro compounds.
The nomenclature was proposed by Adolf von Baeyer. Spiro compounds’ names have three parts-spiro prefix, square bracket and hydrocarbon name. All spiro compounds have the prefix spiro followed by square brackets containing the number of atoms in the smaller ring and the number of atoms in the larger ring excluding the spiro atom itself, the numbers being separated by a dot. Bridge-head carbons are where the rings meet. It is different from bicyclic compounds. Spiro is put as a prefix and insert the two bridge lengths and place the suffix with respect to the number of carbons. In the square brackets, the number of carbon atoms linked to the spiro atom in each ring is indicated in ascending order.
Since $\left[ {3,3} \right]$ denotes the number of carbons linked to spiro atom, there are three carbons
near to the spiro carbon,

which will be the structure. So except the spiro carbon atom, there are six carbons, thus the name heptane.

Hence the correct option is D.

Note: We can obtain spiro compounds using intramolecular cyclization, intra/intermolecular condensation. Isolated rings do not have common atoms. Spiro rings have one common atom and fused rings have one common bond. While bridged rings have two common atoms.