Question

Draw the structure of an alkane or cycloalkane that has a molecular mass of 84.2

Answer 1

Concepts and reason

Determine the molecular formula first using the molecular weight and then draw the possible isomers of alkane or cycloalkane.

Isomers are the compounds with the same molecular formula but the molecules are different.

Fundamentals

Alkanes contain only linear and branched chains of carbon atoms. The molecular formula of alkanes is . Here, n is the integer.

Cycloalkanes contain one or more rings. The molecular formula for cycloalkanes is . Here, n is the integer.

Constitutional isomers have same molecular formula but different in the connectivity of the atoms. They have different IUPAC names.

Stereoisomers have same molecular formula but different in the way of atoms oriented in space. They have different IUPAC names but they differ only in the way of arrangement of atoms. It exhibits as cis and trans isomers.

Divide 84.2 by 12 (here take the approximate value):

Replace 1 C by 12 H’s:

The possible isomer of alkane or cycloalkane with the molecular formula is as follows:

Calculate the molar mass as follows:

Ans:

Thus, the structures of cycloalkane with the molar mass 84.2 are as follows:

In this structure, there are 6 carbon atoms with 12 H atom in the cyclic ring. This compound exhibits the molecular mass of 84.2 g/mol.