Question

Give IUPAC names for the following cycloalkanes.

(a)

(b)

(c)

Short answer

(a)cis-1-ethyl-3-methylcyclobutane

(b)trans-1-tert-butyl-3-ethyl cyclohexane

(c)trans-1,2-dimethyl cyclopropane

Step-by-step solution

Step 1:

A cycloalkane has two distinct faces. If two substituents point toward the same face, they are cis. If they point toward opposite faces, they are trans. These geometric isomers cannot interconvert without breaking and re-forming bonds.

(a)

Two hydrogen atoms pointed towards same face, so they are cis, ethyl group is branched at C1 and methyl group is branched at C3 position, in cyclic ring of four carbon atoms.

(b)

Two hydrogen atoms pointed towards opposite face, so they are trans,ethyl group is branched at C3 and tert-butyl group branched at C1 position, in cyclic ring of six carbon atoms.

(c)

Two hydrogen atoms pointed towards opposite face, so they are trans, two methyl groups are branched at C1 and C2 position, in cyclic ring of three carbon atoms.