JAMB - Chemistry (2005 - No. 15)

How many hydrogen atoms does a single ring cycloalkane have less than the corresponding open-chain alkane?

Two

Three

Four

One

Let's consider an example:

Cycloalkane → Cyclopropane has the formula CH\(_2\)-CH\(_2\)-CH\(_2\) (when drawn in a cyclic form) = C\(_3\)H\(_6\)

Open chain alkane → Propane has the formula CH\(_3\)CH\(_2\)CH\(_3\) (when drawn on a straight chain) = C\(_3\)H\(_8\)

Comparing the two formulas; C\(_3\)H\(_6\) and C\(_3\)H\(_8\), the difference in the hydrogen atoms is two.