Question

The compounds adenine, guanine, cytosine, and thymine are called the nucleic acid bases. What structural features in these compounds make them bases?

Short answer

Adenine, guanine, cytosine, and thymine contain lone pairs of electrons. Due to this electron donating nature, they are considered Lewis bases.

Step-by-step solution

Bases

The compounds that contain at least one atom with a lone pair of electrons or can donate electrons to other electron deficient species are defined as the Lewis base.

Explanation

Adenine, guanine, cytosine, and thymine are bases because they contain nitrogen atoms with lone pair of electrons.

According to the lewis base definition, compounds that can donate lone electron pair are bases, and nucleic acid bases are then lewis bases.

Hence, adenine, guanine, cytosine, and thymine contain lone electron pairs.