What is the structure of a methyl group?

A methyl group is defined as a functional group consisting of one carbon atom bonded to three hydrogen atoms, represented as -CH3. The methyl group is the simplest alkyl group and plays an essential role in organic chemistry as a substituent in various chemical compounds.

The structure -CH3 indicates that the carbon atom is bonded to three hydrogen atoms, fulfilling the tetravalency of carbon by forming four total bonds. This simple structure enables the methyl group to act as a branch or side chain in larger molecules, influencing their chemical properties and reactivity.

The other options represent different groups: -C2H5 is an ethyl group, -OH is a hydroxyl group, and -CHO is an aldehyde group. Each of these has a distinct structure and functional characteristics that differ from those of a methyl group. Therefore, the correct option representing a methyl group is -CH3.