Phenyl or Benzyl?

One of the the most frustrating mistakes made by many organic students is confusing "phenyl" and "benzyl" groups in compounds. The one thing to remember is, "when the benzene ring is attached to something, that is a phenyl group."

Historically, the benzene ring was given a name of "phene" as the chemical name. Consequently, when this aromatic ring was attached to something, it was called the "phenyl" group. Eventually, the name for this aromatic compound was changed to benzene.

When "benz-" is used in a name it is basically used for three different types of compounds or groups. Think of benzoic acid, and the functionality of that compound is on the carbon attached to the benzene ring. Likewise, for benzaldehyde, the functionality of that compound is on the carbon attached to the benzene right, not the benzene ring by itself. Lastly, benzyl alcohol is an alcohol group on the carbon attached to the benzene ring, not to the ring itself.

Examples are listed below:

Phenyl	Benzyl