Video Transcript
Which of the following is the correct molecular formula of phenol? (A) C2H5OH, (B) C3H7OH, (C) C5H4OH, (D) C6H5CH2OH, (E) C6H5OH.
Phenol is the IUPAC name of an organic molecule that is also known as hydroxybenzene and carbolic acid. The phenol molecule consists of a benzene ring with one hydroxy or OH group bonded directly to the aromatic ring. Phenol itself should not be confused with phenols, which are a type of compound that contain a hydroxy group bonded directly to an aromatic ring but also contain additional substituents bonded to the aromatic ring. To write the molecular formula of the phenol molecule, we need to determine the exact number of atoms of each element present in the phenol molecule. To help us do this, let’s draw a displayed formula for phenol.
If we count the atoms in phenol, we find that there are six carbon atoms, six hydrogen atoms, and one oxygen atom. Therefore, we might think that the molecular formula should be written as C6H6O. While this is not an incorrect molecular formula, chemists often write the molecular formula of phenol as C6H5OH. This molecular formula helps to emphasize the presence of the hydroxy group bonded to the aromatic ring. The answer choice that is the correct molecular formula of phenol is therefore answer choice (E), C6H5OH.
