Final answer:
When toluene is reacted with excess chlorine in the presence of heat or light, a halogenation reaction occurs leading to the formation of chlorotoluenes and possibly polychlorinated toluene derivatives.
Step-by-step explanation:
When toluene is reacted with excess chlorine in the presence of heat or light, a reaction called halogenation occurs. This type of reaction is characterized by the substitution of hydrogen atoms in toluene with chlorine atoms, giving rise to chlorinated products like chlorotoluenes. Due to the presence of excess chlorine, along with a single substitution product, polychlorinated products can also form, where more than one hydrogen atom is replaced by chlorine. This reaction is quite similar to the chlorination of alkanes, where methane reacts with chlorine under similar conditions to form a mixture of chlorinated methane derivatives like methyl chloride (CH3Cl), methylene chloride (CH2Cl2), chloroform (CHCl3), and carbon tetrachloride (CCl4).