Difference Between Benzene and Toluene

Key Difference – Benzene vs Toluene
 

Benzene and Toluene are two aromatic compounds having a slight difference between them in their structure. They are both toxic and volatile; exist in liquid form at the room temperature. The main difference between these two aromatic compounds is the structural difference; Toluene has a methyl group attached to the benzene ring; in other words one hydrogen atom in the benzene ring is replaced by a methyl group in Toluene molecule. This leads to other differences in their reactivity and usage.

What is Benzene?

Benzene (C₆H₆) is an aromatic hydrocarbon with an exceptional stability due to its circular conjugated structure. Unlike other hydrocarbons, benzene has a hexagonal molecular structure formed by joining six carbon atoms together with alternative double bonds between carbon atoms. This gives extra stability to the molecule. Six hydrogen atoms are bonded to six carbon atoms via single bonds. It exists in liquid form at room temperature, where a clear colorless liquid with a characteristic sweet smell. It is both volatile and flammable. Benzene contains 92.3% of carbon and 7.7% of hydrogen by weight in its molecular formula C₆H₆.

What is Toluene?

Toluene is also known as methyl benzene. It is a benzene derivative with the molecular formula C₇H₈. One hydrogen atom in benzene is replaced by a methyl (–CH₃) group in the Toluene molecule. Toluene is colorless, non-corrosive, volatile, aromatic liquid with a characteristic odor.

It is a hazardous chemical that causes irritation to eyes, skin, and mucous membranes. It also causes problems in the central nervous system causing headache, drowsiness or other effects. It may cause lung damages if it is swallowed. The severe exposure can cause serious problems such as respiratory depression, unconsciousness, convulsions or death.

What is the difference between Benzene and Toluene?

Structure:

Benzene: The molecular formula of benzene is C₆H₆.

Toluene: Toluene has the molecular formula of C₇H₈. It contains a methyl group (-CH₃) in the benzene ring, instead of the hydrogen atom.

Uses:

Benzene: Some industries use benzene to produce other chemicals; for example to make chemicals that are used to produce plastics, resins, nylon, and synthetic fibers. In addition, it is also used to make some types of rubbers, lubricants, detergents, dyes, drugs and pesticides.

Toluene: Even though, Toluene is toxic and causes health problems; it is used in several industrial application. One of the major uses of Toluene is mixing with gasoline to improve its octane ratings. It is also used to produce benzene and a useful solvent in paints, coatings, synthetic fragrances, adhesives, cleaning agents and inks. In addition, it is used in polymer industry; for example Toluene is used to make nylon, polyurethanes, and plastic soda bottles. Moreover, it is used in pharmaceuticals, cosmetic nail products, dyes and organic chemicals.

Health Effects:

Benzene: Benzene is considered as a toxic and carcinogenic (cancer causing) chemical that causes both acute and chronic health effects. Long-term exposure can cause problems in blood production and affect bone marrow.  Short-term exposure to high levels of benzene may cause dizziness, drowsiness, unconsciousness and death.

Toluene: Main routes of exposure to Toluene are; eye contact, skin contact, inhalation, ingestion and side effects due to long-term (chronic) exposure. All these ways are harmful and show different health effects. Long term exposure can cause skin problems and harmful to the central nervous system. Dermal issues include red, dry or cracked skin. Exposure to high concentrated Toluene over a long period may harm the kidneys.

 

Image Courtesy:

1. Benzene-2D-flat By Benjah-bmm27 [Public domain], via Wikimedia Commons

2. Toluene By Luigi Chiesa (Draw by Luigi Chiesa) [Public domain], via Wikimedia Commons