Benzene Facts: Discovery, Properties And Uses

With the chemical formula C6H6, Benzene is a significant organic chemical compound.

The benzene molecule comprises six carbon atoms arranged in a ring. It has one hydrogen atom connected to each carbon atom.

It is a flavorless, sweet-smelling compound from coal, crude oil, or natural gas. Its main application is as a raw material for producing other chemicals. Additionally, the chemical and pharmaceutical sectors employ benzene as a solvent. Apart from the benefits, benzene has been the subject of discussion in many cancer-based case studies. Institutions like CDC and EPA recommend avoiding daily levels of benzene exposure. They recommend making at least the indoor environment benzene-free. This article primarily discusses all that we should know about benzene exposure and how it could affect us long-term.

What is benzene?

Benzene (C6H6) is the most basic organic aromatic hydrocarbon. It is also the primary compound of several significant aromatic chemicals. Its primary application is in the manufacturing of polystyrene. It melts at 5.5 °C (41.9 °F) and has a boiling point of 80.1 °C (176.2 °F). It is easily solvent-soluble in organic solvents but only moderately so in water.

• English scientist Michael Faraday first identified benzene in lighting gas in 1825. Eilhardt Mitscherlich, a German chemist, heated benzoic acid with lime in 1834 to generate benzene. A.W. von Hofmann, a German chemist, separated benzene from coal tar in 1845. Linus Pauling, an American chemist, proposed that benzene had a single structure in 1931.
• The delocalization of six electrons in modern bonding models explains the benzene structure. This process also explains the stability. The valence-bond and molecular orbital theories add to the evidence.
• Delocalization in this context refers to an electron's attraction to all six carbons of the ring rather than just one or two of them. Since the electrons are stronger held due to this delocalization, benzene is more stable.
• It is also less reactive than what would be predicted for an unsaturated hydrocarbon. Because of this, benzene hydrogenates somewhat more slowly than alkenes. This feature makes it significantly more difficult to oxidize than alkenes.
• Most benzene reactions fall under electrophilic aromatic substitution. It maintains the ring's integrity while substituting one of the connected hydrogens. These processes are adaptable and frequently used to create benzene derivatives.

Origin And Invention Of Benzene

Benzene is popular for being one of the simplest organic hydrocarbons. These are also naturally aromatic. It is also one of the elementary petrochemicals. Benzene is a crude oil constituent with an aroma like gasoline. It is highly toxic, and research has shown that it is also naturally carcinogenic. By this word, the experts mean it is cancer-causing.

• The name 'Benzene' was originally from 'Gum benzoin', an aromatic resin. When Benzoin went under sublimation, Benzoic acid came into the picture. The hydrocarbon extracted from Benzoic acid was named benzene.
• It is also known as Benzol or even Benzin. Michael Faraday was the first person to isolate and identify benzene in 1825. He isolated benzene from the oily residue he derived and named it bicarbonate of hydrogen.
• It was in 1833 that Eilhard Mitscherlich produced benzene using distilled Benzoic acid and lime. He gave this compound the name Benzin. The French chemist Auguste Laurent called the same substance 'phene' in 1836. This word served as the source of the term 'phenol'.
• Charles Mansfield, a junior to August Wilhelm von Hofmann, created benzene by isolating it from coal tar in 1845. He later initiated the first-ever production line of benzene on an industrial level. It was based on the coal-tar isolation method he had used.
• Wilhelm Korner was a German chemist who suggested the prefixes like ortho-, para-, and meta-. He wanted to differentiate between benzene derivatives in 1867. In 1869, Karl Grabe, another German chemist, used these prefixes for the first time.
• He did it to denote substituents and their specific locations on a typical di-substituted aromatic ring. And yet another German chemist, Viktor Meyer, came into the picture. He became the first person to apply Karl Grabe's nomenclature concept to benzene's compound in 1870.

Chemical And Physical Properties Of Benzene

Here are the properties of benzene.

Physical Properties

Benzene is a colorless compound with an aromatic smell similar to gasoline. Benzene exists in the liquid state. The melting point of benzene is 42°F (5.5°C), while its boiling point is 176°F (80.1°C). Benzene does not form a homogenous mixture with water. However, it is solvable in organic solvents like alcohol, acetone, and acetic acid. Benzene is lighter than water since its density is 0.87 g/cm3. It also exhibits the property of resonance and is highly flammable. It can burn easily at low temperatures, producing dark flames after combustion.

Chemical Properties

The chemical compound Benzene comprises six atoms of Carbon and six atoms of hydrogen. Benzene tends to react differently with different substances. These reactions further produce other compounds. Some of these reactions are as follows.

• Nitration of Benzene: At the temperature between 122-140°F (323-333K), benzene actively reacts with Nitric Acid. It forms Nitrobenzene in the presence of Sulphuric acid.
• Benzene reacts with Halogens in Lewis acids like Iron(II)chloride and Iron(II)bromide and forms Alkyl Benzene.
• In the process called Sulfonation of Benzene, Benzene is heated along with Sulphuric acid, which is fuming. It leads to the formation of Benzene Sulphuric acid. This process is reversible.
• Benzene burns and produces a sooty flame during the process of combustion. This reaction also leads to the release of Carbon Dioxide.
• When benzene combines with Alkyl Halide in the presence of a Lewis acid, it forms Alkyl Benzene. This process is Friedel Craft's Alkylation Reaction.
• When benzene, in the presence of any Lewis acid, reacts with an acyl halide, acyl Benzene is formed. This reaction is also known as Friedel Craft's Acylation Reaction.

Uses Of Benzene

Many different industries use benzene. Gasoline contains a significant amount of benzene, a substance utilized extensively in industry. Benzene is also used in producing plastics, synthetic fibers, and rubber lubricants. They also become dyes, resins, detergents, and more.

• Benzene is frequently employed as a solvent in various industrial, business, and academic tasks. Companies use products containing benzene as solvents during different production stages. They are made into chemical and plastic products.
• Resins, synthetic goods like nylon, Styrofoam, and others are a few examples. Asphalt used by roofing and paving businesses is made with the help of benzene.
• In addition to making rubber and tires, benzene is a component of the adhesives used to attach shoe bottoms. Detergents, pesticides, insecticides, herbicides, and dyes are other chemical compounds benzene produces
• There are items made specifically for cleaning printing equipment that includes benzene. The focus is on extending their lifespan and improving their functionality.
• A fraction of benzene is also present in ink and various painting supplies. Supplies include spray paint, sealers, lacquers, and stains. It maintains the paint's liquid state.
• Many individuals and manufacturers use benzene as fuel. They do so because of their high octane rating and natural availability.
• Nevertheless, exposure to benzene is also accompanied by health hazards. It can cause several side effects, including headaches, shakiness, convulsions, unconsciousness, and irritability. It can have both immediate and long-term impacts depending on the exposure.
• Benzene is a non-polar, colorless, flammable liquid with a pleasant scent. It is also highly poisonous and can cause many health hazards if a person makes direct contact with it. Michael Faraday discovered it in 1825 and it has been useful since then. Due to its various properties, it produces multiple products in the industrial sector.

Trivia

• Tobacco smoke is a major source of benzene exposure. Benzene exposure affects people by making them drowsy and unconscious. In some cases, it could be fatal. The rapid heartbeat, headaches, and tremors are a part of the symptoms. However, people who breathe high benzene levels experience these.
• Consuming food items and beverages with a high level of benzene can lead to vomiting, stomach irritation, and sleepiness. People also experience most of the symptoms listed due to the previous source of benzene exposure.
• Skin exposure is also a common scenario for people working with gasoline. However, liquid benzene evaporates quickly, making it less common.
• Such exposure to benzene, especially in the long term, could directly affect the blood. It further affects bone marrow, leading to a decrease in red blood cells. Now, this could make people anemic. It can also damage immunity by fluctuating blood levels of antibodies, and it causes the loss of white blood cells. Various studies have confirmed the link between benzene and cancer blood cells.
• Animal studies confirm that exposure to benzene results in low birth weight problems. It also develops issues like bone marrow damage and delayed bone formation in pregnant animals.
• While benzene is a natural part of gas, cigarette smoke, and crude oil, volcanoes are a major source of benzene. In 2018, California forest fires caused increased exposure to benzene, contaminating drinking water.
• Considering this ability, the U.S. EPA has classified benzene as a human carcinogen for all sorts of exposure. In addition, International Agency for Research on Cancer also classified benzene as one of the human carcinogens. The experts confirmed with evidence that benzene causes acute myeloid leukemia.
• Studies reveal that benzene causes chromosome changes in bone marrow cells. These changes are usually seen in human leukemia cells.
• Centers for Disease Control and Prevention has been spreading awareness about this benzene exposure. They also discuss carcinogenic risks and similar issues.
• Apart from these known methods, there are other ways to experience benzene poisoning. Outdoor air contains benzene, especially due to industrial emissions from chemical plants.
• Indoor air contains higher levels of benzene as compared to the outdoor atmosphere. Starting from paints to detergents and furniture wax, a lot of benzene emissions need to be dealt with.
• The air surrounding hazardous areas have comparatively higher levels of benzene. By hazardous, we mean industrial chemicals and toxic substances or gas stations. Regarding hazardous waste, benzene can also leak from underground storage tanks. It will contaminate the well water.
• People working in the industrial atmosphere are prone to occupational exposure. According to the Centers for Disease Control and Prevention, almost 238,000 people are under threat in this category. About 20% of total national exposure to benzene happens due to industrial emissions and auto exhaust.
• Considering the cancer risk, the Centers for Disease Control and Prevention recommends keeping benzene-exposed areas clean. They recommend reducing clothing, furniture, and items emitting benzene. All experts strongly suggest getting medical care immediately upon exposure.
• It is possible to avoid issues like cigarette smoke and tobacco smoke that contribute to benzene poisoning. Even in occupational situations, industries should share awareness about protection from this.