What is Benzoic Acid?
Benzoic acid refers to a white solid substance and is considered a simple aromatic carboxylic acid. The name of benzoic acid is taken from the word gum benzoin, which was its only source for the longest time. It has been found occurring naturally in plants and it serves as the immediate biosynthesis for a large number of secondary metabolites. Benzoic acid also has salt in it used for preserving food. Benzoic acid is found in yoghurts, apples, strawberries, prunes, and cranberries. In some foods, benzoic acid may leave a disagreeable taste that is described as burning or peppery.
Benzoic Acid Formula: C7H6O2
Structure
The structure of benzoic acid is a complex one and its molecule consists of a ring that is known as benzene ring and a carboxyl group is linked to it. Benzoic acid consists of 15 atoms out of which it has 7 carbon atoms, 6 hydrogen atoms, and 2 hydrogen atoms.
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Properties of Benzoic Acid
2) Physical Properties
Benzoic acid is colourless in its solid situation and is crystalline.
The crystal structure of the compound is monoclinic.
There is a presence of an aromatic ring that gives the compound a very pleasant odour.
The density of benzoic acid reduces to 1.075 when it reaches a very high temperature.
3) Chemical Properties
Benzoic acid is soluble when put in water.
It is also soluble in various other chemicals such as carbon tetrachloride, benzene, alcohol, and acetone.
The dissociation of the benzoic acid is correspondent to 4.2 at a constant level of (pKa)
Benzoic acid’s reaction only occurs at the aromatic ring or when it is present at the carboxyl group.
Benzoic Acid Uses
Benzoic acid can be used in various places like
Benzoic acid is used in the manufacturing process of phenol.
Benzoic acid is also used in the production of various ointments that can treat any kind of fungal infection diseases in the skin.
It is also used as a source of preservation by the food industry.
It is also an important ingredient in many fashion cosmetic items like lipstick and lip gloss.
It is also used as a precursor for benzoyl chloride.
One of the major components of face wash, toothpaste, and mouthwash is benzoic acid.
It is also used to manufacture insect repellents and dyes.
Benzoic Acid Ointment Uses
Benzoic acid along with salicylic acid helps to prevent various infections that are caused by dangerous bacteria. Salicylic acid protects the body from shedding dead and rough skin cells. Benzoic acid with salicylic forms a combination of medications that can be used to treat inflammation and skin irritation that is caused by burns, fungal infections, insect bites.
There are few things that you must keep in mind during benzoic acid ointment use. You must avoid using dry or wet packs on the affected area of the skin. This can damage the cure that the medicine was going to do in the affected area. Also, avoid using other medicines in the affected area where you apply the benzoic acid.
Benzoic Acid for Skin
Benzoic acid appears in cherry bark, cassia bark, anise, tea, and raspberries naturally. The benefits of this compound on the skin include reducing ageing in women. It also has moisturizing and soothing properties. Also, an important form of benzoic acid that is known as veratric acid has properties of high concentrative antioxidants in them that help to neutralize all the free-radicals appearing in our surrounding environment. Benzoic acid is also present in a variety of cosmetic products that are applied to the face.
Benzoic Acid in Food
Benzoic acid is used as a food preservative for soft drinks and fruit juices that have an acidic pH level present in them. It is present in the form of sodium benzoate and sodium salt. Benzoic acid in food is regarded as safe and healthy.
Benzoic Acid uses in Pharmacy
Benzoic acid is also used in the pharmaceutical industry as a preservative drug. It is present in various baby products, nail and hair products, skin products, bath products and is preferred by many doctors. It is also referred to as antifungal, antimicrobial and is also present in capsule form.
Did You Know?
Benzoic acid is naturally present in many forms. One of the largest naturally occurring sources is from the gum that is present in the Chinese Balsam tree which is also called gum benzoin.
Benzoic acid was first discovered by Nostradamus in the early sixteenth century.
Interesting Fact
Benzoic acid also has a very niche use. In laboratories, it is used as a common standard by the lab instructors to calibrate a bomb calorimeter.
FAQs on Benzoic Acid Uses
1. What is benzoic acid and what is its chemical formula?
Benzoic acid is a simple aromatic carboxylic acid that appears as a white, crystalline solid. Its chemical formula is C₇H₆O₂, often written as C₆H₅COOH to show its structure, which consists of a benzene ring attached to a carboxyl (-COOH) functional group.
2. What are the main industrial and laboratory uses of benzoic acid?
Benzoic acid has several important uses across different fields. Its primary applications include:
- Food Preservation: It effectively inhibits the growth of mould, yeast, and some bacteria in acidic foods.
- Chemical Synthesis: It serves as a precursor for producing other important chemicals like phenol, benzoyl chloride, and various plasticisers.
- Medicine: It is a key ingredient in ointments, often combined with salicylic acid, for its antifungal properties.
- Cosmetics: It is used as a preservative and pH adjuster in products like lipsticks, face washes, and mouthwashes.
- Laboratory Standard: It is used to calibrate a bomb calorimeter because its heat of combustion is precisely known.
3. Which common foods and beverages contain benzoic acid as a preservative?
Benzoic acid, usually in the form of its salt sodium benzoate, is commonly used to preserve acidic foods and drinks. You can typically find it in products such as:
- Carbonated soft drinks
- Fruit juices, jams, and jellies
- Pickles and salad dressings
- Yoghurts and certain sauces
4. How is benzoic acid utilised in cosmetic and skincare products?
In cosmetics and skincare, benzoic acid primarily functions as a preservative to prevent the growth of microorganisms and extend product shelf life. It also acts as a pH adjuster. In medicated ointments, such as Whitfield's ointment, it functions as an active antifungal and keratolytic agent, helping to treat skin infections by shedding dead skin cells and inhibiting fungal growth.
5. What are the key physical and chemical properties of benzoic acid?
The key properties of benzoic acid relevant to the CBSE syllabus are:
- Appearance: It is a colourless or white crystalline solid with a faint, characteristic odour.
- Solubility: It is only slightly soluble in cold water but becomes much more soluble in hot water, as well as in organic solvents like alcohol, benzene, and acetone.
- Acidity: It is a weak acid with a pKa of approximately 4.2.
- Reactivity: It undergoes reactions typical of carboxylic acids, such as esterification, and can also undergo electrophilic aromatic substitution on its benzene ring.
6. Why is benzoic acid an effective food preservative, especially in acidic foods?
Benzoic acid's effectiveness as a preservative stems from its molecular (un-dissociated) form. In an acidic environment (pH below 4.5), the equilibrium favours the un-ionised C₆H₅COOH molecule. This nonpolar form can easily pass through the cell walls of microorganisms like yeast and mould. Once inside the cell, where the pH is nearly neutral, the acid dissociates, releasing protons (H⁺) that lower the internal pH and disrupt essential metabolic functions, thus inhibiting microbial growth.
7. What is the difference between using benzoic acid and its salt, sodium benzoate, in applications?
The primary difference is their solubility in water. Benzoic acid itself is poorly soluble in water, which limits its application in liquid formulations. In contrast, its salt, sodium benzoate (C₆H₅COONa), is highly soluble. For this reason, sodium benzoate is the preferred form for use as a preservative in aqueous products like soft drinks and juices. In an acidic solution, the sodium benzoate converts to benzoic acid, which is the active antimicrobial agent.
8. Beyond preservation, what is the importance of benzoic acid as a precursor in chemical synthesis?
As per the NCERT syllabus, benzoic acid is a vital starting material, or precursor, in industrial chemistry. One of its most significant applications is in the commercial production of phenol through a process of oxidative decarboxylation. It is also used to synthesise benzoyl chloride (C₆H₅COCl), an important acylating agent used to produce dyes, perfumes, herbicides, and pharmaceuticals.
9. How does benzoic acid's structure relate to its properties and uses?
Benzoic acid's structure, a benzene ring attached to a carboxyl group (-COOH), dictates its functions. The carboxyl group makes it an acid, enabling its use as a preservative by disrupting cell pH. The stable aromatic ring makes it a useful building block for synthesising other complex compounds like phenol and dyes. The combination of these two parts gives it the specific solubility and reactivity profile needed for its diverse applications in food, medicine, and industry.
10. What are the safety considerations for using products containing benzoic acid?
When used within the approved concentrations set by food safety authorities, benzoic acid and its salts are considered safe for human consumption. The human body can metabolise and excrete it effectively. The primary safety concern is with high concentrations, which are not found in consumer products. While generally safe, some individuals may experience mild allergic reactions or skin sensitivity from topical products. It is the dose and application that determine its safety profile.
