What is Benzaldehyde?

The simplest aromatic aldehyde, which consists of a benzene ring with a formyl (-CHO) substituent, is termed benzaldehyde (C6H5CHO). This organic chemical compound has several industrial applications, including dyes, flavouring agents, perfumes and the manufacturing of several other organic compounds. Found naturally in glycoside amygdalin, this aromatic aldehyde is known for its distinct, almond oil-like taste and odour. 

The molecular formula of this compound is C7H6O, and its IUPAC name is benzenecarbaldehyde. It is also referred to as several other names, including benzenedicarboxaldehyde, phenylmethanal, or benzoic aldehyde. It appears as a clear liquid with a smell like almonds. It is miscible with volatile oils, ether, and alcohol. It is denser than and thus only slightly soluble in water and has a solubility of 3 g/L.

Discovery of Benzaldehyde

Benzaldehyde occurs in a variety of natural items such as almonds or cherries. The isolation of benzaldehyde from bitter almonds goes back to 1803 and is credited to a French pharmacist Martrès. It was later studied by the German chemists Justus von Liebig and Friedrich Wöhler, who first synthesized it successfully in the 1830s. This led to the establishment of the structural theory of organic chemistry.

Structure of Benzaldehyde

The structure of benzaldehyde consists of a benzene ring substituted with an aldehyde unit. This formyl unit has one atom of carbon, hydrogen and oxygen. The number of benzaldehyde sigma bonds is 14, formed by the head to head overlapping of atomic orbitals. 

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Structure of Benzaldehyde

Preparation of Benzaldehyde

This simple aromatic aldehyde can be derived from a variety of natural sources. 

It can also be manufactured synthetically from toluene which is found in crude oil, for industrial usage. This is done by a series of chemical reactions in which toluene reacts with chlorine. This leads to the formation of benzal chloride, which can be further treated with water to form benzaldehyde. 

Benzaldehyde can also be synthesized by the oxidation of benzyl alcohol and carbonylation of benzene. Alkaline hydrolysis of benzal chloride also yields benzaldehyde. 

Properties of Benzaldehyde

The most distinct characteristics of benzaldehyde are its flavour and odour. Some of the properties of benzaldehyde are:

  • This liquid is colourless to yellow in colour. 

  • Benzaldehyde has an odour of almond. 

  • The molecular weight of Benzaldehyde is 106.12 g/mol.

  • It is slightly soluble in water. 

  • Benzaldehyde is completely soluble in alcohol and ether. 

  • It is generally stable when stored under ordinary conditions. 

  • Benzaldehyde is a neutral compound (neither acidic nor basic).

  • The melting point of benzaldehyde is −26 °C (−14.8 °F).

  • The boiling point of benzaldehyde is 179 °C (354.2 °F).

  • It is highly refractive with a refractive index of 1.5456.

  • The density of benzaldehyde is 1.044 g/mL.

Uses of Benzaldehyde

Benzaldehyde is an aromatic compound with a distinct odour resembling almonds. It can be extracted from a variety of natural sources and can also be synthesized by liquid phase chlorination of toluene. There is no chemical distinction between these two types of benzaldehyde. 

Benzaldehyde is a widely used compound in the chemical industry. It also finds usage in several other items. The most common applications of benzaldehyde that make it such an important compound are listed below- 

1. The most common use of benzaldehyde is to provide almond flavouring to items. It is used in food and beverages to provide a scent of almonds.  Various scented products also use benzaldehyde as an additive for having a distinct odour.

2. The industrial usage of benzaldehyde is that it acts as an intermediate in the production of several organic compounds. It is a precursor to various chemical additives, plastics and pharmaceutical products.

3. Another significant use of the odour of benzaldehyde is as a bee repellent. It is used to draw the bees away from a honeycomb in order to extract the honey from these structures. 

4. Some cosmetic products and personal care products also contain benzaldehyde.

5. Benzaldehyde is also used in the production of dyes (acridine and aniline dyes), soaps and perfumes.

6. It is also used in cakes and baked goods as almond extract. Benzaldehyde is also used in additives like antibacterial and antifungal preservatives.

7. It is an intermediary product in the formation of compounds like cinnamic acid, benzoic acid etc.

8. It is used as a solvent for oils, resins, ethers etc. 

The flavouring and fragrance of benzaldehyde are the reason for its widespread use amongst several industries.

Storage of Benzaldehyde

Benzaldehyde is usually stable but should be stored as per the recommended conditions. It should be properly stored in a sealed container away from heat and light. It should be kept away from reactive substances such as acids and reducing agents. It is also recommended to store this compound under nitrogen. 

FAQs (Frequently Asked Questions)

1. What are the Different Types of Chemical Reactions that Benzaldehyde Can Undergo?

Ans- Benzaldehyde undergoes all the chemical reactions that aromatic aldehydes undergo, such as electrophilic substitution and the Cannizzaro reaction.

It can also undergo an oxidation reaction to yield benzoic acid. Benzaldehyde can undergo additional reaction with hydrocyanic acid and sodium bisulfite. It reacts with alcoholic potassium cyanide to form benzoin. The hydrogenation of benzaldehyde produced benzyl alcohol.

The reaction between benzaldehyde, anhydrous sodium acetate and acetic anhydride yields a compound called cinnamic acid. The reaction of benzaldehyde with potassium hydroxide produces an oxidation and reduction reaction known as the Cannizzaro reaction. This reaction yields products including potassium benzoate and benzyl alcohol.

2. How is Benzaldehyde Produced Naturally?

Ans- Benzaldehyde is produced both naturally and synthetically. The natural source of this organic compound is amygdalin. This chemical compound can be found in items like bitter almonds, cherries, peaches and apricot pits. It is also found in a plant known as Chinese cassica. 

Amygdalin can be broken down with the enzyme emulsion. This yields benzaldehyde and hydrogen cyanide (HCN). While HCN is a lethal poison, benzaldehyde is a compound that finds several applications such as a flavouring agent and perfume etc.