BENZALDEHYDE: PROPERTIES, SYNTHESIS, STRUCTURE AND USES - CHEMISTRY - 2025

The benzaldehyde is an organic compound whose chemical formula is C ₆ H ₅ CHO. At room temperature it is a colorless liquid that may turn yellowish on storage. Benzaldehyde represents the simplest aromatic aldehyde and the one most used industrially. In this the formyl group is linked directly to the benzene ring.

It is found naturally in the bark of the stems, leaves and seeds of plants, such as: almond, cherry, peach and apple. It can also be found in bitter almond, patchouli, hyacinth, and cananga oils. Benzaldehyde can be absorbed through the skin and through the lungs, but is rapidly metabolized to benzoic acid.

This is conjugated with glucuronic acid or with glycine, and is excreted in the urine. It is used as a flavoring for some foods, in the perfume industry and in the pharmaceutical industry. Its greatest importance lies in the fact that, from benzaldehyde, compounds such as benzyl acid, cinnamic acid, mandelic acid, etc. are obtained.

The above-named compounds have numerous uses. Also, benzaldehyde is a fuel incompatible with strong oxidizing agents, strong acids and reducing agents, and light.

Physical and chemical properties

Chemical names

Benzaldehyde, benzoic aldehyde, benzenecarbon, phenylmethanal, and benzenecarboxaldehyde.

Molecular formula

C ₇ H ₆ O or C ₆ H ₅ CHO

Color

It is a colorless liquid that can turn yellowish.

Odor

Similar to that of bitter almond.

Taste

Aromatic burning.

Boiling point

354ºF to 760mmHg.

178.7 ° C.

Melting point

-15ºF

-26 ºC

Solubility

In water, 6,950 mg / L at 25 ºC, because it is a predominantly nonpolar compound and interacts weakly with water molecules.

Miscible with alcohol, ether, fixed and volatile oils.

Soluble in liquid ammonia, apolar solvent.

Density

1,046 g / cm ³ at 68ºF

1,050 g / cm ³ at 15 ºC

Its vapor is denser than air: 3.65 times in relation to it.

Stability

It is stable at room temperature. However, it oxidizes in air to benzoic acid.

Viscosity

1,321 cP at 25 ºC

Structure

As can be seen in the first image, the structure of benzaldehyde reveals its aromatic character -the benzene ring on the left- and also the formyl group (-CHO), on the right, responsible for the polar character of the molecule. So, benzaldehyde is an organic, aromatic and polar compound.

What is its molecular geometry? Because all the carbon atoms that make up the benzene ring have sp2 hybridization, as well as that of the formyl group, the molecule rests on the same plane, and consequently it can be visualized as a square (or rectangle, seen axially).

Intermolecular interactions

The formyl group establishes a permanent dipole moment in the benzaldehyde molecule, although remarkably weak compared to that of benzoic acid.

This allows it to have stronger intermolecular interactions than benzene, whose molecules can only interact through London forces (induced dipole-dipole scattering).

This is reflected in its physical properties, such as its boiling point, which is twice that of benzene (80 ºC).

Also, the formyl group lacks the ability to form hydrogen bonds (hydrogen is bonded to carbon, not oxygen). This makes it impossible for benzaldehyde molecules to form three-dimensional arrangements, like those seen in benzoic acid crystals.

Applications

Additive and flavoring and flavoring agent

It is a compound that serves as the basis for medicines, colorants, perfumes and in the resin industry. It can also be used as a solvent, plasticizer and low temperature lubricant. It is used to flavor or season food and tobacco.

It is used in the preparation of flavors, such as almond, cherry and walnut. It is also used as a flavoring agent in canning cherry syrup. It intervenes in the elaboration of violet, jasmine, acacia, sunflower fragrances, etc., and is used in the manufacture of soaps. It is used as a fuel and fuel additive.

Unconventional applications

It intervenes as a reagent in the determination of ozone, phenol, alkaloids and methylene. It acts as an intermediary for the regulation of plant growth.

Benzaldehyde and N-heptaldehyde inhibit the recrystallization of snow, preventing the formation of deep ice deposits that cause snow avalanches. However, this use is objected to as a source of environmental contamination.

Repellent

Benzaldehyde is used as a repellent for bees, being used in apiaries in conjunction with smoke to keep the bees away from the hives and to be able to work safely in them, avoiding stings.

In the synthesis of malachite

Malachite green is a compound synthesized with the intervention of benzaldehyde. The dye is used in fish farming to combat fish diseases, such as the well-known whitehead and fungal infections.

It can only be used in aquariums, since harmful effects have been reported in mammals, among which are carcinogenesis, mutagenesis, teratogenesis and chromosomal turnover; this is why its use has been banned in many countries.

It is also used in microbiology for the staining of bacterial spores.

Synthetic intermediary

-Benzaldehyde is an intermediate in the synthesis of cinnamic acid used in condiments, but its main use is in obtaining methyl, ethyl and benzyl esters used in the perfume industry. Cinnamic acid induces cytostasis and reversal of malignant properties of human tumor cells in vitro.

-Benzaldehyde is involved in the synthesis of benzyl alcohol, which although it is used as a food seasoning and industrial solvent, its main function is to serve as an intermediary for the synthesis of compounds used in the pharmaceutical industry and production of perfumes, spices and some colorants of aniline.

-Benzaldehyde is an intermediate in the synthesis of mandelic acid. This is used in the treatment of skin problems, such as aging from exposure to sunlight, uneven pigmentation, and acne.

-It has antibacterial use acting as an oral antibiotic in urinary tract infections.

Synthesis

The most used form of synthesis of benzaldehyde is by catalytic oxidation of toluene, using manganese oxide (MnO ₂) and cobalt oxide (CoO) catalysts. Both reactions are carried out with sulfuric acid as the medium.

References

1. Steven A. Hardinger, Department of Chemistry & Biochemistry, UCLA. (2017). Illustrated Glossary of Organic Chemistry: Benzaldehyde. Taken from: chem.ucla.edu
2. Pubchem. (2018). Benzaldehyde. Taken from: pubchem.ncbi.nlm.nih.gov
3. Wikipedia. (2018). Benzaldehyde. Taken from: en.wikipedia.org
4. William H. Brown. (December 2, 2011). Benzaldehyde. Taken from: britannica.com
5. DermaFix. (2017). Mandelic Acid and it's benefits. Taken from: dermafix.co.za
6. Chemical Book. (2017). Benzaldehyde. Taken from: chemicalbook.com