The key difference between carvacrol and thymol is that carvacrol contains a hydroxyl group at the ortho position of the benzene ring whereas thymol contains a hydroxyl group at the meta position of the benzene ring.
Both carvacrol and thymol have the same chemical formula (C10H14O), but they have slightly different structures. Although these two chemical structures appear closely similar, there is a difference in the position of the hydroxyl group in their benzene ring structure.
CONTENTS
1. Overview and Key Difference
2. What is Carvacrol
3. What is Thymol
4. Side by Side Comparison – Carvacrol vs Thymol in Tabular Form
5. Summary
What is Carvacrol
Carvacrol is an organic compound having the chemical formula C10H14O. A synonym for this compound is cymophenol. It is a monoterpenoid phenol. When considering the physical properties of this compound, it has the characteristic pungent, warm odour of oregano. This compound is insoluble in water but soluble in organic solvents such as ethanol, and diethyl ether, acetone. We may find carvacrol naturally in the essential oils of oregano, thyme, pepperwort, and wild bergamot. These essential oils typically contain carvacrol ranging from 5 to 75%.
Figure 01: Chemical Structure of Carvacrol
As shown in the above image, the chemical structure of carvacrol contains a methyl group. Hydroxyl group is in para position to the methyl group and an isopropyl group.
We can also synthetically produce carvacrol by the fusion of cymol sulfonic acid in the presence of caustic potash. In addition, we can use another method which includes the action of nitrous acid on 1-methyl-2-amino-4-propyl benzene. Another rarely used method is prolonged heating of five parts of camphor with one part of iodine.
When considering the reactions of carvacrol, oxidation with ferric chloride can convert carvacrol into dicarvacrol and oxidation with phosphorous pentachloride converts it into chlorcymol. In vitro, this substance shows antimicrobial activity against about 25 different periodontopathic bacteria strains.
What is Thymol?
Thymol is an organic compound having the chemical formula C10H14O. It is a natural monoterpenoid phenol and a derivative of cymene. It is a structural isomer of carvacrol because carvacrol has its hydroxyl group in para position while thymol has its hydroxyl group at the meta position. This compound has a pleasant aromatic odour, and we can extract it from various plants as a white crystalline solid. It has strong antiseptic properties and also provides the distinctive, strong flavour of the culinary herb, thyme.
Figure 02: Chemical Structure of Thymol
Unlike carvacrol, thymol is slightly water-soluble at neutral pH values. But it is extremely soluble in organic solvents such as alcohols. Apart from that, it can also dissolve in strong alkaline solutions due to its ability to deprotonate. In addition to extraction from its natural sources, we can synthesize thymol chemically via the reaction between m-cresol and propene. This reaction takes place in the gas phase.
What is the Difference Between Carvacrol and Thymol?
Carvacrol and thymol are cyclic organic compounds. Both these compounds have the same chemical formula; they are structural isomers. The key difference between carvacrol and thymol is that carvacrol contains a hydroxyl group at the ortho position of benzene ring whereas thymol contains a hydroxyl group at the meta position of the benzene ring.
The below infographic tabulates more differences between carvacrol and thymol.
Summary – Carvacrol vs Thymol
Carvacrol and thymol are cyclic organic compounds containing a methyl group, hydroxyl group and an isopropyl group. The two structures differ from each other according to the position of the hydroxyl group. The key difference between carvacrol and thymol is that carvacrol contains a hydroxyl group at the ortho position of benzene ring whereas thymol contains a hydroxyl group at the meta position of the benzene ring.
Reference:
1. “Thymol.” Wikipedia, Wikimedia Foundation, 31 July 2020, Available here.
Image Courtesy:
1. “Carvacrol structure” By Edgar181 – Own work (Public Domain) via Commons Wikimedia
2. “Thymol2” By NEUROtiker – Own work (Public Domain) via Commons Wikimedia