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Review of δ-Terpineol

Review of δ-Terpineol

By: Foreverest

Terpineol is a general term for monocyclic monoterpene tertiary alcohols, which specifically includes α-Terpineol, β-Terpineol, γ-Terpineol, δ-Terpineol, and Terpinen-4-ol (Christina Khaleel, 2018)1. In recent years, with the continuous basic research on terpineol, the understanding and application of δ-Terpineol have started to deepen in the industry.

Natural terpineol is mainly α-Terpineol and Terpinen-4-ol, and other isomers are present in small amounts in pine oil, camphor oil, miscellaneous lavender oil, canola oil, orange leaf oil, neroli oil, etc. Among the volatile oils of plants, α-Terpineol and Terpinen-4-ol are the most abundant and the most easily separated. In nature, the content of natural β-Terpineol and δ-Terpineol is very small (Bauer K., 2001)2, and the direct separation from plant volatile oil lacks commercial value. Since the content of α-Terpineol and its isomers in camphor, eucalyptus, and melaleuca is higher, the raw material of natural terpineol can be extracted from 1,4-Cineole, 1,8-Cineole, Eucalyptol, Linalool by-products.

Biobased Volatile component %, avg.Content %, avg.Content
C.camphora Terpineol 19.26% FU Yuxin et al, 2016 (FU Yuxin., 2016)3
Eucalyptol 24.67%
Linalool 21.94%
M.alternifolia Terpineol 24.49% QIN Rongxiu et al, 2020 (QIN Rongxiu., 2020)4
1,8-cineole 41.92%

Currently commercially available synthetic Terpineol mainly includes three isomers of α-Terpineol, β-Terpineol and γ-Terpineol. It can be used to synthesize high value-added downstream products such as Terpineol acetate, 1,8-Cineole, Camphor, Borneol, Linalool, etc. Industrially synthesized Terpineol is generally prepared from α-Pinene and β-Pinene, the main components of Turpentine oil, through hydration, using the one-step process or two-step process5. Another synthetic route uses Limonene as a starting material to react and synthesize Terpineol in the presence of a solid sulfonic acid type cation exchange resin. The reaction product components of this route are less than those using turpentine as raw material, and the total alcohol yield can be as 67.8%6.

α-Terpineol β-Terpineol γ-Terpineol δ-Terpineol Terpinen-4-ol
℃, Boiling point 217 210 218 215 209
℃, Flash point 87.9 87.3 89.1 86.7 86.0
℃, Melting Point 36.0 32.5 40.9 28.3 47.0
g/cm3, Density 0.927 0.916 0.938 0.915 0.935
Data Source: EPA, USA
NOTE: Above data volume are predicted average.

The separation process of δ-Terpineol is more difficult. This is because the content of δ-Terpineol is very small in nature, and the melting point and boiling point of Terpineol isomers are close to each other, and it is difficult to separate them. Among them, the melting point of β-Terpineol is about 27.5℃, the melting point of δ-Terpineol is about 28.3℃; the boiling point of β-Terpineol is about 218 to 219℃, and the boiling point of δ-Terpineol is about 209 to 210℃. Such physchem properties increase the difficulty of separation operation of δ-Terpineol. According to feedback from the manufacturers, the separation of δ-Terpineol currently has the following difficulties:

  1. High melting point and easy crystallization, it is easy to block the distillation tower during the rectification process, which increases the difficulty of rectification.
  2. In the later stage of extraction, the material liquid is very thick, the crystallization process changes obviously, and is easily affected by the distillation environment. It results in a lot of inclusions, high loss and high cost7. In view of the above issues, the patented technology7 of improving the discharge device of the rectification tower in the industry can produce δ-Terpineol with a purity of 95%~99% through the three major processes of rectification, crystallization and centrifugation.

δ-Terpineol can also use 1,8 Cineole as a starting material, and use alkali metal aryl compounds as elimination reagents to perform elimination by the E2 reaction. This route has excellent selectivity to δ-Terpineol. And can produce high-purity by-product trans-β-Terpineol 8.

Through the research on δ-Terpineol bromination, acidification and other reactions (Carman, 1993)9, it is now known that δ-Terpineol can produce the following substances, These substances, such as 7-hydroxycineole, are related to the Eucalyptol metabolism (Wanda Mączka, 2021)10.

Substance Description
7-hydroxycineole 7-hydroxycineole is a derivative of the terpene 1,8-cineole, which is also known as eucalyptol. It is formed when 1,8-cineole undergoes hydroxylation at the 7 position of its molecular structure. 7-hydroxycineole can be found in certain essential oils, such as Eucalyptus radiata leaf oil and tea tree oil, where it contributes to their characteristic aroma and potential biological activity.

7-hydroxycineole is a derivative of the terpene 1,8-cineole, which is also known as eucalyptol. It is formed when 1,8-cineole undergoes hydroxylation at the 7 position of its molecular structure. 7-hydroxycineole can be found in certain essential oils, such as Eucalyptus radiata leaf oil and tea tree oil, where it contributes to their characteristic aroma and potential biological activity.
crystalline 7-bromocineole Crystalline 7-bromocineol is a compound that is derived from the terpene known as 1,8-cineole (or eucalyptol). It is formed when 1,8-cineole undergoes bromination at the 7 position of its molecular structure. The resulting compound is a white crystalline solid with a slightly bitter taste and a faint, sweet odor.

Crystalline 7-bromocineol has been used in various applications, including as a building block for the synthesis of other organic compounds. It has also been investigated for its potential use in the preparation of fragrances and flavors.

However, it is important to note that brominated compounds like 7-bromocineol can be potentially harmful to human health and the environment, and proper safety measures should be taken when handling and using them.
(r-1 ,t-4)-1.7-Dibromo-p-menthan-8-ol
(r-1 ,c-4)-1,7-Dibromo-p-menthan-8-ol		 (R-1, T-4)-1,7-dibromo-p-menthane-8-ol is a chemical compound that belongs to the family of terpene derivatives. It is also known by other names such as bromochlorophen and 2-bromo-3-chloro-5-(2,4-dichlorophenoxy)phenol.

This compound is an organic halogenated molecule and its chemical formula is C10H11Br2ClO. It is used as a pesticide and herbicide due to its effective insecticidal, bactericidal, and fungicidal properties.

However, it is important to note that the use of this compound has been restricted or banned in some countries due to its potential toxicity and environmental impact. Furthermore, exposure to high concentrations of this compound can cause skin and eye irritation, respiratory problems, and other health hazards.
(r-l,t-4)-p-menthane-1,7,8-triol (R-L, T-4)-p-menthane-1,7,8-triol is a chemical compound that belongs to the family of terpene derivatives. It is also known as 1,7,8-trihydroxy-p-menthane or simply trihydroxymenthane.

This compound is a triol, meaning it has three hydroxy (-OH) groups on its molecular structure. Its chemical formula is C10H20O3 and its molecular weight is 188.27 g/mol.

Trihydroxymenthane can be found in certain herbs and essential oils, such as thyme (Thymus vulgaris) oil and peppermint (Mentha piperita) oil. It has been investigated for its potential use in various applications, including as an antioxidant, anti-inflammatory, and antimicrobial agent.

However, further research is needed to fully understand the properties and potential uses of this compound.
(r-1,t-4)-p-menthane-1,8-diol (R-1,T-4)-p-menthane-1,8-diol is a chemical compound that belongs to the family of terpene derivatives. It is also known as p-mentha-1,8-diol or simply menthol diol.

This compound is a diol, meaning it has two hydroxy (-OH) groups on its molecular structure. Its chemical formula is C10H20O2 and its molecular weight is 172.27 g/mol.

Menthol diol is a derivative of menthol and can be found in certain essential oils, such as peppermint (Mentha piperita) oil and eucalyptus (Eucalyptus globulus) oil. It has been investigated for its potential use in various applications, including as an antimicrobial agent and as an ingredient in cosmetic and personal care products.

However, it is important to note that like other compounds derived from menthol, menthol diol may cause skin irritation and other allergic reactions in some individuals.
(r-1 ,c-4)-p-Menthane-7,8-diol
(r-1 ,t-4)-p-Menthane-7,8-diol		 (R-1, C-4)-p-menthane-7,8-diol is a chemical compound that belongs to the family of terpene derivatives. It is also known as 7,8-dihydroxy-p-menthane or simply dihydroxymenthane.

This compound is a diol, meaning it has two hydroxy (-OH) groups on its molecular structure. Its chemical formula is C10H20O2 and its molecular weight is 172.27 g/mol.

Dihydroxymenthane can be found in certain herbs and essential oils, such as thyme (Thymus vulgaris) oil and peppermint (Mentha piperita) oil. It has been investigated for its potential use in various applications, including as an antimicrobial agent and as an ingredient in cosmetic and personal care products.

However, further research is needed to fully understand the properties and potential uses of this compound.
7-bromo-1,8-cineole 7-bromo-1,8-cineole is a chemical compound that belongs to the family of monoterpenoids. It is also known as 7-bromo-1,8-epoxy-p-menthane or simply bromocineole.

This compound is a derivative of cineole and has a molecular formula of C10H17BrO. It is used in the fragrance industry and can be found in some essential oils, such as tea tree (Melaleuca alternifolia) oil.

However, it is important to note that like other organic halogenated compounds, bromocineole may have potential health and environmental impacts, and its use has been regulated or banned in some countries.

The odor of monocyclic monoterpene alcohols appears woody and floral sense, and the characteristic of Terpineol is weak and does not last long. It is a often used as a flavoring agent for tobacco to enhance the fresh flavor of cigarettes. A perfumer evaluate the scent of Terpineol: “It smells like clove with a hint of lemon freshness, and of course, the woody aroma of pine resin, with a powdery feel of purple flowers. The hazy feeling is come from here (Kokenkun, 2021)11.”

Terpineol is naturally accompanies clove-like floral fragrances, it has been used as a fragrance component in perfumes and daily chemical products to add a fresh feeling to the scent. The downstream product of Terpineol, Terpineyl acetate, is also used in the fougere family with lemon and lavender scents. This heavy and hazy feeling mixed with the freshness of floral fragrances is popular in many countries’ religious incense.

With the in-depth research on the application of δ-Terpineol, it will be more application. In addition to the fragrance flavoring application. δ-Terpineol, as a new product, is also used as a broad-spectrum bactericidal ingredient, which has antibacterial effects on mold, streptococcus and candida. In the field of veterinary medicine, it can be used for the treatment activity ingredient of foot-and-mouth disease, rabbit mildew, ringworm and poultry plague. And it can be used as solvent of ethyl cellulose or plasticizer of epoxy resin. (Mączka, 2021)

References

  1. Christina Khaleel, Nurhayat Tabanca, Gerhard Buchbauer, α-Terpineol, a natural monoterpene: A review of its biological properties, Open Chemistry, 2018
  2. Bauer K., Garbe D., Surburg H., Common Fragrance and Flavor materials: Preparations, properties, and uses, 4th ed., Wiley, New York, 2001.
  3. FU Yuxin., JIANG Xiangmei., LUO Liping., ZHANG Ting., GUO Xiali., HE Yichang., A GC－MS analysis of volatile oil from different types of Cinnamomum camphora leaves, Journal of Forestry Engineering, 2016
  4. QIN Rongxiu., LIANG Zhongyun., LI Guizhen., CHEN Haiyan., Analysis on Chemical Components in Volatile Oils from Flowers and Leaves of Melaleuca alternifolia of 1,8-Cineole-Terpineol Type, Guangxi Forestry Science, 2020
  5. MENG Zhonglei et al., Synthetic method and application of terpineol, China Patent CN108164395
  6. WANG Hongtao et al., Reaction device for preparing terpineol from limonene and synthesis method thereof, China Patent CN115569615
  7. JIANG Shipping et al,. High-purity Delta terpilenol separation and purification method, China Patent CN104045519
  8. Peter W. D. Mitchell, Preparation of delta-terpineol, US Patents US4638103
  9. Raymond M Carman, Chemistry Around δ-Terpineol, Australian Journal of Chemistry, 1993
  10. Wanda Mączka, Anna Duda-Madej, Aleksandra Górny, Małgorzata Grabarczyk, Katarzyna Wińska, Can Eucalyptol Replace Antibiotics, Molecules, 2021
  11. Kokenkun, Nathanology Fragrance Design Studio, Facebook