November 20, 2023
Mmmm—I could be one of your favorite flavors and aromas at Thanksgiving.
What molecule am I?
Image of Borneol

Borneol is a chiral bicyclic alcohol that exists in nature as two enantiomers, (–)- or L-borneol (shown) and (+)- or D-borneol1. Along with former Molecules of the Week eucalyptol (aka 1,8-cineole), camphor, and α-pinene, (–)-borneol is a principal component of the oil and leaves of the herb rosemary (Salvia rosmarinus, formerly Rosmarinus officinalis).

Borneol was known as early as 1842, when French chemist Charles Frédéric Gerhardt identified it and named it “camphre de Bornéo”, or “Borneo camphor”. In the 1870s, English chemist Henry E. Armstrong and others measured the properties and reactions of borneol (which he called “camphol”) and related compounds. The 19th century chemists did not realize that borneol existed in two isomers and their publications are listed under racemic borneol2.

Borneol can be oxidized to camphor by treating it with sodium hypochlorite and other oxidizing agents. But when camphor is reduced to borneol (e.g., with sodium borohydride), the main product is borneol’s positional isomer isoborneol3. As seen in the fast facts table, (–)-borneol’s melting and boiling temperatures are very close to each other. As a result, when the compound is heated up to ≈207 °C, it melts and sublimes.

All of which brings us back to rosemary, which you might use  to season stuffing and vegetables for your Thanksgiving dinner. According to S. Kokkini, R. Karousou, and E. Hanlidou at Aristotle University (Thessaloniki, Greece) in the second edition of the Encyclopedia of Food Sciences and Nutrition, “[Rosemary oils] with a decreased amount of α-pinene and camphor and increased amounts of 1,8-cineole and borneol are judged to be of a better quality.”

For more information on rosemary and borneol, see the ScienceDirect rosemary topic page.

1. CAS Reg. No. 464-43-7.
2. CAS Reg. No. 507-70-0.
3. CAS Reg. No. 124-76-5 (racemic).

(–)-Borneol hazard information*

Hazard class**GHS code and hazard statement
Flammable solids, category 1H228—Flammable solidChemical Safety Warning
Skin corrosion/irritation, category 2H315—Causes skin irritationChemical Safety Warning
Skin sensitization, category 1H317—May cause an allergic skin reactionChemical Safety Warning

Serious eye damage/eye irritation, category 2A

H319—Causes serious eye irritationChemical Safety Warning
Short-term (acute) aquatic hazard, category 3H402—Harmful to aquatic life

Long-term (chronic) aquatic hazard, category 3

H412—Harmful to aquatic life with long-lasting effects

*Compilation of multiple safety data sheets.
**Globally Harmonized System (GHS) of Classification and Labeling of Chemicals. Explanation of pictograms.

Molecule of the Future

Explosives chemists are always looking to make materials that are safer to handle and have lower environmental impact. The current trend is toward organic compounds that contain several nitrogen atoms; these substances are targeted to replace heavy metal–containing explosives such as lead azide1 [Pb(N3)2].

Last March, Hongwei Yang, Chuan Xiao, Guangbin Cheng, and colleagues at Nanjing University of Science and Technology (China) and China Northern Industries Group (Nanjing), reported the synthesis and properties of DTAT-K2, a [5,6,5]-tricyclic bistetrazole molecule (see image) that could replace lead azide as a “green” primary explosive with good priming ability.

Molecule of the Future

DTAT-K, with the chemical name 5-azido-10-nitro-bis(tetrazolo)[1,5-c:5′,1′-f]pyrimidine, potassium salt, was synthesized from commercially available, inexpensive 4,6-dichloro-5-nitropyrimidine3 by treating it with sodium azide and then replacing the sodium ion with potassium. The authors’ discovery was somewhat serendipitous because they only expected the reaction to displace the chlorine atoms on the pyrimidine ring with azide groups. The formation of the tricyclic molecule and the addition of a third azide moiety were a big surprise.

1. CAS Reg. No. 13424-46-9.
2. CAS Reg. No. 2918805-26-0.
3, CAS Reg. No. 4316-93-2.

Molecule of the Future

Once a month we bring you a newly discovered or developed molecule that has important implications for the future of chemistry or society in general. Look for it the third week of each month. Learn more about this month's Molecule of the Future below.

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(–)-Borneol fast facts

CAS Reg. No.464-45-9
SciFinder nomenclatureBicyclo[2.2.1]heptan-2-ol, 1,7,7-trimethyl-, (1S,2R,4S)-
Empirical formulaC10H18O
Molar mass154.25 g/mol
AppearanceWhite crystals, powder, or solid
Melting point207–209 °C
Boiling point210–212 °C
Water solubility0.74 g/L (25 °C)
Chemical Abstract Service - a division of ACS

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