Geraniol

Structural formula
General
Surname	Geraniol
other names	2,6-dimethyl- trans -2,6-octadien-8-ol 3,7-dimethyl- trans -2,6-octadien-1-ol ( E ) -3,7-dimethyl-2,6-octadien-1-ol Lemonol Geranyl alcohol
Molecular formula	C 10 H 18 O
Brief description	colorless or slightly yellowish liquid with a floral odor
External identifiers / databases
CAS number 106-24-1 EC number 203-377-1 ECHA InfoCard 100.003.071 PubChem 637566 Wikidata Q410836
properties
Molar mass	154.25 g mol −1
Physical state	liquid
density	0.89 g cm −3
Melting point	−15 ° C
boiling point	229-230 ° C
Vapor pressure	1 hPa (70.6 ° C)
solubility	little in water (686 mg l −1 at 20 ° C)
Refractive index	1.4766 (20 ° C)
safety instructions
GHS labeling of hazardous substances danger H and P phrases H: 315-317-318 P: 280-305 + 351 + 338
Toxicological data	3600 mg kg −1 ( LD 50 ,  rat ,  oral )
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . Refractive index: Na-D line , 20 ° C

Geraniol is an acyclic monoterpene - allyl alcohol and is in ( E , Z ) isomerism to nerol : geraniol is the ( E ) isomer, nerol is the ( Z ) isomer. As a floral note, it is part of many perfumes. Geraniol is an intermediate in the manufacture of geranyl esters , citronellol and citral .

Occurrence

It is part of most essential oils and is found in coriander , bay leaf , and nutmeg , among others .

Geranium essential oil is rich in geraniol.

The largest amounts are contained in palmarosa oil ( Cymbopogon martinii , 70–85%), geranium and rose oil.

Extraction and presentation

Most of the geraniol is synthetically produced on an industrial scale. A widely used manufacturing method is the hydrogenation of citral.

Another synthetic route is the isomerization of linalool in the presence of orthovanadate catalysts. This creates a geraniol-nerol mixture with a yield of over 90%, which is separated by means of fractional distillation.

Smaller quantities are obtained for the perfume industry from the distillation of essential oils, such as Javanese citronella oil , possibly with prior saponification of the esters.

properties

Physical Properties

Geraniol is a colorless to slightly yellowish liquid with a floral-rose-like odor. The density of geraniol is 0.88 g · cm ⁻³ . The liquid solidifies at around −15 ° C and boils at around 230 ° C. It is poorly soluble in water at 686 mg · l ⁻¹ . The flash point is 76 ° C.

Chemical properties

As an acyclic unsaturated alcohol, geraniol undergoes rearrangement and cyclization reactions . Rearrangement in the presence of copper catalysts leads to citronellal , partial or complete hydrogenation to citronellol or 3,7-dimethyloctan-1-ol , oxidation or catalytic dehydrogenation to citral , esterification to the respective geranyl esters. In an acidic environment, both geraniol and nerol can be cyclized to the isomer α- terpineol .

Analytics

For the reliable qualitative and quantitative determination of geraniol in complex mixtures, the coupling of gas chromatography with mass spectrometry can be used after appropriate sample preparation .

Biological importance

While geraniol itself is only a weak contact allergen, its auto-oxidation products have a much stronger allergenic effect.

literature

• H. Surburg, J. Panten: Common Fragrance and Flavor Materials: preparation, properties, and uses. Wiley-VCH, Weinheim 2006, ISBN 3-527-31315-X , pp. 28-29.

Individual evidence

1. ↑ ^{a b} Geraniol data sheet (PDF) from Carl Roth , accessed on December 14, 2010.
2. ↑ ^{a b} Geraniol data sheet at AlfaAesar, accessed on December 15, 2010 ( PDF )(JavaScript required) .
3. ↑ Geraniol in the hazardous substances database of the University of Hamburg .
4. ↑ Data sheet Geraniol at Sigma-Aldrich , accessed on May 12, 2017 ( PDF ).
5. ↑ ^{a b c d} Entry on geraniol in the GESTIS substance database of the IFA , accessed on February 1, 2016(JavaScript required) .
6. ↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Physical Constants of Organic Compounds, pp. 3-266.
7. ↑ Juliane Daphi-Weber, Heike Raddatz, Rainer Müller: Investigation of fragrances - controlled fragrances. In: Gesellschaft Deutscher Chemiker (Ed.): HighChem up close. Volume V, Frankfurt am Main 2010, ISBN 978-3-936028-64-5 , pp. 94-95.
8. ^ ^{A b c} Horst Surburg & Johannes Panten: Common Fragrance and Flavor Materials . 6. Completely revised and expanded edition. Wiley-VCH, 2016, ISBN 978-3-527-33160-4 , pp. 30-32 .
9. ↑ DS Pedersen, DL Capone, GK Skouroumounis, AP Pollnitz, MA Sefton: Quantitative analysis of geraniol, nerol, linalool, and alpha-terpineol in wine. In: Anal Bioanal Chem. 375 (4), Feb 2003, pp. 517-522. PMID 12610703
10. ↑ B. Sgorbini, MR Ruosi, C. Cordero, E. Liberto, P. Rubiolo, C. Bicchi: Quantitative determination of some volatile suspected allergens in cosmetic creams spread on skin by direct contact sorptive tape extraction-gas chromatography-mass spectrometry. In: J Chromatogr A. 1217 (16), Apr 16, 2010, pp. 2599-2605. PMID 20074740
11. ↑ L. Hagvall, C. Bäcktorp, S. Svensson, G. Nyman, A. Börje, AT Karlberg: Fragrance compound geraniol forms contact allergens on air exposure. Identification and quantification of oxidation products and the effect on skin sensitization. In: Chemical Research in Toxicology . Volume 20, No. 5, pp. 807-814. PMID 17428070 .