106-23-0

Basic information

• Product Name: 6-Octenal,3,7-dimethyl-
• Synonyms: 2,3-Dihydrocitral;3,7-Dimethyl-6-octenal;3,7-Dimethyloct-6-en-1-al;Citronellal;NSC 46106;Rhodinal;dl-Citronellal;b-Citronellal
• CAS NO: 106-23-0
• Molecular Formula: C₁₀H₁₈O
• Molecular Weight: 154.2493
• EINECS: 203-376-6
• Product Categories: Furans ,Coumarins
• Mol File: 106-23-0.mol

Chemical Properties

• Melting Point: -16°C (estimate)
• Boiling Point: 208.4 °C at 760 mmHg
• Flash Point: 75.6 °C
• Appearance: clear light yellow liquid
• Density: 0.85 g/cm³
• Vapor Pressure: 0.215mmHg at 25°C
• Refractive Index: 1.437
• Storage Temp.: 2-8°C
• Water Solubility: Slightly miscible with water and ethanol.
• Merck: 14,2329
• BRN: 1720789
• CAS DataBase Reference: 6-Octenal,3,7-dimethyl-(CAS DataBase Reference)
• NIST Chemistry Reference: 6-Octenal,3,7-dimethyl-(106-23-0)
• EPA Substance Registry System: 6-Octenal,3,7-dimethyl-(106-23-0)

Safety Data

• Hazard Codes: Xi:Irritant
• Statements: R36/37/38:
• Safety Statements: S26:; S37/39:
• RIDADR: UN 3082 9/PG 3
• WGK Germany: 3
• RTECS: RH2140000
• F: 8
• TSCA: Yes
• Hazardous Substances Data: 106-23-0(Hazardous Substances Data)

Usage

Uses

Used in Fragrance Industry:
6-Octenal,3,7-dimethylis used as a fragrance ingredient for its characteristic citronella, rose-, and lemon-like odor. It is often used in perfumes and other scented products due to its refreshing and pleasant scent.
Used in Flavor Industry:
Citronellal is used as a flavoring agent, providing a floral, green, rosy, and citrus-lemon taste. It is commonly used in the food and beverage industry to add a unique flavor to various products.
Used in Insect Repellent Applications:
Citronella oil, which contains Citronellal as its main component, is known for its insecticidal properties. 6-Octenal,3,7-dimethylis used as an active ingredient in insect repellents to help protect against insects.
Used in Pharmaceutical Industry:
(±)-Citronellal has been studied for its fumigant antifungal activity against Pyricularia (Magnaporthe) grisea, indicating its potential use in the development of antifungal medications.
Used in Essential Oils:
Citronellal is a key component in essential oils derived from various plants, such as Ceylon citronella (C. nardus) and Java citronella (C. winterianus). These essential oils are used in aromatherapy and other therapeutic applications.
Used in Synthesis of Other Compounds:
Citronellal can be used as a starting material in the synthesis of other compounds, such as dihydrocitronellal, citronellol, dihydrocitronellol, and isopulegol, which are used in various industries, including the fragrance and flavor industries.

Preparation

Citronellal is still isolated from essential oils in considerable quantities; it is also produced synthetically. 1) Isolation from essential oils:(+)-Citronellal is obtained from citronella oils by fractional distillation. Racemic citronellal is isolated from E. citriodora oil; when necessary, it is purified by using an addition compound, for example, the bisulfite derivative. 2) Synthesis from geraniol or nerol: Racemic citronellal can be obtained by vaporphase rearrangement of geraniol or nerol in the presence of, for example, a barium-containing copper–chromium oxide catalyst. 3) Synthesis from citronellol: Racemic citronellal can also be obtained by dehydrogenation of citronellol under reduced pressure with a copper chromite catalyst. 4) Synthesis from citral: Selective hydrogenation of citral to citronellal can be accomplished in the presence of a palladium catalyst in an alkaline alcoholic reaction medium. A continuously operating process for the hydrogenation on a palladium catalyst in the presence of trimethylamine has been developed. 5) Synthesis from myrcene: (+)- and (?)-Citronellal are available from myrcene via geranyldiethylamine, which is enantioselectively isomerized to (+)- or (?)-citronellalenamine. Hydrolysis yields pure (+)- or (?)-citronellal; see monograph menthol.

Essential oil composition

Citronella oil contains a number of fragrant fractions of which citronellal, geraniol and citronellol are the major components. Ceylon citronella oil contains 55 to 65% total acetylizable alcohols (calculated as citronellol) and 7 to 15% total aldehyde (calculated as citronellal). The main constituents are geraniol (18 to 20%), citronellol (6.4 to 8.4%), citronellal (5 to 15%), geranyl acetate (2%); limonene (9 to 11%) and methyl isoeugenol (7.2 to 11.3%). Other constituents are camphene, caryophyllene, linalool, citral (neral and geranial), methylheapenone, methyleugenol, l-borneol, nerol, eugenol and farnesol.* Java citronella oil contains not less than 35% alcohols (calculated as citronellol) and not less than 35% aldehydes (calculated as citronellal). The Java type appears to have higher concentrations of citronellol (35%) and geraniol (21%) than does the Ceylon type (citronellol 10% and geraniol 18%).

Synthesis Reference(s)

Journal of the American Chemical Society, 108, p. 7314, 1986 DOI: 10.1021/ja00283a029Tetrahedron Letters, 30, p. 5677, 1989 DOI: 10.1016/S0040-4039(00)76168-5The Journal of Organic Chemistry, 49, p. 2279, 1984 DOI: 10.1021/jo00186a038

Flammability and Explosibility

Nonflammable

Synthesis

Can be prepared by chemical synthesis or by fractional distillation of natural oils, such as citronella. Industrially prepared by hydrogenation of β-citronellol or by catalytic hydrogenation of citral; also in the laboratory by dehydration of hydroxydihydrocitronellal.

Metabolism

Feeding 50 g citronellal to rabbits was followed by the isolation of 13 g of a crystalline glucuronide, which proved to be p-menthane-3.8-diol-D-glucuronide. The citronellal appeared to have been cyclized and the glucuronide obtained was identical with that obtained on feeding p-menthane-3,8-diol (menthoglycol) (Kühn & Low, 1938). However, evidence was produced to show that the cyclization was not, strictly speaking, a biological reaction, but a chemical one which took place in the stomach under the influence of the gastric hydrochloric acid. The conjugation of the menthoglycol with glucuronic acid was, of course, a purely biological reaction. It was found that on shaking 20 g citronellal with 200 ml 0-5% HCl for 48 hr at 37 C, 12 g menthoglycol was formed (Kühn & Low, 1938).

InChI:InChI=1/C10H18O/c1-9(2)5-4-6-10(3)7-8-11/h5,8,10H,4,6-7H2,1-3H3/t10-/m1/s1

Upstream product

• 40776-23-6 (1EZ)-3,7-dimethyl-1-triethylsilyloxyocta-1,6-diene 
• 104870-56-6 (+)-isopulegol 
• 22457-25-6 rac-3,7-dimethyloct-6-enenitrile oxime 
• 5392-40-5 (E/Z)-3,7-dimethyl-2,6-octadienal 
• 106-22-9 Citronellol 
• 624-15-7 geraniol 
• 106-24-1 Geraniol 
• 64-17-5 ethanol 
• 89-79-2 isopulegol 
• 93031-45-9 1-methyl-2-(1'-hydroxy-3',7'-dimethyloct-6-en-1-yl)-1H-imidazole 
• 56841-52-2 2-(2,6-dimethyl-5-heptenyl)-1,3-dithiane 
• 111-42-2 2,2'-iminobis[ethanol] 
• 106-25-2 Nerol 
• 141-27-5 3,7-dimethyl-2,6-octadienal 

Downstream Products

• 923-69-3 3,7-dimethyl-oct-6-enal-dimethylacetal 
• 107833-82-9 6-Methoxy-3,7-dimethyl-7-octenal 
• 107833-81-8 6-Methoxy-3,7-dimethyl-7-octenal dimethyl acetal 
• 84161-98-8 8-methoxy-p-menth-3-ene 
• 121637-45-4 8-methoxymenthol 
• 121637-45-4 8-methoxyneomenthol 
• 89-79-2 Isopulegol 
• 89-79-2 (rac)-neo-isopulegol 
• 89-79-2 (rac)-iso-Isopulegol 
• 89-79-2 isopulegol 
• 89-79-2 (rac)-neo-iso-Isopulegol 
• 78963-09-4 2-methyl-5-(prop-1-en-2-yl)cyclopentanecarbaldehyde 
• 3058-01-3 3-methyladipic acid 
• 67-64-1 acetone 

Relevant articles and documents

Negatively Charged N-Heterocyclic Carbene-Stabilized Pd and Au Nanoparticles and Efficient Catalysis in Water

Herein we describe the synthesis of negatively charged N-heterocyclic carbene (NHC)-functionalized palladium and gold nanoparticles (NPs), which are stable in water for over 3 months. The formation of these NHC-NPs proceeds via an efficient ligand exchange procedure. This method was successfully applied to different negatively charged NHCs bearing sulfonate and carboxylate groups. The obtained PdNPs were investigated as catalysts in hydrogenation reactions and showed high catalytic activity (TON up to 2500 and TOF up to 2000 h-1).

Preparation of well-defined dendrimer encapsulated ruthenium nanoparticles and their application as catalyst and enhancement of activity when utilised as SCILL catalysts in the hydrogenation of citral

Silica supported dendrimer encapsulated ruthenium nanoparticles were prepared and evaluated as catalysts in the hydrogenation of citral. The dendrimer encapsulated nanoparticles were prepared using the generation 4 (G4), generation 5 (G5) and generation 6 (G6) hydroxyl-terminated poly(amidoamine) (PAMAM-OH) dendrimers as templating agents with different Ru metal:dendrimer ratios. The effects of ionic liquids as catalyst coatings on the catalytic activity were investigated for the ionic liquids [BMIM][NTf2], [OMIM][NTf2], [BMIM][BF4], [BMIM][PF6], [EMIM][OcS] and [EMIM][EtS]. An enhancement in catalytic activity was observed when utilising [BMIM][NTf2] as an ionic liquid coating with selectivity towards citronellal.

Quinolinium Fluorochromate (QFC), C9H7NH: An Improved Cr(VI)-Oxidant for Organic Substrates

Yellow-orange crystalline quinolinium fluorochromate (QFC) is easily prepared in a nearly quantitative yield by the interaction of quinoline with CrO3 and hydrofluoric acid in 1:1.5:1 molar ratio.The reagent is stable.Compared with pyridinium fluorochromate (PFC), the new reagent is more soluble in organic solvents and less acidic.QFC in CH2Cl2 readily oxidizes primary, secondary, and allylic alcohols to the corresponding carbonyls, benzoin to benzil, and anthracene and phenanthrene to anthraquinone and 9,10-phenanthrenequinone, respectively.Oxidations work well also in a variety of sensitive environments, e.g. isopropylidene functionality and trimethylsilyl ethers.Organic sulfides are transformed to sulfoxides at room temperature.The facile oxidation of triphenylphosphine to triphenylphosphine oxide by QFC in CH2Cl2 or CH3CN provides a clear evidence for an oxygen-transfer reaction.The reduced product of QFC, isolated after such reactions, has been ascertained to be C9H7NH, a chromium(IV) species.The advantages of QFC have been highlighted.

ENHANCEMENT OF THE HYDROLYSIS OF GERANYL PYROPHOSPHATE BY BIVALENT METAL IONS. A MODEL FOR ENZYMIC BIOSYNTHESIS OF CYCLIC MONOTERPENES

Hydrolysis of geranyl pyrophosphate is catalyzed by salts of Mn2+ and involves C-O bond cleavage.The first order rate constants reach limiting values with 2+> 10E-2 M, and the most reactive species is GPP (Mn2+)2 at the optimum pH of 6.5-7.The products are similar to those from acid hydrolysis except that more cyclic hydrocarbons are formed in the presence of metal ions.Hydrolysis of geranyl phosphate is inhibited, and that of citronellyl pyrophosphate is weakly catalyzed by Mn2+.Other divalent metal cations catalyze the hydrolysis of geranyl pyrophosphate and the sequence of effectiveness is Cu2+>Mn2+>Co2+>Mg2+ Ca2+.

A highly reduced graphene oxide/ZrOx-MnCO3 or -Mn2O3 nanocomposite as an efficient catalyst for selective aerial oxidation of benzylic alcohols

Highly reduced graphene oxide (HRG) nanocomposites of manganese carbonate doped with (1%) zirconia (ZrOx) nanoparticles [ZrOx(1%)-MnCO3/(X%)HRG (where X = 0-7)] were prepared employing a facile coprecipitation method in which the percentage of HRG was varied. The resulting nanocomposite was calcined at 300°C. Further calcination of the catalyst at 500°C resulted in the conversion of manganese carbonate to manganese oxide [ZrOx(1%)-Mn2O3/(X%)HRG]. The effect of the inclusion of HRG on the catalytic activity along with its comparative performance between carbonates and their respective oxides was studied for the liquid-phase selective oxidation of benzylic alcohols into corresponding aldehydes using molecular oxygen as the eco-friendly oxidizing agent without adding any external additives or bases. The influence of different parameters such as different percentages of HRG, reaction times, calcination temperatures, catalyst dosages and reaction temperatures have also been systematically studied in order to optimize the catalyst composition and reaction conditions. The inclusion of HRG as a dopant remarkably enhanced the catalytic efficiency of ZrOx-MnCO3 nanocatalysts for the aerobic oxidation of alcohols. The as-prepared catalysts were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), powder X-ray diffraction (XRD), thermal gravimetric analysis (TGA), Brunauer-Emmett-Teller (BET) surface area analysis, Raman spectroscopy and Fourier transform infrared spectroscopy (FT-IR). The catalyst with composition ZrOx(1%)-MnCO3/(1%)HRG obtained by calcination at 300°C exhibited excellent specific activity (60.0 mmol g-1 h-1) with 100% benzyl alcohol conversion and more than 99% product selectivity within an extremely short time (4 min). The same catalyst is employed for the oxidation of a wide range of substituted benzylic and aliphatic alcohols. The catalyst i.e. ZrOx(1%)-MnCO3/(1%)HRG calcined at 300°C yielded corresponding aldehydes with complete convertibility and selectivity in short reaction times under mild conditions whereas the as-prepared catalyst exhibited high selectivity for aromatic alcohols over aliphatic alcohols. The catalyst was recycled and reused at least five times without any obvious loss in its activity or selectivity.

A highly selective Pd(OAc)2/pyridine/K2CO3 system for oxidation of terpenic alcohols by dioxygen

Molecular sieves, complex organic bases and radical oxidants are commonly used in alcohols oxidation reactions. In this work, we have evaluated the beneficial effects of addition of K2CO3 to Pd(II)-catalyzed oxidation alcohols, which resulted in a remarkable increase in the oxidation reaction rates without selectivity losses. Herein, in a metallic reoxidant-free system, terpenic alcohols (β-citronellol, nerol and geraniol) were selectively converted into respective aldehydes from Pd(II)-catalyzed oxidation reactions in presence of dioxygen. High conversions and selectivities (greater than 90%) were achieved in the presence of the Pd(OAc)2/K2CO3 catalyst and pyridine excess. The exogenous role of others auxiliary anionic and nitrogen compounds was appraised. Graphical Abstract: Reaction conditions: β-citronellol (2.75 mmol); Pd(OAc)2 (0.05 mmol); pyridine (5.0 mmol); K 2CO3 (2.5 mmol); toluene (10 mL); MS3A (0.5 g); O2 (0.10 MPa); 60 °C.[Figure not available: see fulltext.]

Oxidation of alcohols by [Cp*Rh(ppy)(OH)]+

Rh(III) polypyridine complexes ([Cp*Rh(ppy)(H2O)]2+; ppy = 2,2′-bipyridine, 2,2′-bipyridine-4,4′-dicarboxylate, o-phenanthroline, tetrahydro-4,4′-dialkyl-bis-oxazole) oxidize in organic or aqueous alkaline solution primary and secondary alcohols to aldehydes or ketones and are thereby reduced to the Rh(I) complexes Cp*Rh(ppy). The Rh(III) form can be regenerated by oxidants like pyruvate or oxygen, making the reaction quasi-catalytic. The reaction follows an autocatalytic pathway; hydrogen transfer from the a-CH2 group of an alcoholate complex [Cp*Rh(ppy)(OR)]+ to Cp*Rh(I)(ppy) is suggested to yield the Rh(II) intermediate Cp*Rh(ppy)H as the key and rate determining step. The knowledge of Rh(III)/Rh(I) redox potentials allows to estimate the thermodynamic driving force of the reaction which is not more than about 300mV.

Heterologous expression and characterization of the ene-reductases from Deinococcus radiodurans and Ralstonia metallidurans

The Old Yellow Enzyme (OYE) homologues or ene-reductases (ER) from Deinococcus radiodurans (DrER) and Ralstonia metallidurans (RmER) were cloned and characterized. Sequence and phylogenetic analysis revealed both these enzymes to belong to the YqjM-like or "thermophilic-like" group of OYEs, both sharing more than 60% sequence similarity to the ER from Thermus scotoductus. This group of OYEs is characterized by a conserved cysteine residue modulating the redox potential of the flavin cofactor as well as a conserved tyrosine residue located at the N-terminus region involved in binding certain ligands. The genes were recombinantly expressed in Escherichia coli as functional soluble proteins. Both ERs have monomer molecular weights of approximately 40 kDa, with DrER a homodimer in solution and RmER a monomer. DrER and RmER are optimally active at pH 7-7.5 at 30 C and 35 C respectively. Although the enzymes showed comparable affinities towards the ubiquitous ER substrate 2-cyclohexenone, the specific activity and catalytic efficiency of DrER were more than twice those observed for RmER. Similar to other members of this subclass of ERs, no conversion was detected with cyclic Cβ substituted enones, and only DrER was able to convert citral. Both DrER and RmER were highly active at reducing N-phenyl substituted maleimides. The selectivity of the ERs was assessed using both the isomers of carvone, which were converted with high diastereomeric excesses. Ketoisophorone and 2-methylcyclopentenone were converted to their (R)- and (S)-enantiomeric products respectively. Finally, a light-driven cofactor regeneration system was used to drive enzymatic reduction in the absence of NAD(P)H.

Aerobic oxidation of monoterpenic alcohols catalyzed by ruthenium hydroxide supported on silica-coated magnetic nanoparticles

Ruthenium hydroxide supported on silica-coated magnetic nanoparticles was shown to be an efficient heterogeneous catalyst for the liquid-phase oxidation of a wide range of alcohols using molecular oxygen as a sole oxidant in the absence of co-catalysts or additives. The material was prepared through the loading of the amino modified support with ruthenium(III) ions from an aqueous solution of ruthenium(III) chloride followed by treatment with sodium hydroxide to form ruthenium hydroxide species. Characterizations suggest that ruthenium hydroxide is highly dispersed on the support surface, with no ruthenium containing crystalline phases being detected. Various carbonylic monoterpenoids important for fragrance and pharmaceutical industries can be obtained in good to excellent yields starting from biomass-based monoterpenic alcohols, such as isoborneol, perillyl alcohol, carveol, and citronellol. The catalyst undergoes no metal leaching and can be easily recovered by the application of an external magnet and re-used.

Physically and chemically mixed TiO2-supported Pd and Au catalysts: unexpected synergistic effects on selective hydrogenation of citral in supercritical CO2

The selective hydrogenation of citral was studied with various TiO2-supported monometallic and bimetallic Pd and Au catalysts and their physical mixtures in supercritical CO2 (scCO2). Significant synergistic effects appeared when active Pd species was chemically or physically mixed with less active Au species. The total rate of conversion was greatly enhanced and the selectivity to citronellal (CAL) was improved. The physical properties of those catalysts were characterized by TEM, HRTEM-EDS, XPS, and UV/Vis and their features of H2 desorption were examined by TPD. The physical and chemical characterization results were used to discuss the reasons for the unexpected synergistic effects observed. The same selective hydrogenation was also conducted in a conventional non-polar organic solvent of n-hexane to examine the roles of scCO2. The use of scCO2 was effective for accelerating the hydrogenation of citral and improving the selectivity to CAL.