Organic citral

It is immediately clear that Acanthomyops need not rely on dietary sources of terpenes but can synthesize citronellal and citral from either acetate or mevalonate. The higher total activity of the citronellal as compared with the citral probably reflects the natural preponderance of citronellal (ca. 90%) in the ant secretion. As the specific activities show, these results are consistent with a common biogenetic origin of both terpenes. In the mevalonic acid pathway as described from other organisms (13), the radioactive carbon of l-C14-mevalonate is lost upon formation of isopentenyl pyrophosphate. 

Hydrogenation reactions, particularly for the manufacture of fine chemicals, prevail in the research of three-phase processes. Examples are hydrogenation of citral (selectivity > 80% [86-88]) and 2-butyne-l,4-diol (conversion > 80% and selectivity > 97% [89]). Eor Pt/ACE the yield to n-sorbitol in hydrogenation of D-glucose exceeded 99.5% [90]. Water denitrification via hydrogenation of nitrites and nitrates was extensively studied using fiber-based catalysts [91-95]. An attempt to use fiber-structured catalysts for wet air oxidation of organics (4-nitrophenol as a model compound) in water was successful. TOC removal up to 90% was achieved [96]. 

Prior to the kinetic experiments, possible deactivation phenomena of the catalytic system were checked by recycling experiments with prenal and citral as substrates. These results provide not only important hints on the form of the rate equation, but also on which reaction is convenient for long-term investigations in the loop reactor. After the reaction, the aqueous and organic phases were separated and the catalyst phase was reused without further purification. Results on the hydrogenation of prenal are shown in Fig. 7. The reaction rate clearly decreases if the catalyst phase is reused. According to GC analysis and H-NMR studies, this can be attributed to the fact that the product of the reaction, prenol, is highly soluble in water. Consequently, a simple phase... 

The reaction order of one is also in good accordance with the film theory, where the rate of mass transport linearly correlates with the equilibrium concentration of citral in the aqueous phase. As a matter of fact, the mass transport rate is of first order regarding the substrate concentration in the organic phase. Therefore, what is measured is in fact the rate of mass transport and not the rate of chemical reaction. This result is in our opinion a good example of how kinetic parameters could be falsified when the reaction is limited by mass transport and not kinetics. 

The volatilities of the reactive organic components (citral, its reaction products as well as the sugars) were negligible under the actual experimental conditions. 

Some simulation results for trilobic particles (citral hydrogenation) are provided by Fig. 2. As the figure reveals, the process is heavily diffusion-limited, not only by hydrogen diffusion but also that of the organic educts and products. The effectiviness factor is typically within the range 0.03-1. In case of lower stirrer rates, the role of external diffusion limitation becomes more profound. Furthermore, the quasi-stationary concentration fronts move inside the catalyst pellet, as the catalyst deactivation proceeds. 

Synthesis from Dehydrolinalool. Dehydrolinalool is produced on a large scale from 6-methyl-5-hepten-2-one and acetylene and can be isomerized to citral in high yield by a number of catalysts. Preferred catalysts include organic orthovanadates [55], organic trisilyl oxyvanadates [56], and vanadium catalysts with silanols added to the reaction system [57]. 

The substances of different classes of organic compounds - monoterpene hydrocarbons, alcohols, esters, aldehydes, aldehyde-alcohols and phenols were selected as antioxidants. The next substances have been investigated lemonene ( Lluch , Spain), linalool ( Moellhausen , Italy), octyl acetate ( Ventos , Spain), anise aldehyde ( Lluch , Spain), vanillin ( Dinos , China) and eugenol ( Ventos , Spain). All compounds, including test-substance - citral ( Moellhausen , Italy), were characterized by gas chromatography. 

Among typical organic compounds found in Nature are marsh gas and all the constituents of natural petroleums acetic, lactic, tartaric, benzoic, and a very large number of other acids carbohydrates, including sugars, starches, and celluloses the constituents of plant and animal fats, and waxes the proteins organic bases, such as quinine, strychnine, and other alkaloids indigo, alizarin, and other natural dyes camphor, citral, and other constituents of the... 

In the present study a novel knitted silica-fiber was developed and enployed as a catalyst carrier. Different silica-fiber supported catalysts were prepared and studied for their performance in removal of volatile organic compounds (VOC) emissions, gas-phase hydrogenation of o-xylene, liquid-phase hydrogenation of citral and liquid-phase enantioselective hydrogenation of 1-phenyl-1,2-propanedione. 

These rules apply in principle also to compounds containing several C=C double bonds (isoprene, geraniol, citral, etc.). Epoxidation by organic peroxy acids has been reviewed by Swern.28... 

It is usually unnecessary to isolate such hydrazones during the working up the mixture is partitioned between water and a water-insoluble solvent such as ether. The hydrazones then remain in the aqueous phase, and the other organic substances are removed in the organic phase. The carbonyl components are finally regenerated from the aqueous hydrazone phase by acid hydrolysis. Considerable fractionation of mixed carbonyl compounds can be achieved by varying the reaction conditions, notably the temperature or pH, of either the condensation or the hydrolysis. Acid-sensitive carbonyl compounds, e.g., citral, may be isolated by exchange from the hydrazone by an excess of formaldehyde.932... 

In this paper we will report on the selective hydrogenation of o /3 unsaturated aldehydes using a supported palladium catalyst in a range of ionic liquids. We will also compare their reactivity and selectivity to conventionally used organic solvents. Two systems have been investigated, cinnamaldehyde to form hydrocinnamaldehyde and citral... 

Table 1 compares the results from the selective hydrogenation of citral, at a variety of pressures and temperatures in both ionic liquids and organic solvents using palladium supported on carbon (Pd/C) and platinum supported on graphite (Pt/G). It is clear that the ionic liquid systems are highly selective solvents for the reduction of C=C without any reduction of the carbonyl group over palladium and similar selectivities can be achieved for the carbonyl group over platinum. 

Hydrogenations of citral (Z and E) and cinnamaldehyde were carried out in a 100 ml four-necked flask fitted with a reflux condenser, dropping funnel, thermocouple and a stirrer head. The catal3rst was added to the required amount of solvent (95% ethanol) then treated at 70 °C for 1 h under H2 flow. After cooling at reaction temperature (60 °C), the organic substrate (0.5 ml) was injected throu one arm of the flask. The progress of the reaction was followed... 

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