Pinenes citral from

Numerous components are offered on the market like citral from Litsea cubeba oil, geraniol from palmarosa oil, linalool from ho oil, coriander oil or lavandin, pinenes from different Pinus species, citronellal from Corymbia citriodora, cedrol from cedarwood, or even the santalols from different sandalwood species. All these are added to nish essential oils. As already mentioned before, synthetic chemicals can no more be applied as enantiomeric separation is a state of the art today and will convict the matter of fact of adulteration. By using synthesized, correct chiral compounds, the detection is hardly to be recognized but with NMR method, but this is an expensive analysis. 

A typical example is the hydroformylation of linalool, a monoterpenoid allyhc alcohol with a pleasant lily odor. It is a key building block for the synthesis of various vitamins and fragrances, such as vitamin A, vitamin E, citral, citronel-lol, and phnol (see Scheme 6.44). Linalool is found in the essential oils of several plants, for example, Brazihan rosewood and Chinese Ho leaf oils, but mostly it is produced industrially from a-pinene or from the petrochemically derived source 6-methylhept-5-en-2-one (Hoflimann-La Roche Process) [144]. 

Linalool and citral are important building blocks for the synthesis of isoprenoid natural products, e.g. vitamins A, E and K, carotenoids and a broad variety of fragrances. In view of changing starting materials in future decades due to limited amounts of fossil resomces, pinenes might be interesting somces for the fine chemical industry to produce linalool via pinane-2-hydroperoxide. The synthesis of linalool and citral from natural somces is discussed herein. 

The production of myrcene (7) from P-pinene is important commercially for the synthesis of a wide variety of flavor and fragrance materials. Some of those include nerol and geraniol, citroneUol (27) and citral (5). 

Thymol (20-35, rarely 42 %)> carvacrol (little), cymene pinene (trace), bomeol, linalool, camphor, citral Oil of turpentine, alcohol, mineral oils, oil free from thymol... 

Asahina and Nakamura (J. Pharm. Soc. Japan, No. 322, Dec. 1908, via SchimmeVs Report, April 1909, 59) have obtained somewhat different oil from one-year-old twigs from the Japanese Province of Shizuoka. Its characters were specific gravity 0.892, optical rotation -1-6° 8, acid value 4.3, saponification value 19.1, ditto after acetylation 56.5 soluble in 14 volumes of 85 per cent alcohol, opalescent on further dilution. Methyl chavicol was the chief constituent, with 6 per cent of citral eugenol and cineole. A trace of pinene also seemed to be present with caprinic and oleic acids. It is of interest to note that this oil contained no anethole it differed from the preceding oils in containing eugenol and in being dextro-rotatory. 

On a commercial basis, lemon Petitgrain oil is produced from citrus leaves in Italy. In contrast to other Petitgrain oils, its composition resembles more to the peel oil of the corresponding fruits. The main constituents are limonene (app. 30%), P-pinene (10-20%) and citral (15-28%) [104, 109-114]. 

The reports indicate the presence of terpenes, a-pinene, camphene, citral and beta-caryophyllene in the essential oil from the leaves and flavonoids such as casticin, orientin, isoorientin, luteolin, luteolin-7-O-glucoside, corymbosin, gardenins A and B, 3-O-desmethylartemetin, 5-0-desmethylnobiletin, 3, 4, 5,5, 6,7,8-heptamethoxyflavone, 3, 5-dihydroxy-4, 7,8-trimethoxyflavanone and 3, 5-dihydroxy-4, 6,7-trimethoxy... 

The major producers of the rose alcohols and citral have become so for a variety of reasons. Companies which manufacture wood and paper products produce sulfate turpentine or similar by-products rich in pinenes. They, or their subsidiaries, may then produce terpenoid fragrance materials from pinenes as a way of generating income from their by-product. Pharmaceutical companies which manufacture vitamins use terpenoid intermediates and so will often diversify into the manufacture of aroma chemicals. Their basic feedstocks are likely to be of petrochemical origin. Similarly, manufacturers of synthetic rubber possess technology for the use of isoprene as a feedstock and so are also likely to diversify into terpene aroma chemical manufacture. Fragrance companies will develop a position in terpenoid chemistry because of the importance of terpenoids as ingredients. 

Figure 1. Vapor pressure vs. temperature curves of important components of orange essential oil (0 0) a-pinene, ( - ) d-limonene, ( A - A ) myrcene, ( o - o ) linalool, ( - ) a-terpineol, ( - ) decanal, ( A - A ) a-citral (Data from (38)).

Studies on the house fly, Muaca domeatica, revealed the considerable acute larvicidal activity of several terpenoids, especially carvacrol and d-limonene (19). Several metamorphosis inhibition effects were also observed, including inhibition of pupal ecdysis, uneclosed pupae, and deformed adults. Numerous compounds exhibited potency in these developmental mortalities camphene, carvacrol, carvone, cineole, citral, citronellal, citronellol, eugenol, farnesol, geraniol, limonene, linalool, B-phellandrene, and a-pinene. Egg hatch was also inhibited by exposure to the terpenoids the most effective ovicidal compounds were carvacrol, citronellal and B-phellandrene, with no acutely toxic effects noted to the embryos, but rather show inhibition of development of the embryo and inability to eclose from the egg... 

Plants especially from the Lamiaceae family can inhibit the growth of several weeds by releasing phytotoxic monoterpenes (a-pinene, P pinene, camphene, limonene, a-phellandrene, p-cymene, 1,8-cineole, borneol, pulegone, and camphor) (Angelini et al., 2003). The herbicide effect of 1,4-cineole and 1,8-cineole is also described by Dayan et al. (2012). Plants that are exposed to essential oils often metabolize them, and when citral was added geraniol, nerol and their acids appeared. When citronellal metabolization was tested, citronellol and citronellic acid were formed, and with pulegone (iso)-menthone, isopulegol and menthofuran were found (Dudai et al., 2000). 

ISO standard 3053 shows character and data for this oil. Pure oils possess as marker the compound nootkatone from traces up to 0.8%, depending on the fruit status. This compound is used for blending, together with n-octanal, w-nonanal, n-decanal, and synthetic citral. Adulteration is performed by orange terpenes and distilled grapefruit residues from expression and limonene—80°. Detection must be done exclusively by multidimensional enantiomeric separation. Dugo and Mondello (2011) published the following chiral data (/ ) (-)-a-pinene (0.3%-0.8%) (5)-(+)-a-pinene (99.2% 99.7%) (/ )-(+) P pinene (62.0% 76.8%) (5) ( ) p-pinene (23.2%-38.0%) (/ )-(+)-sabinene (98.4%-98.5%) (5)-(-)-sabinene (1.5%-1.6%) (5)-(-)-limonene (0.5%-0.6%) (/ )-(+)-limonene... 

Citral can be obtained from pinene extracts by pyrolysis of -pinene to myrcene and subsequent oxidation in the presence of palladium(II) complexes and oxoanionic salts (Fig. 16.10). o- 2... 

Among the aldehydes isolated from the oil methyl-vanillin was found, which had never previously been found in an essential oil. Citral, Z-a-pinene, and methyl-isoeugenol are also present in the oil. 

Sassafras leaves also yield a small quantity ( 03 per cent.) of an essential oil, differing entirely from the oil from the wood, lliis has also been investigate by Power and Eleber. Tbe oil obtained from 8000 lb. of leaves was only about 2 lb., and was of a light yellow colour and agreeable lemon odour. Its specific gravity was 872, and its optical rotation -I- 6 25. Tbe constituents identified were citral, pinene, phellandrene, a hydrocarbon of the paraffin series, a hydrocarbon also found in oil of bay and called by the discoverers myrcene, and the acetic and valerianic (isovalerianic ) esters of linalol and probably of geraniol, and, possibly, cadinene. No safrol could be detect. ... 

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