Oxidation terpene

Isoprene and terpene oxidation to CO following reaction with OH. 

Flavoring agents proper are commonly volatile oils that have been dissolved in alcohol and sprayed onto the dried granules or have simply been adsorbed onto another excipient (e.g., talc). They are added immediately prior to compression to avoid loss through volatilization. In some cases they may even have some lubricating activity. If the oil normally contains ter-penes, a low terpene grade is better so as to avoid possible deterioration in taste due to terpene oxidation... 

Calogirou, A., B. R. Larsen, and D. Kotzias, Gas-Phase Terpene Oxidation Products A Review, Atmos. Environ., 33, 1428-1439... 

The ring-opening of oxiranes, leading to the formation of isomeric carbonyl compounds by the action of acid catalysts as a result of rearrangement, is of continuing interest (refs. 1-4). However, most of these studies focus mainly on the transformations of terpene oxides or oxiranes with other functional groups in the liquid phase, under homogeneous reaction conditions. 

Fig. 6 Other terpenes oxidized with the MT0/H202 system...

Simple aliphatic oxiranes can be converted to fluorohydrin with hydrogen fluoride only with great difficulty, but the reaction can be carried out in systems with rigid conformations (e.g., steroids, 9,10-epoxydecalin). Good yields can be attained from cyclopentene and cyclohexene oxides with 42% pyridine-polyhydrogen fluoride and in a series of terpene oxides with an amine-hydrogen fluoride complex. ... 

The reactions can be performed more simply with hydrochloric acid and hydro-bromic acid. The reaction between terpene oxides and hydrochloric acid has been examined, for example, in the cases of p-mentadiene dioxide, a-3,4-epoxy-carane, and a-4,5-epoxycarane. Studies have been made of the reactions of steroid oxiranes with hydrochloric acid and hydrobromic acid. The acidic opening of compounds containing two oxirane rings can be carried out selectively and in good yield (Eq. 309). ... 

Terpene oxides have been favorite substrates for ZnBr2-catalyzed reactions, probably because early work indicated that certain reactions afforded high yields of unusual materials. Indeed some of these claims have held up well to later analytical scrutiny. For example, a-pinene oxide (342 equation 143) yields essentially pure (343 88%) upon brief treatment with ZnBr2 (catalytic amount) in refluxing benzene. ... 

Isoprene and terpene oxidation to CO following reaction with OH oxidation mechanism and CO yield not well known. 

The isomerization of many terpene oxides (see Section 5.4) has been investigated using a wide range of solid acids (and bases). Arata and Tanabe are responsible for much of this work which includes d-limonene oxide [16], 2- and 3-carene oxide [17], and carvomenthene oxide [18]. 

The tools of molecular genetics provide the opportunity to express individual terpene-oxidizing enzymes in new bacterial hosts, or to selectively knock out steps (reverse genetics) in the host strain. In this way, several of the above mentioned problems can be overcome, and a specific biocatalyst can be constructed which can be used for the production of one specific product. 

This main rule works in terpene oxide chemistry. In the presence of solid bases, the terpene oxides are mainly transformed to derivatives of a3-unsaturated alcohols. 

CALOGIROU, A., LARSEN, B. R., KOTZIAS, D., Gas-phase terpene oxidation products A review, Atmos. Environ., 1999,33, 1423-1439. 

In addition to the important role biogenic terpenes play in gas-hase chemistry, their impact also extends to heterogeneous air chemistry. Although Went (1960) linked the formation of the blue haze over coniferous forests to the biogenic emission of 20 monoterpenes over 40 years ago, it was not until recently that terpenes received their due attention with respect to their role in secondary organic aerosol (SOA) formation. O Dowd et al. (2002) reported that nucleation events over a boreal forest were driven by the condensation of terpene oxidation products. Formaldehyde (HCHO) is a high-yield product of isoprene oxidation. The short photochemical lifetime of HCHO allows the observation of this trace gas to help constrain isoprene emissions (Shim et al. 2005). 

Terpene oxides, epoxides or peroxides are encountered more often than is usually believed during TLC of essential oils [248]. Eucalyptol (1,8-cineole) and ascaridole, which is easily accessible by photochemical treatment of a-terpinene, are the best known. These compound types play a special part in the determination of the value of individual oils. 

As 1965 opened, Crawford and I completed the identification of the enzymatic defects of a series of tryptophan auxotrophic mutants on the fluorescent pseudomonads used in terpene oxidation. All clues needed for their genetic analysis were at hand. Dioxygen reduction of the participation of the 2 electron monoxygenase stoichiometry were... 

Some aromatic hydrocarbons are probably generated in spices by terpene oxidation. Examples are l-methyl-4-isopropenylbenzene (XI, Formula 22.3) derived from p-men-tha-l,3,8-tri-ene (X) and (+)-ar-curcumene (XIV) from zin-giberene (XII) or 3-sesquiphel-landrene (XIII) [cf. Formula 22.4]. 

The rearrangement of a variety of terpene oxides has been examined (eq 24). While ZnBr2 is generally a satisfactory catalyst for this purpose, other Lewis acids, including ZnCl2 and Magnesium Bromide are advantageous in some instances. 

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