Limonene oxide structure

FIGURE 5.1 Structure of d-limonene, oxidated forms and derived methadienes. 

Cineole Ascaridole Limonene Oxide Pinene Oxide Figure 12.6 Structural formulas of some terpenes used as penetration enhancers. 

An example of terpenic 1,2-epoxides is -caryophyllene oxide, also known as (-)-epoxycaryophyllene (8-31), which occurs in many essential oils. An example of terpenic 1,4-epoxides is the so-called (-l-)-dill ether, (3J ,4S,8S)-3,9-epoxy-p-menth-l-ene (8-31), which is a typical component of the essential oil of caraway (30%) and dill. An example of unsaturated 1,4-epoxides is (-l-)-menthofuran (8-31), the metabolite of ketone (-l-)-pulegone. Both compounds are components of peppermint oil (see Table 8.32, later) and are hepatotoxic. Monoterpenoid compound (- -)-l,8-cineole (also known as limonene oxide, eucalyptol or 1,8-epoxy-p-menthane 8-31) is an example of more complex structures. It is present in essential oils of many types of spices, and higher quantities are found in the essential oil of trees of the genus Eucalyptus (Myrtaceae). Trivial and systematic names of selected ethers are given in Table 8.8. 

A study with houseflies (7) shows clearly that very small differences in the molecular structure can result in drastically different biological effects as exemplified in Table III by the optical Isomers (-)-limonene, a fly attractant, and (+)-limonene, a fly deterrent. A difference in oxidation state In the functional group as in citronellol, a fly attractant, and citronellal, a fly deterrent, also causes different responses. A difference in the length of the carbon chain as in farnesol (C15), a fly attractant, and geranlol (CIO), a fly deterrent, also confers different... 

Key Words Ethylene oxide, Propylene oxide. Epoxybutene, Market, Isoamylene oxide. Cyclohexene oxide. Styrene oxide, Norbornene oxide. Epichlorohydrin, Epoxy resins, Carbamazepine, Terpenes, Limonene, a-Pinene, Fatty acid epoxides, Allyl epoxides, Sharpless epoxidation. Turnover frequency, Space time yield. Hydrogen peroxide, Polyoxometallates, Phase-transfer reagents, Methyltrioxorhenium (MTO), Fluorinated acetone, Alkylmetaborate esters. Alumina, Iminium salts, Porphyrins, Jacobsen-Katsuki oxidation, Salen, Peroxoacetic acid, P450 BM-3, Escherichia coli, lodosylbenzene, Oxometallacycle, DFT, Lewis acid mechanism, Metalladioxolane, Mimoun complex, Sheldon complex, Michaelis-Menten, Schiff bases. Redox mechanism. Oxygen-rebound mechanism, Spiro structure. 2008 Elsevier B.V. 

Previous studies indicated that the structure of the alkyl hydroperoxide in molybdenum catalyzed epoxidations has only a minor effect on the rate and selectivity [10]. Hence, we were initially surprised to observe that PHP failed to give the expected epoxidation of cyclohexene (1) and limonene (2) in the presence of a molybdenum catalyst (Tablel). Epoxidation of limonene with TBHP as oxidant, in contrast, gave the epoxide of the more highly substituted double bond in 84% selectivity, consistent with nucleophilic attack of the olefin on the alkylperoxomolybdenum(Vl) [3,5]. We tentatively concluded that this low reactivity of PHP is a result of steric hindrance in the putative alkylperoxomolybdenum(VI) intermediate. This prompted us to carry out a systematic investigation [8] of steric effects of the alkyl substituents in the alkyl hydroperoxide on the rate of molybdenum catalyzed epoxidations. 

Topical Exposure. Dosing of female house fly females with five monoterpenoids yielded toxic effects when applied alone at high doses. d-Limonene was the most active of the five (Table I). Use of the synergist piperonyl butoxide enhanced the activity of d-limonene, pulegone, and linalool considerably, by 17, 21, and >14 fold, respectively. These results indicate that those three terpenoids insecticidal activity is expressed more fully when the oxidative detoxification process is inhibited. It is not surprising that flies can detoxify them rapidly, considering the relatively simple hydrocarbon structures of the monoterpenoids. 

Fig. 10 SOA product volatility distributions for a-pinene and limonaketone in dark green and mass yields vs Cqa as dark green curve. Precursors with similar volatility, structure, and chemistry have similar yields. Product volatility distribution and yields fOTD-limonene ozonolysis are shown as light green bars and a light green curve (and gray data points). Oxidation of the additional exocyclic double bond in limonene results in substantially less volatile SOA products and correspondingly higher SOA yields...

The release and the oxidation processes of the encapsulated D-limonene are closely related to the structural changes in the capsule matrices. Physico-chemical changes caused by the phase transition of carbohydrate from amorphous glass to rubbery are commonly expressed with the temperature difference between the storage temperature, T, and the glass transition temperature, Tg, of the carrier matrices, T — Tg. The idea is based on the fact that the viscosity (or relaxation time) of the carrier matrices follows the Wflliams-Landel-Ferry (WLF) equation expressed as a function of T — Tg (Williams et al., 1955). Therefore, the release rate constants k and the oxidation rate... 

As exemplified by the stmctural formulas of a-pinene, P-pinene, A -carene, isoprene, and limonene, shown in Figure 16.1, terpenes contain alkenyl (olefinic) bonds, in some cases two or more per molecule. Because of these and other structural features, terpenes are among the most reactive compounds in the atmosphere. The reaction of terpenes with hydroxyl radical is very rapid, and terpenes also react with other oxidizing agents in the atmosphere, particularly ozone, O3. Turpentine, a mixture of terpenes, has been widely used in paint because it reacts with atmospheric oxygen to form a peroxide, then a hard resin. It is likely that compounds such as a-pinene and isoprene undergo similar reactions in the atmos-... 

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