A!-Limonene

H)- and (+)-1imonenes are widely used ia the manufacture of terpene resias. Additionally, a (-)-limonene and (+)- P-pheUandrene mixture from sulfate turpentine has been used to produce terpene resias. (+)-Limoaeae from the citms iadustry coatiauaHy fiads aew uses as a solveat aot only for its solvency properties but also for its orange oil fragrance. 

Very characteristic derivatives are obtained by the action of organic bases on the limonene nitrosochlorides. If d-a-limonene nitrosochloride be so treated, two nitrolamines are obtained, a-nitrolamine (dextro-rotatory), and /S-nitrolamine (laevo-rotatory). If d-)8-limonene nitrosochloride be treated in the same manner, exactly the same reaction products are obtained. If, on the other hand f-a-nitrosochloride or f-)8-nitrosochloride be treated in the same manner, a mixture of a-nitrolamine (laevo-rotatory) and )8-nitrolamine (dextro-rotatory) is obtained. 

N.A. Limonene, coumarins, apiin, oleic, linoleic, palmitic, paliloleic, petroselinic, petroselaidic, stearic, myristic, and myristoleic acids, bergapten.99-102 110 It is carminative and antirheumatic. 

N.A. Limonene, terpineol, linalool, tannins, flavonoids, terpenes." For gastrointestinal problems such as diarrhea and dysentery. Treat bleeding hemorrhoids, bladder problems, gonorrhea. 

Analysis of Spray Dried Samples. Moisture content was determined in duplicate via toluene distillation and total volatile oil by Clevenger (l ). Surface oil was measured by Soxhlet extraction (2). Shelf-life was determined by gas chromatography (6) the end of shelf-life was the time taken (at 37 C storage) to reach a limonene epoxide concentration of 2 mg/g oil. 

This wets" the needle, creating a limonene residue on the inside surface. 

Dipentene (= a ,/-Limonene) (monoterpene) Boswellia sacra (frankincense) (Burseraceae) [magi gift to infant Jesus], Mynstica fragrans (Myristicaceae), Myrtus communis (Myrtaceae), Pinus spp. (Pinaceae), Hper cubeba (Piperaceae), Andropogon citratus, A. nardus, A. schoenanthus (Poaceae), Citrus aurantium (orange peel, bergamot oil) (Rutaceae) OD-R [irritant]... 

However, in this section, the total synthesis of yingzhaosu A, the lead compound of a particular class of antimalarial 1,2-dioxocins, is reported. The synthesis involves eight steps and a 7.3% overall yield starting from (A)-limonene (Scheme 64). Besides the TOCO procedure that allowed the formation of five bonds in one step, the most intriguing steps involved the selective hydrogenation of a C-C double bond in the presence of a peroxide and an aldehyde functionalities (step vi) and the stereoselective reduction of the side-chain carbonyl with (R)-CBS catalyst (step viii). Last but not least, the old classical fractional recrystallization allowed the separation of yingzhaosu A from its C-14 epimer and saved two synthetic steps <2005JOC3618>. 

Singlet photosensitized polar addition of methanol to (A )-(>)-limonene (102) in nonpolar solvents afforded a mixture of the diastereomeric ethers 103 and 104 and the rearrangement product 105 (Scheme 6.42).677 The diastereomeric excess (de) of the photoadduct was optimized by varying the solvent polarity, reaction temperature and nature of the sensitizer. The first step of the reaction is the Z E photoisomerization (Section 6.1.1) of 102 to a highly strained /i-isomer, followed by protonation and methanol addition. The initial formation of a carbocation via the protonation step has been excluded under those reaction conditions. The Markovnikov-oriented methanol attack on the less-hindered (Rp)-(E)-102 compared with that of (Sp)-(E)-U)2 explains why 103 can be obtained in up to 96% de upon sensitization with methyl benzoate in a methanol solution. The hypothesis that Z E isomerization of the cyclohexene moiety affords a strained (reactive) alkene, whereas isomerization of the exocyclic double bond does not, was supported by the observation of an exclusive nucleophilic addition to the cyclohexene double bond. 

LEH originates from the bacterium Rhodococcus erythropolis DCL14." ° LEH is part of a limonene degradation pathway where it catalyzes the conversion of limonene-1,2-epoxide to limonene-1,2-diol (Scheme... 

On the other hand, R-exchanged zeolites have also been used in combination with a metal function, for carrying out the isomerization and hydrocracking of paraffins and cycloalkanes. This is the case for isomerization of n-hexane to isohexane and 2,2-dimethyl-butane (Rabo et al. 1961) the isomerization of n-undecane to mixed Ci 1 isomers at 275°C on Pt/Ce-Y zeolite (Weitkamp et al. 1985) the isomerization of c (7o-exo-tricyclo[5.2.1.02,6]-decane or exo-tricyclo[6.2.1.02,7]-undecane into adamantane or 1-methyladamantane, respectively, on R-Y at 150-270°C (Lau and Maier 1987) the isomerization of tetrahydrodicyclopentadiene into adamantane on Re-Y in a H2/HC1 atmosphere at 250°C (Honna et al. 1986) or the double bond relocation of 2-alkyl acrolein into fran.j-2-methyl-2-alkenals over Ce,B-ZSM-5 (Fisher et al. 1986). Recently, it has been reported that Ce-promoted Pd/ZSM-5 is an active and selective catalyst in the dehydroisomerization of a-limonene to / -cymene (Weyrich et al. 1997). 

Figure 3.3-4. Concentration vs time profiles for emission of selected VOCs from coated surfaces and cabinet furniture. A limonene (ECO, painting) B tripropyleneglycol diacrylate (UV-cured, roller coating) C benzophenone (UV-cured, roller coating) D l-butanol-3-methoxy-acetate (NC, spray coating). The upper and lower curves in C and D represent cabinet air and chamber air, respectively. The test chamber conditions were T =23 °C, r.h. = 45 %, V = 1.0 h L = 1.0 rrfixtf.

The permeability of hmonene through PLA, has been estimated by Auras et al. [140]. at a maximal value of 9.96 xlO kg.m.m. s lPa" at 45°C and with a limonene partial pressure of 258 Pa. The permeabihty value of this more hydro-phobic molecule is lower than that of ethyl acetate in PLA and is lower than those measured for PET, PP and LDPE [140]. Haugaard et al. have confirmed the low limonene sorption in PLA by comparison with the one in HDPE [141]. 

Other approaches to synthesize selectively />-cymene start from a-limonene, a material with the same carbon structure as p-cymene. a-Limonene is widely available as a cheap by-product in the orange juice production and paper industry. In early studies it was shown that a-limonene can be disproportio-nated to / -menthane and / -cymene over Pt and Pd catalysts on carrier materials. According to Scheme 4, 33% of the a-limonene is lost as a saturated compound. Also, Se promoted PdO on charcoal as carrier material has been suggested. However, such a catalyst is not favourable from an environmental point of view. 

Using zeolite-supported, Ce-promoted Pd catalysts brought enhanced dehydrogenation activity during a-limonene conversion. Thereby, they used preferably weakly acidic boron-pentasil zeolites and obtained p-cymene yields around 85%. 

Conversion over Pd-modified H-ZSM-5 - Dehydrogenation of a-limonene to cymenes is only obtained in the presence of strong acidic sites of H-ZSM-5... 

Conversion over PdICe-modified H-ZSM-5 - A way to promote the noble metal function is the addition of rare earth metals to the catalyst system. It has been reported that rare earth metals can act as anchors for noble metals and thus enhance dispersion and accessibility of noble metal sites in a zeolite. " The product distribution for a-limonene conversion over first Ce-exchanged, afterwards Pd-exchanged, H-ZSM-5-(55) is given in Table 7. 

The conversion of a-limonene remains complete. The selectivity to p-cymene increased from initially 20% to 77% over the whole observed period of 600 h. This can again be attributed to the slow decrease of the formation of cracked products, indicating a much slower deactivation of the acid sites of the catalysts. Formation of CiqHi isomers (terpenes) was not observed. No coke precursors were formed. 

The conversion of a-pinene over the Ce-promoted, zeolite-supported Pd catalysts proceeds via an acid-catalysed ring opening of the bicyclic terpene to a monocyclic terpene, e.g. a-limonene. This is followed by dehydrogenation, possibly via isomerization to a-terpinene or y-terpinene. 1,8-Cineole is dehydrated on the acid sites to p-menthadiene prior to dehydrogenation to p-cymene on the Pd sites of the catalyst. The conversion of all reactants is complete during the test run of 8 h. The results are quite similar to a-limonene conversion, as expected from the reaction pathway via p-menthenes and p-menthadienes. 

Chang, H.C. and P. Oriel (1994) Cloning and expression of a limonene degradation pathway from Bacillus stearothermophilus in Escherichia coli. J. Food Sci. 59 660-662. 

PRACTICE PROBLEM 5.5 Which atom is the chirality center of (a) limonene and (b) of thalidomide ... 

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