L-limonene

Crude turpentine is distilled to obtain refined products used in the fragrance and flavour industry. Only the unsaturated mono- and bicyclic terpenes are of interest for resin production. These are mainly a-pinene, p-pinene and dipentcne (D,L-limonene) (Fig. 17). D-Limonene is obtained by extraction of orange peel in citrus fruits. 

Dehydrogenation of dipentene (d,l-limonene) and 4-vinylcyclohexene has been studied using both the lithium-ethylenediamine catalyst system (4) and the sodium-alumina catalyst system (12). The aromatic compounds p-cymene and ethylbenzene are produced by both types of catalyst however, while vinylcyclohexene yields ethylbenzene rapidly at 0° over a sodium on alumina catalyst, dipentene yields mainly mixed dienes at 0 but at 25 is also rapidly dehydrogenated to p-cymene (12). 

Cinene Citrene Clavacin ( )-Limonene (-l-)-Limonene Patulin... 

Electrochemical reduction of the ozonization products from monoterpenes, i.e., />-meth-l-ene, (-l-)-limonene, (+ )-a// /ia-pinene, (+)-car-3-ene, provides the corresponding double-bond cleavage products in 45-70% yields57. The electrolysis of the acetyloxy hydroperoxide 28 derived from p-menth-l-ene 27 is carried out in an Ac0H/H20(6/1 v/v)— AcONa— (Pb/Pb) system at —1.1 to —1.4V vs. SCE, 2.0 to 2.2 A/dm2 in a divided cell to give the corresponding keto-alcohol 29 in 70% yield (Scheme 3-10). 

SYNS FENL-t No. 2633 (-H)-4-ISOPROPENYL-l-METHYLCYCLOHEXENE d-(-l-)-LIMONENE (-l-)-R-LLMONENE d-p-MENTHA-1,8-DIENE j MENTHA-1,8-DIENE D (R)-l-METHYL-4-(l-METHYLETHENYL). CYCLOHEXENE NCI-C55572... 

C10H16 L-limonene 5989-54-8 451.15 38.282 1,2 20436 C10H16O trans-5-methyl-2-(1-methylvinyl)cyclohexanone 29606-79-9 489.51 42.877 2... 

Chemical Abstracts Service Registry Number CAS 5989-27-5 (Closely related to o-Limonene are L-Limonene (CAS 5989-54-8), Chemical Name (S)-l-Methyl-4-(l-methylethenyl) cyclohexene D,L-Limonene (commonly known as Dipen-tene) is a mixture of the above two isomers. The isomers are chemically identical except that their molecular structures are mirror images of one another (optical isomers) (CAS 138-86-3), Chemical Name l-Methyl-4-(l-methylethenyl) cyclohexene) Synonyms o-Limonene 4-Isopropenyl-l-methyl-cyclohexene (R)-( + )-Limonene ( + )-Limonene D-( + )-Limonene (o)-Limonene Limonene ... 

Use For artificial cinnamon oil, in flavors and aromas, and to a limited extent in perfumes [on account of its sensitizing properties only in combination with equal amounts of (-t-l-limonene (see p-menthadienes) or eugenol], in addition as an intermediate in the production of cinnamyl alcohol and subsequent products. World-wide requirements ca. 40001 per year. . -Baueret al. (2.),p. 82 Bedoukian(3.),p. 98-10S Beil-stein EIV 7,984ff. Food Cosmet. Toxicol. 17,253 (1979) Synthesis 1994, 369 (synthesis). - [HS291229 CAS 104-55-2 (Z.) l437I-IO-9(trans-Z.)]... 

The "right half of the sesquiterpene (+)-p-selinene (as drawn below) includes (R)-(+)-limonene as a substructure. Retrosynthetic disconnection to (if)-(+)-limonene leads to the intermediate carbenium ions la and lb via 15-nor-ll-eudesmen-4-one (carbonyl alkenylation) and 15-nor-13-chloro-2-eudesmen-4-one (dehydrogenation, protective masking of the double bond in the side chain). These carbenium ions arise from (if)-9-chloro-p-menth-l-ene and the acylium ion Ic (synthone) originating from 3-butenoic acid as reagent (synthetic equivalent). (i )-/7-Menth-l-en-9-ol, on its part obtained by hydroboration and oxidation of (if)-(-l-)-limonene, turns out to be the precursor of the chloromenthene. 

Kover and co-workers demonstrated how to use 1,3-dipolar cycloaddition reactions in a protection cycle to distinguish between the two double bonds in (-l-)-limonene [11]. 

Definition Derived from Piper nigrum] main constituents incl. a and p-pinene, p-caryophyllene, l-limonene, d-hydrocarveol, piperidine Toxicology Primary irritant mod. skin irritant mutagenic data TSCA listed Hazardous Decomp. Prods. Heated to decomp., emits acrid smoke and fumes Uses Natural flavoring agent in foods and pharmaceuticals... 

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