Limonene molecular structure

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... 

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 ... 

Figure 10.2 The A -P-ocimcne receptor neuron type in heliothine moths and the strawberry weevil. Gas chromatograms of a standard sample and simultaneously reeordcd neuron activity (spikes/s) of a receptor neuron of Heliothis virescens (left) and of Anthonomus rubi (right). Both neurons responded to dihydromyrcene, p-myrcene, Z-P- and -P-ocimene, The neuron of A. rubi also responded to the solvent and limonene. Below The molecular structures of odorants activating the -p-ocimene receptor neuron type in the strawberry weevil. The bracket indicates the molecular receptive range of the ii-p-oeimene receptor neuron type in H. virescem.

Molecular structures of monoterpenoids are present as three major types acyclic, monocyclic and bicyclic. Oxygenated derivatives of acyclic monoterpenes are more widespread in nature than acyclic monoterpenes themselves. Such derivatives are the monoterpene alcohols citronellol and geraniol, or the monoterpene aldehydes citronellal and geranial. Mononocyclic monoterpene hydrocarbons are exemplified by limonene, which is a major component of orange and lemon peel oils, and p-phellandrene, which is emitted by conifer trees under biotic stress. These compounds are relatively common in nature. Bicyclic monoterpenes are represented by the aforementioned a-pinene, one of the most abundant and important monoterpenes. 

FIGURE 2.1. Molecular structures of a-pinene enantiomers and d-limonene. 

Terpenes are a class of unsaturated hydrocarbons made up of isoprene C5 units and found in essential oils and oleoresins of plants such as conifers. The two most commonly used as solvents are turpentine and o-limonene. Their physical properties are compared with those of toluene and methylene chloride in Table 5.7. They are both immiscible with water. As can be seen in Figure 5.3, D-limonene and other small terpenes have similar molecular weights and structures to substituted cyclohexanes and toluene and are therefore to likely have solvent properties intermediate between these two VOCs. 

Limonene is a hydrocarbon found in the peels of lemons and contributes significantly to the smell of lemons. Limonene has a molecular ion peak at m/z= 136 in its mass spectrum, and it has two double bonds and one ring in its structure. What is the molecular formula of limonene ... 

Terpin n Terpinol, 4-Hydroxy-oc,a,4-trimethylcyclohexa-nemethanol. Additional Names p-menthane-l,8-diol dipenteneglycol. Molecular Formula C10H20O2. Molecular Weight 172.26. Percent Composition C 69.72%, H 11.70%, O 18.58%. Literature references from Merck index (2001) 13th edn. Both ds-and frans-modifica-tions are known. The ds-compd is obtained most readily in the hydrated form, cfs-terpin hydrate. Prepn of ds-form from oil of turpentine Hempel (1876) Ann 180 71 Wallach (1885) Ann 230 225 Schmitt (1955) Mfg Chemist (1955) 26 350. From d-limonene Sword (1925) J Chem Soc (1925) 127 1632. Prepn of trans-form from 1,8-cineole, a-terpineol or ds-terpin hydrate Matsuura et al (1958) Bull Chem Soc Japan 31 990 Lombard R, Ambroise G (1961) Bull Soc Chim France 230. Structure of ds- and trans-forms Baeyer Ber (1893) 26 2861. 

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