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S-(+)-Carvone is the principal constituent (60–70%) of the oil from caraway seeds (Carum carvi), [8] which is produced on a scale of about 10 tonnes per year. [3] It also occurs to the extent of about 40–60% in dill seed oil (from Anethum graveolens), and also in mandarin orange peel oil.
In 1908, it was reported that exposure of carvone to "Italian sunlight" for one year gives carvone-camphor. [2] Subsequent investigations demonstrated the utility of the photochemical [2+2] cycloaddition of enones to alkenes, requiring only "sunlight in California for 6.5 months". [3] [4]
[1] [2] Fractions are collected based on differences in a specific property of the individual components. A common trait in fractionations is the need to find an optimum between the amount of fractions collected and the desired purity in each fraction. Fractionation makes it possible to isolate more than two components in a mixture in a single run.
Levopropoxyphene is an antitussive.It is an optical isomer of dextropropoxyphene.The racemic mixture is called propoxyphene.Only the dextro-isomer (dextropropoxyphene) has an analgesic effect; the levo-isomer appears to exert only an antitussive effect.
In chemistry, racemization is a conversion, by heat or by chemical reaction, of an optically active compound into a racemic (optically inactive) form. This creates a 1:1 molar ratio of enantiomers and is referred to as a racemic mixture (i.e. contain equal amount of (+) and (−) forms).
The (3+2) cycloaddition itself is a concerted, pericyclic process whose regiochemistry is controlled by the frontier molecular orbitals on the nitrone (the dipole) and the dipolarophile. [3] When R' is an electron-donating group, alkyl, or aryl, the dominant FMOs are the HOMO of the dipolarophile and the LUMO of the nitrone.
Structures of the two enantiomeric forms (S left, R right) of mecoprop Enantiomers of citalopram. The top is (R)-citalopram and the bottom is -citalopram. An example of such an enantiomer is the sedative thalidomide, which was sold in a number of countries around the world from 1957 until 1961. It was withdrawn from the market when it was found ...
In case of penicillamine, the (S-isomer is used in the treatment of primary chronic arthritis, whereas the (R)-isomer has no therapeutic effect, as well as being highly toxic. [30] In some cases, the less therapeutically active enantiomer can cause side effects. For example, (S-naproxen is an analgesic but the (R-isomer causes renal problems. [31]