Isomerization definition

Regulatory El NECS, Japan ENCS, Philippines PICCS, Canada DSL, Australia listed Manuf./Distrib. S. Black http //www.sblack.com Isomerized jojoba oil Synonyms Jojoba oil, isomerized Definition End prod, of controlled isomerization of jojoba oil... 

The definitions of the empirical rate laws given above do not exclude empirical rate laws of another fomi. Examples are reactions, where a reverse reaction is important, such as in the cis-trans isomerization of 1,2-dichloroethene ... 

Hydrocupreidine (Dihydrocupreidine), C19H24O2N2. a H20. This base, isomeric with the foregoing, is made by demethylating dihydroquinidine, and was first definitely obtained by Heidelberger and Jacobs. It forms glistening, cream-tinted, hexagonal plates, m.p. 195° (dec.), -(- 227-2°... 

Recently, Nesmeyanov and co-workers have published definitive evidence that dwaZ reactivity (the formation of derivatives of two different structural formulas) extends beyond tautomerism (isomers in equilibrium or reversible isomeric transformation). A single molecular species can form two series of derivatives, in one of which a transfer of the reaction center occurs in the reaction. 

Nevertheless, a number of gas chromatographic applications exist, epecially those for the determination of crude oil indicators. Such indicators are used as geochemical parameters for the thermal history of the crude as well as to indicate the possible relationship between crudes from different wells. These indicators comprise a number of isomeric aromatic species, such as the individual alkylnaphthalenes (44, 45), the individual Cio-mono-aromatics or the individual C9-mono-aromatics. The ratio between these isomers gives a definite indication of the crude oil. In general, these systems use a Deans switching unit to make a heart-cut, which then is focused, reinjected and separated on a second column with a different polarity. 

The above considerations indicate the complex nature of the hydrocarbons known as caryophyllene. For practical purposes, however, the compounds indicated are obtained of practically definite melting-points, and, in spite of the complicated isomerism existing amongst most of them, are useful for identification of the sesquiterpene or mixture of sesquiterpenes, occurring naturally and known as caryophyllene . 

Compound 6 crystallizes from cyclohexane as colorless needles which have no definite melting point there is a change of color to yellow at 128-134 C and the compound then melts sharply at 187-189 r C. When the colorless form is kept for a long time or recrystallized from pyridine or dimethyl sulfoxide it is changed into the yellow modification of mp 187-189 C recrystallization from cyclohexane reverses the process. It has been suggested that the yellow stable form has structure 6A and that the colorless metastable compound is the tautomer 2-methyl-l//-pyrido[2,3-6][l, 4]diazepin-4(5//)-one (6B). There is evidence from 1H NMR spectroscopy that the isomeric pyridodiazepin-2-one, yellow crystals, mp 195—197 " C, exists as an inseparable mixture of the tautomers 4-methyl-l//-pyrido[2,3-6][l,4]diazepin-2(3//)-one (7 A) and 4-methyl-l H-pyrido[2,3-6][l, 4Jdiazepin-2(5//)-one (7B) in the ratio 1 3. 

Nitrimines seem to exist in several isomeric forms and their structures have not been definitely established. For instance, four different structures for mesityl nitrimine are given by Suggitt et al in Ref 11... 

To date, direct asymmetric synthesis of optically active chiral-at-metal complexes, which by definition leads to a mixture of enantiomers in unequal amounts thanks to an external chiral auxiUary, has never been achieved. The most studied strategy is currently indirect asymmetric synthesis, which involves (i) the stereoselective formation of the chiral-at-metal complex thanks to a chiral inductor located either on the ligand or on the counterion and then (ii) removal of this internal chiral auxiliary (Fig. 4). Indeed, when the isomerization of the stereogenic metal center is possible in solution, in-... 

The carbeniiun ion so formed then reacts in the ICC 1 manner except perhaps for not abstracting a hydride ion from another alkane. Although initial views that zeolites in general were super acids have come into question, definite super acids have been found such as calcined H2S04 Zr(0H)4 which catalyze the isomerization of alkanes at low T. 

The steric outcome in the above cyclization can be explained on the basis of either a zwitterionic intermediate or a concerted [7t2s -I- 7t2s] process , depending on the nature of the reactants . Definite predictions are practically impossible as yet. The more stable trans-isomers (i.e. 221a) can be obtained by stirring the isomeric mixture with catalytic amounts of potassium t-butoxide in t-butyl alcohol for several days . 

In contrast, although all are not readily interpretable upon observation, the proton spectra of the three isomeric difluorobenzenes are definitely distinctive (Figs. 3.20-3.22, all run in benzene-d6). 

However, the pathways for these reactions, particularly in the gas phase, have been only -.rtially characterized. In a wide variety of these reactions, coordinatively unsaturated, highly reactive metal carbonyls are produced [1-18]. The products of many of these photochemical reactions act as efficient catalysts. For example, Fe(C0)5 can be used to generate an efficient photocatalyst for alkene isomerization, hydrogenation, and hydrosilation reactions [19-23]. Turnover numbers as high as 3000 have been observed for Fe(C0)5 induced photocatalysis [22]. However, in many catalytically active systems, the active intermediate has not been definitively determined. Indeed, it is only recently that significant progress has been made in this area [20-23]. 

One exception to the preservation of selectivity in microwave reactions was the C2 arylation of 2,3-dihydrofuran, which yielded an isomeric byproduct under the action of microwaves (2-phenyl-2,3-dihydrofuran/byproduct = 71/29), in contrast with the reported procedure using conventional heating (Eq. 11.4). The desired product could be isolated in 58% yield. Attempts to reduce the reaction time by using oil baths (125 °C or 150 °C) did not result in similar yields, but instead furnished complicated reaction mixtures, in definite contrast with the microwave procedure [17]. 

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