Isomers naming

In principle, the intermediates obtained under these conditions could have the structure of a nitrosoamine such as 3.12, but they could also be one of the isomers, namely a (Z)- or (ii)-nitrosoimine (3.14 or 3.15, respectively), or a (Z)- or (ii)-diazo-hydroxide (3.16 or 3.17, respectively). Analogous isomers exist, of course, for other nitrosation products of heteroaromatic amines. 

Since diazoates can be considered to be derived from oximes by substitution of nitrogen for the methine group, Hantzsch (1894) put forward the hypothesis that configurational isomerism was also occurring here. He therefore represented the isomeric diazoates by the structures 7.1 and 7.2, assigning the syn structure (7.1) to the labile diazoate and the anti (7.2) to the stable isomer. Nowadays the description recommended by IUPAC (1979) for such configurational isomers, namely (Z) instead of syn and (E) instead of anti, should be used. 

The reactions of Y with four butene isomers, namely 1-butene, cis-2-butene, trans-2-butene, and isobutene, were studied at a collision energy (/ ycoii) of 26.6kcal/mol (see Table 2). In reactions with 1-butene and cis- and trans-2-butene, four processes were observed ... 

The Levafix P dyes have been replaced by the Levafix PN (DyStar) range, which is based on the 5 chloro-2-fluorO 4-methylpyrimidine system. These two systems are essentially similar, but the Levafix PN dyes have a fluorine atom as the labile entity rather than the methylsulphonyl grouping. The necessary intermediate 5-chloro-2,6-difluoro-4-methyl-pyrimidine (7.25) can be made from 4-methyl-2,5,6-trichloropyrimidine by an exchange reaction with potassium fluoride (Scheme 7.20). Condensation with the dye base (Scheme 7.21) will give a mixture of isomers, namely, the 5 chloro-6-fluoro-4-methyl (7.26) and 5-chloro-2-fluoro-4-methyl (7.27) derivatives. 

A similar strategy was also applicable for the synthesis of six- and eight-membered siloxanol-ring systems. Hydrolysis of z-PrRSiCl2 (R = Ph, o-Tol) with ZnO and KOH provided the six-membered siloxane rings as a mixture of two constitutional isomers cis-trans-(i-PrRSiO)3 (539, R = Ph 540, R = o-Tol) and Wzr-(z-PrRSiO)3 (541, R = Ph 542, R = o-Tol) which were separated by preparative HPLC. Subsequent reaction with HC1/A1C13 and hydrolysis of the chloro intermediates yielded the same product for both isomers, namely Wzr-[z-Pr(OH)SiO]3 543, implying that isomerization occurs under these conditions (Scheme 75).484... 

PhCCSiF3 are in equilibrium with the pentacoordinated 1 1 complex 843. Only at low temperatures, a second equivalent of pyridine slowly coordinates to the silicon to selectively form one of three conceivable isomers, namely, the hexacoordinated 1 2 complex 844 having the two pyridine molecules in /raor-position (Scheme 118).832... 

Formation of the second most abundant dimer, namely XXXIII, as well as of the least abundant isomer, namely XXXIV, presumably involves the addition of the pinacolyl carbonium iontotert-butylethylene ... 

In another study, the arenium ions of protonation and the two-electron oxidation dications derived from BaP and three of its nonalternant isomers, namely, azu-leno[5,6,7-c phenalene 69 (a strong carcinogen reported to be as potent as BaP), azuleno[l,2,3-cJ phenalene 70 (a strong mutagen/weak carcinogen), and... 

Under all applied conditions only C 0F4g is formed, probably as three different optical isomers [24—26] (Figure 9.1). Gakh and co-workers determined the correct structure on the basis of F NMR spectroscopy [24]. The structure was confirmed by resolution of the X-ray crystal structure [25, 26]. This shows that, probably, all three optical isomers - namely the two enantiomeric forms with Dj-symmetry and the mesoform with Sg-symmetry- can be foimd in the crystal (Figure 9.1, structures 11 and 12). 

The alkylation of naphthalene and 2-methylnaphthalene with methanol and their ammoxidation were investigated by F r a e n k e 1 et al. [22-25] on zeolites ZSM-5, mordenite and Y. In the alkylation over HZSM-5 - unlike on H-mordenite or HY - the slim isomers, namely 2-methylnaphthalene as well as 2,6- and 2,7-dimethylnaphthalene, again clearly predominated. These authors suggest that such shape selective reactions of naphthalene derivatives occur at the external surface of zeolite ZSM-5, in so-called "half-cavities" [22, 24, 25]. D e r o u a n e et al. [26,27] went even further and generalized the concept of shape selectivity at the external surface. Based, in part, on Fraenkel s experimental results, Derouane [26] coined the term "nest effect". This whole concept, however, is by no means fully accepted and has recently been severely questioned in the light of results obtained in catalytic studies with a much broader assortment of ten-membered ring zeolites [28]. 

FIGURE 5.S Anthocyanin reactions with caffeoyltartaric acid o-quinone coupled oxidation of cyanidin 3-glucoside (A) and nucleophilic addition of anthocyanins (B). Anthocyanin-caffeoyltartaric acid adducts are represented as one of the possible isomers, namely 2-(8-anthocyanin) caffeoyltartaric acid (5 1). 

General Comments. The formation of deoxy sugars by hydrogenation over Raney nickel often leads to the abnormal isomer (namely, that formed by diequatorial opening of the oxirane ring) as the major product, in contrast to the product afforded by lithium aluminum hydride this suggests that a different mechanism is involved in the nickel-catalyzed reaction. 

Carbonylation of 2,3-homo-l//-azepines has been effected by means of their metal and carbonyl complexes and provides a useful route to a variety of isomeric azabicyclo-nonadienones. For example, the tricarbonyliron complex with carbon monoxide at 80 °C and 160 atm yields the 9-oxo-2-azabicyclo[3.3.l]nona-3,7-diene (167) (57%) or the 9-oxo-2-azabicyclo[3.2.2]nona-3,6-diene (168) (60%) depending on the exo or endo configuration of the tricarbonyliron complex. A third isomer, namely ethyl 7-oxo-9-azabicyclo[4.2.1]nona-2,4-diene-9-carboxylate (169), is formed on heating (125 °C) the azepine with carbon monoxide under pressure in the presence of the rhodium carbonyl complex [Rh(CO)Cl2] (78CB3927). 

Milk thistle (Silybum marianum) is an annual to biennial plant of the Aster-aceae family. It is native principally to southern Europe and northern Africa. The crude drug consists of the ripe fruits from which the pappus has been removed. Milk thistle fruits contain 15% to 30% proteins. The main active compounds constitute only about 2% to 3% of the dried fruits. The active principle is a mixture of flavolignans called silymarin. Silymarin, a polyphenolic extract isolated from the seeds of milk thistle, is composed mainly of silybin (50 70%), with small amounts of other silybin structural isomers, namely isosilybin, silydianin, and silychristin (Fig. 11) (123-125). The highest concentration of silymarin is found in the ripe fruits (126). Silibinin is the main compound, also considered to be the most active one in several paradigms (127). 

Transition metal complexes in particular show several kinds of constitution isomers, namely ... 

As radafaxine contains two asymmetric centers, there are four possible isomers, namely (R,R)-, (R,S)-, (S,S)- and (S,R)-. In-house knowledge on related molecules, computer modeling, and various calculahons indicated that only two enantiomers, the (S,S)- and (R,R)-, that is compounds 2a and 2b, were likely to be formed and be stable under normal conditions. ... 

A particular selectivity was observed in the isomerization of m-xylene over MCM-41 mesoporous aluminosilicate. When compared to silica-alumina, MCM-41 exhibits very similar acidity characteristics and activities, and the disproportionation to isomerization ratios are not very different. However, there exists a large difference in the relative rates of formation of the para and the ortho isomers namely, the ortho isomer is preferentially formed (ortho para > 2.5). This was attributed to the presence of the regular, noninterconnected channels of MCM-41, in which xylene molecules undergo, before desorption, successive reactions of disproportionation and transalkylation. 

Benzo-fusion to a pyrylium ring can give rise to two isomers, namely the 1- and 2-benzopyrylium ions (6) and (219) both of which are formally aromatic 107r- electron systems. 

In 1966, Johns and Lamberton [45] showed that equilibration of uncarine C and uncarine D in acidic and basic solutions resulted in C-3 isomerizations. Further investigations [46,47] revealed that equilibration of e.g. uncarine C in an aqueous acetic acid solution (50%) resulted in four isomers, namely uncarine C (64), D (65), E (66) and F (67), Fig. 

Bodor claimed (1991) that the "whole molecule" approach using AMI calculations can estimate the difference in log P of diastereoisomers. The supporting examples are betamethasone and dexamethasone, where the latter was calculated as 0.06 log units lower (1.90 vs. 1.96). Eight measured values from the literature (Hansch, 1995) show the same range in the measurements of each isomer, namely, 1.84 to 2.01. (The latest version of CLOGP estimates both at 2.00.) When the formula used to calculate log P via MO has 17 variables (plus I-alkane = 0) and results in a difference less than half of that shown in the measured data, one hardly has accounted for a subtle difference. 

Uses Xylene occurs in the manufacture of different petroleum products and as an impurity in benzene and toluene. It is a colorless and flammable liquid. Commercial xylene is a mixture of three isomers, namely, ortho-, meta-, and paraisomer. It is extensively used in industries associated with paints, rubber, inks, resins, adhesives, paper coating, solvents, and emulsifiers. It also is used in the manufacture of plasticizers, glass-reinforced polyesters, and alkyl resins. Xylene is used as an important raw material. 

Uses Propyl alcohol has two isomers, namely, n-Propyl alcohol and isopropyl alcohol. These alcohols have extensive use in a variety of industries (e.g., manufacturing, pharmaceuticals, perfumes, cosmetics, skin lotions, hair topics, mouthwashes, liquid soaps). It also is used in lacquers, dental lotions, polishers, and surgical antiseptics. 

According to the polymerization-degradation mechanism shown above, trans-butylene sulfide can lead to only two out of the six geometrical isomers, namely, the ds-cis-cis-and the ds-trans-ds isomers. Cis-butylene sulfide can lead only to the tram-ds-tram and trans-trans-tram isomers. It was indeed found that the trithiacycloheptane derivatives consisted of a mixture of two isomers and that those derived from the eis-mono-mer were different from those derived from the trans-monomer. It was, however, not possible to attribute an absolute structure to each of the isomers. 

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