3- methyl, tables

Evaluation of a series of 3-isopropyl-4-methylbenzocycloalkenes (7-9) and 3-isopropyl-4-methylbenzobicycloalkenes (10-13) reveals that methyl is effectively larger than any annelated ring in this series except cyclohexyl which is equal to methyl (Table 1). In addition, the energy difference between the two possible... 

C(7) absorbs to low frequency of C(7) in festuclavine as a result of the /7-effect of the axial hydroxyl group and the reduced //-effect of the axial methyl (Table III). 

With A-pivaloyl 2,6-dimethylaniline chromium complex 69, the chiral lithium amide 70 derived from l-phenyl-2(4/-methylpiperazinyl)ethylamine turned out to be the base of choice for the asymmetric lithiation at the benzylic methyls (Table 3). With almost all electrophiles, chromium complexes bearing different substituents on the nitrogen atom could be obtained in up to 99% ee92,93. In contrast, the chiral bases (R,R)-3, (R)-27 and (S)-4 resulted in modest asymmetric induction ranging from 44% to 78% ee. 

LC separates and detects some OPPs using methanol-water, methanol-acetonitrile-water, or acetonitrile-water gradient mobile phases. LC is suitable for determining some thermolabile and polar compounds such as dichlorvos, temephos, trichlorfon, and oxydemeton-methyl (Table 23.12). 

Rates of methylation (Table II) of iboga derivatives have been used to determine the configuration of the ethyl group 37). 

Replacement of the N,N-di-n-propyl groups of 8-OH-DPAT or 8-MeO-DPAT by smaller or larger di-n-alkyl substituents results in a significant drop in affinity [10]. The rankorder of potency is di-n-propyl > di-n-ethyl > di-n-butyl > di-n-methyl (Table 1). For the smaller di-n-alkyl substituted analogues (Cj-Cg), the (R)-enantiomers are more potent than the (S)-enantiomers. This stereo selectivity however, is reversed if larger di-n-alkyl substituents are introduced. The (S)-enantiomer of the di-n-butyl compound is about two times more potent than the (R)-enantiomer (Table 1). 

One possible model motif was envisaged in an analogous way, by a relocation of one methyl group across close contacts to generate compound 7 (with Ri = 3-pentyl and R2 = methyl) (Table 8.1), which crystallizes in a chiral stmcture. Consequently, an absolute asymmetric synthesis with a quantitative enantiomeric yield was achieved for this monomer [53]. 

DME inhibits alkene oligomerization and at least a part of C3" is formed through Cj" methylation (Table 2). 

The effect is lost, however, when phenyl, ethyl, or other groups are substituted for methyl (Table 17.7). 

The presence of thiophene and its derivatives in crude oils was detected in 1899, but until 1953, the date at which the methyl-thiophenes were identified in kerosene from Agha Jari, Iran crude oil, it was believed that they came from the degradation of sulfides during refining operations. Finally, their presence was no longer doubted after the identification of benzothiophenes and their derivatives (Table 8.9), and lately of naphthenobenzothiophenes in heavy cuts. 

Table Bl.11.1. Effect of an electronegative substituent upon methyl shifts in X- C H. ...

Table B2.5.5. The photochemical decomposition of methyl radicals (UV excitation at 216 nm). ris tire wavenumber linewidth of the methyl radical absorption and /ris the effective first-order decay constant [54].

Tire results of a study of the effect of these catalysts on the model Diels-Alder reaction of methyl vinyl ketone (4.8) with cyclopentadiene (4.6) are summarised in Table 4.1... 

The Diels-Alder reaction provides us with a tool to probe its local reaction environment in the form of its endo-exo product ratio. Actually, even a solvent polarity parameter has been based on endo-exo ratios of Diels-Alder reactions of methyl acrylate with cyclopentadiene (see also section 1.2.3). Analogously we have determined the endo-exo ratio of the reaction between 5.1c and 5.2 in surfactant solution and in a mimber of different organic and acpieous media. These ratios are obtained from the H-NMR of the product mixtures, as has been described in Chapter 2. The results are summarised in Table 5.3, and clearly point towards a water-like environment for the Diels-Alder reaction in the presence of micelles, which is in line with literature observations. 

The operation of the nitronium ion in these media was later proved conclusively. "- The rates of nitration of 2-phenylethanesulphonate anion ([Aromatic] < c. 0-5 mol l i), toluene-(U-sulphonate anion, p-nitrophenol, A(-methyl-2,4-dinitroaniline and A(-methyl-iV,2,4-trinitro-aniline in aqueous solutions of nitric acid depend on the first power of the concentration of the aromatic. The dependence on acidity of the rate of 0-exchange between nitric acid and water was measured, " and formal first-order rate constants for oxygen exchange were defined by dividing the rates of exchange by the concentration of water. Comparison of these constants with the corresponding results for the reactions of the aromatic compounds yielded the scale of relative reactivities sho-wn in table 2.1. 

Acetoxylation and nitration. It has already been mentioned that 0- and m-xylene are acetoxylated as well as nitrated by solutions of acetyl nitrate in acetic anhydride. This occurs with some other homologues of benzene, and with methyl phenethyl ether,ii but not with anisole, mesitylene or naphthalene. Results are given in table 5.4. 

This method is exemplified by its application to quinoline, isoquinoline, cinnoline, and isoquinoline 2-oxide, which are nitrated as their conjugate acids. The rate profiles for these compounds and their N- or O-methyl perchlorates show closely parallel dependences upon acidity (fig. 2.4). Quaternisation had in each case only a small effect upon the rate, making the criterion a very reliable one. It has the additional advantage of being applicable at any temperature for which kinetic measurements can be made (table 8.1, sections B and D). 

Kinetic data are available for the nitration of a series of p-alkylphenyl trimethylammonium ions over a range of acidities in sulphuric acid. - The following table shows how p-methyl and p-tert-h xty augment the reactivity of the position ortho to them. Comparison with table 9.1 shows how very much more powerfully both the methyl and the tert-butyl group assist substitution into these strongly deactivated cations than they do at the o-positions in toluene and ferf-butylbenzene. Analysis of these results, and comparison with those for chlorination and bromination, shows that even in these highly deactivated cations, as in the nitration of alkylbenzenes ( 9.1.1), the alkyl groups still release electrons in the inductive order. In view of the comparisons just... 

For the nine substituents m- andp-methyl, p-fluoro, m- and p-chloro, m- and p-bromo, and m- and p-iodo, using the results for nitration carried out at 25 °C in nitromethane or acetic anhydride - (see tables 9.1, 9.5), a plot of logjoA/ j against cr+ produced a substituent constant p = —6-53 with a standard deviation from the regression line i = 0-335, 2 correlation coefficient c = 0-975. Inclusion of... 

The first quantitative studies of the nitration of quinoline, isoquinoline, and cinnoline were made by Dewar and Maitlis, who measured isomer proportions and also, by competition, the relative rates of nitration of quinoline and isoquinoline (1 24-5). Subsequently, extensive kinetic studies were reported for all three of these heterocycles and their methyl quaternary derivatives (table 10.3). The usual criteria established that over the range 77-99 % sulphuric acid at 25 °C quinoline reacts as its cation (i), and the same is true for isoquinoline in 71-84% sulphuric acid at 25 °C and 67-73 % sulphuric acid at 80 °C ( 8.2 tables 8.1, 8.3). Cinnoline reacts as the 2-cinnolinium cation (nia) in 76-83% sulphuric acid at 80 °C (see table 8.1). All of these cations are strongly deactivated. Approximate partial rate factors of /j = 9-ox io and /g = i-o X io have been estimated for isoquinolinium. The unproto-nated nitrogen atom of the 2-cinnolinium (ina) and 2-methylcinno-linium (iiiA) cations causes them to react 287 and 200 more slowly than the related 2-isoquinolinium (iia) and 2-methylisoquinolinium (iii)... 

Recently kinetic data have become available for the nitration in sulphuric acid of some of these hydroxy compounds (table 10.3). For 4-hydroxyquinoline and 4-methoxyquinoline the results verify the early conclusions regarding the nature of the substrate being nitrated in sulphuric acid. Plots of log Q against — (Lf + logioflHao) fo " these compounds and for i-methyl-4-quinolone have slopes of i-o, i-o and 0-97 at 25 C respectively, in accord with nitration via the majority species ( 8.2) which is in each case the corresponding cation of the type (iv). At a given acidity the similarity of the observed second-order rate constants for the nitrations of the quinolones and 4-methoxy-quinoline at 25 °C supports the view that similarly constructed cations are involved. Application of the encounter criterion eliminates the possibilities of a... 

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