Aromatic compounds Table

A similar circumstance is detectable for nitrations in organic solvents, and has been established for sulpholan, nitromethane, 7-5 % aqueous sulpholan, and 15 % aqueous nitromethane. Nitrations in the two organic solvents are, in some instances, zeroth order in the concentration of the aromatic compound (table 3.2). In these circumstances comparisons with benzene can only be made by the competitive method. In the aqueous organic solvents the reactions are first order in the concentration of the aromatic ( 3.2.3) and comparisons could be made either competitively or by directly measuring the second-order rate constants. Data are given in table 3.6, and compared there with data for nitration in perchloric and sulphuric acids (see table 2.6). Nitration at the encounter rate has been demonstrated in carbon tetrachloride, but less fully explored. ... 

Selecting the naphtha type can be an important processing procedure. For example, a paraffinic-base naphtha is a better feedstock for steam cracking units because paraffins are cracked at relatively lower temperatures than cycloparaffins. Alternately, a naphtha rich in cycloparaffins would be a better feedstock to catalytic reforming units because cyclo-paraffins are easily dehydrogenated to aromatic compounds. Table 2-5 is a typical analysis of naphtha from two crude oil types. 

The allene host 20 exhibits high inclusion selectivity in competition experiments using mixtures of solvents 26). In fact, preliminary results indicate that it can be used for the separation of constitutional isomers, of homologues, and of aliphatic from alicyclic or aromatic compounds (Table 3). Other derivatives of the allene, e.g. 21, are also functional as host molecules, and are currently being subjected to further investigations 22). 

The use of protein immobilised to the surface of a silica gel or to another support has been a very successful approach for the chiral separation of various pharmaceuticals. The AGP stationary phase has been shown to have the broadest enantiorecognition abilities while the BSA stationary phase is especially useful for aromatic compounds. " Table 9 shows some examples of separations that were obtained on the protein-type of CSPs. 

Directed metallation of aromatic compounds TABLE 2. piTa and ortholithiation ... 

Technically interesting are the indirect electrochemical oxidations of benzylic alcohols (Table 11, No. 15-18) benzaldehyde dimethylacetals (Table 11, No. 19) and alkyl aromatic compounds (Table 11, No. 20, 21) It could be proven that benzylic alcohols are oxidizable using tris(2,4-dibromophenyl)amine as mediator not only in acetonitrile in a divided cell but also in methanol in an undivided cell... 

Substituted 1-fluoropyridinium triflates have been used for substitution of hydrogen by fluorine in aromatic compounds (Table 3).46"50 Thus benzene is transformed to fluorobenzene (56 % yield, l-fluoro-2,6-bis(methoxycarbonyl)pyridinium triflate), Af-ethoxycarbonylaniline gives Al-ethoxycarbonyl-2- and -4-fluoroaniline (60 and 27% yield, respectively, 1-fluoropyridinium triflate), and phenylurethane also gives the products of fluorination at position 2 (47%) and 4 (32%) of the aromatic ring [l-fluoro-2,6-bis(methoxycarbonyl)pyridinium triflate]. In the case of fluorination of anisole, 1-fluoropyridinium tetrafluoroborate gives 19% 2- and 17% 4-fluoroanisole.46... 

F-Teda BF4 is effective for the selective addition of fluorine to steroids in good yield, re-gioselectively and, in many cases, stereoselectively at the 6- and 16-positions, under very mild reaction conditions (Table 7).92 Further, 6 will also efficiently fluorinate silyl and alkyl enolates, enamides, carbanions, a-alkenes and actived aromatic compounds (Table 8). As an extension of this method F-Teda BF+ has been used for the electrophilic fluorination of (fluorovinyl)tin compounds affording terminal fluoroalkenes (see Table 9).88... 

All of the group 5 heterobenzenes show mass spectra typical of aromatic compounds (Table 4). The compounds show intense molecular ions which are the base peaks for all the heterobenzenes except bismabenzene. Important fragmentation involves loss of either C2H2 or HCE from the molecular ion. Loss of HCE becomes relatively less important for the heavier heterobenzenes. This observation may be explicable in... 

In Tables 10 to 12 we show the heats of formation calculated by the various methods, together with their deviation from the experimentally observed values for alkanes and cycloalkanes, alkenes and cydoalkenes, and acetylenes and aromatic compounds. Table 13 shows a comparison of heats of formation of hydrocarbon radicals calculated by the MINDO methods. Finally, in Tables 14 and 15 we show the results of MINDO/1 calculations on a selection of oxygen- and nitrogen-containing compounds. 

With simple aromatic compounds (Tables XVII and XVIII) the effect of structure on sensory qualities is easily recognizable, too. In order to determine electrophilic and nucleophilic centers in aromatic compounds their charge distributions were calculated. The values for the atomic charges were obtained from a computer program which is based on a model for partial equalization of orbital electronegativity (26, 27). This model was extended to1T-systems (28). 

Thiophenol is an aromatic compound (Table 6). One hydrogen atom in its benzene core is substituted for a SH-group. The SH-group has a weak negative induction and a positive mesomeric effects. In addition, the unshared pair of -electrons of a sulfur atom contributes to the 7i-electron cloud of the benzene ring. 

Aromatic compounds Nucleophilic displacement of halide ion from haloaromatic compounds containing other electronegative substituents is well known this process has been widely exploited for the synthesis of fluorinated aromatic compounds (Table 2.1) and is discussed later (see Chapter 9, Section 11). 

Ordinary eutectics are formed by nitromannitol with higher nitrated aromatic compounds (Table 27). 

A striking observation is the high solubility of fullerenes in higher aromatic compounds (Table 2.3). Obviously the k-k interactions causing the solubilization of individual Cso-molecules are most effective here. A chlorinated aromatic solvent positively affects the solubility of C, too. In aliphatic solvents only minor amounts... 

Anionic ortho-Fries rearrangement is performed by freafment of variously subsfifufed aryl carbamates with sec-butyllithium at -78°C in tetramethylethylenediamine-tetrahydrofuran solution for 8-12 h. i The reaction involves the selective ortho-metalation of fhe aryl groups. The meta-cooperafive mefalafion effect is responsible for fhe producfion of some extremely hindered aromatic compounds (Table 5.13). 

There are additional rules for carbonyl-containing compounds, such as ketones, aldehydes, carboxylic acids, and so on, and for aromatic compounds. Table 8.30 lists the parameters for conjugated carbonyl systems. Note that in contrast to the conjugated diene compounds, in which we are observing TT TT transitions, the transitions of the carbonyl chromophore... 

The rates of reduction of the aromatic compounds (Table I), appear to increase as AEg g and I decrease, in contrast with the behavior of k2. This trend is to be expected since k5 reflects the electron affinity which decreases when I and AEg g increase. The values of k5 also can be related to the polarographic half-wave potentials, Ei, of the aromatic hydrocarbons and the general trend is, of course, a decrease in k5 when Ei is more negative. 

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