Aromatic anion

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. 

MO calculations, 7, 364 Oxetene, 2-isopropylidene-polysubstituted rearrangement, 7, 377 Oxetene, tetramethyl-structure, 7, 366 Oxetenes, 7, 363-402 decomposition, 7, 375 metabolism, 1, 243 molecular dimensions, 7, 366 thermal stability, 7, 370 Oxetenyl anions aromaticity, 7, 371 Oxetenyl cations aromaticity, 7, 371 Oxichlororaphine occurrence, 3, 196 Oxichromic developers in colour photography, 1, 378-379 Oxidation... 

H-Oxocin-3-one, 2,3,7,8-tetrahydro-synthesis, 7, 667 Oxocins, 7, 668-669 47/-Oxocins synthesis, 7, 669 Oxocinyl anions aromaticity, 7, 669 Oxoiron compounds high valent... 

Aside from its summit position as a DMG (10, Scheme 3) the OCONEt2 provides versatile anionic aromatic chemistry anionic ortho-Fries rearrangement (9, Scheme 3) [11], a useful synthetic step by itself but also one that provides a path, after incipient phenol protection, to further DoM, resulting in a 1,2,3-sub-stituted aromatic derivative (9 —> 12, see also Scheme 13) [12] homo-ortho-Fries rearrangement to aryl acetamides (10 —> 11) providing a route to benzofura-nones which are difficult to prepare by Friedel-Crafts-based strategies [9] intra-... 

Conversely, nucleophilic molecules (Nu) [Lewis bases e.g., catechols, hy-droquinones, phenols, alcohols, and thiols (and their anions) aromatic hydrocarbons and amines (benzene, toluene, pyridine, bipyridine)] can be oxidized by (1) direct electron-transfer oxidation [Eq. (12.3)] or (2) by coupling with the oxidation product of H20 (or HO-), hydroxyl radical (HO-) [Eq. (12-4)] ... 

Bochkarev et al. 16 prepared hyperbranched dendrimers via polymerization of tris(pentafluorophenyl)germanium anions resulting in branched macromolecules with Ge-branching centers. Building block propagation was attributed to metal anion, aromatic substitution of a phenyl, para-fluoro-moiety. Thus, treatment of Ge-monomer 8 with excess Ge-anion afforded hyperbranched macromolecules with an internal framework resembling tetrakisGedendrimer 9 (Scheme 8.4). Subsequently, Sn and Si were employed for hyperbranched dendrimer construction. 

As with other solutes in ionic liquids, the general rule of like dissolving like is applicable i.e. ionic species will generally be soluble as will species capable of interacting with the anion. Aromatic species tend to exhibit poor solubility in ionic liquids consisting of aliphatic cations and vice versa. 

On comparing calculations for pentapnictogen anion aromatics [cyclo-Png] , Tsipis (05CCR2740) reported the following stability order ... 

It was found that addition of hydroxide anion in dimethylformamide or dimethylsulfoxide to metal(II) corrole complexes results in the appearance of much sharper absorption bands relative to the starting compounds. These findings were considered consistent with the idea that an anionic, 18 Jt-electron aromatic corrole complex (e.g., 2.119) is formed as the result of what appears to be a formal deprotonation process (Scheme 2.1.25). That deprotonation actually occurs was inferred from acid-base titrations involving nickel(II) and copper(II) corroles. The conclusion that these species are anionic aromatic compounds came from an appreciation that their electronic spectra resemble those recorded for divalent metallo-porphyrins. In any event, the anion that results was found to be quenched upon acidification, regenerating the corresponding non-aromatic metallocorroles. ... 

Now that complex formation with suitable metals has been established for anionic aromatic (CbHb) rings and for uncharged aromatic compounds like benzene, the question arises as to whether the aromatic (C7H7) + cation, which has become known in recent years, can function similarly. We have made investigations with trcpylium bromide, (C7H7) + Br , obtained from benzene by expansion of the ring with diazomethane. 

Addition of an electron to the LUMO of the carbonyl group to form a radical anion is the first step in the reduction process. Radical anions can be characterized in aprotic solvents by electron spin resonance (esr) spectroscopy. Those derived from unconjugated carbonyl compounds are highly reactive and can only be detected in a matrix at low temperatures [3]. Decay is rapid because the excess carbonyl compound acts as a proton donor toward the basic oxygen center in the radical anion. Aromatic carbonyl compounds give less reactive radical anions in which the free electron is delocalized over the whole... 

Other kinds of molecules besides benzene-like compounds can also be aromatic. For example, the cyclopentadienyl anion and the cycloheptatrienyl cation are aromatic ions. Pyridine, a six-membered, nitrogen-containinp heterocycle, is aromatic and resembles benzene electronically. Pyrrole,. five-membered heterocycle, resembles the cyclopentadienyl anion. Aromatic compounds have the following characteristics ... 

The best nucleophiles for the SrnI mechanism can make a relatively stable radical in the initiation part, either by resonance (enolates) or by placing the radical on a heavy element (second-row or heavier nucleophiles). The best electrophiles for the SrnI mechanism are able to delocalize the odd electron in the radical anion (aromatic leaving groups, carbonyl compounds), can make a stable radical (3° alkyl halides), and have a weak R-X (Br, I) bond. Tosylates and other pseudohalides are very poor SrnI electrophiles. If light is required for substitution to occur, the mechanism is almost certainly SrnI. 

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