Benzene derivatives, time-resolved

The technique has been described in detail elsewhere. [26] In short, a pulse of high energy electrons induces a series of chemical reactions that can be monitored, e.g., using time resolved UV-vis spectroscopy. The reaction of interest is usually induced by a reaction between a radical formed from radiolysis of the solvent (usually water) and a solute molecule. The primary radiolysis products in aqueous solution are HO, e q", H, HjOj, H2 and The major radical species, HO and e q, are formed in equimolar concentrations, 0.28 ol/J each, on electron or y-irradiation.[27] As can be seen in reaction 2, the hydroxyl radical does not yield a benzene radical cation instantly upon reaction with a substituted benzene. For this reason, secondary oxidants, such as S04, Brj and N3, are usually used to generate benzene radical cations. To determine one-electron reduction potentials of radical cations, the redox equilibrium between the radical cation of interest and a redox couple with a known one-electron reduction potential is studied. The equilibrium constant can be derived from the rate constants of the electron-transfer reaction and the back reaction and/or the equilibrium concentrations of the two redox couples (reaction 6).[28]... 

Ferrocene reacts with acetyl chloride and aluminum chloride to afford the acylated product (287) (Scheme 84). The Friedel-Crafts acylation of (284) is about 3.3 x 10 times faster than that of benzene. Use of these conditions it is difficult to avoid the formation of a disubstituted product unless only a stoichiometric amount of AlCft is used. Thus, while the acyl substituent present in (287) is somewhat deactivating, the relative rate of acylation of (287) is still rapid (1.9 x 10 faster than benzene). Formation of the diacylated product may be avoided by use of acetic anhydride and BF3-Et20. Electrophilic substitution of (284) under Vilsmeyer formylation, Maimich aminomethylation, or acetoxymercuration conditions gives (288), (289), and (290/291), respectively, in good yields. Racemic amine (289) (also available in two steps from (287)) is readily resolved, providing the classic entry to enantiomerically pure ferrocene derivatives that possess central chirality and/or planar chirality. Friedel Crafts alkylation of (284) proceeds with the formation of a mixture of mono- and polyalkyl-substituted ferrocenes. The reaction of (284) with other... 

At constant temperature on the SE-30 column, the separation of para- and meta-xylenetricarbonylchromiums is poor the complexes of orthoxylene and ethylbenzene are eluted in the same time and are not completely resolved from the mesitylene complex. The selectivity of the Apiezon L column is greater for the xylene derivatives and the separation of o-xylene and ethylbenzene complexes is improved but the resolution of mesitylene- and pseudocumeme-tricarbonyl-chromiums is bad. Figure 215 shows a chromatogram of a benzene solution of the thirteen derivatives, obtained at 140°C with a SE-30 column. 

Three papers have dealt with NMR relaxation of small organic molecules dissolved in organic solvents. Kathmann et al. reported and spin-lattice relaxation measurements for cyclic amines (pyridine, 2,6-lutidine, 2,2,6,6-tertamethyl piperidine) in toluene and dichloromethane solutions. The rotational correlation times were derived from NMR data and compared with MD simulations. Alemany discussed highly resolved spectra for long-chain n-alkanes with 12-22 carbons, dissolved in benzene or toluene. Besides the chemical shifts, also the Ti data were obtained and related to segmental motions. Ekinci and co-workers studied Ti data for the chiral iV-benzil-2-isobutyl aza-15-crown-5-ether derivative as a function of temperature. The rotational correlation times and their activation energy were derived. 

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