35843-80-2

Upstream product

• 87-85-4 Hexamethylbenzene 
• 13257-51-7 mercury(II) trifluoroacetate 
• 76-05-1 trifluoroacetic acid 
• 484-66-2 2,3,4,5,6-pentamethylbenzyl alcohol 
• 407-25-0 trifluoroacetic anhydride 

Relevant academic research and scientific papers

Charge-Transfer Photochemistry of Aromatic ?-Complexes. Hexamethylbenzene and Mercuric Trifluoroacetate

The ?-complex of hexamethylbenzene (HMB) and mercuric trifluoroacetate (HgT2) is converted with high quantum yields to pentamethylbenzyl trifluoroacetate and either mercurous trifluoroacetate or metallic mercury upon irradiation of the charge-transfer absorption band.X-ray crystallography establishes the charge-transfer (CT) excitation to derive from the η2-bonding of the mercuric atom to only two of the aromatic carbons of HMB.The CT photochemistry proceeds via the radical-ion pair in accord with Mulliken theory.The high quantum efficiency is ascribed to the rapid ligand dissociation of HgT2 anion radical which minimizes the energy wastage due to back electron transfer.The thermal reactions following photoactivation are monitored by following the changes in the CT absorption band and the ESR spectrum of HMB cation radical.The charge-transfer photochemistry of the complex shows an unusually high dependency on the solvent-the nature of the mercury-containing products and the quantum yield ΦP for pentamethylbenzyl trifluoroacetate in dichloromethane being distinctively different from that obtained in trifluoroacetic acid.The formation of metallic mercury with quantum yields in trifluoroacetic acid which can be as high as 3 arises from a radical-chain process which sustains itself after the light is turned off.The critical role played by the mercurous trifluoroacetate radical HgO2CCF3 in the CT photochemistry is described.

Remarkable effect of water on functionalization of the phenyl ring in methyl-substituted benzene derivatives with F-TEDA-BF4

Various N-F reagents reacted with hexamethylbenzene (1) forming side chain substituted alkoxides or esters in protic solvents, Ritter type side chain functionalization was observed in acetonitrile in the presence of trifluoroacetic acid, while in aqueous

Effective and versatile functionalisation of hexamethylbenzene using N-F reagents

Effective direct introduction of alkoxy, amido, azido or halogeno functional groups on the benzylic position in hexamethyl-benzene was mediated by the N-F reagents F-TEDA-BF4, NFTh, NFSi or FP-B800 in the presence of alcohols, carboxylic acids, cyanides or trimethylsilyl derivatives as sources of an external nucleophile.

Formation and characterization of the radical cation of pentamethylbenzyl trifluoroacetate from the oxidation of hexamethyl (Dewar benzene) by thallium(III) trifluoroacetate in trifluoroacetic acid-a slow and complex reaction

The reaction between hexamethyl (Dewar benzene) (HMD) and T1III trifluoroacetate (T1III) in trifluoroacetic acid has been investigated in detail.The first step involves a slow acid-catalysed conversion of HMD into hexamethylbenzene (HMB) which is then oxidized by T1III to pentamethylbenzyl trifluoroacetate in a process which overall is about 15 times faster than the HMD->HMB reaction.In the formal one-electron transfer reaction between HMB and T1III, the corresponding radical cation, HMB-cation radical, appears in significant concentration and with a lifetime which makes it easy to monitor by EPR spectroscopy.It is shown that the true lifetime of HMB-cation radical in trifluoroacetic acid is shorter by a factor of ca. 0.03 (22 deg C) or ca. 0.005 (-11 deg C) than the 'decay' lifetime recorded during an experiment in which it is generated by the reaction between HMB and T1III under otherwise identical conditions.Thus the 'decay' rate constant of HMB-cation radical is actually a reflection of its slow rate of formation from HMB-T1III.The fact that the formal one-electron transfer reaction between HMB and T1III exhibits a significant kinetic isotope effect of both substrate and solvent type, indicates that this apparently simple step must be complex.Pentamethylbenzyl trifluoroacetate, as well as the corresponding acetate, alcohol, methyl ether or chloride, exhibits a characteristic 13*8 line EPR spectrum when irradiated in trifluoroacetic acid with T1III trifluoroacetate at -11 deg C.The similarity of this spectrum to the previously described, less well-resolved 13- line EPR spectrum from the oxidation of HMD in matrices at low temperatures or on a solid substrate,is profound.The fact that HMD on oxidation by T1III in trifluoroacetic acid gives the 13*8 line spectrum of pentamethylbenzyl trifluoroacetate, indicates that the transformation of HMD into a suitable pentamethylbenzyl derivative might be the origin of the 13-line EPR spectrum recorded by the matrix technique.

Highly Selective Aromatic Chlorination. Part 4. The Chlorination of Aromatic Hydrocarbons with N-Chloroamines in Acidic Solution

Benzene, toluene, some polymethylbenzenes, and naphthalene have been treated with N-chlorotrialkylammonium salts and N-chlorodialkylamines in trifluoroacetic acid at room temperature.With benzene, toluene, and 1,3,5-trimethylbenzene the major products arise from aromatic chlorination whereas with the other polymethylbenzenes side-chain reactions predominate.By controlling the acidity of the reaction and the nature of the N-chloroamine, the chlorination of toluene can be made to give preferentially 2- or 4-chlorination.However, the selectivities are not as great as reported previously with electron-rich aromatic compounds with a ?-donor substituent.The products from the reaction of naphthalene are very dependent on the structure of the N-chlorinated amine.The bulky N-chlorotrialkylammonium salts selectively chlorinate the 1-position, but in low yield, whereas the less hindered N-chloropiperidine gives good yields of 1-(1-piperidino)-naphthalene.The results from these studies are discussed in terms of arenium-ion and electron-transfer mechanisms.

Kinetics and Mechanism of Aromatic Thallation. Identification and Proof of Competiting Electrophilic and Electron-Transfer Pathways

The unusual occurrence of simultaneous electrophilic (two-electron) and electron-transfer (one-electron) pathways during the thallation of the homologous methylbenzenes ArCH3 is demonstrated by (1) the careful analysis and identification of three major types of products, (2) the complete dissection of the complex kinetics, and (3) the identification of the reactive intermediates by time-resolved UV-vis and ESR spectroscopy.Side-chain substitution S, dimerization D, and oxidative nuclear substitution O derive from the radical cation ArCH3+. produced as a common intermediate by electron transfer from the methylbenzene to thallium(III) trifluoroacetate in trifluoroacetic acid.The importance of ArCH3+., which is detected by both its electronic and ESR spectra, decreases in the following order, hexamethylbenzene > pentamethylbenzene > durene >> mesitylene, with a concomitant rise in electrophilic nuclear thallation R to account for the complete material balance.The striking color changes that accompany thallation are identified as charge-transfer transition in the series of transient 1:1 ?-complexes of the methylbenzene donors and the thallium(III) acceptor.Quantitative spectrophotometry employing the Benesi-Hildebrand analysis establishes the cationic Tl(O2CCF3)2+ formed by the dissociation of a single trifluoroacetate ligand from the parent thallium tris(trifluoroacetate) as the active electron acceptor.The complete analysis of the complex kinetics including kinetic isotope effects with accompany the nuclear thallation R of mesitylene as well the side-chain substitution S of hexamethylbenzene shows that the cationic Tl(O2CCF3)2+ also serves the dual function as the active electrophile and the active oxidant, respectively.The close competition between these apparently disparate pathways is quantitatively evaluated by the second-order rate constants which differ by less than an order of magnitude.Therefore, the thallation of arometic hydrocarbons represents one of the few systems in which such dual pathways, electrophilic and free radical, apparently occur side under the same experimental conditions of solvent, temperature, etc.Accordingly, it represents an unusual opportunity to delineate two-electron (concerted, electrophilic) from one-electron (stepwise, free radical) mechanism-especially as two whether they represent parallel or sequential events.