42154-08-5Relevant articles and documents
Photochemical nitration by tetranitromethane. Part XXXIV. The photochemical reactions of pentamethylbenzene and hexamethylbenzene with tetranitromethane. The formation and rearrangement of labile adducts from pentamethylbenzene
Eberson, Lennart,Hartshorn, Michael P.,Timmerman-Vaughan, David J.
, p. 1121 - 1136 (2007/10/03)
The photolysis of the charge transfer (CT) complex of tetranitromethane and Pentamethylbenzene (13) in dichloromethane at - 50 or - 78°C gives the labile epimeric 1,2,3,4,6-pentamethyl-3-nitro-6-trinitromethylcyclohexa-1,4-dienes 18 and 19. Adduct 18 rearranges rapidly in [2H2]dichloromethane at 22°C (half-life 9 min) to give 2,3,4,5-tetrarnethyl-1-(2′,2′,2′-trinitroethyl)benzene (21), 2,3,4,5-tetramethylphenylnitromethane (26), 2,3,4,5-tetramethylbenzyl nitrate (32) and 2,3,4,5-tetramethylbenzyl nitrite (36). The photolysis of the tetranitromethane-13 CT complex in dichloromethane at 20°C gives compounds 21, 26, 32 and 36, in addition to their 2,3,4,6-tetramethyl analogues 20, 25, 31 and 35, the latter set of products probably arising from the rearrangement of the highly labile epimeric 1,2,3,5,6-pentamethyl-3-nitro-6-trinitromethylcyclohexa-1,4-dienes 54. The photolysis of the tetranitromethane-13 CT complex in acetonitrile gives mainly the phenylnitromethane 26, while similar reaction in 1,1,1,3,3,3-hexafluoropropan-2-ol yields pentamethylnitrobenzene 24, the latter by a nitrosation/oxidation sequence. Reaction of 13 with nitrogen dioxide in dichloromethane gives mainly compounds 26 and 30. No adducts were detected in the photolysis of the CT complex of hexamethylbenzene 14 in dichloromethane at accessible reaction temperatures (≥ -20°C), but products of side-chain modification 37-46 were formed. In acetonitrile similar reaction gave in addition to the above products 37-46 the N-nitrosoacetamide 47 and its precursor 49. Compounds 47 and 49 are also formed, along with the major products pentamethylbenzyl nitrate 39 and the mono- and di-nitromethyl compounds 40 and 43, on reaction of 14 with nitrogen dioxide in acetonitrile. EPR spectroscopic examination of the photolysis of acidic (trifluoroacetic acid, 0.4 mol dm-3) solutions of tetranitromethane and 13 or 14 demonstrated the formation of the corresponding radical cation or a transformation product thereof, i.e. the 1,2,3,4,5,6,7,8-octamethylanthracene radical cation from 13 or 14·+ from 14. Acta Chemica Scandinavica 1996.
Studies on the Chemistry of Isoindoles and Isoindolenines, XXXVII. - Symmetrically Substituted 2-Alkyl-2H-isoindoles
Kreher, Richard P.,Sewarte-Ross, Guenter,Vogt, Guenther
, p. 1719 - 1727 (2007/10/02)
2-Alkyl-Rn-2H-isoindoles (1; Rn = 4,5,6,7-tetramethyl, 4,5,6,7-tetrachloro) have been prepared efficiently by the N-oxide route and characterized by spectroscopic means.
Direct Observation of the Kinetic Acidities of Transient Aromatic Cation Radicals. The Mechanism of Electrophilic Side-Chain Nitration of the Methylbenzenes
Masnovi, J. M.,Sankararaman, S.,Kochi, J. K.
, p. 2263 - 2276 (2007/10/02)
The transient cation radicals ArCH3(.+) are spontaneously generated by the 532-nm excitation of the charge-transfer complexes with a 10-ns laser pulse.The decay kinetics of the spectral transients in the presence of added base establish the kinetic acidities (kH) for various methylarene cation radicals with different pyridines and trinitromethide.Such a proton transfer from ArCH3(.+) proceeds with a deuterium kinetic isotope effect of kH/kD ca. 3.Side-chain nitration of hexamethylbenzene (HMB) is shown to proceed in high yields via the intimate triad of reactive fragments II, , that is produced upon the charge-transfer excitation.The subsequent annihilation of the reactive triad II occurs via a rapid succession of bimolecular steps involving either (i) the initial ion-pair collapse of by proton transfer, as shown in Scheme VI, or (ii) the alternative sequence with the initial ion-radical collapse of by homolytic coupling, as shown in Scheme VII.The marked variations of kH/kD with solvent polarity and added innocuous salt (Bu4N(+)ClO4(-)), as reflected in ion-pair separation and the "special" salt effect, serve to effectively distinguish these pathways.The direct bearing of Schemes VI and VII on the mechanism of the thermal (adiabatic) nitration of methylarene side chains with nitric acid is delineated.
