16766-57-7Relevant academic research and scientific papers
Charge-transfer probes for molecular recognition via steric hindrance in donor-acceptor pairs
Rathore,Lindeman,Kochi
, p. 9393 - 9404 (2007/10/03)
Molecular association of various aromatic hydrocarbons (D, including sterically hindered donors) with a representative group of diverse acceptors (A = quinone, trinitrobenzene, tetracyanoethylene, tropylium, tetranitromethane, and nitrosonium) is visually apparent in solution by the spontaneous appearance of distinctive colors. Spectral (UV-vis) analyses of the colored solutions reveal their charge-transfer origin (λ(CT)) and they provide quantitative information of the intermolecular association in the form of the K(DA) and ε(CT) values for the formation and visualization, respectively, of different [D,A] complexes. Importantly, such measurements establish charge-transfer absorption to be a sensitive analytical tool for evaluating the steric inhibition of donor-acceptor association. For example, the steric differences among various hindered aromatic donors in their association with quinone are readily dramatized in their distinctive charge-transfer (color) absorptions and verified by X-ray crystallography of the charge-transfer crystals and/or QUANTA molecular modeling calculations of optimum intermolecular separations allowed by van der Waals contacts.
"IPSO" AROMATIC ALKYLATION IN THE GAS PHASE. INTERMEDIACY AND STRUCTURE GASEOUS HEPTAALKYLBENZENIUM IONS
Attina, Marina,Cacace, Fulvio,Petris, Giulia de,Fornarini, Simonetta,Giacomello, Pierluigi
, p. 2297 - 2302 (2007/10/02)
The structure of heptaalkylbenzenium ions has been investigated in the gas phase with complementary techniques, i. e., chemical ionization mass spectrometry, alkylation of hexaalkylbenzenes by radiolytically generated cations, and collisianally induced dissociation mass spectrometry.The results allow us to assign the ?-complex ( Wheland intermedisate ) structure to the free, gaseous heptaalkylbenzenium ions, in agreement with the established structure of their salts in solution and in the solid state.The heptaalkylbenzenium ions represent the charged intermediates of the gas-phase "ipso"-substitution reactions, whose occurence has been demonstrated and whose mechanism is briefly discussed.
