Journal of the Chemical Society - Faraday Transactions p. 3331 - 3338 (1992)
Update date:2022-08-05
Topics:
Parry, Alyn
Fernandez, M. Tereza
Garley, Mike
Mason, Rod
Temperature-variable equilibrium constant measurements have been performed for a number of proton-transfer equilibria in which benzene was a partner, using a newly built high-pressure pulsed source mass spectometer.Entropy values obtained showed that the protons in protonated benzene are not as mobile as previously thought.Systems involving ethanol are found to give anomalous, though self-consistent results owing to the onset of thermal decomposition.In the light of this, previous data involving halotoluenes and xylenes which appear to show unusually large increases in entropy on protonation, have been reassessed.There is evidence of proton-induced isomerisation.In the reaction <4-ClC6H4CH3>H(1+) -> <3-ClC6H4CH3>H(1+) the free energy of activation is derived to be ca. 90 kJ mol-1 from a computer model fit to the results, consistent with the energy calculated to be needed for a proton shift from the 3 to the 4 position in the precursor.The equivalent reaction for protonated 4-fluorotoluene has a barrier which is ca. 10 kJ mol-1 higher.A kinetic scheme is presented which shows how this could account for the observed 'thermodymanimc' behaviour, and also give rise to the 'isokinetic effects' previously noted.There has therefore been some readjustment of the recommended proton affinity values for some of these compounds.
View MoreContact:+86-13666670345
Address:Agricultural Development Zone, Haining, Jiaxing, Zhejiang
Springchem New Material Technology Co.,Limited
website:http://www.spring-chem.com
Contact:86-21-62885108
Address:602B, Building 1, No. 641, Tianshan Road
Shijiazhuang Haitian Amino Acid Co., Ltd.
Contact:+86-311-88908111
Address:Shijiazhuang Hebei province,China
website:http://www.tbbmed.com
Contact:86--21-50498136
Address:Room 6002, Building 7-1, No.160 Basheng Road,Pudong Area,Shanghai China
Shanghai Korey Pharm Co.,Ltd.(expird)
Contact:021-61840961 021-61840962
Address:No.157,Zhuguang Rd, Qingpu, Shanghai, China
Doi:10.1021/ja9608757
(1996)Doi:10.1021/ja8020999
(2008)Doi:10.1021/np800105e
(2008)Doi:10.1002/hlca.19660490531
(1966)Doi:10.1016/S0040-4039(00)01073-X
(2000)Doi:10.1016/j.tet.2012.03.041
(2012)
