Journal of the Chemical Society. Perkin transactions II p. 1259 - 1263 (1992)
Update date:2022-08-05
Topics:
Terrier, Francois
Xiao, Lan
Farrell, Patrick G.
Moskowitz, Danielle
Rate constants (kpB,kpBH) for the reversible deprotonation of 5,5',5''-trimethyl- and 3,3',3'',5,5',5''-hexamethyl-2,2',2'',4,4',4''-hexanitrotriphenylmethanes (2 and 3) by primary aliphatic amines, piperidine and morpholine as well as by phenoxide anions and hydroxide anion have been measured in H2O-Me2SO (20:80) at 25 deg C.Comparison of the results obtained with those for 2,2',2'',4,4',4''-hexanitrotriphenylmethane (1a) shows that the introduction of methyl groups in positions adjacent to the nitro groups decreases markedly the thermodynamic acidity of theexocyclic CH group: ΔpK2a1a = 1.68; ΔpK3a1a = 6.48.It is suggested that these decreases are very likely the reflection of a twisting of the nitro groups out of their attached aromatic planes and therefore of a reduced resonance stabilization of the conjugated carbanions C-2 and C-3.Other important steric effects are operating in the ionization of 2 and 3.These arise from the accumulation of ortho-nitro groups in the triphenylmethane system which makes the approach of the base reagents from the exocyclic carbon of 2 and 3 very difficult.The finding of extremely low intrinsic reactivities for 2 and 3 and the observation of a much greater catalytic efficiency of primary amines than of secondary amines in assisting the proton transfers are the two most striking manifestations of these F-strain effects.
View MoreSuzhou Kangrun Pharmaceutical, Inc
Contact:86-512-63912376，63913329
Address:Building 2, No. 2358 ,Chang'an Rd, Wujiang Economic Development Zone Pioneering park, china
Contact:+86-515-88356562
Address:No.2, West Daqing Road, Yancheng, Jiangsu, China
Shanghai Hongbang Medical Technology CO.,. Ltd
Contact:13671516988 /18917636693
Address:Room1, No67 Building, Yongde Road369, Wujing Town, Minhang Districy, Shanghai CIty, China.
Hubei New Desheng Technology Co., Ltd
website:http://www.whdsbio.cn
Contact:+86-15071057538
Address:C8-2-2, Optical Valley United Technology City, Gedian Development Zone, Ezhou , City Hubei, China.
Contact:+44 (0)161 367 9441
Address:
Doi:10.1016/0040-4020(79)87010-6
(1979)Doi:10.1007/BF00471291
()Doi:10.1039/a905462f
(1999)Doi:10.1002/1521-3765(20010302)7:5<1014::AID-CHEM1014>3.0.CO;2-X
(2001)Doi:10.1021/ic000369p
(2001)Doi:10.1016/j.bmcl.2006.01.123
(2006)
