34235-14-8Relevant academic research and scientific papers
Resonance Effects in the Solvolysis of α -t-Butyl- α-neopentylbenzyl and α-t-Butyl-α-isopropylbenzyl p-Nitrobenzoates
Fujio, Mizue,Ohe, Makoto,Nakata, Kazuhide,Tsuji, Yutaka,Mishima, Masaaki,Tsuno, Yuho
, p. 929 - 936 (2007/10/03)
Substituent effects on the solvolysis rates of α-t-butyl-α-neopentylbenz.yl and α-t-butyl-α-isopropylbenzyl p-nitroben/oates in 50% (v/v) aqueous EtOH at 75 °C were correlated with the Yukawa-Tsuno equation to give p = -3.37 and r = 0.78. and p= -3.09 and r = 0.68, respectively. The reduction in r values from r= 1.00 characteristic of full conjugation is ascribed to deviation from coplanarity of the carbocationic center and the benzylic π-system in the transition state. The torsion angles for twisting out of coplanarity were estimated from the relationship r/rmax = cos2 θ for a series of sterically hindered tertiary dialkylbenzylic solvolyses. The torsion angles assigned for these twisted benzylic systems are in good agreement with theoretically calculated dihedral angles of the corresponding 6-3IG * optimized carbenium ions. This identity provides convincing evidence for occurrence of steric inhibition of resonance through loss of coplanarity, and, in turn, provides strong support for our characterization of the r value as a resonance demand parameter reflecting the degree of resonance (π-delocalization) interaction between an aryl group and the reaction site.
Barriers to Internal Rotation in Neopentylbenzenes Substituted on the Benzyl Group. A 13C NMR Band Shape Study
Andersson, Sven,Drakenberg, Torbjoern
, p. 730 - 744 (2007/10/02)
Two series of neopentylbenzenes with one or two substituents on the benzyl group have been synthesized.In one series the substituents were H, F, Cl, Br, I, OCH3, OCOCH3, OSi(CH3)3, CH3 and CH2CH3, and in the other OH and R R = H, CH3, CH2CH3, (CH2)3CH3,
