The nitration of mono‐alkylbenzenes conformational analysis and steric hindrance: Part II: Secondary alkylbenzenes

Abstract

The isomer distributions for the nitration of six srconclrrry alkylbenzenes and the partial rate factors of three of these compounds have been determined. The stei-ic hindrance of the nitration in the orrho-position of isopropylbenzene is mainly of an enthalpic nature. The increase of this hindrance in the series of isopropylbenzene, s-butylbenzene, ( I -ethylpropyl)benzene is of an entropic nature and can be explained from the conformational analysis u l the initial states and the transition states. The steric hindrance in the orrho-positions of (2-methyl-Iisopropy1propyI)benzene and (I-1-butyl-2.2-dirnethylpropy1)benzcne is very la rye.

Experiments on the Chaperon Effect in the Nitration of Aromatics

“…Since this effect cannot be ascribed to an electron- withdrawing effect, as also confirmed by the smaller incursion of meta substitution, it is likely that the actual size of the lateral substituent in 8 and 9 in H 2 SO 4 is much larger because of close association of solvent molecules. A methyl on the α-carbon of benzeneacetic acid (compound 10 ) is also the cause of a decrease of the chaperon effect, which appears still marked in comparison with, e. g., alkylbenzenes such as isopropyl and sec -butyl ).…”