6214-21-7

A variety of deactivated arenes were nitrated to their corresponding nitro derivatives in excellent yields under high-speed ball milling condition using Fe(NO3)3·9H2O/P2O5 as nitrating reagent. A radical involved mechanism was proposed for this facial, eco-friendly, safe, and effective nitration reaction.

Molecular organic crystals are strategically designed for nonlinear optical applications using push-pull chromophores as the core feature. In this approach, electron-donating and accepting groups are connected through a π-conjugated bridge to obtain planar molecules with high hyperpolarizability. However, the non-centrosymmetric packing that is required for nonlinear optical (NLO) applications is a critical challenge that must be addressed to design useful materials. In this article, we present the new organic cation 6MNEP that shows a large hyperpolarizability and can be crystallized in ideal non-centrosymmetric structures for NLO applications, when paired with T and 4NBS anions. The 6MNEP cation was obtained by extending the conjugation length of already existing chromophores. We compare the 6MNEP crystals with other crystals that also have cations with extended conjugation lengths, but result in centrosymmetric crystal structures. Using the effective hyperpolarizability, we found 6MNEP-T and 6MNEP-4NBS to have 1.6 to 2.5 times larger macroscopic nonlinearities than benchmark NLO organic crystals. Additionally, the significantly lower absorption wavelength compared with other state-of-the-art crystals make 6MNEP-T and 6MNEP-4NBS promising materials for NLO applications like intense terahertz generation.

Nucleophilic substitution on meta- and para-substituted methyl benzenesulphonates was studied with two chloride salts with different structures: NBu4Cl or KCl-Kryptofix 2,2,2. Treating the results with the Acree equation shows that the reaction proceeds by two reaction paths, one involving the chloride ion and the other, slower one, involving the ion pairs. Treating the results with the Hammett equation gives consistent data, and shows that ρ is positive and nearly the same for the two reaction paths (ρ ≈ +2). The reactivity of methyl p-nitrobenzenesulphonate was compared with that of the corresponding ethyl derivative, and it is shown that the methyl derivative reacts faster than the ethyl derivative in both paths. The results are interpreted based on the assumption that in both paths a negative charge is developed on the leaving group in the transition state, and that the activated complex is linear. Copyright

In cyclisations of aryl ο-halogenoalkyl ketones to aryl cycloalkyl ketones with base, cyclopropanes are formed up to 23000 times faster than cyclopentanes.Hydrogen-deuterium exchange experiments and very low bromide-chloride ratios (1.9) for three-membered ring formation are consistent with rate-determining deprotonation of the ketone.By contrast, in five-membered ring formation, hydrogen-deuterium exchange adjacent to the carbonyl group occurs much faster than cyclisation and the chloride-bromide ratio is 'normal' at 99.In formation of arylsulphonylcyclopropanes from arylsulphonylpropyl arenesulphonates, the Hammett ρ value for the leaving group is +1.7, and for intermolecular substitution by bis-sulphonyl stabilised carbanions, +1.2.Attempts to obtain ρLG values for five-membered ring formation were frustrated by competing intermolecular reactions.The results are discussed against the background of previous work on ring formation by intramolecular nucleophilic substitution.

Second-order rate coefficients for the reactions of acetonitrile solutions of tetra-n-butylammonium benzensulphonate and seven meta- and para-substituted derivatives with methyl perchlorate, at 0.3 deg C lead to a Hammet ρ value (-1.10 +/- 0.04) essentially identical to those previously reported for reactions with other powerful methylating agents.When silver ion is substituted for tetra-n-butylammonium ion, the second-oreder rate coefficients become concetration dependent and the fall of with increasing salt concetration can be rationalised on the basis of only free anions being reactive.The calculated degrees of dissociation are applied tothe previously studied silver0ion assisted reaction of silver toluene-p-sulphonate with methyl iodide.

The kinetics of the reactions between trimethyloxonium hexafluorophosphate and a series of tetra-n-butylammonium arenesulfonates have been studied in acetonitrile at -23.4 deg C.With the oxonium salt concentration at about 0.01 M, two series of runs were carried out; Hammett plots of the second-order rate coefficients led to ρ values of -1.18 +/- 0.04 for 0.04 M arenesulfonate salt and -1.07 +/- 0.02 for 0.16 M arenesulfonate salt.Solvolysis kinetics for the trimethyloxonium ion in acetonitrile are also reported.