Aldo Domenicano and the structural chemistry of substituent effects: a personal tribute

Aldo Domenicano has been a provider and interpreter of structural information on substituent effects, especially in benzene derivatives. He started in X-ray crystallography, continued in gas-phase electron diffraction, and eventually added quantum chemical computations to his arsenal of tools of research. He was a charter member of the Editorial Board of Structural Chemistry; he has served the community in other ways as well, such as with directing international schools and editing monographs. He has also been an esteemed colleague and faithful friend.     

t-Butyl Hypochlorite: A Powerful Electrophilic Aromatic Ring Chlorinating Agent

t-Butyl hypochlorite is an excellent aromatic ring chlorinating agent, under mild conditions, without any catalyst, of acetanilide. High regioselectivity is observed, the product being, nearly exclusively, para-chloroacetanilide.     

Invariant cones of positive initial functions for delay differential equations

Consider the scalar delay differential equation x(t) + ∑ a_kx(t-r_k) = 0 (1) where a_k and r_k ≥ 0, (0 ≤k ≤ m), are real numbers.In this paper we show that there exists an invariant cone of the positive initial functions if and only if the characteristic equation of Eq. (1) has a real root. We also give the constraction of the maximal invariant cone among the positive initial functions with respect to Eq. (1). At the end of the paper we show the generalizations of these results for systems     

Erling Norrby,Nobel Prizes and Life Sciences

Structural Chemistry -     

Palladium‐Catalyzed Cyclopropanation of Alkenyl Silanes by Diazoalkanes: Evidence for a Pd0 Mechanism

Pd ⁰ does the trick! Alkenyl silanes are efficiently cyclopropanated by diazoalkanes at low Pd loadings (see scheme). Clear evidence for the involvement of a Pd⁰ resting state for this reaction is given.

     

Transition energies of Rn- and Fr-like actinide ions by relativistic intermediate Hamiltonian Fock-space coupled-cluster methods

The extrapolated intermediate Hamiltonian (XIH) Fock-space coupled cluster method in the 1-hole 1-particle sector is applied to calculate excitation energies of Xe-like La³⁺ and the Rn-like actinides Ac³⁺, Th⁴⁺, Pa⁵⁺ and U⁶⁺. Large basis sets and model spaces are used, the latter made possible by the XIH scheme. Comparison with experiment for the La ion shows very good agreement, with a mean absolute error of 0.11 eV for 14 excitations in the largest basis (37s33p25d23f14g12h11i6k), lending credence to predicted energies for the actinide ions. Significant Breit term contributions appear, and the DCB Hamiltonian is therefore used. Excellent results are obtained in the one-particle sector, where more experimental values are available. The MAE for 17 transition energies of La²⁺ is below 0.01 eV, and 18 levels of the Fr-like actinide ions Ac²⁺, Th³⁺ and U⁵⁺ give a MAE of 0.06 eV. Second-order perturbation theory values differ considerably from all-order and experimental energies.