Crystallographic study and molecular orbital calculations of 1,2,5-thiadiazole 1,1-dioxide derivatives

Abstract

Single-crystal x-ray diffraction studies are reported for 3,4-dimethyl (I), 3-methyl-4-phenyl (II) and 3,4-diphenyl (III) derivatives of 1,2,5-thiadiazole 1,1-dioxide. Ab initio MO calculations on the electronic structure, conformation and reactivity of I, II and III are also reported and compared with the x-ray results. The structural data are related to previous kinetic and electrochemical experimental results on these compounds.

Electrochemical and spectroscopic study of the addition of several nucleophiles to 1,2,5-thiadiazole 1,1-dioxide derivatives

“…27 A much stronger nucleophile, such as PrSH, which reacts practically irreversibly with 1a, is necessary to observe addition reactions to 1c. 27 A much stronger nucleophile, such as PrSH, which reacts practically irreversibly with 1a, is necessary to observe addition reactions to 1c.…”

Local and nonlocal density functional calculations of the molecular structure of isomeric thiadiazole monoxides

“…Although experimental gas‐phase data for the compounds studied is not available, a comparison with the theoretical results can be done by resorting to the structures of compounds with related moieties that have been characterized by X‐ray diffraction studies. For the moiety that is related to the 1,2,5‐thiadiazole 1‐oxide molecule, some statistical analysis has been presented and used to confirm geometrical results provided by the theoretical calculations 31, 40. The results are shown as statistical average (SA) in Table I.…”

“…It is experimentally well known 38–40 that the unsubstituted thiadiazoles as well as the dioxidized ones are planar structures, and this has been related to the aromatic character of these compounds as opposed to the monoxides that are nonplanar and nonaromatic substances. Although not presented in the tables, an analysis of the torsional angles reveals that there exists pyramidalization around the sulfur atom, which is located outside of the plane formed by the other four atoms by 0.134, 0.183, 0.220, and 0.154 Å, for I, II, III, and IV, respectively.…”

“…As a further step in the study of the chemical reactivity of the thiadiazoles and related compounds, some results are presented in this work on the calculation of such indices for the four unsubstituted isomeric thiadiazole monoxide molecules, following previous work along the same line 13–16 and using Hartree–Fock (HF) and local and nonlocal density functional theory (DFT) calculations 12, 17. The atomic net charges from a Mulliken population analysis 6, the electronic density maps 7, the molecular electrostatic potentials 8, the highest occupied and lowest unoccupied molecular orbital (HOMO–LUMO) gap as a measure of aromaticity 18, 19, and related to the energy gap between valence and conduction band of the corresponding polymer 20 and the condensed Fukui functions and condensed local softness indices 21 have been determined in order to find the preferred reactive sites for nucleophilic, electrophilic, and radical attacks.…”

Potenciales aplicaciones tecnológicas de heterociclos nitrogenados y productos naturales: síntesis, inhibición de la corrosión de metales y generación de aniones radicales estables

“…Se observa que EpIc es afectado por la naturaleza de los , evidenciando que el efecto de los dos grupos nitro resulta mayor y más favorable que la presencia de los dos N en el resto de fenantrolina en TFQ.En TFF la estabilización producida por los dos sistemas electrónico-π separados de los dos fenilos es mayor que en el anillo acenafténico de TAC. Estudios estructurales (RX) realizados para TFF[278] indican que existe repulsión estérica entre los sustituyentes fenilo en las posiciones 3-y 4-del heterociclo, la que origina una disminución de la energía de deslocalización eventualmente disponible por la interacción del sistema-π del (los) fenilo(s) y el (los) doble(s) enlace(s) >C=N-. TFF   debe contener un grupo -NC(Ph)C(Ph)N suficientemente acoplado para maximizar la energía de deslocalización del electrón desapareado, pero suficientemente desviado de la planaridad para minimizar la repulsión entre los átomos de H de los grupos fenilo.…”