Fernando Murillo | Universidad Juárez Autónoma de Tabasco (original) (raw)

Papers by Fernando Murillo

Hydroboration of 1,2-dimethylcyclohexene (A) and successive rearrangements yield not only tertiar... more Hydroboration of 1,2-dimethylcyclohexene (A) and successive rearrangements yield not only tertiary alkylboranes but also primary and secondary ones. In addition, nontypical anti-addition products are detected, whose formation mechanism is not apparent. Herein, we revisit three mechanisms proposed in the literature: an elimination and readdition, an intramolecular process involving an intermediate π-complex, and an intramolecular migration. According to our computations, the formation of all products starts from the tertiary alkylborane obtained by hydroboration of olefin A. This alkylborane then undergoes a sequence of further retrohydroborations and hydroborations in a syn fashion. Interestingly, the conformational changes on the ring affect these transformations and decide the rearrangement mechanism. Free olefin intermediates are generated during these reactions, which are then rehydroborated from their opposite faces, explaining the formation of anti-addition products. Moreover,...

An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Chemical Science, 2020

A trans-product is isolated and characterized under traditional hydroboration–oxidation condition... more A trans-product is isolated and characterized under traditional hydroboration–oxidation conditions using Δ5-steroids as substrates. Experimental and theoretical studies indicate that the trans-species occurs via a retro-hydroboration mechanism.

Chemical Science, 2019

Herein we report two crystalline molecular rotors 1 and 4 that show extremely narrow signals in d... more Herein we report two crystalline molecular rotors 1 and 4 that show extremely narrow signals in deuterium solid-state NMR spectroscopy.

Chemistry (Weinheim an der Bergstrasse, Germany), Jan 4, 2018

In this work, we analyze the interaction of alkali metal cations with [6]- and [14]helicene and t... more In this work, we analyze the interaction of alkali metal cations with [6]- and [14]helicene and the cation mobility of therein. We found that the distortion of the carbon skeleton is the cause that some of the structures that are local minima for the smallest cations are not energetically stable for K+, Rb+, and Cs+. Also, the most favorable complexes are those where the cation is interacting with two rings forming a metallocene-like structure, except for the largest cation Cs+, where the distortion provoked by the size of the cation desestabilizes the complex. As far as mobility is concerned, the smallest cations, particularly Na+, are the ones that can move most efficiently. In [6]helicene, the mobility is limited by the capture of the cation forming the metallocene-like structure. In larger helicenes, the energy barriers for the cation to move are similar both inside and outside the helix. However, complexes with the cation between two layers are more energetically favored so tha...

Physical chemistry chemical physics : PCCP, Jan 14, 2017

The possible existence of H4SO5 in aqueous sulfuric acid is analyzed in detail. For bare H4SO5, t... more The possible existence of H4SO5 in aqueous sulfuric acid is analyzed in detail. For bare H4SO5, the computed free energy barrier for the exergonic transformation of H4SO5 into the H2SO4H2O complex is only 3.8 kcal mol(-1). The presence of water or sulfuric acid catalyzes the dehydration to such an extent that it becomes almost a barrierless process. In the gas phase, dehydration of H4SO5 is an autocatalytic reaction as the water molecule produced by the decomposition of one H4SO5 molecule induces further dissociation. Thus, in solution, the surrounding water molecules make the para-sulfuric acid a very vulnerable species to exist. The simulated Raman spectra also corroborate the absence of H4SO5 in solution.

International Journal of Hydrogen Energy, 2018

The structure and stability of V-doped Pd n (n ¼ 2e12) clusters as well as their ability for hydr... more The structure and stability of V-doped Pd n (n ¼ 2e12) clusters as well as their ability for hydrogen dissociation are analyzed using a successive growth algorithm coupled with density functional theory (DFT) computations. From the structural point of view, the lowest energy structures of these clusters are three-dimensional with exohedral geometries for n ¼ 2e7 whereas endohedral for n ¼ 8 onward. From their second-order energy differences, Pd 4 V and Pd 10 V are found to be the most stable ones. Among the Pd n V(H 2) complexes, Pd 6 Ve2H possesses the highest stability, as it is supported by the chemisorption energy, the vertical ionization potential (VIP), and the vertical electron affinity (VEA), respectively. Most importantly, the hydrogen dissociation pathway on Pd n V clusters with n ¼ 3, 4 and 10 e12 shows that these clusters are rigid and suitable to dissociate H 2 while for n ¼ 5e9 the structure of the clusters changes. The H 2 dissociation process on Pd n V clusters with n ¼ 8, 10, and 11 carries out barrierless.

Chemical communications (Cambridge, England), Jan 7, 2018

Herein we propose a general mechanism for the racemization of [n]helicenes up to n = 24. It is a ... more Herein we propose a general mechanism for the racemization of [n]helicenes up to n = 24. It is a concerted process for n = 4-7, but a multi-step mechanism is followed for n≥ 8, involving 2n- 14 intermediates. The changes in the barriers are a delicate consequence of the steric hindrance and the π-interactions.

Molecular Simulation, 2019

ABSTRACT The keto-enol tautomerization of chrysophanol anthrone was systematically investigated v... more ABSTRACT The keto-enol tautomerization of chrysophanol anthrone was systematically investigated via a series of density functional theory computations using the M06-2X/6-31 + G(d,p) level of theory. Bulk solvent effects were taken into account implicitly using the polarisable continuum model and explicitly with one pyridine molecule. Moreover, the tautomeric equilibrium was estimated by calculating the equilibrium constant. The pyridine-assisted tautomerism was found to be the energetically preferred pathway, where the pyridine acts as a proton carrier through a two-step reaction, in which the first one corresponds to the deprotonation of the chrysophanol anthrone and the second step to the protonation yielding the enol form. The results show, in accordance with experimental reports, that in the process of dissociation of the protonated pyridine and the aryloxylate anion, the ion is quite susceptible to oxidation. The highly dipolar structures of the transition states and intermediates are stabilised by pyridine up to 7.0 kcal/mol. The non-covalent interactions stabilising the transition states and the intermediates were analysed. Additionally, an intermolecular hydrogen bonding between the enol form of chrysophanol anthrone and the pyridine is formed at the last stage of the reaction. The keto-enol equilibrium analysis shows that the enol form of chrysophanol anthrone must be present in small amounts in basic solvents.

The Journal of organic chemistry, Jan 4, 2018

The reaction mechanism for the synthesis of 1,3,4-oxadiazole-2(3H)-ones from hydrazonyl chloride ... more The reaction mechanism for the synthesis of 1,3,4-oxadiazole-2(3H)-ones from hydrazonyl chloride and CO2, in the presence of CsF/18-crown-6 and toluene, is revisited via density functional theory computations. Although this reaction was classified as a 1,3-dipolar cycloaddition earlier, we find some competing pathways involved therein. The mechanisms including the (F-CO2)- anion and the nitrile imine intermediate are some options. The dimerization of nitrile imine is also another competing mechanism in this reaction. Our results show that the most favorable mechanism proceeds via a stepwise pathway without involving any nitrile imine intermediate or the (F-CO2)- anion. The F- anion, resulting from the formation of a complex between 18-crown-6 and Cs+ cation, deprotonates easily the nitrile imine precursor, which acts then as a nucleophilic anion, enhancing the reactivity of CO2 towards it. The mechanism for the reaction with COS, an isoelectronic analog of CO2, is also explored.

The interactions between two or three hydrogen halide molecules and the same number of water moie... more The interactions between two or three hydrogen halide molecules and the same number of water moieties are investigated through a systematic exploration of the corresponding potential energy surfaces using a stochastic methodology in conjunction with density functional theory computations. Our results indicate that HF, the weakest acid in the series, is partially dissociated. Similarly, HCl, HBr, and HI undergo dissociation in the presence of three, two, and two water molecules, respectively. The decrease in the number of water molecules required for dissociation, when compared with clusters with one single HX molecule, suggests cooperative effects. Interestingly, the hydrogen-bridged bihalide anions (XHX -) are present in the global minimum of (HX)n(H2O)n clusters with X = Br, I and n = 2, 3. These anions are even persistent at room temperatures. Concomitantly, a broad spectrum of interactions is found, among them water⋯water, HX⋯water, and HX⋯HX hydrogen bonds, halogen bonds, ionic and long-range X⋯H interactions.