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The reported two-step synthesis of 2-isopropoxy-4-nitrobenzoic acid from 2-hydroxy-4-nitrobenzoic acid, using iodopropane/K2CO3 and subsequent hydrolysis of the isopropyl 2-isopropoxy-4-nitrobenzoate intermediate with 45% NaOH/THF-EtOH at 80 °C, was reconsidered. (Z)-1,2-bis(4-carboxy-3-isopropoxyphenyl)diazene-1-oxide derivative (3), which was isolated as main product (92%) of the reaction, was characterized by IR, 1H, 13C, and 15N NMR spectroscopy. The 15N chemical shifts were consistent with the trans-configuration for this azoxybenzene derivative. As an alternative, synthesis of 2-isopropoxy-4-nitrobenzoic acid was accomplished in high yield (82%) working at room temperature and using lithium hydroxide instead of concentrate NaOH. Incorrect reaction temperature report or measurement in the published protocol (J. Org. Chem. 2011, 76, 7040) probably accounts for the discrepancies with our findings. ; This work was supported by the Spanish Ministerio de Ciencia, Innovación y Universidades (MCIU/AEI/FEDER, UE; grant RTI2018-093940-B-I00). J. J. Nué-Martínez fellowship is funded by the Programa Nacional de Becas y Crédito Educativo of the Peruvian Government. The technical assistance of Dr. F. Reviriego (IR spectroscopy) is gratefully acknowledged.

A theoretical study on some carboxylic acid dimers formed by positively or negatively charged molecules has been carried out by using DFT methods. The resulting dimers possess either a charge of +2 or −2. In addition, the corresponding neutral complexes have also been considered. The electron density distribution described by the atoms in molecules and the natural bond orbital methods, as well as the electric field maps of the systems, have been analyzed and compared without finding significant differences between the neutral and ionic complexes. The interaction energy along the dissociation path of the charged dimers shows both a local minimum and a local maximum, defining a stability region between them. When this energetic profile is recalculated by removing the repulsion between the charged groups, it resembles to those of the neutral molecules. Hence, the characteristics of the charged dimers are similar to those of the neutral ones: the addition of a repulsion term for the charged groups permits to retrieve the energetic profiles dependence with the distance in the charged system. The interacting quantum atom (IQA) method has been used to calculate the interaction energy terms, including the classic Coulombic term between the whole molecules and the corresponding of the carboxylic acid groups. The IQA results show repulsive electrostatic interactions when the whole molecules are considered in the ionic complexes, but attractive ones between the carboxylic groups in both neutral and ionic complexes. ; This work was supported by the Spanish Ministerio de Economía y Competitividad (Grants CSD2007-00041, ENE2012-36368-C02-02, ENE2015-63969, SEV2015-0496 and CTQ2015-63997-C2-2-P), the Catalan Government (Grant PRC 2014SGR-1643), and the Autonomous Community of Madrid (S2013/MIT2841, Fotocarbon). ; Peer reviewed

The potential reaction of the nitrate radical (NO3), the main nighttime atmospheric oxidant, with five alkyl halides, halons (CH2ClBr, CH2ICl, CH2BrI, CHCl2Br, and CHClBr2) has been studied theoretically. The most favorable reaction corresponds to a hydrogen atom transfer. The stationary points on the potential energy surfaces of these reactions have been characterized. The reactions can be classified into two groups based on the number of hydrogen atoms in the halon molecules (1 or 2). The reactions with halons with only one hydrogen atom show more exothermic profiles than those with two hydrogen atoms. In addition, the kinetics of the reaction of NO 3 + CH2 BrI was studied in much higher detail using a multi-well Master Equation solver as a representative example of the nitrate radical reactivity against these halocarbons. These results indicate that the chemical lifetime of the alkyl halides would not be substantially affected by nitrate radical reactions, even in the case of NO3 -polluted atmospheric conditions. ; IA: This work was carried out with financial support from the Ministerio de Ciencia, Innovación y Universidades (PGC2018- 094644-B-C22) and Comunidad de Madrid (P2018/EMT-4329 AIRTEC-CM). Thanks are also given to the CTI (CSIC) for their continued computational support. This study received funding from the European Research Council Executive Agency under the European Union's Horizon 2020 Research and Innovation Programme (Project ERC-2016-COG 726349 CLIMAHAL) ; Peer reviewed