Oxidation of 2‐Phenylethylamine with N‐Bromosuccinimide in Acid and Alkaline Media: A Kinetic and Mechanistic Study

A kinetic study of oxidation of 2‐phenylethylamine (PEA), a bioactive compound, with potent oxidant, N‐bromosuccinimide (NBS) has been carried out in HCl and NaOH media at 313 K. The experimental rate laws obtained are: ‐d [NBS] /dt = k[NBS][PEA][H⁺] in hydrochloric acid medium and ‐d [NBS]/dt = k[NBS][PEA]^x[OH^?]^y in alkaline medium where x and y are less than unity. Accelerating effect of [Cl^?], and retardation of the added succinimide on the reaction rate have been observed in acid medium. Variation of ionic strength of the medium shows negligible effect on rate of reaction in both media. Decrease in dielectric permittivity of the medium decreased the rate in both media. The stoichiometry of the reaction was found to be 1:1 in acid medium and 1:2 in the case of alkaline medium. The oxidation products of PEA were identified as the corresponding aldehyde and nitrile in acid and alkaline medium, respectively. The reactions were studied at different temperatures and the activation parameters have been evaluated. The reaction constants involved in the proposed mechanisms were computed. The reaction was found to be faster in alkaline medium in comparison with the acid medium, which is attributed to the involvement of different oxidizing species. The proposed mechanisms and the derived rate laws are consistent with the observed experimental results.     

Crossover Sorption of C2H2/CO2 and C2H6/C2H4 in Soft Porous Coordination Networks

Porous sorbents are materials that are used for various applications, including storage and separation. Typically, the uptake of a single gas by a sorbent decreases with temperature, but the relative affinity for two similar gases does not change. However, in this study, we report a rare example of “crossover sorption,” in which the uptake capacity and apparent affinity for two similar gases reverse at different temperatures. We synthesized two soft porous coordination polymers (PCPs), [Zn₂(L1)(L2)₂]_n (PCP-1) and [Zn₂(L1)(L3)₂]_n (PCP-2) (L1= 1,4-bis(4-pyridyl)benzene, L2=5-methyl-1,3-di(4-carboxyphenyl)benzene, and L3=5-methoxy-1,3-di(4-carboxyphenyl)benzene). These PCPs exhibits structural changes upon gas sorption and show the crossover sorption for both C₂H₂/CO₂ and C₂H₆/C₂H₄, in which the apparent affinity reverse with temperature. We used in situ gas-loading single-crystal X-ray diffraction (SCXRD) analysis to reveal the guest inclusion structures of PCP-1 for C₂H₂, CO₂, C₂H₆, and C₂H₄ gases at various temperatures. Interestingly, we observed three-step single-crystal to single-crystal (sc-sc) transformations with the different loading phases under these gases, providing insight into guest binding positions, nature of host–guest or guest-guest interactions, and their phase transformations upon exposure to these gases. Combining with theoretical investigation, we have fully elucidated the crossover sorption in the flexible coordination networks, which involves a reversal of apparent affinity and uptake of similar gases at different temperatures. We discovered that this behaviour can be explained by the delicate balance between guest binding and host–guest and guest-guest interactions.     

Shape-Memory Effect Enabled by Ligand Substitution and CO2 Affinity in a Flexible SIFSIX Coordination Network

We report that linker ligand substitution involving just one atom induces a shape-memory effect in a flexible coordination network. Specifically, whereas SIFSIX-23-Cu, [Cu(SiF₆)(L)₂]_n, (L=1,4-bis(1-imidazolyl)benzene, SiF₆²⁻=SIFSIX) has been previously reported to exhibit reversible switching between closed and open phases, the activated phase of SIFSIX-23-Cu^N, [Cu(SiF₆)(L^N)₂]_n (L^N=2,5-bis(1-imidazolyl)pyridine), transformed to a kinetically stable porous phase with strong affinity for CO₂. As-synthesized SIFSIX-23-Cu^N, α, transformed to less open, γ, and closed, β, phases during activation. β did not adsorb N₂ (77 K), rather it reverted to α induced by CO₂ at 195, 273 and 298 K. CO₂ desorption resulted in α′, a shape-memory phase which subsequently exhibited type-I isotherms for N₂ (77 K) and CO₂ as well as strong performance for separation of CO₂/N₂ (15/85) at 298 K and 1 bar driven by strong binding (Q_st=45–51 kJ/mol) and excellent CO₂/N₂ selectivity (up to 700). Interestingly, α′ reverted to β after re-solvation/desolvation. Molecular simulations and density functional theory (DFT) calculations provide insight into the properties of SIFSIX-23-Cu^N.     

A sterically congested cis‐stilbene and its phosphonium salt precursor

Triphenyl(2,4,5‐trimethoxybenzyl)phosphonium chloride is formed in solvent‐free form by the reaction under anhydrous conditions between triphenylphosphane and 2,4,5‐trimethoxybenzyl chloride, but when it is crystallized from a mixture of ethyl acetate and chloroform in the presence of air it forms a stoichiometric monohydrate, C₂₈H₂₈O₃P⁺·Cl⁻·H₂O, (I). The reactions between the anhydrous phosphonium salt and alkoxy‐substituted benzaldehydes, using Wittig reactions in the presence of potassium tert‐butoxide, provide a series of multiply substituted stilbenes, most of which were assigned the Z configuration on the basis of their NMR spectra. However, no such deduction could be made for the symmetrically substituted (Z)‐2,2′,4,4′,5,5′‐hexamethoxystilbene, C₂₀H₂₄O₆, (II). Compound (II) does in fact have the Z configuration and the molecular geometry provides evidence for steric congestion around the central double bond; in particular, the central alkene fragment is nonplanar, with a C—C=C—C torsion angle of 7.8 (4)°. In hydrated salt (I), the chloride anions and water molecules are linked by O—H...Cl hydrogen bonds to form C₂¹(4) chains; each cation is linked by C—H...O hydrogen bonds to two different chains, so forming a sheet structure. There are no direction‐specific intermolecular interactions in the structure of (II).     

Environment Friendly g-C3N4-Based Catalysts and Their Recent Strategy in Organic Transformations

High Energy Chemistry - Organic molecules synthesized in an environmentally friendly manner have excellent therapeutic potential. The entire preparation technique was examined in the existence of a...     

A review on various aspects of organic synthesis using Comins’ reagent

Molecular Diversity - Recently, researchers have shown great interest in compounds such as triflate and enotriflate that are synthesized by Comins reagent. For the above-mentioned reason, we...     

Synthesis of Benzo[c][2,7]Naphthyridines by One-Pot Multicomponent Reaction Using Ceric(IV) Ammonium Nitrate

A new, one-pot, three-component reaction for the synthesis of benzo[c][2,7]naphthyridines has been achieved from aromatic amines, aromatic aldehydes, and N-carbethoxy-4-piperidone in the presence of a catalytic amount of ceric ammonium nitrate in good yields at room temperature. The advantages of this procedure are mild reaction conditions, low toxicity, and the use of inexpensive reagents. Apart from milder and environmentally benign conditions, this method involves a simple, reliable approach to give good yields of the desired products and is compatible with a wide range of functional groups.     

Semmler–Wolff aromatisation: a concise route for the synthesis of 5-amino-quinazolines and 4-amino-indoles

A simple and efficient methodology for the synthesis of 5-amino-quinazolines and 4-amino-indoles via Semmler–Wolff aromatisation reaction has been carried out. The oximation of keto intermediates followed by Semmler–Wolff aromatisation using acetic anhydride and a catalytic amount of sodium iodide in xylene provided the desired quinazolines and indoles.     

Environmentally benign one-pot synthesis and antimicrobial activity of 1-methyl-2,6-diarylpiperidin-4-ones

An efficient and environmentally benign one-pot method for the synthesis of 1-methyl-2,6-diarylpiperidin-4-ones using montmorillonite K-10 as a catalyst has been developed. Antimicrobial activity of the compounds has been tested against selected representatives of Gram-positive and Gram-negative bacteria and fungi.