Earthline Journal of Chemical Sciences

Hypergolic Systems based on Hydrogen Peroxide Oxidizer

2023-02-14T17:16:46+00:00

Hydrogen peroxide, H₂O₂, is a promising and nontoxic oxidant. In recent years considerable attention has been paid to the development of hypergolic system compositions, because the use of them not only markedly simplifies the engine design and rocket system operation but also provides the possibility of their repeated use. Moreover, their high performance, high environmental compatibility and low toxicity make them highly preferable. The present review considers recent works on hypergolic systems involving hydrogen peroxide as the oxidizer and various green propellants of organic and inorganic nature with or without certain additives.

The Mechanism of Schiff Test for Uric Acid in Urine

2023-02-15T15:11:23+00:00

Uric acid in urine can be detected by reaction with silver nitrate in alkaline medium. A redox reaction occurs and black elemental silver is observed in the filter paper used in this test. However, the mechanism of the series of steps occurring in the uric acid molecule, including a second redox reaction, has not been advanced. A reaction route is provided, each step is fully commented giving also the electron flow. The mechanism involves free radicals and ionic intermediates as well. There is ring contraction with concomitant oxo-aziridine formation, imide hydrolysis, imine hydration to carbinol-amine, isomerization to ketone with concurrently ring opening, and assisted decarboxylation.

Chemical Investigation of the Senegalese Marine Sponge Luffariella geometrica

2023-02-20T15:21:40+00:00

One new γ-hydroxybutenolide (1) together with the known compounds (2-7) were isolated from the Senegalese marine sponge Luffariella geometrica. Their chemical structures were established on the basis of spectroscopic methods 1D and 2D NMR, in addition to mass spectrometry and comparison with literature data.

Tin(IV) Halides Zero-dimensional based Inorganic-Organic Hybrid Materials: Crystal Structures and Hirshfeld Surface Analysis

2023-02-22T16:56:05+00:00

Two tetramethylguanidinium halostannate inorganic-organic hybrid compounds was isolated and structurally investigated by single crystal X-ray crystallography and Hirshfeld surface analysis. The compound [(C₆H₁₄N₃)₂SnCl₆] (1), crystallizes in the orthorhombic space group Fddd with Z = 8 / Z’ = 0.25, a = 7.3474(3) Å, b = 22.3678(8) Å, c = 28.4908(10) Å and V = 4682.3(3) Å³. The compound [(C₆H₁₄N₃)₂SnBr₆] (2), crystallizes in the orthorhombic space group Fddd with Z = 8 / Z’ = 0.25, a = 7.5767(5) Å, b = 23.0591(17) Å, c = 29.008(2) Å and V = 5068.0(6) Å³. The isolation of 1 undergoes a redox process from Sn(II) to Sn(IV) in solution and in a non-controlled atmosphere. Both compounds 1 and 2 describe TMG⁺ ions with a central carbon atom in a trigonal–planar fashion. With respect to this CN₃plane, the pairs of dimethylammonium groups are twisted by 13.70 (8) and 32.21 (8)° for 1, 14.88 (13) and 31.95(13)° for 2. The SnX₆dianions evidence a slightly distorted octahedron (Oh) about Sn centre for hybrids 1 and 2. Within the structures of the hybrid materials 1 and 2, N-H···Cl inter-species hydrogen bonding patterns between the inorganic stannate and the organic entities give rise a one-dimensional chain, wherein inorganic and organic species alternate. The propagation of the chain generates rings. The weak C-H···X hydrogen bonds formed from the methyl groups to adjacent tetramethylguanidinium-stannate chains result in a supramolecular three-dimensional hydrogen-bonded network. The Hirshfeld surface analysis shows existence of both strong and weak hydrogen bonding interactions. Inspection of 1 and 2 by the Hirshfeld surface analysis, show isostructural behavior. Hybrids 1 and 2 are the first crystal reports of a tetramethylguanidinium tetra- or hexa-halostannate.

DFT Treatment of Some Cantharidine Isomers and Some Radicals from Them

2023-03-21T15:15:27+00:00

Cantharidine (cantharidin) has been used as a medicine for centuries for many purposes. It is also known for its anticancer properties. In the present study, some cantharidine isomers and some radicals from them are considered within the realm of density functional theory. The isomers have been subjected to B3LYP/6-311++G(d,p) level of theory and the radicals from them are treated at the level of UB3LYP/6-31+G(d) level. The isomers considered are stereoisomers having the methyl groups at different stereo orientation. The calculations have revealed that the isomers are all thermally favorable and electronically stable. In each case, the mono radical formed from the isomer considered by the homolytic cleavage of C-H bond at the α-position of the etheric oxygen atom. These radicals are also thermally favorable and electronically stable. Various calculated properties of the isomers and the radicals have been harvested and discussed.

Some Isomers of Nevirapine - A DFT Study

2023-04-18T16:27:02+00:00

Nevirapine is a dipyridodiazepinone and representative of a new class of anti-HIV agents, the non-nucleoside reverse transcriptase inhibitors. The effect of some centric perturbations on some properties of nevirapine have been investigated within the limitations of density at the level of B3LYP/6-31++G(d,p). The calculations have revealed that the isomers constructed are all thermally favorable and electronically stable. Various calculated properties of the isomers including geometrical, electronic, thermo chemical, quantum chemical and some spectral properties have been harvested and discussed. Additionally, nucleus-independent chemical shift, NICS(0), calculations have been performed and the effect of perturbations on the local aromaticity of six-membered rings have been investigated. The effect of monocentric carbon to nitrogen perturbations on the chemical function descriptors have been determined. Also, the variation of polar surface areas (PSA) of the isomers have been considered in relation to their ability to penetrate the blood-brain barrier.

Moroxydine Tautomers - A DFT Treatment

2023-05-09T16:47:38+00:00

Moroxydine is an orally active non-nucleoside type antiviral agent of biguanide structure. Biguanides constitute an important class of therapeutic agents suitable for the treatment of a wide spectrum of diseases. In the present density functional study (B3LYP/6-311++(d,p)) tautomers of moroxydine have been investigated within the constraints of the theory and the basis set employed. Moroxydine may exhibit 1,3- and 1,5-type proton tautomerism. Presently, all those possible tautomeric forms are considered. All the tautomers are electronically stable and have thermo chemically favorable formation values at the standard conditions. Some quantum chemical and spectral properties of those tautomeric systems have been obtained and discussed. The effect of tautomeric variations on the chemical function descriptors have been determined. Also, the variation of polar surface areas of the tautomers have been considered in relation to their ability to penetrate the blood-brain barrier.

The Mechanism of Frabot Test for Uric Acid

2023-05-15T15:20:31+00:00

Uric acid is an Analyte. Excess uric acid ─ hyperuricemia ─ leads to gout and renal stones. Frabot noted that uric acid added to an alkaline tungstate solution developed an intense blue colour. A colorimetric method widely utilized to quantify uric acid depends on the reduction of the chromogen sodium tungstate by uric acid to produce a measurable colour change. The reaction route from the initial products to the coloured compounds and the oxido-degradation of the organic substance has not been advanced. In this communication the electron flow is given in each step of the series of reactions that take place. These are isomerization to imidol, Michael addition to enone, oxirane formation in a redox step, hydrolysis of imido group, oxirane ring opening, ring contraction to five- member ring, ring opening via alkoxide, and finally assisted decarboxylation to the end product, 5-ureido hydantoin (allantoin).