Advanced Journal of Chemistry, Section B: Natural Products and Medical Chemistry
Volume:3 Issue: 1, Winter 2021

The gas-phase elimination reaction of O-isopropyl S-methyl dithiocarbonate was studied using density functional theory with a hybrid B3LYP correlation with large 6-31G*, 6-311+G** basis sets. Calculated values of the activation and thermodynamics parameters for the thermal breakdown were estimated at 623.0K at interval of 25K. The entropy change was ∆S = (-29.842) and (-28.48) J/mol/K; free energy change ∆G = 181.491 and 131.164kJ/mol and enthalpy change ∆Hreaction = 162.808 and 113.720kJ/mol; activation energy Ea = 167.988 and 118.897kJ/mol; Arrhenius factor A = 3.56x1011 and 4.20x1011 and rate constant k = 1.4 x 10-2 and 2.9 x 10-3, 4.45x10-1S-1 compared well with the experimental results at 623K ∆S(-29.842J/mol/K) ∆G= (181.491kJ/mol) , ∆H = (162.808 kJ/mol),  Ea = (167.988 kJ/mol) , A = (3.56x1011) rate constant k = (1.4 x 10-2). The results showed the influence of electron donating group on the kinetics and thermodynamics parameters of xanthates. It affirms concertedness of the elimination mechanism via a two-step reaction. The first being the liberation of ethylene an intermediate (methyl dithiocarbonate) through a 6-membered transition state (TS). The second step involves decomposing the intermediate through 4-membered cyclic TS to produce carbonylsulphide and thiol which involves a C-H and C-O bond breaking and S-H bond formation. Intrinsic reaction coordinate (IRC) calculation was done on each of the TS structures to verify that they each connect to their respective minima. Wilberg bond index was employed to monitor the reaction progress and it shows that the TS possess ‘an early’ character closer to the reactant than the products

The presence of heavy metals in water sources is worrisome because heavy-metal pollutants are associated with severe health problems. The resultant health challenges as a result of heavy metal pollution have necessitated the removal of these pollutants from wastewater before being discharged into the environment. This research was carried out to investigate the potentials of avocado pear (Persea americana) seed coat as biosorbent of lead(II) and cadmium(II), in single and binary metal systems, from aqueous solutions. Biosorbent particle sizes and dosage were varied in the study. Desorption of biosorbed metal ions was studied using sodium salt of ethylene diaminetetraacetic acid (EDTA) and hydrochloric acid (HCl). Biosorbent of 106 µm particle size gave the best uptake of lead and cadmium from aqueous solutions than those of 850, 1180, 1400 and 2000 µm particle sizes. Biosorption of lead (II) and cadmium(II) increased with an increase in biosorbent dosage (up to threshold dosage). The uptakes of lead(II) and cadmium(II) in single systems are higher than those of binary systems. Biosorption capacities of lead(II) were higher than those of cadmium(II) for both single and binary systems. The observation could be linked to low hydration energy of lead(II) compared with that of cadmium(II). Biosorbed lead(II) and cadmium(II) were desorbed using 1.0 mol/L EDTA (for single system) and 1.0 mol/L HCl (binary system). Lead and cadmium ions were easily desorbed from single metal system unlike binary system. In overall, the avocado pear biosorbent could be used for treatment of wastewater contaminated with lead(II) and cadmium(II).

< p>This study investigates the role of microorganisms in removing oil pollution from water. The fight against oil pollution since the emergence of this black and precious substance, has been part of scientific research which had been attracted the attention of experts. For nearly 50 years, microbiologists have been researching removal of heterocyclic compounds, including sulfur heteroatoms, from petroleum fractions. The first patent for this was in Zobel''s research in the early 1950s. Research in this area continued until 1989, when the 4S pathway for the decomposition of sulfur compounds was identified by Dr. Kilbane at the I.G.T. It should be noted that in this pathway, the bacteria separate and release sulfur from the model compound, di benzothiophene in a completely specific manner without damaging the carbon skeleton. The final product of this reaction is mono hydro xybiphenyl which is dissolved in oil and organic cut, and as a result, while maintaining the calorific value of the fuel, the separation step is easier in the reactor.

This review aims to highlight the morphology, taxonomy, and biological activities of Tinospora cordifolia along with its ethnobotanical uses and its micropropagation techniques. Relating to the global pandemic, this review introduces a comprehensive update of COVID-19 scientific reports on T. cordifolia as an indispensable herb. This study also explores the nutritional values and elemental composition from proximate analysis along with its phytochemical and medicinal properties. T. cordifolia is a medicinal plant widely used for the treatment of various diseases such as diabetes and jaundice. This plant is mainly found in the southern part of Asia and is locally known as Gurjo or Guduchi. T. cordifolia exists in the form of a glabrous, ascending shrub belonging to the Menispermaceae family. Owing to its commercial importance, it has been of considerable interest in research in recent decades, incorporating a wide range of pharmacological properties, such as antidiabetic, immunomodulation, antioxidant, anticancer, hepatoprotective, and hypoglycemic values. These properties are enhanced by the presence of diverse compounds such as alkaloids, sesquiterpenoids, diterpenoids, phenolics, glycosides, steroids, and polysaccharides, aliphatic, and other miscellaneous compounds. This review provides new details that can facilitate the careful assessment of the plant as a therapeutic agent against emerging diseases. It also offers insights to the researchers involved in validating traditional claims to develop safe and efficient herbal medicines to several diseases including COVID-19

One of the methods of removing, storing, recovering or transferring carbon dioxide (as one of the greenhouse gases) is the use of hydrate formation. In this study, the effect of the presence of zinc oxide nanoparticles and steel trimethyl ammonium bromide (CTAB) surfactant on the amount of mol consumed and carbon dioxide storage capacity between carbon dioxide hydrate and water at different temperatures, pressures and concentrations of the solution was investigated. For this purpose, a laboratory system was developed to perform hydrate formation experiments. Experiments were performed in the pressure range of 20 to 30 bar, temperature range from 275 to 279 degrees Kelvin. Experimental results (for mole consumption and storage capacity) showed that with increasing pressure at constant temperature for pure water, the amount of mole consumed increased and storage capacity increased by 15%. With decreasing temperature at constant pressure (20 bar), the amount of mol consumed increased by 17% and the storage capacity by 19%. Addition of zinc oxide by 0.05 wt% at constant temperature and pressure increased the amount of mol consumed by 14% and storage capacity by 13%. And 0.1% by weight of zinc oxide increases the amount of mol consumed and storage capacity by 26% and 22%, respectively

The issue of environmental pollution is one of the most important concerns of human societies. Adsorption is one of the simple and inexpensive methods of environmental protection. Adsorption is the process of transferring materials from the fluid phase to the solid phase. Adsorption isotherms have the ability to describe the mechanisms between adsorbent and absorbed at constant temperature. In this paper, we have extracted the equations of different isotherms with new and simple methods. In this regard, we have proved the isotherms of Langmuir, Brunauer, Emmett and Teller (BET) and Anderson

Physiochemical and health risk assessment was conducted on seawater and oilfield produced water collected at Gulf of Guinea Oilfield Location, Nigeria. Analytical parameters such as pH, conductivity, dissolved oxygen, salinity and total dissolved solids were determined, while polycyclic aromatic hydrocarbons (PAHs) and total petroleum was detected and evaluated concentration using gas chromatography-flame ionization detector (GIC-FID). Baseline assessment showed that pH was basic (alkaline), conductivity, salinity, and total dissolved was low indicating less reactive ions, dissolved oxygen was okay across water sources. Concentration of PAHs and TPHs results showed that oilfield produced water was highest compared to seawater (seaboard and portside), which was low. Carbon preference index (CPI) conducted on TPHs showed that TPHs had phytoplankton and man-made induced contribution to chemical composition. Risk assessment conducted on PAHs showed that non-carcinogenic assessment was highest in causative impact compared to carcinogenic assessment, as inhalation exposure was a major contribution less than ingestion (oral) and dermal. Risk assessment conduced on aliphatic and aromatic TPHs showed that carcinogenic assessment had high impact via aromatic than aliphatic while non-carcinogenic assessment had high impact via aliphatic than aromatic. Exposure pathway from risk assessment of PAHs and TPHs showed that inhalation had high carcinogenic and non-carcinogenic health impact compared to dermal and ingestion pathways. Specific care must be taken into consideration when working in an offshore environment as inhalation of these pollutants can cause respiratory and tumours related health issues over a prolong period from oilfield produced water compared to seawater portside and starboard.

The phytochemical composition of brown, green and red propolis collected from an apiary in Umudike, Abia State, Nigeria, was analyzed using the GC-FID technique. The phytochemical analysis results revealed that anthocyanin was the predominant photochemical, which occurred highest in red propolis (84.68 µg/g) followed by brown propolis (79.35 µg/g) but was not detected in green propolis. The brown propolis contained anthocyanin (79.35 µg/g), phenols (29.11 µg/g), flavanones (23.64 µg/g), naringenin (19.30 µg/g), flavan-3-ol (14.79 µg/g), proanthocyanins (12.79 µg/g) and steroids (10.35 µg/g) as major constituents while the green propolis showed significant presence of proanthocyanins (60.63 µg/g), lunamarin (19.90 µg/g), phenols (14.68 µg/g) and naringenin (10.64 µg/g). Proanthocyanins (69.18 µg/g), anthocyanin (84.68 µg/g), spartein (13.57 µg/g), phenols (46.99 µg/g), catechin (13.49 µg/g), and quinine (21.09 µg/g) were most abundant in the red propolis. The quantities of flavonoids / phenolic revealed may therefore be regarded as an important tool for recognizing the propolis color and floral type. This study has given scientific backing to attributing propolis color as one of the determinants of its floral origin and therapeutic properties. Propolis color should therefore be incorporated in future standardization and at the same time influence its acceptability by the consumers.