C5H9N Isomers: Pointers to Possible Branched Chain Interstellar Molecules

The astronomical observation of isopropyl cyanide further stresses the link between the chemical composition of the ISM and molecular composition of the meteorites in which there is a dominance of branched chain amino acids as compared to the straight. However, observations of more branched chain molecules in ISM will firmly establish this link. In the light of this, we have considered C5H9N isomeric group in which the next higher member of the alkyl cyanide and other branched chain isomers belong. High-level quantum chemical calculations have been employed in estimating accurate energies of these isomers. From the results, the only isomer of the group that has been astronomically searched, n-butyl cyanide is not the most stable isomer and therefore, which might explain why its search could only yield upper limits of its column density without a successful detection. Rather, the two most stable isomers of the group are the branched chain isomers, tert-butylnitrile and isobutyl cyanide. Based on the rotational constants of these isomers, it is found that the expected intensity of tert-butylnitrile is the maximum among this isomeric group. Thus, this is proposed as the most probable candidate for astronomical observation. A simple LTE (Local thermodynamic equilibrium) modelling has also been carried out to check the possibility of detecting tert-butyl cyanide in the millimetre-wave region.Comment: 16 pages, 1 figur

Chemical modeling for predicting the abundances of certain aldimines and amines in hot cores

We consider six isomeric groups (CH3N, CH5N, C2H5N, C2H7N, C3H7N and C3H9N) to review the presence of amines and aldimines within the interstellar medium (ISM). Each of these groups contains at least one aldimine or amine. Methanimine (CH2NH) from CH3N and methylamine (CH3NH2) from CH5N isomeric group were detected a few decades ago. Recently, the presence of ethanimine (CH3CHNH) from C2H5N isomeric group has been discovered in the ISM. This prompted us to investigate the possibility of detecting any aldimine or amine from the very next three isomeric groups in this sequence: C2H7N, C3H7N and C3H9N. We employ high-level quantum chemical calculations to estimate accurate energies of all the species. According to enthalpies of formation, optimized energies, and expected intensity ratio, we found that ethylamine (precursor of glycine) from C2H7N isomeric group, (1Z)-1-propanimine from C3H7N isomeric group, and trimethylamine from C3H9N isomeric group are the most viable candidates for the future astronomical detection. Based on our quantum chemical calculations and from other approximations (from prevailing similar types of reactions), a complete set of reaction pathways to the synthesis of ethylamine and (1Z)-1-propanimine is prepared. Moreover, a large gas-grain chemical model is employed to study the presence of these species in the ISM. Our modeling results suggest that ethylamine and (1Z)-1-propanimine could efficiently be formed in hot-core regions and could be observed with present astronomical facilities. Radiative transfer modeling is also implemented to additionally aid their discovery in interstellar space.Comment: 32 pages, 18 Figures, Accepted for publication in the Astrophysical Journa

In vitro antiplasmodial, cytotoxic and antioxidant effects, and phytochemical constituents of eleven plants used in the traditional treatment of malaria in Akwa Ibom State, Nigeria

Purpose: To evaluate the antiplasmodial effects of eleven plants (Bombax buonopozense, Carica papaya, Anthocleista djalonensis, Milicia excelsa, Heterotis rotundifolia, Homalim letestui, Starchystarpheta cayennnensis, Ocimum gratissimum, Cleistopholis patens, Chromolaena odorata and Hippocratea africana) reportedly used in the treatment of malaria in Akwa Ibom State of Nigeria. Methods: Phytochemical analysis was done by standard methods, while in vitro antiplasmodial evaluation was carried out using Plasmodium falciparum chloroquine-sensitive and chloroquineresistant strains using lactate dehydrogenase (pLDH) assay.  Cytotoxicity test was undertaken by MTT assay on LLC-MK2 cells and the concentration killing 50 % of the cells (CC50) was calculated.Antioxidant activity of the ethanol extract was evaluated by 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. Results: Milicia excelsa, Heterotis rotundifolia and Chromolaena odorata had moderate antiplasmodial activity. Ocimum gratissimum and Hippocratea africana were weakly active. Milicia excelsa showed a considerable level of cytotoxicity, while Bombax buonopozense exhibited moderate cytotoxicity. Bombax buonopozense (95.3 %) and Ocimum gratissimum (92.0 %) exhibited high DPPH scavengingeffect comparable to Vitamin C (98.7 %). There was a significant correlation (p < 0.05) between DPPH inhibition and the total phenolic contents of the eleven plants studied (r2 = 0.6616), between DPPH inhibition and flavonoids (r2 = 0.3553), between antiplasmodial activity and saponin content (r2= 0.3992), and between the two antiplasmodial evaluation assay methods (r2 = 0.614).Conclusion: The results of this work provide some justification for the use of Milicia excelsa, Heterotis rotundifolia, Chromolaena odorata, Ocimum gratissimum and Hippocratea africana in the treatment of malaria. Keywords: Antiplasmodial, Antioxidant, Cytotoxicity, Phytochemicals, Antimalari

PREDICTING POST BREAKTHROUGH PERFORMANCE OF WATER AND GAS CONING

Water coning is a serious issue for the oil and gas industry. This poses a big concern regarding the costs that to be incurred for separation and equipment capacity. Coning is the production of an unwanted phase with a desired phase. Over the years, many techniques and control methods has been birthed, however, the issue of coning can only be mitigated and not completely discharged. Reservoir and production engineers need to understand the basic framework; the parameters that greatly influence coning and how effective manipulation of it can deal with it. With the introduction of horizontal wells, the production rate is two to four times that of vertical wells, and coning is reduced and the breakthrough time is increased. Numerous papers has been written regarding to coning and vertical wells, only a few emphasize on horizontal wells and simultaneous water coning and gas coning. The objective of this research is to study the post breakthrough performance in simultaneous coning and a black oil simulator was use for the research. Sensitivity analysis was carried out on: the production rate of oil (qt), horizontal permeability, vertical permeability, perforation length, the height above perforation, extent of reservoir area and the formation porosity. A generalized correlation was developed for predicting coning behavior using non-linear analysis

Biochemical parameters in alloxan induced diabetic rats treated with glibenclamide, metformin and two polyherbal bitters

Background: Manufacturers and promoters of various polyherbal bitters claim that, being of natural origin, they could be co-administered with therapeutic drugs with no adverse effects, and that it could be used to treat a wide array of ailments including diabetics. Most Nigerians use the bitters and their conventional drugs concurrently. Objectives: To assess the effects(s) or otherwise of the co-administration of two popular bitters in Nigeria market S-bitter and Y-bitter with two therapeutic antidiabetic drugs glibenclamide and metformin on some liver and kidney  biochemicals and lipid profile. Methodology: Therapeutic doses of glibenclamide, metformin and the bitters alone and a combination of the drugs and the bitters corresponding to the body weight of the rats were administered orally to different groups daily for fourteen days.  On the 15th day, the rats were sacrificed and plasma collected was analyzed for the hepatic biochemicals (alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, albumin, total and direct bilirubin), lipid biochemical (high density lipid cholesterol, low density lipid cholesterol, total cholesterol and triglycerides) and renal biochemicals (creatinine and urea). Results: When metformin, glibenclamide and the bitters were administered alone, there was a marginal decrees in the levels of alanine aminotransferase, and a significant increase (p<0.05) in the plasma levels of creatinine and blood urea nitrogen.  A combination of the bitters with metformin and glibenclamide caused a significant decrease (P<0.05) in the levels of alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase and bilirubin, but there was an increase in the levels of total cholesterol, high density lipid cholesterol, low density lipid cholesterol, triglycerides and albumin. Conclusion: From the results, we conclude that the co-administration of the bitters with therapeutic drugs is hepatoprotective by reducing the levels of liver enzymes and bilirubin, and by increasing levels of lipid biochemicals, it could lead to the development of   heart disease. We therefore advise users of the bitters to do so separately and not in combination with conventional drugs. Key words: Polyherbal bitters, biochemicals, glibenclamide, metformin

Protonation in Heteronuclear Diatomic Molecules: Same Molecule, Different Proton Affinities

Communication in Physical Sciences 2020, 6(2):835-844 Authors: Emmanuel E. Etim* Oko Emmanuel, Godwin and Sulaiman Adeoye Olagboye Received 22 March 2020/Accepted 28 December 2020 Every heteronuclear diatomic molecular species has two possible sites for protonation giving rise to two possible proton affinity values for a single molecule but experimentally only one proton affinity value is measured for each molecular species with no information regarding where the proton is attached in the molecule. This present work aimed at calculating the proton affinity (PA) of heteronuclear diatomic molecules, specifying which site favors protonation and observing common and rare trends in proton Affinity. In this work, quantum chemical calculations were employed to calculate PA of nitrogen (I) oxide, oxygen monofluoride, carbon(ii)oxie, phosphorus monoxide, silicon(II)oxide, silicon monosulfide, phosphorus mononitride, carbon monosulphide,  and phosphorus monosulfide. The indicated that in the heteronuclear diatomic molecules, the best site of protonation corresponds to the most stable protonated analogue, the experimentally assigned value also corresponds to the most stable protonated analogue. These results also aid in indicating the possible factors which could influence the best site of protonation such as  bonding nature, stability of the protonated analogue, electron density/electronegativity  and Periodic trend

Accurate rotational constants for linear interstellar carbon chains: achieving experimental accuracy

Linear carbon chain molecular species remain the dominant theme in interstellar chemistry. Their continuous astronomical observation depends on the availability of accurate spectroscopic parameters. Accurate rotational constants are reported for hundreds of molecular species of astrophysical, spectroscopy and chemical interests from the different linear carbon chains; CnH, CnH-, CnN, CnN-, CnO, CnS, HCnS, CnSi, CH3(CC)(n)H, HCnN, DC2n+1N, HC2nNC, and CH3(C C)(n)CN using three to four moments of inertia calculated from the experimental rotational constants coupled with those obtained from the optimized geometries at the Hartree Fock level. The calculated rotational constants are obtained from the corrected moments of inertia at the Hartfree Fock geometries. The calculated rotational constants show accuracy of few kHz below irrespective of the chain length and terminating groups. The obtained accuracy of few kHz places these rotational constants as excellent tools for both astronomical and laboratory detection of these molecular species of astrophysical interest. From the numerous unidentified lines from different astronomical surveys, transitions corresponding to known and new linear carbon chains could be found using these rotational constants. The astrophysical, spectroscopic and chemical implications of these results are discussed

Partition function and astronomical observation of interstellar isomers: Is there a link?

The unsuccessful astronomical searches for some important astrophysical and astrobiological molecules have been linked to the large partition function of these molecules. This letter reports an extensive investigation of the relationship between partition function and astronomical observation of interstellar isomers using high level quantum chemical calculations. 120 molecules from 30 different isomeric groups have been considered. Partition function and thermodynamic stabilities are determined for each set of isomeric species. From the results, there is no direct correlation between partition function and astronomical observation of the same isomeric species. Though interstellar formations processes are generally controlled by factors like kinetics, thermodynamics, formation and destruction pathways. However, the observation of the isomers seems to correlate well with thermodynamics. For instance, in all the groups considered, the astronomically detected isomers are the thermodynamically most stable molecules in their respective isomeric groups. The implications of these results in accounting for the limited number of known cyclic interstellar molecules, unsuccessful searches for amino acid and the possible molecules for astronomical observations are discussed. (C) 2016 COSPAR. Published by Elsevier Ltd. All rights reserved

Interstellar isomeric species: Energy, stability and abundance relationship

Accurate enthalpies of formation are reported for known and potential interstellar isomeric species using high-level ab initio quantum-chemical calculations. A total of 130 molecules comprising of 31 isomeric groups and 24 cyanide/isocyanide pairs with molecules ranging from 3 to 12 atoms have been considered. The results show an interesting relationship between energy, stability and abundance (ESA) existing among these molecules. Among the isomeric species, isomers with lower enthalpies of formation are more easily observed in the interstellar medium compared to their counterparts with higher enthalpies of formation. Available data in the literature confirm the high abundance of the most stable isomer over other isomers in the different groups considered. Potential for interstellar hydrogen bonding accounts for the few exceptions observed. Thus, in general, it suffices to say that the interstellar abundances of related species could be linked to their stabilities if other factors do not dominate. The immediate consequences of this relationship in addressing some of the whys and wherefores among interstellar molecules and in predicting some possible candidates for future astronomical observations are discussed