Nuclear magnetic resonance and optical absorption spectroscopic studies on paramagnetic praseodymium(III) complexes with beta-diketone and heterocyclic amines

The optical absorption spectra of [Pr(acac)(3)(H(2)O)(2)].H(2)O, [Pr(acac)(3)phen.H(2)O] and [Pr(acac)(3)bpy] (where acac is the anion of acetylacetone, phen is 1,10-phenanthroline and bpy is 2,2'-bipyridyl) have been analyzed in the visible region in a series of non-aqueous solvents (methanol, ethanol, isopropanol, chloroform, acetonitrile and pyridine). The complexes display four non-hypersensitive 4f-4f transitions ((3)P(2), (3)P(1)+(1)I(6), (3)P(0) and (1)D(2)) from the (3)H(4) ground state. The band shape of the transitions shows remarkable changes upon dissolving in different solvents. Distinctively different band shapes have been observed for phen and bpy complexes. The phen is more effective in producing changes and the splitting of the bands is more pronounced in phen complex since it is a stronger ligand and leads to stronger Pr-N(phen) bond. The splitting of the bands is indicative of partaking of f-orbitals in bonding. The NMR signals of heterocyclic amines have been shifted to high fields while the resonances due to acetylacetone moiety have moved to low fields which is the consequence of change in geometry of the complexes upon coordination of the heterocyclic amines and reflects the importance of geometric factor (3cos(2)theta-1) in changing sign of the shift and to a good approximation the shifts arise predominantly from the dipolar mechanism. The phen complexes have narrower line width than bpy complexes. The line broadening in the case of bpy complexes is suggestive of exchange between inter-converting forms. The bpy possesses some degree of rotational freedom about C(6)-C(6') bond and the two pyridine rings undergo scissoring motion with respect to each other.     

Potential Therapeutic Benefits of Honey in Neurological Disorders: The Role of Polyphenols

Honey is the principal premier product of beekeeping familiar to Homo for centuries. In every geological era and culture, evidence can be traced to the potential usefulness of honey in several ailments. With the advent of recent scientific approaches, honey has been proclaimed as a potent complementary and alternative medicine for the management and treatment of several maladies including various neurological disorders such as Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, and multiple sclerosis, etc. In the literature archive, oxidative stress and the deprivation of antioxidants are believed to be the paramount cause of many of these neuropathies. Since different types of honey are abundant with certain antioxidants, primarily in the form of diverse polyphenols, honey is undoubtedly a strong pharmaceutic candidate against multiple neurological diseases. In this review, we have indexed and comprehended the involved mechanisms of various constituent polyphenols including different phenolic acids, flavonoids, and other phytochemicals that manifest multiple antioxidant effects in various neurological disorders. All these mechanistic interpretations of the nutritious components of honey explain and justify the potential recommendation of sweet nectar in ameliorating the burden of neurological disorders that have significantly increased across the world in the last few decades.     

Applications of Cannabis Sativa L. in Food and Its Therapeutic Potential: From a Prohibited Drug to a Nutritional Supplement

Hemp (Cannabis sativa L.) is a herbaceous anemophilous plant that belongs to the Cannabinaceae family. The cannabis seed (hemp) has long been utilized as a food source and is commercially important as an edible oil source. In this review, the positive and negative health effects of cannabis, the relationship between cannabis and various diseases, and the use of cannabis in various food products have been discussed. In addition, the scientific literature on the potential use of cannabis and its derivatives as a dietary supplement for the prevention and treatment of inflammatory and chronic degenerative diseases in animals and humans has been reviewed. Cannabis is being developed as a key ingredient in a variety of food items, including bakery, confectionery, beverages, dairy, fruits, vegetables, and meat. Hemp seeds are high in readily digestible proteins, lipids, polyunsaturated fatty acids (PUFA), insoluble fiber, carbs, and favorable omega-6 PUFA acid to omega-3 PUFA ratio and have high nutritional value. The antioxidants of cannabis, such as polyphenols, help with anxiety, oxidative stress, and the risk of chronic illnesses, including cancer, neurological disorders, digestive problems, and skin diseases. Cannabis has been shown to have negative health impacts on the respiratory system, driving, and psychomotor functions, and the reproductive system. Overall, the purpose of this research is to stimulate more in-depth research on cannabis’s adaptation in various foods and for the treatment of chronic illnesses.     

Standard reactions for comparative rate studies: Experiments on the dehydrochlorination reactions of 2‐chloropropane,chlorocyclopentane, and chlorocyclohexane

Single pulse shock tube studies of the thermal dehydrochlorination reactions (chlorocyclopentane → cyclopentene + HCl) and (chlorocyclohexane → cyclohexene + HCl) at temperatures of 843–1021 K and pressures of 1.4–2.4 bar have been carried out using the comparative rate technique. Rate constants have been measured relative to (2‐chloropropane → propene + HCl) and the decyclization reactions of cyclohexene, 4‐methylcyclohexene, and 4‐vinylcyclohexene. Absolute rate constants have been derived using k(cyclohexene → ethene + butadiene) = 1.4 × 10¹⁵ exp(?33,500/T) s^?1. These data provide a self‐consistent temperature scale of use in the comparison of chemical systems studied with different temperature standards. A combined analysis of the present results with the literature data from lower temperature static studies leads to

• k(2‐chloropropane) = 10^{(13.98±0.08)} exp(?26, 225 ± 130) K/T) s^?1; 590–1020 K; 1–3 bar
• k(chlorocylopentane) = 10^{(13.65 ± 0.10)} exp(?24,570 ± 160) K/T) s^?1; 590–1020 K; 1–3 bar
• k(chlorocylohexane) = 10^{(14.33 ± 0.10)} exp(?25,950 ± 180) K/T) s^?1; 590–1020 K; 1–3 bar

Including systematic uncertainties, expanded standard uncertainties are estimated to be about 15% near 600 K rising to about 25% at 1000 K. At 2 bar and 1000 K, the reactions are only slightly under their high‐pressure limits, but falloff effects rapidly become significant at higher temperatures. On the basis of computational studies and Rice–Ramsperger–Kassel–Marcus (RRKM)/Master Equation modeling of these and reference dehydrochlorination reactions, reported in more detail in an accompanying article, the following high‐pressure limits have been derived:

• k_∞ (2‐chloropropane) = 5.74 × 10⁹T^1.37 exp(?25,680/T) s^?1; 600–1600 K
• k_∞ (chlorocylopentane) = 7.65 × 10⁷T^1.75 exp(?23,320/T) s^?1; 600–1600 K
• k_∞ (chlorocylohexane) = 8.25 × 10⁹T^1.34 exp(?25,010/T) s^?1; 600–1600 K

© 2011 Wiley Periodicals, Inc.

1 This article is a U.S. Government work and, as such, is in the public domain of the United States of America.

Int J Chem Kinet 44: 351–368, 2012     

The decomposition of 2-pentyl and 3-pentyl radicals

The isomerization and decomposition reactions of 2-pentyl and 3-pentyl radicals have been studied in a single-pulse shock tube over a temperature range of 973–1121 K and pressures of 120–800 kPa. The results represent the first direct study of the alkene product branching ratio resulting from the kinetics of the competition between isomerization and beta C–C bond scission for a secondary straight-chain alkyl radical at high temperatures. Such species are representative of intermediates important in the combustion of typical hydrocarbon fuels. In the present work, a small quantity of precursor (～45 μL/L) is used to thermally generate H atoms in the presence of excess (E)-2-pentene, leading to the radicals of interest via addition of H to the double bond. Decomposition of the chemically activated pentyl radicals results in the stable olefin products ethene, propene, and 1-butene, which are detected in postshock gas chromatographic analyses utilizing flame-ionization and mass-spectrometric detection. It is shown that the olefin product ratios can be related to the isomerization and decomposition reactions of the 2-pentyl and 3-pentyl radicals and the results are consistent with the existence of distinct non-overlapping cracking patterns for the two radicals. The data are compared with predictions made on the basis of a model developed from experiments on the decomposition of thermal (i.e. not chemically activated) 1-pentyl radicals. Good agreement is observed. In conjunction with an RRKM/Master Equation analysis, the results for 2-pentyl and 3-pentyl radicals are projected over a wide range of temperatures. In addition, the rate constants for addition of H atoms to the alternate double bond positions of (E)-2-pentene are derived relative to a standard reaction and absolute rate constants for these processes are reported.     

Hypersensitivity in the 4f–4f absorption spectra of tris (acetylacetonato) neodymium(III) complexes with imidazole and pyrazole in non-aqueous solutions. Effect of environment on hypersensitive transitions

The optical absorption spectra of [Nd(acac)₃(H₂O)₂]·H₂O, [Nd(acac)₃(im)₂] and [Nd(acac)₃(pz)₂] (where acac is the anion of acetylacetone, im is imidazole and pz is pyrazole) complexes in the visible region have been analyzed. The transition ⁴G_5/2←⁴I_9/2 located near the middle of the visible region (17,500 cm^?1) is hypersensitive. Its behavior is in sharp contrast to many other typically weak and consistently unvaried, normal 4f–4f transitions. It is overlapped by a less intense transition ²G_7/2←⁴I_9/2. The band shapes of the hypersensitive transition show remarkable changes on passing from aqueous solution to various non-aqueous solutions, which is the result of changes in the environment about the Nd(III) ion in the various solutions and suggests coordination of a solvent molecules. Pyridine has been found especially effective in promoting 4f–4f electric-dipole intensity. The DMSO invades the complexes and replaces the water molecules and heterocyclic amines from the coordination sphere. Two DMSO molecules coordinate and the complexes acquire similar structure, [Nd(acac)₃(DMSO)₂] in solution. The oscillator strength and the band shape of the hypersensitive transition of all the complexes remains the same in this solvent. The IR spectra and the NMR spectra of the complexes have also discussed.     

Thermodynamic aspect: kinetics of the reduction of dicyanobis(phen)iron(III) by acetylferrocene and methylferrocenemethanol

Protonation plays an important role in the redox reactions. We observed this leading role during the reduction of [Fe^III(phen)₂(CN)₂]⁺ by FcCOMe and FcCHOHMe. The kinetic data showed that the reaction(s) followed a complex kinetics due to the formation of protonated acetylferrocene (FcC⁺OHMe), and or, protonated α-methylferrocenemethanol (FcCHO⁺H₂Me) in aqueous dioxane (80% v/v). Our results helped us to conclude that the reactions were completed in three phases. An overall zeroth order was observed in the first phase of the reactions. In the second phase, the kinetic data showed an overall second order reaction. The third phase was a complex phase where the rate of redox reactions and the insolubility of the neutral product ([Fe^II(phen)₂(CN)₂]) competed with each other. We studied the effect of different factors to identify the reacting entities, which take part in the rate-determining step of each reaction in the second phase. Consequently, we determined the effects of selected factors upon the observed pseudo-first order rate constant(s) (k′ _obs) of each reaction. The value of k′ _obs increased upon addition of protons in the reaction mixture in case of FcCOMe, and it decreased during the oxidation of FcCHOHMe. Meanwhile, upon enhancing the ionic strength, we observed an increase in k′ _obs for FcCOMe, and no change in the value of k′ _obs during the reaction of FcCHOHMe. However, a decrease in k′ _obs was noticed upon increasing the dielectric constant of the reaction mixture when the reductant was FcCOMe, and no effect was observed in case of FcCHOHMe. Together, these results suggested oxidation of FcC⁺OHMe and FcCHOHMe in the slow-step, and FcCOMe and FcCHO⁺H₂Me during the fast-step. We refined our results by estimating the thermodynamic parameters of activation. The low values of activation energy and enthalpy of activation confirmed that the reduction of [Fe^III(phen)₂(CN)₂]⁺ hardly depends upon temperature when the reducing agent is FcCOMe. The outcomes justified that the rate of reaction depends upon the unsaturated FcC⁺OHMe. This intermediate species contain a ‘carbonium ion’, which is very reactive and energetic. We obtained comparatively high values of the activation energy and enthalpy of activation for the reaction between [Fe^III(phen)₂(CN)₂]⁺ and FcCHOHMe. The results show that FcCHOHMe is a saturated and stable compound that leads the slow-step and controls the rate of reaction.     

Electrochemical Attributes of Electrochemistry in Tandem with Electrospray Mass Spectrometry

Electrolytic efficiency of battery‐operated flow‐through thin‐layer electrochemical (EC; echem) cell used in EC/ESI‐MS was investigated. Two stainless steel capillaries joined by PTFE tubing formed the thin‐layer EC cell. Echem reaction efficiency of ferrocyanide, dopamine and hydroquinone oxidation in the EC cell was low and decreased with increasing MeOH volume fraction in the MeOH/H₂O carrier solutions with low conductivity. Water oxidation dominated the cell current and migration of ferrocyanide was observed. Flow rate of 50–200 µL/h had a very small effect on EC cell current. Dopamine oxidation current in the EC cell and dopamine ion intensity in EC/ESI‐MS showed a direct correlation.     

Flash Pyrolysis of Lakhara Lignite Utilizing Effective Radical Transfer

Flash pyrolysis of raw and tetralin treated coal samples were carried out in nitrogen atmosphere. Two representative coal samples from Lakhra coalmines labeled Lakhra‐3 (L3) and Lakhra‐6B (L6B) were pyrolyzed in their raw state and after treatment with tetralin. Initial experiments were carried out at 700 °C with 2 milligrams of 80 mesh size samples. The main hydrocarbon products detected from both samples were methane, ethylene, ethane, propane, butane, pentane, benzene, toluene and xylene (BTX). The ratio of the total hydrocarbon yield from L3 and L6B raw samples is 1:1.49, respectively, while the relative yield of aliphatic C₁‐C₅ straight chain products to BTX are 7.65:5.49. Theses differences in product yields clearly indicate the compositional variation between the two samples. The total hydrocarbon yield (C₁‐C₅ +BTX) of tetralin swollen L3 coal and L6B coal was larger than the raw coal at all temperatures, and larger by 50.6% and 32.6%, respectively, at 700 °C. The treatment of coal samples has a more pronounced effect on BTX yield than C₁‐C₅ aliphatic hydrocarbons. BTX yield of tetralin treated L3 coals at 700 °C was 3.5 times higher while for L6B coal the BTX yield was 2.1 times higher than the raw samples. These significant increases in hydrocarbons yields can be explain in terms of the suppression of the cross‐linking reactions of coal fragments due to the penetration of tetralin in to the micropores of coal, as well as the effective H radicals transfer from tetralin to coal fragments during pyrolysis.