Ratio Of Ortho Research Articles

Kinetics of Alkali-Catalyzed Monomethylol Phenol Formation for F/P < 1 by 1H NMR Spectroscopy for Ablative Applications

The formation of monomethylol phenols and their ratio during the polymerization reaction of phenol (P) and formaldehyde (F) dictate the final product and thereby formulated composite properties. Here, we have studied the kinetics of ortho- and para-methylol phenol formation during the polymerization (F/P = 0.89) under alkaline conditions (pH 7.3–7.8) at 60, 70, 80 and 90 °C using 1H NMR spectroscopy. 13C NMR validated the results obtained. On increasing reaction temperature, reactant consumption rate and ratio of ortho- to para-methylol phenol (o/p) formation increased. The o/p also increased with an increase in reaction time for all the temperatures studied. The reaction follows pseudo-first-order kinetics with respect to formaldehyde. The activation energies of the addition reaction between phenol and formaldehyde and the formed prepolymers are determined. Thus, 1H NMR appears handy in studying the kinetics of prepolymers formed.

Solvent‐Controlled Regioselectivity in Nucleophilic Substitution Reactions of 1‐X‐2,4‐Difluorobenzenes with Morpholine Using Deep Eutectic Solvents

AbstractRegioselectivity in aromatic nucleophilic substitution (SNAr) reactions of activated substrates is critical but challenging to control. The use of reaction media to achieve the desired regioselectivity is a promising approach, given the sensitivity of nucleophilic substitutions to solute‐solvent interactions. The present report exploits the sensitivity of SNAr reactions to medium effects by using varying compositions of deep eutectic solvents (DES) to achieve excellent regioselectivity. Substitution reactions of 2,4‐difluoroacetophenone (1), 2,4‐diflurobenzonitrile (3) and 2,4‐difluoronitrobenzene (5) with morpholine (2) were carried out in 15 DES mixtures using the “zero VOC” strategy. The regioselectivity was determined using NMR spectra and was observed to change drastically with the substrate and nature of the eutectic mixture. Substitution reaction (1+2) was the most sensitive to reaction medium. The regioselectivity for (1+2) changed from para‐selective (85 : 15 para:ortho ratio) to ortho‐selective (24 : 76 selectivity ratio) by merely changing the DES medium. The results demonstrate that eutectic mixtures could be effectively used as reaction media to control the desired stereochemical outcome.

Ore bearing factors of breaking-block structures of the Ukrainian shield

Most ore occurrences and mineral deposits are known to be located in tectonic fault zones. In this regard, the article analyzes the ore content of regional and local fault zones developed in the megastructures of the Ukrainian shield: Podolsky, Volynsky, Ingulsky, Dnieprovsky, Priazovsky megablocks and Belotserkovsky-Odessky, Inguletsko-Krivorozhsky, Orekhovo-Pavlogradsky interblock zones. Geological and structural-tectonic features of megablocks and interblock suture zones are characterized; the main stages of their formation are highlighted. Based on the analysis of the distribution patterns of various deposits and ore occurrences in the fault-block tectonics of the Ukrainian Shield, ore-bearing factors and metallogenic features of megablocks and interblock suture zones, which are determined by the geodynamic regime of these structures, are established; specific megablocks and suture zones have their own distinctive features, and the metallogeny of megablocks differs from the metallogeny of interblock suture zones. The metallogeny of the megastructures of the Ukrainian shield and the ore content of regional and local structures is due to a combination of a number of factors of various importance. The main ones are the processes of evolution of mantle fluids and the degree of oxidation of crustal products during geological time. Of great importance was the level of erosion cut of specific structures, which determined the physicochemical conditions for the concentration of specific ore elements.The metallogeny of various fault zones is determined by the combination of a number of favorable factors for the accumulation of metals in geological time and space. The most important ore-concentrating factors are the composition and quantitative ratio of ortho- and para-rocks and the presence in them of above-clark contents of characteristic metals; fault evolution, in which the mobility of metals and their concentration at less deep levels are activated; confinement to faults of igneous rocks; degree of eroded blocks; physicochemical features of fault rocks and uneven distribution of tectonic pressures; conditions and nature of the deformation of structures; lateral structure of faults.

Ammonia excitation imaging of shocked gas towards the W28 gamma-ray source HESS J1801−233

We present 12 mm Mopra observations of the dense (>10^3 cm^-3 ) molecular gas towards the north-east (NE) of the W28 supernova remnant (SNR). This cloud is spatially well-matched to the TeV gamma-ray source HESS J1801-233 and is known to be a SNR-molecular cloud interaction region. Shock-disruption is evident from broad NH3 (1,1) spectral line-widths in regions towards the W28 SNR, while strong detections of spatially-extended NH3(3,3), NH3(4,4) and NH3(6,6) inversion emission towards the cloud strengthen the case for the existence of high temperatures within the cloud. Velocity dispersion measurements and NH3(n,n)/(1,1) ratio maps, where n=2, 3, 4 and 6, indicate that the source of disruption is from the side of the cloud nearest to the W28 SNR, suggesting that it is the source of cloud-disruption. Towards part of the cloud, the ratio of ortho to para-NH3 is observed to exceed 2, suggesting gas-phase NH3 enrichment due to NH3 liberation from dust grain mantles. The measured NH3 abundance with respect to H2 is ~(1.2+/-0.5)*10^-9, which is not high, as might be expected for a hot, dense molecular cloud enriched by sublimated grain-surface molecules. The results are suggestive of NH3 sublimation and destruction in this molecular cloud, which is likely to be interacting with the W28 SNR shock.

Synchronous Oscillations Intrinsic to Water: Applications to Cellular Time Keeping and Water Treatment

A homodimeric, growth-related and time-keeping hydroquinone oxidase (ENOX1) of the eukaryotic cell surface capable of oxidizing intracellular NADH exhibits properties of the ultradian driver of the biological 24 h circadian clock by exhibiting a complex 2 + 3 set of oscillations of copper salts and appear to derive from periodic variations in the ratio of ortho and para nuclear spins of the paired hydrogen atoms of the elongated octahedral structure of the ENOX1 protein bound copper II hexahydrates. A corollary of these observations is that the ortho/para oscillations must occur in a highly synchronized matter. Our findings suggest that water molecules communicate with each other via very low frequency electromagnetic fields and that these fields also appear to be generated by the energetics of the synchronous ortho to para interconversions of the nuclear spin pairs of the water hydrogens. Further evidence for energy absorbed and emitted by water and correlated with ortho/para oscillations of ortho/para spin pairs of water hydrogens is indicated from the auto-oscillations in water luminescence. The emissions oscillate with period lengths of 18.8 min that agree with our previously found period of oscillation of about 18 min for pure water, reflective of ortho to para spin isomers based on measurements of redox potential. The period length of pure water (increased by about 25% in D2O) and varies depending on the dominant cation present (copper salts in solution are unique in that the period length is exactly 24 min). Synchrony is maintained through generation of and response to LFEMF generated by the ortho-para spin pairs. Changes in redox potential sufficient to catalyze NADH oxidation were used to monitor synchronous water oscillations that appear to extend indefinitely over great distances in contiguous bodies of either still or flowing water. Adjacent out-of-phase water samples contained in thin plastic cuvettes auto-synchronize in a matter of seconds when placed side by side. Potential applications from water treatment along with opportunity related to human health are anticipated to derive from a better understanding of how water synchrony is generated and maintained, and to be aided by methodological advances in measurement and analysis.

HIGHLY DEPLETED ETHANE AND MILDLY DEPLETED METHANOL IN COMET 21P/GIACOBINI-ZINNER: APPLICATION OF A NEW EMPIRICAL ν2-BAND MODEL FOR CH3OH NEAR 50 K

We obtained infrared spectra of Comet 21P/Giacobini-Zinner (hereafter 21P/GZ) using NIRSPEC at Keck II on UT 2005 June 3, approximately one month before perihelion, that simultaneously sampled H2O, C2H6, and CH3OH. Our production rate for H2O (3.885?? 0.074?? 1028?molecules?s?1) was consistent with that measured during other apparitions of 21P/GZ as retrieved from optical, infrared, and radio observations. Our analysis also provided values for rotational temperature (T rot?= 51?? 3?K) and the abundance ratio of ortho and para spin populations for water (OPR?= 2.99?? 0.23, implying a spin temperature exceeding 50?K). Six Q-branches in the ?7 band of C2H6 provided a production rate (5.27?? 0.90?? 1025?s?1) that corresponded to an abundance ratio of 0.136?? 0.023?? 10?2 relative to H2O, confirming the previously reported strong depletion of C2H6 from IR observations during the 1998 apparition, and in qualitative agreement with the depletion of C2 known from optical studies of 21P/GZ. For CH3OH, we applied our recently published quantum model for the ?3 band to obtain a rotational temperature (48+10/?7?K) consistent with that obtained for H2O. In addition, we developed a new empirical model for the CH3OH ?2 band, based on observations of Comet 8P/Tuttle with NIRSPEC. The application of our ?2 model to 21P/GZ yielded a production rate in agreement with that obtained from the ?3 band. Combining results from both ?2 and ?3 bands provided a production rate (47.5?? 4.4??1025?s?1) that corresponded to an abundance ratio of 1.22?? 0.11?? 10?2 relative to H2O in 21P/GZ, indicating mild depletion of CH3OH. Together with observations of 21P/GZ in 1998, our study provides a measure of primary volatile production rates for this Jupiter family comet over multiple apparitions using high-resolution IR spectroscopy.

Optimization of alkylphenols used as semiproducts in the production of additives on Amberlyst 36Dry macroporous sulfonic acid cation-exchange resin

The synthesis of alkylphenols used as semiproducts in the production of lube oil additives via the alkylation of phenol by ethylene oligomers in the presence of Amberlyst 36Dry macroporous catalyst is studied. The proposed Amberlyst 36Dry sulfonic acid cation-exchange resin allows us to simplify appreciably its pretreatment before use, and to increase the time of its operation, along with the rate, conversion, and selectivity of the process relative to the traditional KU2-8ChS catalyst. Ethylene oligomers containing the maximum amount of vinylidene and internal olefins are established to be most active in alkylation. Linear α-olefins are much less active in alkylation. The ratio of ortho- and para-alkylphenols is generally determined by the temperature and structure of olefins and remains nearly constant with an increase in the process time. The rate of converting alkylphenyl esters into alkylphenols is found to depend on the structure of the ester alkyl radical. Alkylphenols, which fully correspond to the imposed technical requirements as semiproducts used in the production of additives, can be synthesized with a nearly quantitative yield with respect to ethylene oligomers at 135.0°C and a molar ratio ethylene oligomers : phenol = 1.0 : 6.0.

#2#1 and #2#1 NMR Study of Phosphoric Acid–Doped Polybenzimidazole under Controlled Water Activity

Polybenzimidazole (PBI) membranes doped with excess of phosphoric acid (PA) were studied by and liquid probe NMR methods, under carefully controlled humidity. The results indicate that mobile (or “free”) acid reside between the polymers chains and its properties are reflected from the NMR spectrum in which it appears as a broad single peak. The signal is strongly affected by the water adsorbed under different water activity. Upon drying, the membrane produces pyro-phosphoric acid , which also appears as a broad characteristic peak in NMR spectrum at (vs reference of ). The similarities between the free acid and liquid solutions of PA enabled us to calculate the actual concentration of the mobile PA in the polymer using two methods. The first compares the observed chemical shift of protons in membranes to those of PA liquid solutions. In the second method, the concentration of the acid was evaluated from the ratio of ortho to pyro-phosphoric acid signals in the spectrum. The validity and limitations of each method are discussed, as well as insight into PA species distribution in the mobile phase and in polymer bonded stats.

Density effect in [formula omitted] muon-catalyzed fusion with ortho- and para-enriched D2

The ortho–para dependence of d–d fusion neutrons time spectra was investigated in wide range of the target densities at similar temperatures [ϕ = 0.86 liquid-hydrogen density (LHD), T=35 K for liquid and ϕ=0.03–0.17 LHD, T=36 K for gas]. The result showed significant density dependence. For the first time, a delayed transient structure in the spectra that depends on the ortho ratio, presumably due to the slow dμ thermalization, was found in gaseous D2, whereas no significant structure was observed in liquid. The resonant ddμ formation rates in the gas phase were extracted considering the structure.

Structural observations of time dependent oscillatory behavior of Cu IICl 2 solutions measured via extended X-ray absorption fine structure

Cell surface ECTO-NOX proteins exhibit a clock-related, temperature-independent entrainable pattern of periodic (24 min) oscillations in the rate of oxidation of NAD(P)H. Aqueous solutions of copper salts also oxidize NAD(P)H with a similar temperature-independent pattern. For both, five maxima are observed, two of which are separated by 6 min and the remaining three are separated by 4.5 min. In D 2O, the pattern is retained but the period length is proportionately increased to 30 min in direct relationship to the 30 h circadian day observed with D 2O-grown organisms. With copper solutions, periodic changes in redox potential correlate precisely with the periodic changes in the rates of NAD(P)H oxidation. Consequently, the local environment of the Cu 2+ ion in copper chloride solutions was investigated by X-ray absorption spectroscopy. Detailed extended X-ray absorption fine structure (EXAFS) analyses revealed a pattern of oscillations closely resembling those of the copper-catalyzed oxidation of NADH. With CuCl 2 in D 2O, a pattern with a period length of 30 min was observed. The findings suggest a regular pattern of distortion in the axial and/or equatorial oxygen atoms of the coordinated water molecules which correlate with redox potential changes sufficient to oxidize NADH. A metastable equilibrium condition in the ratio of ortho to para nuclear spin orientation of the water associated hydrogen atoms would be kinetically consistent with a 24–30 min timeframe. The temperature independence of the biological clock can thus be understood as the consequence of a physical rather than a chemical basis for the timing events.

Terahertz absorption spectrum of para and ortho water vapors at different humidities at room temperature

Terahertz time-domain spectroscopy has been used to measure the absorption of water vapor in 0.2–2.4THz range from low to high humidity at room temperature. The observed absorption lines are due to the water molecular rotations in the ground vibrational state. We find that the absorption strength of para transitions increases as humidity increases, while the absorption strength of ortho transitions increases and then decreases in intensity with increasing humidity. We explain this difference based on the nuclear spin statistics based ratio of ortho to para water monomer populations at room temperature. The preferential adsorption on the solid surfaces of para water leads to an ortho dominated vapor cloud whose monomer rotational absorption intensity decreases due to the effects of dimerization, molecular collisions, clustering, and interactions with liquid droplets at high concentrations.

Shape-selective para-chlorination of phenol using sulfuryl chloride with the aid of microporous catalysts

Aluminum-pillared montmorillonite clay, and partially cation-exchanged L type zeolites, efficiently catalyze the selective para-chlorination of phenol using SO 2Cl 2 in 2,2,4-trimethylpentane at 25 °C. A conversion of ∼96%, a para-selectivity of ∼89%, and a para/ ortho ratio of 8.0, were achieved with H +, Al 3+, Na +, and K +-L zeolite. This heterogeneous zeolite-catalyzed process is the first example, which shows a pronounced shape-selectivity in the chlorination of phenol.

Lanthanide(III) complexes of aromatic sulfonic acids as catalysts for the nitration of toluene

Ytterbium(III) complexes of benzenesulfonic acid, Yb(BSA) 3, p-toluenesulfonic acid, Yb(Tos) 3, and 2-naphthalenesulfonic acid, Yb(NSA) 3, were prepared and tested as possible catalyst for the nitration of toluene. With a loading of 5–10 mol% of Yb(BSA) 3 and Yb(NSA) 3, a quantitative conversion of toluene to nitrotoluene was achieved within 5 h, while Yb(Tos) 3 was slightly less active and 77% of nitrated products were obtained. The catalysts can be easily recovered after the reaction, and 1 H NMR spectroscopy of analogous diamagnetic lanthanide(III) catalysts showed that the recovered catalysts were identical to the freshly prepared ones. The ratio of ortho: meta: para products was in all reactions 52:6:42, which is consistent with a direct electrophilic attack by the nitronium ion, NO 2 +.

Water‐Accelerated Claisen Rearrangements.

AbstractFor Abstract see ChemInform Abstract in Full Text.

On the para-selective chlorination of ortho-cresol

Merrifield-bound o-cresol undergoes electrophilic aromatic chlorination using SO 2Cl 2 leading to para/ ortho ratios in excess of 50, the highest such ratio reported for this chlorinating agent. Model studies suggest that this significant para/ ortho ratio results not just from steric effects but that considerable electronic influence can be detected.

Water‐Accelerated Claisen Rearrangements

Allyl aryl ethers undergo accelerated Claisen and [1,3] rearrangements in the presence of a mixture of trialkylalanes and water or aluminoxanes. The ratio of ortho-, meta-, and para-Claisen products depends to a large extent on the presence of water and to a much lesser extent on the nature of the alane.

ITAL]Infrared Space Observatory[/ITAL] Observations of Molecular Hydrogen in HH 54:Measurement of a Nonequilibrium Ratio of Ortho- to Para-H[TINF]2[/TINF

We have detected the S(1), S(2), S(3), S(4), and S(5) pure rotational lines of molecular hydrogen toward the outflow source HH 54 using the Short Wavelength Spectrometer on board the Infrared Space Observatory. The observed H2 line ratios indicate the presence of warm molecular gas with an H2 density of at least 10(exp 5) cm(exp -3) and a temperature approximately 650 K in which the ratio of ortho- to para-H2 is only 1.2 +/- 0.4, significantly smaller than the equilibrium ratio of 3 expected in gas at that temperature. These observations imply that the measured ratio of ortho- to para-H2 is the legacy of an earlier stage in the thermal history of the gas when the gas had reached equilibrium at a temperature approximately less than 90 K. Based upon the expected timescale for equilibration, we argue that the nonequilibrium ratio of ortho- to para-H2 observed in HH 54 serves as a chronometer that places a conservative upper limit of approximately 5000 yr on the period for which the emitting gas has been warm. The S(2)/S(1) and S(3)/S(1) H2 line ratios measured toward HH 54 are consistent with recent theoretical models of Timmermann for the conversion of para- to ortho-H2 behind slow, C-type shocks, but only if the preshock ratio of ortho- to para-H2 was approximately less than 0.2.

Triphase, solvent-free catalysis over the TS-1/H 2O 2 system in selective oxidation reactions

Solvent-free, triphase conditions (solid-liquid-liquid) used in the oxidation of various organic substrates over the TS-1/H 2O 2 system (vis-à-vis conventionally used biphase conditions in the presence of a co-solvent) exhibit: (i) significant enhancement (3–10 times) in the reaction rates in the hydroxylation of aromatics (such as benzene, toluene, anisole and benzyl chloride), along with a reversal in regioselectivity of the products of substituted benzenes; and (ii) Baeyer-Villiger (BV) oxidation/rearrangement of cyclohexanone and acetophenone. In the case of benzyl chloride, triphase conditions resulted in the ring hydroxylation forming p-hydroxy and o-hydroxy benzyl chloride (75%) ( para:ortho ratio 85:15) along with side-chain oxyfunctionalization followed by HCl removal directly forming benzaldehyde (no formation of benzyl alcohol through hydrolysis). During BV oxidation, cyclohexanone and acetophenone gave caprolactone and phenyl acetate, respectively, as major products (70–90% selectivity). The other reaction was ring oxidation (30-10%) to hydroxy cyclohexanone and corresponding diketones (cyclohexanone) or hydroxy-acetophenones (acetophenone). Addition of a catalytic amount of mineral acid (H 2SO 4) significantly increased the conversion. Such reaction routes do not occur at all in the presence of co-solvent under biphase conditions. Factors responsible for enhancement in activity, change in regioselectivity and new routes are: (i) relative hydrophobic nature and restricted pore dimensions of titanium silicates; (ii) competitive diffusion of substrate with co-solvent; and (iii) Brönsted acidity of titanium silicates in the presence of H 2O 2 and water. Thus the present study opens up a new area where titanium silicate will be quite useful in various organic transformations, in an eco-safer way.

Para selective chlorination of toluene with an L-zeolite catalyst

The liquid phase chlorination of toluene with gaseous chlorine using various zeolites as catalysts has been studied. Zeolite K-L is found to be more selective than the other zeolites and the conventional catalyst, FeCl 3. The reaction over SiO 2 shows lower para-selectivity compared to the zeolites. The influence of various parameters such as the type of zeolite, nature of the solvent, reaction temperature, catalyst concentration, ClCH 2COOH/ catalyst ratio and chlorine gas flow rate on the para/ortho-isomer ratio in the chlorination of toluene are reported. The yield of para-chlorotoluene is significantly enhanced by increasing the reaction temperature (studied up to 383 K) and the catalyst amount. The highest para/ ortho ratio (6.66) was obtained over zeolite K-L when a mixture of 1,2-dichloroethane/ toluene in a molar ratio of 1.7 was used. The HCl formed during the reaction deactivates K-L. The selectivity ( para/ ortho) decreases marginally with increasing conversion in zeolite K-L catalyzed chlorination.

Liquid-phase fluorination of aromatic compounds by elemental fluorine

The fluorination of aromatic compounds (benzene, toluene, phenol and benzoic acid) by elemental fluorine diluted with nitrogen has been investigated in various solvents (Freon 11, chloroform, methanol, trifluoroacetic acid, 2,2,2-trifluoroethanol, water) in order to define the influence of the experimental conditions on the reaction. Experiments have been carried out by varying the temperature, the substrate concentration in solution, the molar ratio of fluorine to substrate, and the concentration of fluorine in the fluorine/nitrogen mixture. In all cases, the effects on the yield of fluorinated products were studied. Monofluorinated compounds were mainly found in the reaction mixture, the isomers formed being in accord with the mechanism for electrophilic substitution. The highest yield of monofluorinated products was obtained with polar solvents and the following order was found: CFCl 3 < CHCl 3 < CH 3OH < CF 3CH 2OH < CF 3COOH. Interesting results were also found using particular additives (for instance, KOH or C 4F 9SO 3Na in methanol) or water as the solvent. A direct relationship was observed between the yield of monofluorinated compounds and the molar ratio of fluorine to substrate, which has to be less than one in order to obtain high yields. In contrast, low selectivity, expressed as the yield ratio of ortho to para (or meta) isomers, was found.