Unsubstituted Naphthalene Research Articles

GC-MS analysis of hydrocarbons formed after catalytic cracking of heavy oil

The heavy oil from the Mordovo–Karmalskoye oil field is cracked in the presence of silica-alumina Al-Si catalyst and Al-Si catalyst modified with NiCrWC. The composition of saturated and aromatic compounds before and after catalytic cracking is studied. It is shown that in the presence of a modified NiCrWC/Al-Si catalyst, the destruction reactions resin-asphaltene components proceed more intensively than during cracking in the presence of Al-Si. Transformations of hydrocarbons during cracking of heavy oil in the presence of NiCrWC/Al-Si catalyst are more intensive as evidenced by the predominance of low-molecular homologues of normal and iso-structure alkanes over high-molecular ones and increased contents of C7–C10 alkylbenzenes, unsubstituted naphthalene, and methylnaphthalenes. This catalyst contributes to the complete decomposition of high-molecular cyclanes, mono- and trinaphthenoarenes. It has been shown that NiCrWC/Al-Si catalyst the formation of a larger amount of low-molecular-weight n-alkanes compared to high-molecular ones.

X-ray structures and photophysical properties of Tris(1-naphthyl)silicon(IV) derivatives

Silyl-substituted naphthalene derivatives, tris(1-napthyl)silicon (IV) chloride (1), tris(1-napthyl)silicon (IV) hydroxide (2) and tris(1-napthyl)silicon (IV)-n-butoxide (3) have been structurally characterized by single-crystal X-ray diffraction. The close intermolecular proximity of the naphthyl substituents groups in 1–3 results in a variety of C–H---π intermolecular interactions to form 2D assemblies. The UV–vis spectra of 1–3 display bathochromic (red)-shifts and the extinction coefficients increase with respect to unsubstituted naphthalene. Quantum yield calculations indicate that the fluorescence emission efficiency of 1–3 is significantly decreased with reference to 1-trimethylsilylnaphthalene. The absorptions in the solid-state spectra are broadened and approximately 45 nm red-shifted in comparison with the spectra of 1–3 in solution.

Naphthalene diimides with improved solubility for visible light photoredox catalysis.

Five core-substituted naphthalene diimides bearing two dialkylamino groups were synthesized as potential visible light photoredox catalysts and characterized by methods of optical spectroscopy and electrochemistry in comparison with one unsubstituted naphthalene diimide as reference. The core-substituted naphthalene diimides differ by the alkyl groups at the imide nitrogens and at the nitrogens of the two substituents at the core in order to enhance their solubility in DMF and thereby enhance their photoredox catalytic potential. The 1-ethylpropyl group as rather short and branched alkyl substituent at the imide nitrogen and the n-propyl group as short and unbranched one at the core amines yielded the best solubilities. The electron-donating diaminoalkyl substituents together with the electron-deficient aromatic core of the naphthalene diimides increase the charge-transfer character of their photoexcited states and thus shift their absorption into the visible light (500–650 nm). The excited state reduction potential was estimated to be approximately +1.0 V (vs SCE) which is sufficient to photocatalyze typical organic reactions. The photoredox catalytic activity in the visible light range was tested by the α-alkylation of 1-octanal as benchmark reaction. Irradiations were performed with LEDs in the visible light range between 520 nm and 640 nm. The irradiation by visible light together with the use of an organic dye instead of a transition metal complex as photoredox catalyst improve the sustainability and make photoredox catalysis “greener”.

Questions of Mirror Symmetry at the Photoexcited and Ground States of Non-Rigid Luminophores Raised by Circularly Polarized Luminescence and Circular Dichroism Spectroscopy: Part 1. Oligofluorenes, Oligophenylenes, Binaphthyls and Fused Aromatics.

We report experimental tests of whether non-rigid, π-conjugated luminophores in the photoexcited (S1) and ground (S0) states dissolved in achiral liquids are mirror symmetrical by means of circularly polarized luminescence (CPL) and circular dichroism (CD) spectroscopy. Herein, we chose ten oligofluorenes, eleven linear/cyclic oligo-p-arylenes, three binaphthyls and five fused aromatics, substituted with alkyl, alkoxy, phenyl and phenylethynyl groups and also with no substituents. Without exception, all these non-rigid luminophores showed negative-sign CPL signals in the UV-visible region, suggesting temporal generation of energetically non-equivalent non-mirror image structures as far-from equilibrium open-flow systems at the S1 state. For comparison, unsubstituted naphthalene, anthracene, tetracene and pyrene, which are achiral, rigid, planar luminophores, did not obviously show CPL/CD signals. However, camphor, which is a rigid chiral luminophore, showed mirror-image CPL/CD signals. The dissymmetry ratio of CPL (glum) for the oligofluorenes increased discontinuously, ranging from ≈ −(0.2 to 2.0) × 10−3, when the viscosity of the liquids increased. When the fluorene ring number increased, the glum value extrapolated at [η] = 0 reached −0.8 × 10−3 at 420 nm, leading to (–)-CPL signals predicted in the vacuum state. Our comprehensive CPL and CD study should provide a possible answer to the molecular parity violation hypothesis arising due to the weak neutral current mediated by the Z0-boson.

Promoted catalysts for hydrogenation of bicyclic aromatic hydrocarbons obtained in situ from molybdenum and tungsten carbonyls

Promoted Мo and W catalysts have been prepared in situ via thermal decomposition of precursors, oil-soluble salts Mo(CO)6, W(CO)6, С°C16H30O4, and NiC16H30O4. TiO2, Al2O3, and ZrO(NO3)2 · 6H2O have been used as the acidic additives. Also, Mo and W unsupported sulfide catalysts have been prepared in the presence of elemental sulfur as the sulfiding agent. The catalysts have been characterized by transmission electron microscopy and X-ray photoelectron spectroscopy. The activity of the catalysts prepared in situ has been evaluated in the hydrogenation reaction of bicyclic aromatic hydrocarbons by the example of model mixtures of 10% solutions of naphthalenes (unsubstituted naphthalene, 1- and 2-methylnaphthalenes, and 1,5- and 2,3-dimethylnaphthalenes) in n-hexadecane. The effect of the precursor/acidic oxide ratio on the activity of the formed catalyst has been found. Hydrogenation of bicyclic aromatic hydrocarbons has been conducted at a hydrogen pressure of 2 and 5 MPa and a temperature of 380 and 400°C for 2 h. Hydrogenation of the unsubstituted aromatic ring has been preferable due to the absence of steric hindrances. The degree of conversion of n-hexadecane under the reaction conditions has been 1.5–7.5% depending on the reaction temperature. It has been found that the activity of the sulfided catalyst in the conversion of 1- and 2-methylnaphthalenes is inferior to the activity of the unsulfided analogue, while partial replacement of TiO2 by Al2O3 results in a decrease in the conversion of the substrates as opposed to the unsulfided catalysts, in which the use of nanocrystalline Al2O3 promotes an increase in the conversion.

Development of a novel method for the enrichment of unsubstituted naphthalene and phenanthrene from crude oils for compound-specific stable isotope analysis

A novel, effective and easy-to-operate method to enrich unsubstituted naphthalene and phenanthrene directly from crude oils was developed based on closed-system pyrolysis.

Boron substituted and un-substituted aromatic complexes as hydrogen storage media

Interaction of H2 molecules with functionalized boron substituted and un-substituted naphthalene has been studied. Computational results reveal that gravimetric hydrogen uptake capacities of C10H8Ti4, C6B4H8Ti4 C10H8Li4, and C6B4H8Li4 complexes are 9.16, 8.23, 7.20 and 9.64 wt % respectively from the electronic structure method. The possible H2 desorption temperatures are 369.79 K and 420.80 K for C10H8Ti4(16H2) and C6B4H8Ti4(14H2) complexes respectively. The 4s orbitals of Ti atoms play an important role in hydrogen adsorption process. The C6B4H8Li4 complex interacts very weakly with hydrogen molecules at ambient conditions. ADMP molecular dynamics simulations performed at room temperature reveal that only nine hydrogen molecules can be adsorbed on both C10H8Ti4 and C6B4H8Ti4 complexes. The results obtained using ADMP molecular dynamics simulations at room temperature have shown that C6B4H8Li4 complex does not bind a single hydrogen molecule during simulation. The transition metal containing complexes have positive characteristics over alkali metal containing complexes as a possible hydrogen storage material.

Cavity-promoted Diels–Alder Reactions of Unsubstituted Naphthalene: Fine Reactivity Tuning by Cavity Shrinkage

Abstract By finely tuning the cavity volume of a coordination cage, the Diels–Alder reactivity of aromatic compounds was enhanced. Even unsubstituted naphthalene could be made to undergo the Diels–Alder reaction with N-tert-butylmaleimide, with perfectly controlled syn-selectivity. M6L4 cages with standard and contracted cavities had opposite effects on the reaction: the former favored larger Diels–Alder substrates, whereas the latter favored smaller ones.

Fly ash-mediated formation of polychlorinated naphthalenes during secondary copper smelting and mechanistic aspects

Thermal experiments (at 250–450°C for 10–240min) on fly ash from secondary copper smelting process (SeCu) were performed to study the polychlorinated naphthalene (PCN) formation in the post-zone of a secondary copper smelter. Unexpectedly high concentrations of PCNs were formed. Total PCN concentrations and toxic equivalents were 47–104 and 44–80 times higher than the initial concentration and toxic equivalent, respectively. The thermal disposal of SeCu fly ash should therefore be reconsidered. The kinetic of each homolog was determined under different thermal conditions. Less chlorinated homologs favored 350°C and more chlorinated homologs favored higher temperature. Most of the homologs reached an equilibrium of formation and degradation within 30min, except octachloronaphthalene which did not appear to reach such an equilibrium even after 240min. Chlorine substitution of the formed PCNs was identified and a similar pattern was found in chlorination products starting with naphthalene and chlorine. Furthermore, inorganic chlorine and unsubstituted naphthalene were found in the reaction products, confirming that the formation of naphthalene and the chlorination of that naphthalene could occur and could be suggested to be an important PCN formation route. A detailed formation pathway from naphthalene through octachloronaphthalene is proposed.

Is Chlorination One of the Major Pathways in the Formation of Polychlorinated Naphthalenes (PCNs) in Municipal Solid Waste Combustion?

The chlorination patterns of unsubstituted naphthalene were studied using a laminar flow reactor with a 1 cm particle bed of 0.5% (mass) copper(II) chloride (CuCl2) mixed with silicon dioxide (SiO2), operated over a temperature range of 100 to 400 °C and at gas velocities of 2.7 and 0.32 cm/s. The polychlorinated naphthalene (PCN) yield increased until a temperature reached at 250 °C, where a peak yield of 3.07% (percent of naphthalene input, carbon basis) was observed. All PCN homologue groups, mono- through octa-chlorinated naphthalenes, were observed. To test the hypothesis that PCNs in combustion processes are formed via chlorination pathways, the PCN homologue and isomer patterns from the experiments were compared with those observed in municipal solid waste combustion (MSW) incinerators. PCN congeners with 1,4-substituents dominated formation in the naphthalene chlorination experiments, whereas 2,3-substituents were major congeners in both MSW combustion flue gas and fly ash samples. These results suggest that contrary to the hypothesis, chlorination is not a primary PCN formation route in either the flue gas or fly ash from MSW combustion. Even so, naphthalene chlorination pathways presented in this paper provide an improved means for evaluating PCN formation mechanisms in combustion processes.

Alkylation Effects on the Energy Transfer of Highly Vibrationally Excited Naphthalene

The energy transfer of highly vibrationally excited isomers of dimethylnaphthalene and 2-ethylnaphthalene in collisions with krypton were investigated using crossed molecular beam/time-of-flight mass spectrometer/time-sliced velocity map ion imaging techniques at a collision energy of approximately 300 cm(-1). Angular-resolved energy-transfer distribution functions were obtained directly from the images of inelastic scattering. The results show that alkyl-substituted naphthalenes transfer more vibrational energy to translational energy than unsubstituted naphthalene. Alkylation enhances the V→T energy transfer in the range -ΔE(d)=-100~-1500 cm(-1) by approximately a factor of 2. However, the maximum values of V→T energy transfer for alkyl-substituted naphthalenes are about 1500~2000 cm(-1), which is similar to that of naphthalene. The lack of rotation-like wide-angle motion of the aromatic ring and no enhancement in very large V→T energy transfer, like supercollisions, indicates that very large V→T energy transfer requires special vibrational motions. This transfer cannot be achieved by the low-frequency vibrational motions of alkyl groups.

Liquid Phase Separation of Polyaromatics on [Cu2(BDC)2(dabco)

The porous coordination polymer (PCP) [Cu(2)(BDC)(2)(dabco)] is capable of selectively adsorbing up to 25 wt % of either 1-methylnaphthalene or 2-methylnaphthalene. Uptakes of unsubstituted naphthalene and 1,4-dimethylnaphthalene are significantly lower (7-13 wt %), suggesting that monomethyl substituted polyaromatics can be separated from the other fractions. Furthermore, this PCP can perform the difficult separation of 1-methylnaphthalene from 2-methylnaphthalene with separation factors as high as 2.6, proving that specific interactions of the methyl group with the lattice play an important role in determining the adsorption selectivity.

Large-volume sample stacking for on-capillary sample enrichment in the determination of naphthalene- and benzenesulfonates in real water samples by capillary zone electrophoresis.

We investigated the on-line preconcentration of a test mixture of 15 substituted and unsubstituted naphthalene(NSs) and benzenesulfonates (BZSs) by large-volume sample stacking (LVSS). Analyses were carried out by capillary zone electrophoresis (CZE) with on-column UV detection. In particular, we focused on how experimental variables such as the inside diameter of the capillary, the volume of sample introduced and polarity switching influenced the enrichment procedure. The best results were obtained when 300 nl were injected and stacked using a bubble cell capillary. Under these conditions, LVSS increased the detector response of conventional hydrodynamic injection by a factor of 40. The limits of detection of the method were between 5 and 10 microg l(-1). Determinations were reproducible, in terms of peak area and migration time, under such conditions. The performance of the method was examined by determining NS and BZS in real samples, such as tap, river and surface waters and inflow/outflow waters from a water treatment plant. Real samples were injected directly into the CZE column with little or no preparation.

Solid-State 13C NMR Measurements in Methoxynaphthalenes: Determination of the Substituent Chemical Shift Effects in the Principal Values

The principal values of the 13C chemical shift tensor are measured in 1-methoxy-, 2-methoxy-, 1,4-dimethoxy-, 2,6-dimethoxy-, and 2,7-dimethoxynaphthalene using the triple echo version of the 2D magic angle turning (MAT) experiment. In the case of 1-methoxynaphthalene, a room-temperature liquid, the experiment was performed at low temperature. Assignments of the measured principal values of the chemical shift tensors to the individual carbons are made by both comparison of the solid-state isotropic chemical shift to the known solution values and comparison of the experimental principal values to the results of ab initio calculations of the chemical shielding tensor. The methoxy group substituent chemical shift parameters for each of the three components is determined relative to the parent unsubstituted naphthalene for the protonated and ipso carbons. The substituent parameters are very similar to those previously observed for methoxy substituted benzenes. The bond populations, determined using ab initio ...

Phase transitions in 2-bromonaphthalene. The structure of the low temperature phase from X-ray powder diffraction

Abstract The crystal structure of the low temperature stable form of 2-bromonaphthalene has been solved ab initio from laboratory X-ray powder diffraction data. Crystal data: a = 9.572(2), b = 9.599(2), c = 10.307(1) A , α = 100.75(1), β = 109.04(1), γ = 101.76(1) ° , P 1 space group, C 10 H 7 Br, Z = 4, 298 K. 2-bromonaphthalene occurs in three polymorphic varieties. While the crystal structures of the high temperature form and of the metastable form at 25 °C were already known, the structure of the low temperature form remained unsolved due to the difficulty of growing single-crystals. In spite of its complexity (two molecules in the asymmetrical unit), the structure has been solved from powder data at moderate resolution (2.2 A) combining direct with search methods. The subsequent Rietveld refinement with the bromonaphthalene molecules as rigid groups converged to R p = 7.6% and R wp = 10.3%. The structure is almost ordered and built of molecular layers stacked along [001] with the long molecular axis normal to the layer. The orientation of the naphthalenes within the layers is nearly the same as in the structure of the unsubstituted naphthalene. The probable mechanism of the transition from metastable to low temperature form has been established.

Spectroscopy and dynamics of the first excited state of 1- and 2-cyanonaphthalene cooled in a supersonic jet

The fluorescence excitation and dispersed fluorescence spectra of 1- and 2-cyanonaphthalene (1-CNN and 2-CNN) cooled in a supersonic expansion have been studied in the region of the first singlet electronic transition. The main vibronic transitions have been tentatively assigned by comparison with unsubstituted naphthalene. In contrast to naphthalene, vibronically induced Herzberg–Teller transitions do not appear very strongly in the spectra, whereas intense Condon-allowed transitions are observed. Mode mixing has been evidenced in both molecules, for Evib > 700 cm–1 in 2-CNN and 450 cm–1 for the 1-derivative, and the onset of intramolecular vibrational redistribution is discussed in 1-CNN.

A new radical cation salt: Electrocrystallization of trans‐1,2‐bis(2‐naphthyl)ethene and model character of the resulting salt for conducting arylenevinylene polymers

AbstractA single‐crystal radical cation salt was obtained by anodic oxidation of trans‐1,2‐bis‐(2‐naphthyl)ethene (1,2‐DNE) with SbF−6 as the counter‐ion. The crystal structure of (1,2‐DNE)SbF6 was solved and found to be similar to the radical cation salts of unsubstituted naphthalene. The crystal structure is disordered, i.e. two orientations of the 1,2‐DNE molecules are statistically occupied. The molecular overlap, resulting from these two orientations, models the structure of the salt of poly(2,6‐naphthylenevinylene). In contrast to most other radical cation salts which are one‐dimensional conductors, a conduction mechanism of higher dimensionality is predicted on the basis of the crystal structure of (1,2‐DNE)SbF6. The identical type of disorder is also present in the crystal structure of trans‐1,2‐bis(1‐naphthyl)ethene.

Recruitment of naphthalene dissimilatory enzymes for the oxidation of 1,4-dichloronaphthalene to 3,6-dichlorosalicylate, a precursor for the herbicide dicamba.

Pseudomonas putida expresses plasmid-encoded enzymes and regulatory proteins for the dissimilation of naphthalene through salicylate and the alpha-keto acid pathway. A strain of P. putida (NAH:Tn5/G67) defective in salicylate hydroxylase (nahG) was assessed for its ability to oxidize 1,4-dichloronaphthalene. Washed cell suspensions were shown to accumulate 3,6-dichlorosalicylate, which, after further chemical treatment, yields the herbicide dicamba (3,6-dichloro-2-methoxybenzoate). However, the rate of dichlorosalicylate formation from dichloronaphthalene was less than 1% of the rate of salicylate formation from unsubstituted naphthalene.

The peri effect in aromatic hydrocarbon carcinogenesis: An empirical force field examination

AbstractMethyl substitutents located peri to bay‐region benzo rings of polycyclic aromatic hydrocarbons generally reduce or eliminate carcinogenic activity, most likely because such substituents force the hydroxyl groups of dihydrodiol intermediates to adopt preferentially pseudodiaxial, rather than pseudodiequatorial, conformations. Empirical force field calculations have been employed to examine the influences of peri and other positional substituents on hydroxyl conformation, taking naphthalene, anthracene, and phenanthrene as model compounds. For the unsubstituted naphthalene and anthracene dihydrodiols, the pseudodiequatorial conformation is preferred. This preference is reduced by adjacent methyl substitution and reversed by peri methyl substitution. Because of steric crowding the phenanthrene bay‐region dihydrodiol preferentially adopts a pseudodiaxial conformation. The results are discussed in relation to recent experimental evidence.

Enthalpy and entropy changes for the intercalation of small molecules to DNA. I. Substituted naphthalene monoimides and naphthalene diimides

Calorimetric studies have been performed on the intercalation of a series of nitro and amino substituted naphthalene monoimide cations to calf thymus DNA. For comparison, we also included in the study the unsubstituted naphthalene diimide dication. All of the substituted naphthalene monoimides formed dimers at the concentrations used in the calorimetric titrations, and dimerization constants for these compounds were derived from spectroscopic studies and used in calculating the ΔH parameters from the calorimetric data. The dimerization constants increase in the order 3-NO2MI=4-NO2MI>3-NH2MI>4-NH2MI. For the unsubstituted naphthalene monoimide and 3-NO2MI and 4-NO2MI, the ΔH parameters are within experimental error equal to that found for the naphthalene diimide, i.e., −4.3 kcal-mol−1. Thus, changes in entropy cause the K B for the diimide to be 40 times larger than that for the monoimide. This observation is consistent with the current electrostatic theory for counterion binding to DNA: a dication should cause the release of more counterions than a monocation and produce a more positive ΔS . For the amino substituted naphthalene monoimides, the K B values are similar to the other monoimides, but ΔH =−6.7 kcal-mol−1. We propose that a hydrogen bond is responsible for the unusual enthalpy and entropy effects seen for 3-NH2MI and 4-NH2MI.