Terphenyl Isomers Research Articles

Designing Highly Ordered Helical and Nonhelical Porous Crystalline and Disordered Nonhelical Columnar Liquid Crystalline Self-Organizations.

Helical self-organizations are equilibrium structures responsible for the assembly of nonequilibrium and equilibrium living and synthetic systems. Racemic helical columnar systems transform into one-handed systems with the help of enantiomerically rich or pure components. Racemic, enantiomerically rich, and enantiomerically pure helical periodic arrays of columns are analyzed by oriented fiber X-ray diffraction (XRD). With few exceptions, highly ordered helical 3-D organizations as generated from homochiral columns cannot be obtained from achiral, racemic, or enantiomerically rich helical columns. Here, we report an unprecedented class of nonhelical porous ordered, disordered nonhelical columnar liquid crystalline (LC) self-organizations and columnar liquids constructed from AB4 to AB9 isomeric terphenyls by molecular design unwinding of a 3-D helical organization. A library of 16 nonhelical porous ordered, disordered columnar and four liquids was designed by employing as a model a closely related achiral AB4 meta-terphenyl, which self-organizes one of the most perfect synthetic ordered columnar hexagonal helices known. A general molecular mechanism to unwind highly ordered 3-D helices into nonhelical porous columnar ordered LCs and liquids was elaborated to design this transformation, which provided unprecedented nonequilibrium synthetic systems. This methodology is expected to be general for transformation of helical macromolecular and supramolecular organizations into nonhelical crystals, LCs, and liquids.

The occurrence and distribution of phenylated aromatic hydrocarbons and terphenyls during heating experiments of marine and lacustrine source rocks in a semi-open system

This study aimed to explore the presence and distribution of phenyl substituted polycyclic aromatic hydrocarbons (Ph-PAHs) and polyphenyls in one Middle Devonian marine carbonate sample from the Western Canada Sedimentary Basin and one Cretaceous lacustrine shale sample from the Songliao Basin by artificially heating them in a semi-open system. GC-MS analysis of residual extracts and expelled oils showed no trace of phenylnaphthalenes, terphenyls, phenylphenanthrenes and binaphthyls in original extract and low temperature pyrolysates, but these compounds emerged at high temperatures, indicating a pyrogenic origin. Compared to the lacustrine shale, the marine carbonate consistently exhibited higher concentrations of these compounds that are likely controlled by the depositional environment. The main reaction mechanisms involve consecutive reactions of free radicals, with phenylation of unsubstituted aromatic hydrocarbons being the predominant reaction under high thermal stress. While oxidized organic matter may facilitate the formation of Ph-PAHs and polyphenyls, they can be formed from any type of organic matter. The presence of metal oxidants was found to be unnecessary, as high temperatures alone were sufficient to promote the formation of these compounds. Thus, their occurrence indicates abnormal heating regardless of the maturity of the host rocks. Phenylnaphthalenes were produced earlier than other Ph-PAHs and polyphenyls. While stable Ph-PAH and terphenyl isomers increase with simulation temperature, thermal maturity parameters derived from phenyl-PAHs and polyphenyl are insensitive to maturity except for p-TrP/m-TrP, which increases almost linearly with temperature in Brightholme shale. Ph-PAHs and polyphenyls were found to be less thermodynamically stable than conventional PAHs. Under extremely high thermal stress, they lose hydrogen atoms and transform into more stable condensed PAHs. The study provides valuable insights into the occurrence of high abundance phenyl-aromatic and polyphenyl compounds in sedimentary organic matter, enhancing our understanding of these complex organic molecules.

Influence of steric factors on reversible reactions of hydrogenation-dehydrogenation of polycyclic aromatic hydrocarbons on a Pt/C catalyst in hydrogen storage systems

The reversible reactions of hydrogenation-dehydrogenation of polycyclic aromatic hydrocarbons with a different extent of condensation (naphthalene, anthracene, biphenyl, meta- and para-terphenyl isomers) were studied in comparison with benzene on a 3%Pt/C catalyst. Hydrogenation of naphthalene and anthracene was carried out at T = 280 °C, P = 90 atm, whereas the reaction of benzene, biphenyl and terphenyl isomers was performed at T = 180 °C, P = 70 atm in an autoclave. Dehydrogenation of the corresponding polycyclic naphthenes (cyclohexane, decalin, perhydroanthracene, bicyclohexyl, ortho, meta, and para-isomers of perhydroterphenyl) was carried out in the temperature range of 280 to 340 °C in a flow setup at the volume hourly space velocity of 1 h−1 and atmospheric pressure. Correlation dependences of the reaction rates of hydrogenation-dehydrogenation of the studied substrates on their structure and extent of condensation were found.

Hydrogenation of biphenyl and isomeric terphenyls over a Pt-containing catalyst

Catalytic hydrogenation of benzene, biphenyl, and ortho-, metha-, and para-isomers of terphenyl over a 3 wt.% Pt/C at 180 °C and 70 atm was studied. The directions of hydrogenation of each substrate were revealed. Relationships between structures of the substrate and hydrogen consumption rates were found. It was shown that hydrogenation rate decreases on going from benzene to terphenyl and with increasing degree of the substrate hydrogenation. Hydrogenation rate of terphenyl isomers decreases in the following order: p-terphenyl > > m-terphenyl > o-terphenyl.

Effects of Alignment of Weak Interaction Sites in Molecular Shape Recognition High-Performance Liquid Chromatography

This paper introduces organic phases with aligned carbonyl groups derived from l-aspartic acid, l-glutamic acid, and l-α-aminoadipic acid; their stationary phases are denoted as Sil-Asp-2Cn, Sil-Glu-2Cn, and Sil-Adi-2Cn, respectively. The stationary phases were used in high-performance liquid chromatography to investigate the alignment effect of carbonyl groups, which act as π-interaction sites, on molecular shape selectivity. The selectivities of the synthesized organic phases were evaluated using polyaromatic hydrocarbons (PAHs), including geometric isomers (e.g., cis- and trans-stilbenes). The PAH selectivities of the prepared stationary phases were higher than that of conventional octadecyl silica. Among the stationary phases prepared in this study, Sil-Glu-2Cn (n = 18) showed the highest selectivity toward terphenyl isomers with different twist configurations and the lowest selectivity toward planar PAHs with different aspect ratios. The results show that the molecular shape selectivity of the phases was affected by the alignment of interaction sites. As a practical application of the octadecylated amino acid derivative-bonded stationary phases, we evaluated their selectivity for tocopherol isomers and achieved good separation. Furthermore, Sil-Asp-2Cn (n = 1) showed hydrophilic interaction chromatography mode retention behavior for the separation of polar molecules like nucleosides.

The occurrence and distribution of phenylnaphthalenes, terphenyls and quaterphenyls in selected lacustrine shales and related oils in China

Phenylnaphthalenes (PhNs), terphenyls (TrPs), quaterphenyls (QtPs) and triphenylbenzenes were identified by the use of authentic standards in GC–MS analysis. Phenyl derivatives of fused ring polycyclic aromatic hydrocarbons (PhPAHs) and polyphenyls (PPhs) were observed in selected lacustrine shales and related oils from the Tarim, Liaohe and Bebuwan Basins in China. All isomers of phenylnaphthalene and terphenyl were observed in these oils. The more stable 2-PhN and m-Trp, p-TrP isomers are predominant among phenylnaphthalenes and terphenyls, respectively. The effect of maturity on the distribution patterns of phenylnaphthalenes and terphenyls in a set of lacustrine shales from the Liaohe Basin, East China was investigated. The depth trends of three currently used maturity indicators were investigated. Analysis was based on the relative abundance of phenylnaphthalene and terphenyl isomers, namely PhNR (2-PhN/1-PhN), TrP1 (p-TrP/o-TrP) and TrP2 ((m-TrP+p-TrP)/o-TrP) in lacustrine shales from well S202 in the Liaohe Basin, East China. The indicators increase slightly with relatively great deviations within low to intermediate maturation stages and then increase abruptly in high maturity stages. Therefore, they are not suitable maturity indicators for lacustrine source rocks in this study. An alternative thermal maturity indicator, defined as p-TrP/m-TrP was proposed. It exhibits a uniform increase with increasing maturity and is probably a more suitable indicator for use in maturity assessment in lacustrine source rocks and related oils. This study broadens the current understanding of the occurrence and distribution of PhPAHs and PPhs in sedimentary organic matter of various origins.

Pressure-induced oligomerization of benzene at room temperature as a precursory reaction of amorphization

Oligomerization of benzene at high pressures up to 16 GPa was investigated at room temperature using an opposed-anvil type pressure apparatus. The recovered samples were analyzed using GC-MS to identify and quantify the products after the high-pressure experiments. Some structural isomers of benzene dimer as well as biphenyl, naphthalene, and terphenyl isomers were detected at pressures higher than 13 GPa. The molar yield of the polycyclic aromatic hydrocarbons increased concomitantly with increasing pressure, although benzene still remained. The oligomerization is likely to occur when the neighbor distance of the benzene molecules exceeds the threshold of the reaction distance. The oligomerization is regarded as a precursory phenomenon of the amorphization that occurs at higher pressure.

Experimental Study of Gas-Phase Pyrolysis Reaction of Benzene to Investigate the Early Stage of Coke Formation

Gas phase pyrolysis of benzene was performed at 1,123, 1,173, and 1,223 K using a flow type reactor to examine the mechanism of the initial stage of coke (poly-aromatic hydrocarbons; PAHs) formation. The pyrolysis products including hydrogen, tar, and coke were quantified as the function of benzene residence time using gas chromatography, gas chromatography-mass spectrometry, LDI-TOFMS, and elemental analysis to establish the carbon balance within 95 to 105% for all of the experiments. Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS) was applied to determine individual components in coke. Main tar components quantified were biphenyl (C12H10), terphenyl isomers (C18H14), quaterphenyl isomers (C24H18), phenanthrene (C14H10), and triphenylene (C18H12). Phenanthrene was found to be formed by the H-abstraction-C2H2-addition (HACA) mechanism and the other components were judged to be formed by the phenyl addition (PA) and the phenyl addition/cyclization (PAC) mechanisms. One of the smallest molecules identified within the coke was dibenzo[fg,op]naphthacene (C24H14) that is formed from triphenylene by the PAC mechanism. Larger molecules formed by the PAC mechanism and the HACA mechanism were also identified as coke components at the initial stage of pyrolysis. The phenyl addition to PAHs by the PAC mechanism and the HACA mechanism were judged to be main pathways to form larger PAHs. Main reaction mechanisms at the early stage of coke formation were suggested based on the detailed experimental data.

ChemInform Abstract: Vasicine Catalyzed Direct C—H Arylation of Unactivated Arenes: Organocatalytic Application of an Abundant Alkaloid.

AbstractThe naturally occurring alkaloid vasicine is developed as an efficient catalyst for the formation of biaryls and isomeric terphenyls via transition metal‐free coupling of unactivated arenes with aryl iodides and bromides.

Molecular Shape Selectivity for Polycyclic Aromatic Compounds on a Core–Shell Octadecylsilica Stationary Phase at Subambient Column Temperatures

Molecular shape selectivity for polycyclic aromatic compounds on a core–shell-type octadecylsilica (ODS) phase at subambient column temperatures was studied in reversed-phase liquid chromatography. The plate height on the core–shell ODS column was relatively stable at subambient column temperatures when compared with that of a conventional ODS column. In order to compare the sample diffusivities in the conventional and core–shell ODS columns, van Deemter plots were prepared. The plate height of the core–shell column was significantly lower than that of conventional column, suggesting an advantageous feature of the core–shell-type stationary phase especially at a high flowrate of the mobile phase. An enhanced molecular shape recognition capability of the core–shell ODS phase was also confirmed at subambient column temperature. The result could be consistent with an improved shape selectivity as normally observed on conventional ODS phases at low temperatures, however, the enhanced molecular shape recognition capability of the core–shell phase enables a good separation between benz[a]anthracene and chrysene at subambient column temperatures. Similar improved shape selectivities for terphenyl isomers were also confirmed on the core–shell phase.

Isomerization effect on the heat capacities and phase behavior of oligophenyls isomers series

In this work an analysis of the effect of ortho, meta and para isomerization and the number of phenyl rings on the heat capacity and phase behavior of oligophenyls, n(Ph), from 3 up to 5 is presented. The phase behavior from 298.15K to the melting temperature was analysed by differential scanning calorimetry (DSC) and the temperature, enthalpies and entropies of fusion along the oligophenyls series were determined. With the exception of terphenyl isomers, the meta oligophenyls series show lower melting temperatures and higher entropies of fusion. Heat capacities, at T=298.15K, were determined for the ortho and meta quaterphenyl and p-quinquephenyl oligomers by means of high precision drop calorimetry. The heat capacities of the ortho and meta isomers are systematically lower than those of the corresponding para isomers. It was found that the subtle isomerization effect on the heat capacity is partially related to the ring rotation restrictions in their supramolecular structure and increases with the increase of the number of phenyl rings.

Phenyl Shifts in Substituted Arenes via Ipso Arenium Ions

The isomerization of substituted arenes through ipso arenium ions is an important and general molecular rearrangement that leads to interconversions of constitutional isomers. We show here that the superacid trifluoromethanesulfonic acid (TfOH), ca. 1 M in dichloroethane (DCE), provides reliable catalytic reaction conditions for these rearrangements, easily applied at ambient temperature, reflux (84 °C), or in a microwave reactor for higher temperatures. Interconversion of terphenyl isomers in TfOH/DCE at 84 °C gives an ortho/meta/para equilibrium ratio of 0:65:35, nearly identical to values reported earlier by Olah with catalysis by AlCl(3). For the three triphenylbenzenes, TfOH-catalyzed equilibration strongly (>95%) favors the 1,3,5-triphenyl isomer. Equilibration of the three possible tetraphenylbenzenes gives a 61:39 mixture of the 1,2,3,5- and 1,2,4,5-substituted isomers. Under the reaction conditions explored, none of these structures undergoes significant Scholl cyclization. DFT calculations with inclusion of solvation support a mechanistic scheme in which all of the phenyl migrations occur among a series of ipso arenium ions. In every case studied, the preferred isomers at equilibrium are those that yield highly stable cations by the most exothermic, hence least reversible 1,2-H shift.

Standard molar enthalpies of formation and of sublimation of the terphenyl isomers

The standard ( p ∘ = 0.1 MPa) molar enthalpies of formation in the crystalline phases of ortho, meta and para-terphenyl isomers, at T = 298.15 K, were derived from the standard molar energies of combustion, measured by mini-bomb combustion calorimetry. The Knudsen mass-loss effusion technique was used to measure the dependence of the vapour pressure of the crystals with the temperature, thus deriving their standard molar enthalpies of sublimation by means of the Clausius–Clapeyron equation. Combining the standard molar enthalpies of formation and sublimation of the crystalline terphenyls, the standard molar enthalpies of formation in the gaseous state, at T = 298.15 K, were derived for the three isomers. Compound - Δ c U m ∘ ( cr ) / ( kJ · mol - 1 ) Δ cr g H m ∘ / ( kJ · mol - 1 ) Δ f H m ∘ ( g ) / ( kJ · mol - 1 ) o-Terphenyl 9257.8 ± 2.8 103.0 ± 0.4 285.5 ± 3.6 m-Terphenyl 9236.6 ± 3.0 118.6 ± 0.7 279.9 ± 3.9 p-Terphenyl 9234.1 ± 2.4 125.6 ± 0.8 284.4 ± 3.5 The results show small but detectable isomerization enthalpies between the terphenyls, indicating the following relative enthalpic stabilities: m- > p- ≈ o-terphenyl.

Study on Terphenyl Isomers by Second-Derivative Solid-Substrate Room Temperature Phosphorescence

ABSTRACT Terphenyl (TP) isomers p-terphenyl (p-TP) and m-terphenyl (m-TP) were studied by second-derivative solid-substrate room temperature phosphorescence (d2-SS-RTP) with thallous sulfate as a heavy atom perturber and filter paper as substrate. Various factors affecting d2-SS-RTP were discussed in detail. The method for the simultaneous determination of p-TP and m-TP was proposed without any preliminary separation.

Acid generation in the thermal decomposition of diaryliodonium salts

Diphenyliodonium tetrafluoroborate and diphenyliodonium hexafluorophosphate have been found to generate up to two equivalents of hydrogen fluoride per equivalent of the iodonium salt by pyrolysis at 239°C in the neat state and at 150°C in the presence of anisole or nitrobenzene. The formation of hydrogen fluoride is presumed to arise by dissociation of hydrogen tetrafluoroborate or hydrogen hexafluorophosphate initially formed, due to the high temperatures, thus giving rise also to the Lewis acids boron trifluoride and phosphorus pentafluoride, respectively. A detailed analysis of the volatile organic products of the decomposition of the diphenyliodonium salts was also carried out. Many products were identified in all of the cases studied. For example, the neat decomposition of diphenyliodonium tetrafluoroborate afforded benzene, fluorobenzene, iodobenzene, the three isomeric iodobiphenyls, biphenyl, three isomeric terphenyls, and one or more of the diiodobiphenyls, iodoterphenyls, and polyaromatics. Among the iodobiphenyls, the ortho and para isomers were found to predominate over the meta isomer. The terphenyl isomers did not exhibit this ortho, para selectivity. It was significant that decomposition of the diaryliodonium salts in anisole suspension did not afford methoxybiphenyls or iodomethoxybiphenyls. An interpretation of these results is presented. © 1996 John Wiley & Sons, Inc.

Acid generation in the thermal decomposition of diaryliodonium salts

Diphenyliodonium tetrafluoroborate and diphenyliodonium hexafluorophosphate have been found to generate up to two equivalents of hydrogen fluoride per equivalent of the iodonium salt by pyrolysis at 239°C in the neat state and at 150°C in the presence of anisole or nitrobenzene. The formation of hydrogen fluoride is presumed to arise by dissociation of hydrogen tetrafluoroborate or hydrogen hexafluorophosphate initially formed, due to the high temperatures, thus giving rise also to the Lewis acids boron trifluoride and phosphorus pentafluoride, respectively. A detailed analysis of the volatile organic products of the decomposition of the diphenyliodonium salts was also carried out. Many products were identified in all of the cases studied. For example, the neat decomposition of diphenyliodonium tetrafluoroborate afforded benzene, fluorobenzene, iodobenzene, the three isomeric iodobiphenyls, biphenyl, three isomeric terphenyls, and one or more of the diiodobiphenyls, iodoterphenyls, and polyaromatics. Among the iodobiphenyls, the ortho and para isomers were found to predominate over the meta isomer. The terphenyl isomers did not exhibit this ortho, para selectivity. It was significant that decomposition of the diaryliodonium salts in anisole suspension did not afford methoxybiphenyls or iodomethoxybiphenyls. An interpretation of these results is presented. © 1996 John Wiley & Sons, Inc.

Ein theoretischer Beitrag zur radiativen und nicht-radiativen S1-Desaktivierung der isomeren Terphenyle unter Ber�cksichtigung ihrer stabilen Konformationen

A Theoretical Contribution to the Radiative and Non-Radiative S1 Deactivation of the Isomeric Terphenyls by Including their Stable Conformations On the basis of completely optimized S0 and S1 molecular geometries of isomeric terphenyls the radiative and non-radiative S1 deactivations were investigated theoretically within the Condon and Herzberg-Teller approach, respectively. The theoretical vibronic S1 S0 ‘line’ spectra are compared with the experimental fluorescence data. The influence of stable conformations on the vibronic spectral behaviour is discussed. For the internal S1 S0 conversion the rate constants were calculated by including the promoting and accepting modes, and the electronic factor as well. In all cases the photophysically relevant vibrational modes are analyzed.

Pyrolysis of benzene-naphthalene mixtures

Solutions of naphthalene in benzene were pyrolyzed under vacuum at 803 K. Biphenyls, isomeric terphenyls and phenylnaphthalenes, together with triphenylene and fluoranthene were found among the products. A kinetic treatment based upon the steady state approximations shows that the rate constants of similar processes do not differ very much each other. The presence of the two polycyclic aromatic hydrocarbons is ascribed to competitive reactions involving the radicalic intermediates.

Vibronic spectral behaviour of molecules. XV. Study on the T1 → S0 Phosphorescence of Isomeric Terphenyls

AbstractUnderlying the completely‐optimized S0 and T1 molecular geometries of isomeric terphenyls the corresponding theoretical vibronic T1 → S0 ‘line’ spectra calculated within the CONDON approach, are presented and compared with the experimental phosphorescences. The influence of possible conformations on the vibronic spectral behaviour is studied theoretically. The DUSHINSKY effect is found to be most important to the T1 → S0 phosphorescence of m‐terphenyl. An analysis of the spectroscopically relevant vibrational modes is given.

Doubly charged ions from polyphenyls

The vertical ionization energies Q min of eight polyphenyl molecular ions have been determined by charge-stripping mass spectrometry. This leads to new values for double-ionization energies which differ in most cases from previous data obtained by electron impact measurements. In particular, it was possible to distinguish between isomers according to their Q min values, which give three distinct double-ionization energies of 22.3, 21.2 and 21.3 eV for p-, m-, and o-terphenyls, respectively, insteady of the single value of 21.5 eV available previously. Charge separation reactions of the doubly charged molecular ions were studied by the mass-analyzed ion kinetic energy (MIKE) technique and show that the three terphenyl isomers decompose via a single transition structure.