Homologous Series Of Compounds Research Articles

ChemInform Abstract: First‐Principles Investigation of R2O3(ZnO)3 (R: Al, Ga, and In) in Homologous Series of Compounds.

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Air–Water Partitioning of Gasoline Components in the Presence of Sodium Chloride

We have measured the Henry’s constants of several components of gasoline, including methyl tert-butyl ether (MTBE), ethyl tert-butyl ether (ETBE), toluene, ethylbenzene, and o-xylene in pure water and in 0.5 and 1.0 m solutions of sodium chloride. The data were obtained at four temperatures between 313 and 343 K using differential headspace gas chromatography. We have also correlated our data using a previously derived expression based on dilute solution theory. The expression contains one salt-effect parameter that is obtained by regressing data at one salt concentration, thus allowing extrapolation to other salt concentrations. We show that the salt-effect parameter can be replaced by published values of the Setchenov constant for the system of interest. It has been suggested that the salt effect should increase with the size of the volatile organic compound, at least within a homologous series of compounds. However, our data do not validate this hypothesis.

First-principles investigation of R2O 3(ZnO) 3 ( R=Al, Ga, and In) in homologous series of compounds

Atomic and electronic structures of R 2O 3(ZnO) 3 ( R=Al, Ga, and In), which are included in homologous series of compounds, are investigated using first-principles calculations based on density functional theory. Three models with different R atom arrangements in the five-fold and four-fold coordination sites are examined. Al and Ga prefer the five-fold coordination sites. The formation energies are much larger than those of the competing phases, Zn R 2O 4, with a normal spinel structure. On the other hand, In 2O 3(ZnO) 3 shows no clear site preference and can be more stable than the spinel at high temperatures when configurational entropy contribution is taken into account. Electronic states near the conduction band bottom are mainly composed of Zn-4 s orbital in Al 2O 3(ZnO) 3, while the contributions of Ga-4 s and In-5 s are comparable to Zn-4 s in Ga 2O 3(ZnO) 3 and In 2O 3(ZnO) 3.

Comprehensive two-dimensional gas chromatography using a high-temperature phosphonium ionic liquid column

A high-temperature ionic liquid, trihexyl(tetradecyl)phosphonium bis(trifluoromethane)sulfonamide, was used as the primary column stationary phase for comprehensive two-dimensional gas chromatography (GC x GC). The ionic liquid (IL) column was coupled to a 5% diphenyl/95% dimethyl polysiloxane (HP-5) secondary column. The retention characteristics of the IL column were compared to polyethylene glycol (DB-Wax) and 50% phenyl/50% methyl polysiloxane (HP-50+). A series of homologous compounds that included hydrocarbons, oxygenated organics, and halogenated alkanes were analyzed with each column combination. This comparison showed that the ionic liquid is less polar than DB-Wax but more polar than HP-50+. The most unique feature of the IL x HP-5 column combination is that alkanes, cyclic alkanes, and alkenes eluted in a narrow band in the GC x GC chromatogram; whereas, these compounds occupied a much larger portion of the DB-Wax x HP-5 and the HP-50+ x HP-5 chromatograms. Each column combination was used to analyze diesel fuel. The IL x HP-5 chromatogram displayed narrow bands for three major compound classes in diesel fuel: saturates, monoaromatics, and diaromatics. The IL column was used at temperatures as high as 290 degrees C for several months without any noticeable changes in column performance.

Lipids of human meibum: mass-spectrometric analysis and structural elucidation

The purpose of this study was to structurally characterize the major lipid species present in human meibomian gland secretions (MGS) of individual subjects by means of ion trap atmospheric pressure ionization mass spectrometry analysis (API MS(n)). The samples of MGS and authentic lipid standards were analyzed in direct infusion and high-pressure liquid chromatography (HPLC) experiments with API MS(n) detection of the analytes (HPLC API MS(n)). The major precursor ions were isolated and subjected to further sequential fragmentation in MS(n) experiments, and their fragmentation patterns were compared with those of authentic lipid standards. Multiple precursor ions were observed in the positive-ion mode. Among those, previously identified cholesterol (Chl; m/z 369; [M - H(2)O + H](+)) and oleic acid (OA; m/z 283; [M + H](+)) were found. The other major compounds of the general molecular formula C(n)H(2n-2)O(2) were consistent with wax esters (WEs), with OA as fatty acyl component. Accompanying them were two homologous series of compounds that fit the molecular formulas C(n)H(2n-4)O(2) and C(n)H(2n)O(2). Subset 2 was found to be a homolog series of linoleic acid-based WEs, whereas subset 3 was, apparently, a mixture of stearic acid-based WEs. HPLC API MS(n) analysis revealed the presence of large quantities of cholesteryl esters (Chl-Es) in all of the tested samples. Less than 0.1% (w/w) of oleamide was detected in human MGS. In the negative-ion mode, three major compounds with m/z values of 729, 757, and 785 that were apparently related to anionogenic lipids of the diacylglyceryl family were found in all of the samples. Common phospholipids and ceramides (Cers) were not present among the major MGS lipids. Phosphocholine-based lipids were found in MGS in quantities less than 0.01% (w/w), if at all. This ratio is two orders of magnitude lower than reported previously. These observations suggest that MGS are a major source of nonpolar lipids of the WE and Chl-E families for the tear film lipid layer, but not of its previously reported (phospho)lipid, Cer, and fatty acid amide components.

The melting and boiling points of compounds in homologous series of monohalogenated n-alkanes

The available data on the melting and boiling points in homologous series of normal 1-fluoro-, 1-chloro-, 1-bromo-, and 1-iodoalkanes were critically analyzed. A correlation was observed between the melting and boiling points of halogenated even and odd n-alkanes. This allowed us to obtain an interpolation equation for predicting compound melting points.

Synthesis and Antioxidancy of Some n‐Alkyl, t‐Alkyl, Homologous and Isomeric Lipidic Alkylthiobisphenols

AbstractTo study the relationship between structure and properties of members of the lipidic thiobis phenol series, as extreme pressure additives in lubricants, a series of homologous compounds has been synthesised by the reaction of alkylphenols with sulphur dichloride. The isomeric n‐nonylphenols have been reacted to form the C9 isomeric 2,2′‐and 4,4′‐thiobisphenols. Longer alkyl side‐chains resulted mainly in the formation of 4,4′‐thiobisphenols and some of the 2,2′ isomer. With short alkyl, particularly t‐alkyl side‐chains, steric hindrance resulted in the 2,2′‐compound. Additive studies have indicated that the longer chain 4,4′ compounds possessed antioxidant properties comparable and superior to former commercial branched chain 2,2′ compounds produced from petrochemical intermediates.

Retention factor and retention index of homologous series compounds in microemulsion electrokinetic chromatography employing suppressed electroosmosis

The retention factor (k) and retention index (I) of homologous series compounds such as alkylbenzenes (BZ), alkylaryl ketones, alkylbenzoates, and alkylparabens in microemulsion electrokinetic chromatography (MEEKC) with suppressed electroosmosis were investigated in a wide range of SDS concentrations ([SDS]), temperatures, and concentrations of organic cosolvents (phi). Using BZ as standards, the retention indices of other homologous series compounds were determined and they were found to be independent of [SDS] and temperature, while are dependent on the types and concentrations of organic cosolvents. The retention factor linearly increases with increasing [SDS], while linearly decreases with increasing temperature. The value of log k linearly decreases with increasing phi for methanol, ethanol, or ACN, while decreases by a second-degree polynomial with increasing phi for 2-propanol. Excellent agreement was found between the observed and predicted values of log k of analytes in MEEKC at given [SDS] and phi, where the predicted values were obtained from modified equations of the linear relationship of log k as functions of [SDS], the number of carbons, and phi. Therefore, both k and I can be used for peak identification of homologous series compounds.

Magnetic structures in Pr6Ni2Si3 and Pr5Ni2Si3

The temperature dependence of magnetization in Pr6Ni2Si3 and Pr5Ni2Si3 compounds has been studied with the objective of providing a theoretical understanding of the behavior of the magnetic properties of the material. The ternary Pr–Ni–Si system contains the homologous series of compounds R(n+2)(n+1)Nin(n−1)+2Sin(n+1), where R is a rare earth element which provides a range of materials with different but related structures. The crystal structures and unit cells of Pr6Ni2Si3 (n=2) and Pr5Ni2Si3 (n=3) compounds are closely related consisting of an overall hexagonal structure comprising trigonal columns of atoms, in which the only difference is in the size of the triangular base of the column which depends directly on the chemical composition, specifically the index n. The calculations were based on a nearest neighbor exchange interaction approximation under two kinds of conditions: collinear and noncollinear magnetic structures. The results of these calculations show the Curie temperature, but do not yet predict quantitatively the spin reorientation transition at lower temperatures.

Organic Matter of the Troposphere—II.: Natural Background of biogenic lipid matter in aerosols over the rural western United States

Higher plant waxes are the predominant natural components in the lipid fractions (> C 15) of aerosols sampled over rural and oceanic regions. Hydrocarbon, fatty acid, ketone and fatty alcohol fractions of the lipids were characterized in terms of their contents of homologous compound series and specific biogenic molecular markers. Particulate samples from the rural western United States have been analyzed and compared with samples from urban Los Angeles and remote areas over the Atlantic Ocean. The samples from rural sites contained predominantly vascular plant wax and lesser amounts of higher plant sterols and resin residues. Urban samples and, to varying degrees, some rural samples contained primarily higher weight residues of petroleum products. The loadings of hydrocarbons derived from higher plant waxes ranged approximately from 10 to 160 ng m −3 of air (for fatty acids, 10–100 ng m −3 and for fatty alcohols, 10–200 ng m −3). Higher molecular weight lipids (i.e. plant epicuticular wax, terpenes, etc.) from flora comprise a significant component of the organic carbon in rural aerosols. Primary biogenic residues are major components of aerosols in all areas and they are important components in the global cycling of organic carbon.

Crystal growth of nonstoichiometric compounds

A key issue in materials research is the preparation of crystals of inorganic compounds with predetermined composition, structure, and, hence, properties. In connection with this, this paper scrutinizes the concepts of stoichiometry, nonstoichiometry, and deviation from stoichiometry and the use of phase diagrams in selecting conditions for the crystal growth of nonstoichiometric compounds. Since nonstoichiometry is associated with structural defects, attention is also paid to defect classification and formation. The behavior of defects in crystals of oxides, chalcogenides, carbides, and other compounds of transition metals ranges from the pointdefect regime, controlled by entropy, to the enthalpy-controlled regime. To develop an appropriate theory of nonstoichiometric compounds, it is then necessary to address crystal-chemical and thermodynamic issues. This paper is also concerned with the defect structure of highly imperfect crystals of nonstoichiometric compounds with a broad homogeneity range: the concepts of defect and structural transition due to defect interactions and temperature effect. The thermodynamic aspect of the problem includes criteria for evaluating the stability of imperfect nonstoichiometric crystals. We also consider the specifics of the concepts of existing, stable, and metastable phases, spinodal decomposition conditions, and issues associated with phase equilibria in homologous series of compounds with narrow homogeneity ranges. The paper also deals with synthesis methods, nonstoichiometry control, and criteria for evaluating the homogeneity of nonstoichiometric crystals.

Prediction of properties in homologous series with a shortcut QS2PR method

AbstractFor prediction of properties of pure compounds in homologous series a shortcut version of the authors' QS2PR technique is introduced. The structure–structure relationship between a target compound and three predictive compounds from its homologous series is described in the short version with the number of carbon atoms and one easily calculated noncollinear molecular descriptor. This correlation provides predictions of high precision for properties of members of the homologous series, if property data for interpolation are available. It can also be used for short‐range extrapolation with precision similar to that of asymptotic relationships. The advantages of the proposed method over the existing methods are that with the structural correlation parameters it predicts all structure‐dependent properties of the target and enables estimation of its missing properties even if properties for only three predictive compounds are available. The method can also use as a descriptor the normal boiling temperature. © 2006 American Institute of Chemical Engineers AIChE J 2007

Application of recurrence relations to melting points of homologs

The previously established recurrence equations A(n + 1) = aA(n) + b characterizing variations in the majority of physicochemical constants of organic compounds in homologous series and relating the properties of adjacent homologs with n + 1 and n carbon atoms are applicable in the modified form [Tm(n + 2) = aTm + b] to the melting points. This second-order recurrence is observed with a high accuracy, despite significant alternations in the melting points of even and odd homologs. The method for calculating melting points, based on this recurrence, has no analogs among the previously suggested methods and makes it possible, in particular, to reveal errors in reference data, originating in most cases from the low purity of the samples dealt with.

Neutron structure investigation of Ca2Y2Cu5O10

Ca2Y2Cu5O10, a calcium yttrium cuprate, is the yttrium rich endmember of a homologous series of compounds with composition (Ca1-xYx)4Cu5O10 (0<x<0.5) [1]. According to the chemical formula the formal charge of copper can be varied between +2 and +2.4. The structure is incommensurate and related to the structure of NaCuO2 [2]. In both case the central structural elements are one dimensional Cu-O chains. According to the x-ray experiments we found a Ca/Y disorder. Instead of having 5 Na and 5 Cu positions in the quintupled supercell in the case of NaCuO2 there are 4 Ca/Y and 5 Cu positions in the supercell of Ca2Y2Cu5O10. Therefore Ca/Y positions and Cu-O chains have to be rearranged and distorted. Single crystals were grown in an optical floating zone furnace and were examined by single crystal diffraction experiments (x-ray and neutron scattering). Structure refinement was done with Shelxl-97 [3] (supercell: P21/c, a=5.4730(10)A, b=6.1801(10)A, c=14.081(2)A, β=104.550(14)°, z=2) and 3+1dimensional with Jana2000 [4]. As a result of the neutron experiment we got the cell metrics of both composite parts and the associated q vectors. One can describe one composite part as P21/c(α0λ)00 (a=5.474(5)A, b=6.181(9)A, c=2.,818(7)A, β=104.87(15)°), the other one as P21/m(α0λ)0s (a=5.458(5)A, b=6.181(9)A, c=3.523(9)A, β=104.24(15)°). The associated q vectors are (-0.0177 0 0.8) and (0.0221 0 1.25). On the poster a detailed description of the contents of the composite parts, positions of the atoms and distortion of the Cu-O chain will be given.

Multi-isotopic constraints on the origin and fate of n-alkyl lipids in recent sediments

Recent analytical advances now make it feasible to determine multiple isotopic characteristics of individual organic compounds within complex mixtures. In particular, hydrogen isotopic compositions and radiocarbon contents can now be readily determined to complement information derived from stable carbon isotopic analysis. When used in concert, these lines of geochemical information can yield important new insights into the origins and histories of the biomarker compounds, and lead to new and refined interpretation of molecular proxy records of paleoenvironmental variability. We present multi-isotopic data on n-alkyl lipids isolated from a range of recent aquatic sediments in order to demonstrate both the complexity of geochemical signals preserved in environmental matices, and the utility of multi-isotopic information in constraining inputs. In particular, we focus on long-chain lipids derived from terrestrial and marine precursors. Marked radiocarbon age and stable isotopic variability is apparent, even within closely related homologous series of compounds recovered from the same sample. Based on multi-isotope characteristics, we interpret these variations in terms of differences in source versus reactivity of individual organic compounds, and discuss implications for interpretation of the sedimentary record.

Identification and Quantification of Homologous Series of Compound in Complex Mixtures: Autocovariance Study of GC/MS Chromatograms

The paper describes a method for determining homologous classes of compounds in a multicomponent complex chromatogram obtained under programming elution conditions. The method is based on the computation of the autocovariance function of the experimental chromatogram (EACVF). The EACVF plot, if properly interpreted, can be regarded as a "class chromatogram" i.e., a virtual chromatogram formed by peaks whose positions and heights allow identification and quantification of the different homologous series, even if they are embedded in a random complex chromatogram. Theoretical models were developed to describe complex chromatograms displaying random retention pattern, ordered sequences or a combination of them. On the basis of theoretical autocovariance function, the properties of the chromatogram can be experimentally evaluated, under well-defined conditions: in particular, the two components of the chromatogram, ordered and random, can be identified. Moreover, the total number of single components (SCs) and the separated number of the SCs belonging to the random and ordered components can be determined, when the two components display the same concentration. If the mixture contains several homologous series with common frequency and different phase values, the number and identity of the different homologous series as well as the number of SCs belonging to each of them can be evaluated. Moreover, the power of the EACVF method can be magnified by applying it to the single ion monitoring (SIM) signals to selectively detect specific compound classes in order to identify the different homologous series. By this way, a full "decoding" of the complex multicomponent chromatogram is achieved. The method was validated on synthetic mixtures containing known amount of SCs belonging to homologous series of hydrocarbon, alcohols, ketones, and aromatic compounds in addition to other not structurally related SCs. The method was applied to both the total ion monitoring (TIC) and the SIM signals, to describe step by step the essence of the procedure. Moreover, the systematic use of both SIM and TIC can simplify the decoding procedure of complex chromatograms by singling out only specific compound classes or by confirming the identification of the different homologous series. The method was further applied to a sample containing unknown number of compounds and homologous series (a petroleum benzin, bp 140-160 degrees C): the results obtained were meaningful in terms of both the identified number of components and identified homologous series.

Seasonal abundance of organic molecular markers in urban particulate matter from Philadelphia, PA

Organic molecular markers were measured in airborne particulate matter (PM10) from the City of Philadelphia North Broad Street air quality monitoring site to identify the seasonal abundance of key tracer compounds together with their dominant sources. Daily PM10 samples were collected seasonally in 2000 for four 2-week periods (January, April, August, and October). The North Broad Street site is within a heavily populated location in Philadelphia, PA. A suite of 52 individual organic marker compounds was monitored in the PM10 samples. Molecular markers, homologous compound series, and nonpolar and polar organic compounds were detected at ng m −3 ambient concentrations using gas chromatography/ion trap mass spectrometry (GC/IT MS). Organic diacids (C 3–C 9) and monoacids (C 10–C 30) had seasonal mass concentrations ranging from 91.0 (winter) to 261.8 ng m −3 (summer). Total n-alkanes (C 25–C 33) ranged from 25.9 (spring) to 49.5 ng m −3 (fall), total PAHs from 2.1 ng m −3 (summer) to 4.1 ng m −3 (winter), and total hopanes ranged from 4.0 ng m −3 (winter) to 7.4 ng m −3 (fall). The molecular marker ambient mass concentrations were normalized by the annual average mass of PM10 elemental carbon (EC) for the central Philadelphia area. The ambient mass concentrations to EC and OC ratios ranged from 2.6×10 −3 for total PAHs to EC to 115.3×10 −3 for total n-alkanoic acids to EC, 0.5×10 −3 for total PAHs to OC to 23.8×10 −3 for total n-alkanoic acids to OC. Ambient concentrations of individual markers are similar to other reported levels for metropolitan Los Angeles, CA and Atlanta, GA. Seasonal and daily variations of marker compounds are consistent with motor vehicle exhaust, particularly in winter. Summer concentration patterns indicate the importance of secondary organic aerosol to the PM10 ambient mass.

Fluorine containing nonsymmetrical five-ring achiral banana-shaped compounds with columnar and synclinic antiferroelectric layered phases.

The phase transitional behavior of two homologous series of five-ring banana-shaped compounds comprising fluorine substituents synthesized through covalent linking of two chemically dissimilar rod-like anisometric cores (arms) to central 1,3-phenylene is reported. The novelty of these molecules originates from the fact that the molecules are highly nonsymmetrical. One of the arms, which is either salicylaldimine or Schiff base core, possesses two vicinal fluorine atoms at the terminal ring having a -decyloxy tail; while the -alkyl tail attached to the other arm was varied to realize a homologous series of compounds. The mesophases have been characterized by several complementary studies. The banana-shaped systems having short or medium alkyl chain lengths form apolar columnar (two-dimensional) structures, while on ascending the series, a polar smectic phase is stabilized. Detailed electro-optical investigations on one of the polar smectic phases revealed a synclinic antiferroelectric (racemic) ground state structure, which switches, as expected, to an anticlinic ferroelectric state by the application of an electrical field. At higher field strengths applied for an extended time interval, the anticlinic ferroelectric state switches to a synclinic ferroelectric (chiral) state. Upon field removal, these domains switch to an anticlinic antiferroelectric (chiral) state, which eventually nucleates to the original antiferroelectric synclinic (racemic) state. Remarkably, the associated spontaneous polarization value exceeds 800 nC cm, which is among the highest reported hitherto.

Superconductivity in the Y-Ba-Ca-Cu-O system

The search for the mechanisms of high-temperature superconductivity and novel superconducting materials are the most challenging tasks of condensed-matter physicists as well as material scientists [1–3]. The yttrium barium copper oxide (YBCO) YBa2Cu3O7 or CuBa2YCu2O7, often called “Y-123” or “Cu-1212” superconducting compound, is the first member of the homologous series of compounds of general formula Y2Ba4Cu6+nO14+n (n = 0, 1, 2). Cu-1212 phase exhibits a highest superconducting transition temperature (TC) inside YBCO family, at around 90–92 K, and till now remains the most extensively studied high-TC superconductor [4–8]. By the analogy to the Hg-based cuprates [9], we have tried to introduce additional CaO layers to the structure of CuBa2YCu2O7−δ (Cu-1212 or Cu-12102) superconductor. The purpose of the present work was to prepare new superconducting phases using the sol–gel synthesis method: (a) having a single layer of CaO between two CuO2 sheets with the nominal composition of CuBa2YCaCu3O9−δ (Cu–12113), and (b) having two CaO layers between triple CuO layers with the composition of CuBa2YCa2Cu4O11−δ (Cu–12124). The results of this study are presented herein. CuBa2YCaCu3O9−δ and CuBa2YCa2Cu4O11−δ samples were prepared by an acetate-tartrate sol–gel method developed previously for the synthesis of pure YBa2Cu4O8 superconductor [10]. As starting compounds stoichiometric amounts of analytical grade Y2O3, Cu(CH3COO)2·H2O, Ba(CH3COO)2 and Ca(CH3COO)2·H2O were used. In the sol–gel process, Y2O3 was first dissolved in 0.2 M acetic acid solution by stirring at 55–60 ◦C. After stirring the mixture for 10 hr in a beaker covered with a watch-glass a clear solution was obtained. In the next step, mixtures of the appropriate amounts of Ba(CH3COO)2, Ca(CH3COO)2·H2O, and Cu(CH3COO)2·H2O, all of them dissolved in small amounts of distilled water, were added with continuous stirring during several hours at the same temperature. An

Extending, and Repositioning, a Thermochemical Ladder: High-Level Quantum Chemical Calculations on the Sodium Cation Affinity Scale

High-level ab initio quantum chemical calculations, at the CP-dG2thaw level of theory, are reported for coordination of Na+ to a wide assortment of small organic and inorganic ligands. The ligands range in size from H to C6H6, and include 22 of the ligands for which precise relative sodium ion binding free energies have been determined by recent Fourier transform ion cyclotron resonance and guided ion beam studies. Agreement with the relative experimental values is excellent (+/-1.1 kJ mol(-1)), and agreement with the absolute scale (obtained when these relative values are pegged to the CH3NH2 "anchor" value measured in a high-pressure mass spectrometric study) is only marginally poorer, with CP-dG2thaw values exceeding the absolute experimental DeltaG(298) values by an average of 2.1 kJ mol(-1). The excellent agreement between experiment and the CP-dG2thaw technique also suggests that the additional 97 ligands surveyed here (which, in many cases, are not readily susceptible to laboratory investigation) can also be reliably fitted to the existing experimental scale. However, while CP-dG2thaw and the experimental ladder are in close accord, a small set of higher level ab initio calculations on sodium ion/ligand complexes (including several values obtained here using the W1 protocol) suggests that the CP-dG2thaw values are themselves too low by approximately 2.5 kJ mol(-1), thereby implying that the accepted laboratory values are typically 4.6 kJ mol(-1) too low. The present work also highlights the importance of Na+/ligand binding energy determinations (whether by experimental or theoretical approaches) on a case-by-case basis: trends in increasing binding energy along homologous series of compounds are not reliably predictable, nor are binding site preferences or chelating tendencies in polyfunctional compounds.