Odd Carbon Number Research Articles

ENSO modulates soil organic carbon retention and deposition in the East China Sea

Accurately quantifying the contribution of terrestrial soil organic carbon (SOC) in marine environment is still a challenge. Moreover, reassessing the effect of climate change on SOC variability is necessary, with the increasing variability of El Niño under greenhouse warming. Here, we present new insights from bacterial 3-hydroxy fatty acids (3-OH-FAs) by systematically analyzing the distributions of 3-OH-FA in soils, lake/river sediments and marine sediments, and propose a novel proxy (RIA, the ratio of odd carbon number iso to anteiso 3-OH-FAs) to quantificationally evaluate the contribution of OC from different components. The reliability of the RIA proxy is tested by using a three end-member model and Monte Carlo simulations along a transect from the Yangtze River estuary to the ECS shelf. Then the RIA proxy is applied to a core in the East China Sea covering the past 700 years, and the results reveal that El Niño (La Niña) induced more (less) precipitation and increased (decreased) SOC deposition. This study provides a novel approach for quantifying terrigenous OC inputs and burial in marginal seas and shows the impact of El Niño-Southern Oscillation (ENSO) modes on SOC loss and burial in marginal seas under global warming.

Molecular dynamics study on phase change properties and their nano-mechanism of sugar alcohols: Melting and latent heat

Sugar alcohol phase change materials have gained considerable attention for heat storage in recent years owing to their higher thermal conductivity and larger latent heat compared to traditional paraffin materials. However, knowledge about the reason of large latent heat and latent heat difference among diverse sugar alcohols as well as the mechanism of melting process remains elusive. In this study, molecular dynamics simulation was employed to investigate the melting process and latent heat of four sugar alcohols (glycerol, erythritol, arabinitol, and mannitol). Melting points and latent heat of fusion were determined first, different melting temperatures were observed under different one-dimensional heat conduction directions in several sugar alcohols. It was found that the strength of intermolecular interactions within molecular crystal layers has a positive correlation with the anisotropic melting tendencies, which can be more intuitively reflected by the difference in the number of hydrogen bonds within the molecular layers. In addition, the decomposition of the latent heat of fusion revealed that the latent heat is mainly composed of van der Waals and Coulombic contributions, where the interaction between hydroxyl groups accounts for a major part. Hydrogen bond analysis demonstrated that the latent heat of fusion is partly due to the breakage of hydrogen bonds during the phase transition of melting. It was also noted that the differences in the hydrogen bonding lifetimes between different sugar alcohols may be related to the magnitude of latent heat of fusion. Erythritol and mannitol which coincidentally happened to have an even number of carbon atoms can fulfill the properties of better PCMs compared to glycerol and arabinitol, which have an odd number of carbons. Those results will pave the way for better design optimization and performance evaluation of sugar alcohols as phase change materials.

Synthesis of straight-chain C49H100 alkane using a modular splicing strategy

Ultra-long n-alkanes are highly valuable in both scientific research and as major constituents of specialty high-melting-point waxes. Unlike conventional methods (e.g., Fischer–Tropsch (FT), ethylene oligomerization, and polyethylene cracking) typically resulting in wide n-alkane distributions, the elaborate design strategy presented herein allows the direct synthesis of pure, long n-alkanes using a modular splicing method with acetone, furfural, and fatty acid anhydrides or acyl chlorides as bio-blocks. The herein approach is based on a simple four-step catalytic reaction scheme involving C–C chain elongation and C–O bond activation. The synthesized pure n-alkanes had a carbon chain length as high as C49 (total yield of 49%). The synthesis approach also allows to selectively prepare n-alkanes with even and odd carbon numbers ranging from C15 to C49. This process represents a great breakthrough in the synthesis of long-chain pure n-alkanes, surpassing the carbon number limitations reported in previous methodologies.

Synthesis and thermal-optical behaviors of non-conventional benzidine-based oligomers containing tetrasubstituted Schiff base arms

New benzidine-based oligomers containing four Schiff base arms with terminal alkoxy chains CnH2n+1 (n = 6–12) were characterized by elemental, spectroscopic (UV, FT-IR, and NMR) and DFT techniques. The thermal-optical behaviors were observed using differential calorimetry and polarized optical microscope. Upon heating the molecules with n = 8, 10, and 12 exhibited endothermic peaks characteristic of the crystal-soft crystal B transition in addition to crystal-crystal subphases. It can be generalized that all oligomers showed unusual curing temperature of which the compounds with odd alkoxy chain carbon numbers possess lower curing temperatures in comparison with the analogous compounds of even parity.

Trapping the Short‐Chain Odd Carbon Number Olefins Using Nickel(II)‐Catalyzed Tandem Ethylene Oligomerization and Friedel‐Crafts Alkylation of Toluene

Comprehensive SummaryNickel(II) complexes with pyrazole‐based ligands are widely employed in catalysis of ethylene oligomerization and subsequent Friedel‐Crafts alkylation of toluene. We have prepared ten new nickel(II) dibromide complexes with various substituted bis(azolyl)methanes. They have been characterized using 1H NMR, IR, high resolution mass spectrometry and elemental analysis. The structures of three complexes have been unambiguously established using X‐ray diffraction. It was found that these complexes in the presence of Et2AlCl or Et3Al2Cl3 are active both in ethylene oligomerization and Friedel‐Crafts alkylation processes (activity up to 3720 kgoligomer·mol[Ni]−1·h−1). The use of Et3Al2Cl3 results in a higher share of alkylated products (up to 60%). Moreover, catalytic systems activated with Et3Al2Cl3 produced small amounts of odd carbon number olefins (up to 0.8%). The Friedel‐Crafts alkylation was used as a trap for previously undetected short‐chain odd carbon number olefins (C3 and C5).

Comparing extraction methods for analyzing n-alkyl lipids in shelf sediments from the China Sea

n-Alkyl lipids including n-alkanes, n-alkanols, and n-alkanoic acids, are essential biomarkers in oceanic sediments and have been widely employed in both modern- and paleo-ecological and environmental studies. The selection of appropriate extraction methods for different research purposes, particularly for compounds with different polarities, remains a challenge. In this study, we compared the efficacy of Bligh-Dyer extraction (BDE), ultrasound-assisted extraction (UAE), accelerated solvent extraction (ASE), as well as a combination of Bligh-Dyer extraction and ultrasound-assisted extraction (BD + UAE) to extract n-alkanes, free n-alkanols, and free n-alkanoic acids from ocean sediments. Our findings indicate that BD + UAE is a suitable method for extracting n-alkanes, ASE is an optimal for extracting free n-alkanols, and BDE provides a suitable method for simultaneous extraction of free n-alkanoic acids with intact polar lipids (IPLs). Additionally, BDE exhibited a preference for compounds with an odd carbon number and short chains, whereas the UAE favored compounds with an even carbon number and long chains, particularly for n-alkanes. These results offer novel insights into the investigation of past paleoclimate and sediment chemistry and serve as a basis for future research on organic matter extraction from ocean sediments.

Physico-chemical characterization of Synperonic™ 91/5 self-assembly behaviour in water

We studied the self-assembled aggregates of Synperonic™ 91/5 (SYN) in water solution. This surfactant presents the peculiarity of having an odd number of aliphatic carbons, with a tail composed of C9H19 and C11H23, and the headgroup having an average of 5 ethoxy units. While the general family of CiEOj nonionic surfactants has been widely studied, there is little knowledge for the case of surfactants with odd-number carbons. For this reason, we carried out an in depth physico-chemical characterization of water solutions containing SYN in the wide range of concentration from 2 % to 50 % (i.e. 0.05–1.4 M), considering that high concentrated systems are relevant for industrial applications. This class of surfactants is also interesting as remediation agent since they can incorporate different polluting molecules, both polar and nonpolar, such as volatile Organic Compounds (VOCs) and Dense Non Aqueous Phase liquids (DNAPLs). The rheological and transport properties of SYN solutions were investigated through diffusion coefficients and viscosity, while shape and size of self-assemblies were determined by Dynamic Light Scattering and by Small Angle Scattering of Neutrons (SANS) and X-rays (SAXS). Results show that SYN generally behaves as other nonionic surfactants in dilute solutions, but shows some peculiarity of aggregate packing at high concentration. We recently demonstrated the efficiency of the Synperonic™ family of surfactants in solubilising trichloroethylene (TCE), in particular above a critical concentration of 0.1 M, thus being a good candidate for remediation purposes. Here, the solubility of TCE was correlated with the number and the size of micelles at different surfactant concentrations. Our work helps filling a gap in the literature about technical grade surfactants with odd-number carbons, and the results can help in assessing the performances of Synperonic™ products for technical tasks.

Performance of production of polyhydroxyalkanoates from food waste fermentation with Rhodopseudomonas palustris

The use of waste as a carbon source can significantly reduce the cost of production of Polyhydroxyalkanoates (PHAs). In this study, an acidified hydrolysate solution derived from food waste (FW) was used as a carbon source for the synthesis of PHAs by Rhodopseudomonas palustris (R. palustris) and optimized the process parameters. The results showed that the PHAs yield reached 48.62% under optimal conditions (an incubation time of 30 days, volatile fatty acids (VFAs) in substrate concentration of 2202.21 mg⋅L−1, an initial pH of 8.0, and inoculum concentration of 15%). The fraction of VFAs affects the composition of PHAs, R. palustris first uses VFAs with an even number of carbons to synthesize poly(3-hydroxybutyrate)(3HB), and later uses VFAs with an odd number of carbons to synthesize poly-3-hydroxyvalerate (3HV). Pathways for the synthesis of PHAs by R. palustris were inferred. R. palustris is a strain with the potential to synthesize PHAs.

Structures and Stabilities of Carbon Chain Clusters Influenced by Atomic Antimony.

The C-C bond lengths of the linear magnetic neutral CnSb, CnSb+ cations and CnSb- anions are within 1.255-1.336 Å, which is typical for cumulene structures with moderately strong double-bonds. In this report, we found that the adiabatic ionization energy (IE) of CnSb decreased with n. When comparing the IE~n relationship of CnSb with that of pure Cn, we found that the latter exhibited a stair-step pattern (n ≥ 6), but the IE~n relationship of CnSb chains took the shape of a flat curve. The IEs of CnSb were lower than those of corresponding pure carbon chains. Different from pure carbon chains, the adiabatic electron affinity of CnSb does not exhibit a parity effect. There is an even-odd alternation for the incremental binding energies of the open chain CnSb (for n = 1-16) and CnSb+ (n = 1-10, when n > 10, the incremental binding energies of odd (n) chain of CnSb+ are larger than adjacent clusters). The difference in the incremental binding energies between the even and odd chains of both CnSb and pure Cn diminishes with the increase in n. The incremental binding energies for CnSb- anions do not exhibit a parity effect. For carbon chain clusters, the most favorable binding site of atomic antimony is the terminal carbon of the carbon cluster because the terminal carbon with a large spin density bonds in an unsaturated way. The C-Sb bond is a double bond with Wiberg bond index (WBI) between 1.41 and 2.13, which is obviously stronger for a carbon chain cluster with odd-number carbon atoms. The WBI of all C-C bonds was determined to be between 1.63 and 2.01, indicating the cumulene character of the carbon chain. Generally, the alteration of WBI and, in particular, the carbon chain cluster is consistent with the bond length alteration. However, the shorter C-C distance did not indicate a larger WBI. Rather than relying on the empirical comparison of bond distance, the WBI is a meaningful quantitative indicator for predicting the bonding strength in the carbon chain.

Structural geometry and molecular dynamics of hybrid organic–inorganic [NH3(CH2)6NH3]CdCl4 crystals close to phase transition temperatures

Organic–inorganic hybrid perovskites are highly promising for application in various electrochemical devices, such as batteries and fuel cells. The physical properties of crystals of the organic–inorganic hybrid perovskite [NH3(CH2)6NH3]CdCl4 are important for their future application. Therefore, these crystals were grown and their phase transition temperatures TC1 = 337 K and TC2 = 472 K were determined using powder X-ray diffraction and differential scanning calorimetry. We observed that the crystallographic surroundings of 1H and 13C in the cation near TC1 did not show significant changes, whereas those of 113Cd in the anion changed significantly. The change in the coordination geometry of C1 around Cd near TC1 changed the N–H···Cl bond by connecting with the 1H of NH3. The nuclear magnetic resonance spin-lattice relaxation time T1ρ suggested that the 1H energy transfer processes in phases III and II were easier, whereas the 13C energy transfer processes were easier in phase III than in phase II. The results of the current study for [NH3(CH2)nNH3]CdCl4 (n = 6) were compared with those for n = 2, 3, 4, and 5 obtained from previous studies. The features of the length of CH2 and even–odd number of carbons in the diammonium chain are expected to facilitate potential applications in the future.

Molybdenum carbide, supercritical ethanol and base: Keys for unlocking renewable BTEX from lignin

Supported molybdenum hemicarbide catalysts were prepared and employed for the depolymerization and deoxygenation of waste lignins to aromatics in supercritical ethanol. Titanium nitride appears be a particularly beneficial support material. Depolymerization at 330 °C led to a higher yield and selectivity for arenes than at 280 °C. Base is essential for efficient substrate conversion: the basic constituents inherent in waste lignins are suitable, as is added sodium hydroxide. Without base, depolymerization is poor, the yield of aromatics is very low, and substrate defunctionalisation does not occur. A significant proportion of aromatic products is formed from supercritical ethanol itself, including benzene, which is likely to be present in all catalytic runs due to ethanol aromatization. Hence the total arene content produced is actually higher than has been widely reported. Catalytic cracking of ethanol leads to C1-units, which add to reaction intermediates to give aromatics containing odd numbers of carbons (e.g. toluene).

Microplastics and hydrocarbons in soils: Quantification as an anthropic carbon source.

The literature on the presence of microplastics (MPs) and their potential impact on terrestrial ecosystems is still scarce. Interestingly, soil MPs are detected as organic carbon (SOC) using traditional quantification methods (e.g., loss on ignition [LOI]), although its dynamics in the environment will be different. The objective of this study was to quantify the carbon (C) contribution of MPs to the SOC in superficial soil samples from a coastal urban wetland (Avellaneda, Buenos Aires, Argentina) with the features of a humid subtropical forest and compare with hydrocarboncontribution. Soil samples were split for analysis of moisture content; texture (sieve and pipet method); organic matter as a LOI (8 h at 450 °C); total hydrocarbons (THCs; gravimetry of solvent extractable matter); n-alkanes (solvent extraction and gas chromatography-flame ionization detection analysis);and extraction of MPs (floatation in NaClaq , filtration, H2 O2 digestion, and visual sorting under a stereomicroscope). The superficial soil was a sandy clay loam with a large organic matter content (19%-30%). The THC averaged 2.5 ± 1.9 g kg and the marked predominance of odd-numbered carbon n-alkanes maximizing at C29 and C31show the contribution of the terrestrial plant waxes. The average number of MPs was 587 ± 277 items kg of dry soil, predominantly fibers. Taking account of the C content, THCs and MPs add to the soil 1.23 ± 1.10 ton C ha and 0.10-0.97 ton C ha, respectively. Therefore, inthis system with humid forest characteristics, the MPs represent between 0.12% and 1.25% of soil estimated carbon, in a magnitude similar to the C contribution of THCs (0.6%-4.2%). This preliminary study shows the relevance of discriminating MPs from other carbon sources and presents a description of their impact on soils to advance future research or tools for decision-makers. Integr Environ Assess Manag 2023;19:698-705. © 2022 SETAC.

Engineering Yarrowia lipolytica to Produce Tailored Chain-Length Fatty Acids and Their Derivatives.

Microbial production of value-added chemicals derived from fatty acids is a sustainable alternative to petroleum-derived chemicals and unsustainable lipids from animals and plants. Fatty acids with different carbon chain lengths including short- (<C6), medium- (C6-C12), long- (C14-C20), and very-long- (>C20), with either even or odd number of carbons, have significantly different characteristics and wide applications in energy, material, medicine, and nutrition. Tailoring chain-length specificity of these compounds using metabolic engineering would be of high interest. Yarrowia lipolytica, as an oleaginous yeast, is a superior industrial chassis for the production of tailored chain-length fatty acids and their derivatives due to its hyper-oil-producing capability. In this Review, we cover metabolic engineering approaches that can lead to fatty acid chain length control in this microorganism. These approaches involve the manipulation of the fatty acid synthase, the thioesterase, the β-oxidation pathway, the elongation and desaturation pathway, the polyketide synthase-like polyunsaturated fatty acid synthase pathway, and the odd-chain fatty acids synthesis pathway. Finally, we also discuss alternative strategies that can be used in the future to tailored chain-length control.

Volatilomic Signatures of AGS and SNU-1 Gastric Cancer Cell Lines

In vitro studies can help reveal the biochemical pathways underlying the origin of volatile indicators of numerous diseases. The key objective of this study is to identify the potential biomarkers of gastric cancer. For this purpose, the volatilomic signatures of two human gastric cancer cell lines, AGS (human gastric adenocarcinoma) and SNU-1 (human gastric carcinoma), and one normal gastric mucosa cell line (GES-1) were investigated. More specifically, gas chromatography mass spectrometry has been applied to pinpoint changes in cell metabolism triggered by cancer. In total, ten volatiles were found to be metabolized, and thirty-five were produced by cells under study. The volatiles consumed were mainly six aldehydes and two heterocyclics, whereas the volatiles released embraced twelve ketones, eight alcohols, six hydrocarbons, three esters, three ethers, and three aromatic compounds. The SNU-1 cell line was found to have significantly altered metabolism in comparison to normal GES-1 cells. This was manifested by the decreased production of alcohols and ketones and the upregulated emission of esters. The AGS cells exhibited the increased production of methyl ketones containing an odd number of carbons, namely 2-tridecanone, 2-pentadecanone, and 2-heptadecanone. This study provides evidence that the cancer state modifies the volatilome of human cells.

Biosynthesis of Odd-Carbon Unsaturated Fatty Dicarboxylic Acids Through Engineering the HSAF Biosynthetic Gene in Lysobacter enzymogenes.

Fatty dicarboxylic acids (FDCA) are useful as starting materials or components for plastics, polyesters, nylons, and fragrances. Most of the commercially available FDCA contain an even number of carbons, and there remain few sustainable methods for production of FDCA with an odd number of carbons (o-FDCA). In this work, we explored a novel biosynthetic route to unsaturated o-FDCA. The approach was based on genetic modifications of hsaf pks-nrps, encoding a hybrid polyketide synthase-nonribosomal peptide synthetase (PKS-NRPS) in Lysobacter enzymogenes, an environmental bacterium emerging as a new biocontrol agent. This single-module PKS-NRPS catalyzes the biosynthesis of lysobacterene A, a polyene-containing precursor of the antifungal natural product Heat-Stable Antifungal Factor (HSAF). We genetically removed the NRPS module from this gene and generated a new strain of L. enzymogenes, in which the PKS module was fused to the thioesterase domain of hsaf pks-nrps. The chimeric gene was verified by DNA sequencing, and its expression in L. enzymogenes was confirmed by reverse transcription-polymerase chain reaction (RT-PCR). The total fatty acids were extracted, esterified, and analyzed by GC-MS. The results showed that the engineered strain produced new fatty acids that were absent in the wild type. The main product was identified as hepta-2,4-dienedioic acid, an unsaturated o-FDCA. This work sets the foundation to explore a sustainable and environment-friendly approach toward unsaturated o-FDCA, which could be used as precursors for new compounds that can serve as versatile feedstock for industrial materials.

Carbon Isotope Composition and Geochemical Features of Sediments From Gongga Mountain, China, and Potential Environmental Implications

Using gas chromatography-triple quadrupole tandem mass spectrometry (GC-MS/MS), the soluble organic matter was analyzed for the first time in twenty-two sediment samples from the eastern slopes of the Gongga Mountain, China, at high altitudes between 4,600 and 6,700 m. The C11-C33n-alkanes and C9-C33n-alkan-2-ones were identified in these samples. Both compounds were dominated by odd carbon numbers in the long-chain molecules and contained a maximum of n-C27 or n-C29, indicating that the sediments were predominantly of higher plant origin. However, the short-chain n-alkan-2-ones, with a maximum content of n-C17 or i-C18 (phytone, 6, 10, 14-trimethylpentadecan-2-one), did not show a predominance of odd and even numbers, suggesting that they were predominantly derived from bacteria and algae. Therefore, we suggest that the organic matter in Gongga Mountain comes from three sources, i.e. bacteria, algae, and higher plants. Stable carbon isotope (δ13C) values ranged from −24.6‰ to −27.3‰, indicating that C3 plants were the dominant organic input to the sediments and suggesting a relatively colder and drier depositional environment. However, C4 plants increase sharply at high altitudes of 6,300–6,600 m, suggesting that the paleoclimate of Gongga Mountain became drier and wetter with the increase of altitude.

The retention of precursor biotic signatures in the organonitrogen and organooxygen compounds of immature fine-grained sedimentary rocks

To reveal the impact of biomass input (marine algae, terrestrial plants and lacustrine Botryococcus braunii) on the composition of high molecular weight organooxygen and organonitrogen compounds (Ox, Ny and NyOx), solvent extracts of immature–early mature rock and coal samples were systematically characterized by Fourier transform ion cyclotron resonance mass spectrometry using different ionization modes. In total, 16 samples from the marine Schöneck, Dynow and Posidonia formations, the lacustrine Wealden Formation and the terrestrial New Zealand coals were investigated.Coals as the in-situ deposits of terrestrial plants consist to a great degree of aromatic polyoxygenated Ox and N1Ox compounds, representing the degradation products of lignin like phenolic ketones and carboxylic acids as well as their condensation products with the degradation intermediates of labile organonitrogen compounds. Aliphatic Ox moieties derived from plant protective constituents principally waxes and cutan show a pronounced even or odd carbon number predominance of the C23–C33 species with C26, 28, 30 or C27, 29, 31 as the major homologs. In contrast, marine and lacustrine microbial communities contribute plentiful middle-chain C22, C24 or C23, C25 Ox compounds. Marine rock extracts are characterized by abundant organonitrogen compounds, especially N2 and N2Ox classes, interpreted as signatures of protein-rich marine algae that were successfully preserved via a degradation-recondensation pathway, whereas the low protein content of lacustrine Botryococcus braunii is reflected by a low amount of N1Ox and N1 classes. Highly aliphatic algaenan of Botryococcus braunii sterically protected its oxygen-bearing groups from degradation, leading to a great abundance of Ox compounds, furthermore, it characterizes the Botryococcus braunii source by substantial heteroatomic species containing more than 40 carbon atoms.

N-C27 Predominance and 13C enrichment by bicarbonate assimilation of race A of Botryococcus braunii in Chinese Maoming oilshales

In Maoming oilshales, the presence of races B and L of Botryococcus braunii (B. braunii) was confirmed by the detection of botryococcanes and C40 lycopanes and their derivatives. However, there were no specific biomarkers for race A of B. braunii. The contribution of race A of B. braunii has been implied by the distribution of non-specific n-alkanes with an odd carbon-number preference and a predominance of n-C27. However, confirmation of its contribution to oilshales has been lacking until now. We found that n-C27 is a dominant n-alkane in most Maoming samples which exhibits a positive δ13C excursion (approximately 2–3‰) compared to other homologues. In addition, the extremely heavy δ13C values of botryococcanes (−6.0‰ to −8.5‰) are rationalized to reflect bicarbonate assimilation in race B of B. braunii. The positive excursion of the δ13C values of n-C27 extracted from the same samples could be attributed to bicarbonate assimilation by race A in a similar manner. Bicarbonate assimilation by race A would also explain the isotopic enrichment of n-C14 ~ n-C33 alkanes in the range of −20.1‰ to −26.1‰. They are close to the values of some higher plant sources (C4 plant) and largely different than that of the reported algal n-alkanes (<−30.6‰). The bicarbonate consumption mechanism utilized by both races A and B of B. braunii in Maoming oilshales was triggered by the sharp decrease in pCO2 during the Late Eocene period, recorded globally at the Eocene-Oligocene transition. The presence of race A of B. braunii in most of Maoming sediments indicates that it was wide spread and populated in Maoming Basin over a long period of time, serving as the main biological source material of oilshales on a large scale.

N – alkanes in molluscs of Shatt Al-Arab river

This study comprises monitoring of the n-alkanes in the Shatt Al-Arab river by using the seven molluscs species as bioindicators. These species are: snails Lymnaea auricularia, Theodoxus jordani, Physa acuta, Melanopsis nodosa, and Melanoides tuberculata and bivalves Corbicula fluminea and Corbicula fluminalis. The species of molluscs are collected from different locations of the Shatt Al-Arab river (along the region extended from Abu Al-Khasib to Garmat-Ali) during 2004 and 2005. Each species consisted of at least 3500 adult of individuals of uniform sizes. The hydrocarbons from these species were extracted and analyzed both by spectroflurometer (total hydrocarbons) and high resolution capillary gas chromatography (n-alkanes). The concentrations of total hydrocarbons in mollusc’s species of the Shatt Al-Arab river ranged from 1.93 μg/g dry weight in T. jordani to 26.56 μg/g dry weight in C. fluminea. The range of carbon chain length of n-alkanes in these individuals was ranging from C13 - C32. The bimodal distribution with two maxima around C17 and C27 suggested two different sources of hydrocarbons both biogenic and anthropogenic. The dominance of the odd carbon numbers n-alkanes (C15, C17, C25 and C29) in the mollusc’s species indicated biogenic origin of hydrocarbons .The pristane values were more than those of phytane. Pristane and phytane in the mollusc’s species suggest biogenic origin. CPI values are more than one indicating a biogenic origin of hydrocarbons in these species. Squalane is also present in some these species intimately related to anthropogenic sources of hydrocarbons. The presence of Unresolved Complex Mixture (UCM) reflects the anthropogenic sources. The lower fat contents were found in T. jordani (0.33 mg/g) and the higher were in C. fluminea (0.98 mg/g). A significant relationship is found between the fat contents and hydrocarbons concentrations in the tissues of molluscs species (r = 0.8 - 0.9).&#x0D;

The cycloaddition reaction of ethylene and methane mediated by Ir+ to generate a half-sandwich structure IrHCp+

The cycloaddition reactions of methane and ethylene mediated by Ir+ have been designed and studied by the techniques of mass spectrometry in conjunction with theoretical calculations. Studies have shown that Ir+ can mediate the cycloaddition reaction of CH4 and two C2H4 to generate a half-sandwich structure IrHCp+ (Cp = η5-C5H5) including pentamethylcyclopentadienyl ligand by continuous dehydrogenation reaction with the forming of three C-C bonds and seven C-H bonds. The orbital analysis indicates the mechanism of the cyclization reaction to generation of pentamethylcyclopentadienyl ligand with odd number carbon atom depends on the overlap of π orbitals in -C2H2 and carbene, which is more difficult than the forming of cyclobutadiene ligand and benzene. This study may help to understand the reaction mechanism in the cycloaddition reactions of organic compounds, which will be useful to guide the rational design of new catalysts with tailored selectivity and increased efficiency.