Analysis of a C9?C10 aromatic hydrocarbon pyrolysis distillate by multidimensional capillary GC and multidimensional capillary GC-MS

This paper describes the use of multidimensional capillary gas chromatography for analysis of individual components in a C₉? C₁₀ aromatic hydrocarbon pyrolysis distillate containing substantial amounts of aromatic olefins. By coupling this GC-GC system on-line to a mass spectrometer difficulties in identifying overlapping compounds were overcome. No coelution of different types of compound was observed, but a few isomeric compounds such as methylstyrenes were poorly separated.     

吹扫/捕集-热脱附气质联用法对荷叶挥发油成分的对比分析

采用同时蒸馏萃取提取得到荷叶挥发油, 通过吹扫/捕集-热脱附法(P&T-TD)对上述提取物中挥发性成分进行富集, 以气质联用(GC/MS)进行定性检测, 同时与直接进样GC/MS法分析的成分进行比较. 两种方法成功分离分析出有机酸、酯、醛、醇、酚、烷烃、芳香烃、烯烃以及含氮、硫、氧杂原子的化合物等共计84种成分, 其中P&T-TD GC/MS鉴定出63种有机化合物, GC/MS鉴定出41种有机化合物, 有20种成分共同检出. 对比分析表明: P&T-TD GC/MS的吹扫/捕集-热脱附过程能富集各种组分, 相比GC/MS分析, 可以鉴定出微量成分及更多挥发性和半挥发性成分, 在精油等挥发性成分的分析检测中使用优势明显.     

Bromine number determination by coulometric flow-injection titration

The bromine number, the number of grams of bromine which react with 100 grams of a substance under given conditions, is a widely used parameter in the chemical and petroleum industries. A method of performing the bromine number determination by coulometric flow-injection titration, using both sequential injection with sinusoidal flow and single zone techniques, is described. Titrations of olefins, known interfering compounds, and petroleum distillates were performed and compared with the results of conventional bromine number titrations. Analyses yielded a relative standard deviation of 2%. Results compared favorably with those obtained by the conventional method for both pure (97%) olefins and petroleum distillates. The method was found to be insensitive to interference from nitrogen compounds. The CFIT technique combines the advantages of coulometric titrations: controlled generation of reagent, avoidance of reagent standardization requirements and reagent storage and stability problems; with the advantages of FIA: small volume requirements which reduce cost and waste, controllable dilution through flow programming, toxic materials contained within a closed environment, and the capability of being automated.     

Engineering Cytochrome P450BM3 Enzymes for Direct Nitration of Unsaturated Hydrocarbons

Applications of the peroxidase activity of cytochrome P450 enzymes in synthetic chemistry remain largely unexplored. We present herein a protein engineering strategy to increase cytochrome P450BM3 peroxidase activity for the direct nitration of aromatic compounds and terminal aryl-substituted olefins in the presence of a dual-functional small molecule (DFSM). Site-directed mutations of key active-site residues allowed the efficient regulation of steric effects to limit substrate access and, thus, a significant decrease in monooxygenation activity and increase in peroxidase activity. Nitration of several phenol and aniline compounds also yielded ortho- and para-nitration products with moderate-to-high total turnover numbers. Besides direct aromatic nitration by P450 variants using nitrite as a nitrating agent, we also demonstrated the use of the DFSM-facilitated P450 peroxidase system for the nitration of the vinyl group of styrene and its derivatives.     

Flow Injection Zymography - A Novel Procedure For the On-Line Detection of Enzyme Activity

Abstract

This paper describes a new method - Flow Injection Zymography - for the detection of enzyme activity during purification procedures using flow injection analysis (FIA). High sampling frequency (3 samples per minute), small sample volume requirement and a wide range of linearity (up to 70 IU) of enzyme activity was achieved. Reagent costs were minimized using the merging zones mode. the zone sampling technique for sample dilution was successfully incorporated into this system to maintain a reliable signal/response ratio. Most importantly, this new FIA method allowed on the spot identification of the active fractions.     

Application of capillary gas chromatography mass spectrometry/computer techniques to synoptic survey of organic material in bed sediment

A bed sediment sample taken from an area impacted by heavy industrial activity was analyzed for organic compounds of environmental significance. Extraction was effected on a Soxhlet apparatus using a freeze-dried sample. The Soxhlet extract was fractionated by silica gel micro-column adsorption chromatography. Separation and identification of the organic compounds was accomplished by capillary gas chromatography/mass spectrometry techniques. More than 50 compounds were identified; these include saturated hydrocarbons, olefins, aromatic hydrocarbons, alkylated polycyclic aromatic hydrocarbons, and oxygenated compounds such as aldehydes and ketones. The role of bed sediments as a source or sink for organic pollutants is discussed.     

Highly chemoselective reduction using a Rh/C-Fe(OAc)2 system: practical synthesis of functionalized indoles

Here, we report a highly effective and chemoselective method of preparing substituted indoles from (E)-2-nitropyrrolidinostyrenes via hydrogenation in the presence of a rhodium catalyst doped by additives such as Ni(NO₃)₂·6H₂O, Fe(OAc)₂ or Co(acac)₃. These hydrogenation conditions may also be applied to other substrates. Aromatic nitro compounds and olefins can be selectively reduced in the presence of aromatic benzyl ethers, aromatic halides and aromatic aldehydes.     

Alkoxybromination of Olefins Using Ammonium Bromide and Oxone

A mild, efficient, and highly regio- and stereoselective method for the methoxy and ethoxy bromination of olefins has been developed using NH₄Br as a bromine source and Oxone as an oxidant. Various kinds of olefins (aromatic, linear, and cyclic olefins) afforded the corresponding alkoxy brominated products in moderate to excellent yields.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resources: Full experimental and spectral details.]     

The amidoalkylation of aromatic compounds and olefins with 5-alkoxyhydantoins

5-Butoxyhydantoin (2a), 3-benzyl-5-methoxyhydantoin (2b) and 3-p-chlorophenyl-5-methoxy hydantoin (2c) were found to react, in the presence of an acid catalyst, with aromatic compounds and olefins to give 5-arylhydantoin (3) and 5-alkylhydantoins with an unsaturated side chain. Isomers which differ in the location of the double bond (4,5,6) as well as cis-trans isomers were isolated and characterized.     

THE [4 + 2]CYCLOADDITION REACTIONS OF AROMATIC THIONES WITH MALEIC ANHYDRIDE,NORBORNENE, AND NORBORNADIENE

Abstract

The reactions of aryl 1-naphthyl thiones and aryl 2-naphthyl thiones with maleic anhydride, norbornene, and norbornadiene gave the 1,4-cycloadducts containing 3,4-dihydro-2 H-thiopyran rings. 7H-Benz[de]anthracene-7-thione also reacted with norbornene and norbornadiene to give similar 1,4-cycloadducts. In the reaction of aryl phenyl thiones with norbornene, initially formed cycloadducts rearranged to aromatized compounds.

In these reactions, the aromatic thiones reacted with the olefins as a heterodiene system.     

Aromatic‐Amide‐Derived Olefins as a Springboard: Isomerization‐Initiated Palladium‐Catalyzed Hydrogenation of Olefins and Reductive Decarbonylation of Acyl Chlorides with Hydrosilane

A highly efficient catalytic protocol for the isomerization of substituted amide‐derived olefins is presented that successfully uses a hydride palladium catalyst system generated from [PdCl₂(PPh₃)₂] and HSi(OEt)₃. The Z to E isomerization was carried out smoothly and resulted in geometrically pure substituted olefins. Apart from the cis–trans isomerization of double bonds, the selective reduction of terminal olefins and activated alkenes was performed with excellent functional group tolerance in the presence of an amide‐derived olefin ligand, and the products were obtained in high isolated yields (up to >99 %). Furthermore, the palladium/hydrosilane system was able to promote the reductive decarbonylation of benzoyl chloride when a (Z)‐olefin with an aromatic amide moiety was used as a ligand.     

Polyphenolic profile by FIA/ESI/IT/MSn and antioxidant capacity of the ethanolic extract from the barks of Maytenus cajalbanica (Borhidi & O. Muñiz) Borhidi & O. Muñiz

Abstract

Medium and high polarity extracts from Maytenus species are known to contain polyphenolic compounds such as proanthocyanidins. The high polarity and structural complexity of these compounds make very difficult their isolation even by modern chromatographic techniques. Maytenus cajalbanica (Borhidi & O. Muñiz) Borhidi & O. Muñiz is endemic from Cuba. So far, there are reports neither of phytochemical work nor of biological evaluation of extracts from this subspecies. The goal of this work is to determine the polyphenolic profile and the antioxidant capacity of the ethanolic extract from the barks of Maytenus cajalbanica. FIA/ESI/IT/MSⁿ analysis allowed the identification of 5 flavan-3-ol monomers, 33 proanthocyanidins, 2 free flavonoids and their respective glycosides as major compounds of the ethanolic extract, which showed a strong radical scavenging capacity and a significant ferric reduction power. FIA/ESI/IT/MSⁿ technique led the rapid, effective and sensitive determination of the polyphenolic profile of Maytenus cajalbanica without previous separation.     

Estimation of unsaturated hydrocarbon pollutants in air based on selective gas chromatography with ozone

Regular monitoring of toxic organic pollutants in air is a very important issue in environmental pollution control. Among these, unsaturated hydrocarbon pollutants (UHP) such as ethylene and beta-propylene and another 18 olefins are of prime importance. A very fast method for the individual identification of UHPs in air is proposed. This method is based on gas-chromatographic separation with selective detection of unsaturated organic compounds (UOC) and on the chemical reaction of UOC with ozone in the gas phase. In view of the mathematical model derived for this ozonation process, a comparison of FID-chromatogram and ozonogram can be carried out for identification of the contaminants. This identification can be performed without preliminary separation in the presence of the main components. The method provides a high sensitivity (< 0.005 to 0.72 mass %) and selectivity.     

Synergetic effects in the co-pyrolysis of samca coal and a model aliphatic compound studied by analytical pyrolysis

Pyrolysis is claimed as an alternative method to improve the quality of the products obtained from materials of a hydrocarbon nature such as coal and residues from petroleum distillation. Appearance of synergy in the production of light olefins and aromatic compounds during the co-pyrolysis of coal and petroleum residues has been previously stated. The aliphatic fraction of the petroleum residue (PR) previously studied, might play an important role in the occurrence of the synergy in coal/PR co-pyrolysis reactions. For that reason, different mixtures of Samca coal and a model aliphatic compound (C₅₀), have been co-pyrolysed at 900 °C and atmospheric pressure in a Pyroprobe 1000 CDS. Three different weight ratios coal/PR (70:30, 50:50, 40:60) were studied. Important synergetic effects were observed for the production of light olefins, specially ethylene, after the co-pyrolysis of the three mixtures, but the most intense effects appeared for the 50:50 one. Synergy in the evolution of small aromatic compounds was also observed when 70:30 mixtures were pyrolysed, but the synergy for these compounds disappeared when the ratio of pentacontane in the mixture was increased. These effects are similar to those observed when mixtures of Samca coal and PR were co-pyrolysed in the same experimental conditions, and so that, it can be concluded that the aliphatic fraction of PR is the one that leads the mechanism of the co-pyrolysis process.     

An international round-robin study for the analysis of particulate semi-volatile organics by thermal desorption gas chromatography mass spectrometry

Thermal desorption gas chromatography mass spectrometry (TD-GC/MS) is becoming more commonly used for the quantification and identification of organic compounds in particulate matter (PM), including ambient and source PM such as diesel particulate matter (DPM). It has been proven as an alternative to the traditional solvent extraction (SE) method and liquid injection gas chromatograph mass spectrometry (LI-GC/MS). However, little information is available on how different types of TD-GC/MS systems compare to each other for analysis of real-world PM samples or to direct LI-GC/MS for analysis of PM components in a test solution. To address this, CanmetENERGY Characterization Laboratory initiated a round robin with the participation of 10 laboratories worldwide. Three sample types were analysed: (i) a test solution with a suite of pure compounds commonly found in PM, analysed by TD-GC/MS and LI-GC/MS; (ii) a DPM sample, analysed by TD-GC/MS and SE; and (iii) an ambient PM sample, analysed by TD-GC/MS. The first part of the study showed good overall performance and comparability between the different TD-GC/MS systems and LI-GC/MS method for the analysis of PM components in a test solution, with some variability of results due to system types and parameters used, concentration of calibration standards, and whether or not an internal standards was used. The analysis of the DPM sample showed greater variability between laboratories and methods as many PM components were present near the detection limit and matrix effects particularly affected the TD-GC/MS analysis of heavier n-alkanes. In the last part of the study, for the analysis of an ambient PM sample by TD-GC/MS, the analysis of variance showed good comparison between labs for polycyclic aromatic hydrocarbons (94% non-significant), but slightly lower for n-alkanes (68%) and biomarkers (57%).     

Metallophthalocyanine catalyzed olefination of aldehydes

The Wittig reaction to synthesize olefins is a very attractive method in organic synthesis. Recently, this methodology has been achieved utilizing simple metal catalysts and diazo compounds in addition to a phosphine and an aldehyde. The following work investigates the use of a variety of metallophthalocyanines (MPc’s) to catalyze Wittig-like reactions from ethyldiazoacetate. We also examine the influence of substitution on the aromatic ring of the aldehyde as well as various phosphines, arsines and antimony complexes. We have been able to exclusively synthesize the trans-olefins in excellent yields in short periods of time (1?h).     

Selective hydrogenation of aromatic compounds using modified iridium nanoparticles

Till now, Ionic liquid‐stabilized metal nanoparticles were investigated as catalytic materials, mostly in the hydrogenation of simple substrates like olefins or arenes. The adjustable hydrogenation products of aromatic compounds, including quinoline and relevant compounds, aromatic nitro compounds, aromatic ketones as well as aromatic aldehydes, are always of special interest, since they provide more choices for additional derivatization. Iridium nanoparticles (Ir NPs) were synthesized by the H₂ reduction in imidazolium ionic liquid. TEM indicated that the Ir NPs is worm‐like shape with the diameter around 12.2 nm and IR confirmed the modification of phosphine‐functionalized ionic liquids (PFILs) to the Ir NPs. With the variation of the modifier, solvent and reaction temperature, substrate like quinoline and relevant compounds, aromatic nitro compounds, aromatic ketones as well as aromatic aldehydes could be hydrogenated by Ir NPs with interesting adjustable catalytic activity and chemoselectivity. Ir NPs modified by PFILs are simple and efficient catalysts in challenging chemoselective hydrogenation of quinoline and relevant compounds, aromatic nitro compounds, aromatic ketones as well as aromatic aldehydes. The activity and chemoselectivity of the Ir NPs could be obviously impacted or adjusted by altering the modifier, solvent and reaction temperature.     

Advanced Methodologies for Adsorption/Thermal Desorption with Tenax-TA for the Analysis of Polycyclic Aromatic Hydrocarbons and Sulfur Compounds

We have evaluated an analytical method for the determination of polycyclic aromatic hydrocarbons (PAHs) and sulfur compounds in air by means of adsorption/temperature-programmed thermal desorption (ATPTD) with small bed volume (0.08g) Tenax-TA cartridges, followed by a cryogenic trap in a precolumn with liquid nitrogen as an appropriate concentration method before capillary gas chromatography is described. The enriched components from the adsorption cartridges are transferred to the capillary column with a valveless switching system. Recoveries were determined for the complete ATPTD method. Desorption recoveries near 100% were found for various of polycyclic aromatic hydrocarbons and sulfur compounds. The sulfur compounds known to cause nuisance odors in the atmosphere near sulfur recovery and sewerage treatment works were also determined.     

Direct and automatic capillary GC analysis for molecular weight determination and distribution in crude oils and condensates up to C20

A direct and automatic method has been developed for molecular weight (MW) determination and distribution in crude oils and condensates up to C₂₀ (340°C) by gas chromatography. Chromatographic separation has been achieved with a 50 m OV-1 fused silica capillary column, fitted with a pre-column to eliminate the fraction boiling above 340°C. The internal standard is added for quantification. Approximately 550 peaks have been identified by the use of GC/MS on different paraffinic, naphthenic, and aromatic crude oils or condensate samples. From identification and by correlation with MS group-type analysis, a carbon number and a hydrocarbon group are attributed to each peak or group of peaks. Further molecular weights have been calculated from these groups. A comparison between results from this GC method and cryometry of narrow and wide fractions shows good agreement, within the precision of cryometry. An automatic identification by computer using programmed temperature indices was used for the direct determination of molecular weight. The final report gives weight percentage, molar percentage, and molecular weight for every boiling range group and hydrocarbon group.     

Chemiluminescence Flow-Injection System for Rapid Detection of Red Tide Phytoplankton

Abstract

A chemiluminescent flow-injection analysis (FIA) system for the detection of the red tide phytoplankton Chattonella antiqua has been developed based on a Cypridina luciferin analog, 2-methyl-6-(p-methoxyphenyl)-3,7-dihydroimidazo[1, 2-α]-pyrazin-3-one (MCLA), which strongly emits light at 465 nm in the presence of superoxide. The system consisted of a two reagent feeding stream, a sample injector, a joint for mixing MCLA and sample, a chemiluminescence (CL) reaction cell, a CL detector and a recorder unit. The response time is approximately 1 min for one measurement cycle. The FIA system has an optimum pH of 10.7. The calibration curves for C. antiqua displayed linearity from 2 × 10³ to 2 × 10⁴ cells ml^?1. When applied to the measurement of C. antiqua, the sensitivity obtained using the FIA system is approximately 10 times higher than that of the cytochrome c method. The FIA system is a rapid practical method for the detection of C. antiqua.