Simultaneous determination of carbonyl compounds and polycyclic aromatic hydrocarbons in atmospheric particulate matter by liquid chromatography-diode array detection-fluorescence detection

Simultaneous analysis of 24 carbonyl compounds (alkanals, unsaturated, dicarbonylic and aromatic aldehydes and ketones) derivatized with 2,4-dinitrophenylhydrazine and 16 polycyclic aromatic hydrocarbons (PAHs) using a photodiode-array (PDA) and a fluorescence (FL) detector in series is proposed.The separation is carried out with a reversed-phase column and gradient elution using four solvents (acetonitrile, water, tetrahydrofuran and methanol) in less than 35 min. Several critical pairs of carbonyl compounds with 3 and 4 carbon atoms and different functional groups, isomers of tolualdehyde, aromatic and aliphatic aldehydes were conditional on the gradient elution. Common pre-treatment for two groups of compounds consists in a step of extraction and derivatization in aqueous medium and a further clean-up using a polymeric phase SPE and concentration in a mixture of dichloromethane:methanol. A pre-concentration factor of 50 was achieved by this procedure. Acetone and formaldehyde blanks were minimized and remain controlled with a specific cleaning of glass material and washing the SPE cartridge.The limits of detection (LOD) ranged from 0.006 to 0.18 ng mL⁻¹ for PAHs and from 2.4 to 10.1 ng mL⁻¹ for carbonyl compounds and method precision was ≤15% for all analysed compounds. Recoveries were within the range of 95-104% for PAHs except for more volatile compounds (acenaphthene and fluorene) and within the range of 72-113% for carbonyl compounds. The method was applied in water-soluble fraction of PM₁₀ (atmospheric particulate matter with an aerodynamic diameter less than 10 μm) and the spectral contrast technique was used in the identification of carbonyl compounds.     

Selective preparation of 1-substituted 2,2-difluoroethenyl phosphates or 1-hydroxyalkanephosphonates through the reaction of chlorodifluoromethyl ketones with dialkyl or diaryl phosphites

Various chlorodifluoromethyl ketones react readily with dialkyl or diaryl phosphites in the presence of triethylamine at the reflux temperature of tetrahydrofuran to give the corresponding dialkyl or diaryl 1-substituted-2,2-difluoroethenyl phosphates in good yields, whereas the similar reaction conducted at lower temperature (0-20 °C) affords 1-(chlorodifluoromethyl)-1-hydroxyalkanephosphonates almost exclusively. The latter compounds are converted to the former enol phosphates by the treatment with triethylamine or sodium methoxide in refluxing tetrahydrofuran.     

Trifluoromethylation of carbonyl compounds with sodium trifluoroacetate

In the presence of copper(I) iodide as catalyst, a variety of carbonyl compounds, such as aldehydes, ketones and acid anhydrous, could be trifluoromethylated with sodium trifluoroacetate to give the corresponding alcohols in moderate to high yields, and a possible mechanism was proposed to explain the roles of catalyst and solvent in the reaction system.     

Reductive Amination of Aldehydes and Ketones with Sodium Triacetoxyborohydride. Studies on Direct and Indirect Reductive Amination Procedures(1)

Sodium triacetoxyborohydride is presented as a general reducing agent for the reductive amination of aldehydes and ketones. Procedures for using this mild and selective reagent have been developed for a wide variety of substrates. The scope of the reaction includes aliphatic acyclic and cyclic ketones, aliphatic and aromatic aldehydes, and primary and secondary amines including a variety of weakly basic and nonbasic amines. Limitations include reactions with aromatic and unsaturated ketones and some sterically hindered ketones and amines. 1,2-Dichloroethane (DCE) is the preferred reaction solvent, but reactions can also be carried out in tetrahydrofuran (THF) and occasionally in acetonitrile. Acetic acid may be used as catalyst with ketone reactions, but it is generally not needed with aldehydes. The procedure is carried out effectively in the presence of acid sensitive functional groups such as acetals and ketals; it can also be carried out in the presence of reducible functional groups such as C-C multiple bonds and cyano and nitro groups. Reactions are generally faster in DCE than in THF, and in both solvents, reactions are faster in the presence of AcOH. In comparison with other reductive amination procedures such as NaBH(3)CN/MeOH, borane-pyridine, and catalytic hydrogenation, NaBH(OAc)(3) gave consistently higher yields and fewer side products. In the reductive amination of some aldehydes with primary amines where dialkylation is a problem we adopted a stepwise procedure involving imine formation in MeOH followed by reduction with NaBH(4).     

Trends in structure–toxicity relationships for carbonyl-containing α,β-unsaturated compounds

Using toxicity data for 30 aliphatic polarized α,β-unsaturated derivatives of esters, aldehydes, and ketones, a series of six structure–toxicity relationships were evaluated. The structure feature of all assessed compounds, an acetylenic or olefinic moiety conjugated to a carbonyl group, is inherently electrophilic and conveys the capacity to exhibit enhanced toxicity. However, the toxic potency of α,β-unsaturated carbonyl compounds is dependent on the specific molecular structure with several trends being observed. Specific observations include: (1) between homologues, the acetylenic-substituted derivative was more toxic than the corresponding olefinic-substituted one, respectively; (2) between olefinic-homologues, terminal vinyl-substituted derivative was more toxic than the internal vinylene-substituted one; (3) within α,β-unsaturated ketones, methyl substitution on the vinyl carbon atoms reduces toxicity with methyl-substitution on the carbon atom farthest from the carbonyl group exhibiting the greater inhibition; (4) between α,β-unsaturated carbonyl compounds with the carbon–carbon double bond on the end of the molecule (vinyl ketones) and those with carbon–oxygen double bonds on the end of the molecule (aldehydes), the ketones are more toxic than the aldehydes; (5) between homologues of α,β-unsaturated esters, those with additional unsaturated moieties (allyl, propargyl, or vinyl groups) were more toxic than homologues having relevant unsaturated moieties (propyl or ethyl groups); (6) between α,β-unsaturated carbonyl compounds with different shaped alkyl-groups (i.e. different degrees of branching), homologues with straight-chain hydrocarbon moieties were more toxic than those with branched groups.     

Trends in structure-toxicity relationships for carbonyl-containing alpha,beta-unsaturated compounds

Using toxicity data for 30 aliphatic polarized alpha,beta-unsaturated derivatives of esters, aldehydes, and ketones, a series of six structure-toxicity relationships were evaluated. The structure feature of all assessed compounds, an acetylenic or olefinic moiety conjugated to a carbonyl group, is inherently electrophilic and conveys the capacity to exhibit enhanced toxicity. However, the toxic potency of alpha,beta-unsaturated carbonyl compounds is dependent on the specific molecular structure with several trends being observed. Specific observations include: (1) between homologues, the acetylenic-substituted derivative was more toxic than the corresponding olefinic-substituted one, respectively; (2) between olefinic-homologues, terminal vinyl-substituted derivative was more toxic than the internal vinylene-substituted one; (3) within alpha,beta-unsaturated ketones, methyl substitution on the vinyl carbon atoms reduces toxicity with methyl-substitution on the carbon atom farthest from the carbonyl group exhibiting the greater inhibition; (4) between alpha,beta-unsaturated carbonyl compounds with the carbon-carbon double bond on the end of the molecule (vinyl ketones) and those with carbon-oxygen double bonds on the end of the molecule (aldehydes), the ketones are more toxic than the aldehydes; (5) between homologues of alpha,beta-unsaturated esters, those with additional unsaturated moieties (allyl, propargyl, or vinyl groups) were more toxic than homologues having relevant unsaturated moieties (propyl or ethyl groups); (6) between alpha,beta-unsaturated carbonyl compounds with different shaped alkyl-groups (i.e. different degrees of branching), homologues with straight-chain hydrocarbon moieties were more toxic than those with branched groups.     

Titanium Tetrachloride in Organic Synthesis [New synthetic methods (21)]

Titanium tetrachloride can accelerate numerous organic reactions. Valuable syntheses of, e.g., allyl sulfides, amides, enamines, and ketones are based upon transformations of functional groups with TiCl₄. Particular mention should also be made of carbon-carbon linkage with TiCl₄ which permits the synthesis of hydroxy ketones and carbonyl compounds of the Michael adduct type. TiCl₄ reduced in situ is suitable for the reduction of chloroarenes or the linkage of two aldehyde molecules to give an alkene.     

Chemical profile and biological potential of non-polar fractions from Centroceras clavulatum (C. Agardh) Montagne (Ceramiales, Rhodophyta)

The present study reports the Gas Chromatography-Mass Spectrometry (GC-MS) evaluation of the hexanes and dichloromethane fractions from extracts of the red alga Centroceras clavulatum (C. Agardh) Montagne. Twenty three compounds were identified, totaling ca. 42% of both fractions (0.18 g mass extract). The main constituents of the fractions were hexadecanoic acid (17.6%) and pentadecanoic acid (15.9%). Several secondary metabolites with interesting biological activity, such as (-)-loliolide, neophytadiene, phytol were identified. In addition, several classes of secondary metabolites, including phenolic compounds (e.g., phenylacetic acid), terpene derivatives, fatty acids, halogenated compound (e.g., 2-chlorocyclohexenol), lignoids, steroids, esters, amides (e.g., hexadecanamide), ketones, carboxylic acids, aldehydes and alcohols were observed. The occurrence of several of these structural classes is described for the first time in this species. The same fractions analyzed by GC-MS, and a separate set of polar fractions, were evaluated against two life cycle stages (epimastigote and trypomastigote forms) of the protozoan Trypanosoma cruzi and against phytopatogenic fungi Cladosporium cladosporiodes and C. sphaerospermum. The dichloromethane fraction was active against both T. cruzi forms (epimastigote IC(50) = 19.1 μg.mL-1 and trypomastigote IC(50) = 76.2 μg.mL-1). The hexanes and ethyl acetate fractions also displayed activity against both fungi species (200 μg) by TLC-bioautography.     

A Simple Synthesis of Oximes

Summary. The conversion of alicyclic and aliphatic carbonyl compounds as well as aromatic aldehydes into the corresponding oximes (up to quantitative yields) was achieved by simply grinding these reactants, hydroxylamine hydrochloride and sodium hydroxide without solvent. However, this procedure was unsuccessful in the case of aromatic ketones. In this case it was necessary to add silica gel as a catalyst.     

Sample preparation of atmospheric aerosol for the determination of carbonyl compounds

Sample preparation including sonication and solid phase extraction has been developed for the determination of carbonyl compounds in atmospheric aerosol. Aerosol samples were sonicated in acidified acetonitrile containing 2,4-dinitrophenylhydrazine (DNPH) to form hydrazone derivatives of aldehydes and ketones. Water was added to the extract to increase its polarity. Then the solution was passed through an octadecyl or phenyl solid phase extraction cartridge. The concentrated hydrazone derivatives were eluted with tetrahydrofuran, the eluate was evaporated to dryness then dissolved in acetonitrile/water mixture and finally analysed by RP-HPLC with UV detection at 360 nm. The absolute detection limits of the individual carbonyl compounds range from 0.4 to 5.8 ng.     

Reductive Deoxygenation of Carbonyl to Methylene

The reductive deoxygenation of aldehydes and ketones into the corresponding alkanes is accomplished by LiAlH4, in the presence of Lewis acid InBr3. It provides a convenient method to complete the transformation from carbonyl compounds to alkanes.     

Cyanosilylation of Prochiral Ketones Catalyzed by Lanthanide Complexes

A new series of silylene‐bridged rare‐earth complexes involving fluorenyl are shown to be the very efficient Lewis acid catalysts, giving some cyano trimethylsilyl ethers of ketones in >99% yields.     

Esters of 2-iodoxybenzoic acid: hypervalent iodine oxidizing reagents with a pseudobenziodoxole structure

Esters of 2-iodoxybenzoic acid (IBX-esters) were prepared by the hypochlorite oxidation of the corresponding 2-iodobenzoate esters and isolated as chemically stable, microcrystalline products. These hypervalent iodine compounds are potentially valuable oxidizing reagents belonging to a new class of pentavalent iodine compounds with a pseudobenziodoxole structure. Methyl 2-iodoxybenzoate can be further converted to the diacetate or a bis(trifluoroacetate) derivative by treatment with acetic anhydride or trifluoroacetic anhydride, respectively. Single-crystal X-ray diffraction analysis of methyl 2-[(diacetoxy)iodosyl]benzoate 8a reveals a pseudobenziodoxole structure with three relatively weak intramolecular I...O interactions. The dimethyl and diisopropyl esters of 2-iodoxyisophthalic acid were prepared by oxidation of the respective iodoarenes with dimethyldioxirane. Single-crystal X-ray diffraction analysis of diisopropyl 2-iodoxyisophthalate 6b showed intramolecular I...O interaction with the carbonyl oxygen of only one of the two carboxylic groups, while NMR spectra in solution indicated equivalency of both ester groups. IBX-esters, methyl 2-[(diacetoxy)iodosyl]benzoate, and 2-iodoxyisophthalate esters can oxidize alcohols to the respective aldehydes or ketones in the presence of trifluoroacetic acid or boron trifluoride etherate. The bis(trifluoroacetate) derivative can oxidize alcohols to carbonyl compounds without acid catalyst.     

Chiroptical spectroscopy of surfactants

Three different chiroptical spectroscopic methods, namely, optical rotation, electronic circular dichroism (ECD), and vibrational circular dichroism (VCD) have been evaluated for studying the aggregation of sodium dodecylsulfate (SDS), an achiral surfactant, using garcinia acid disodium salt (GADNa) as a chiral probe. The specific rotation and ECD of GADNa are found to be altered by the aggregation of SDS, suggesting for the first time that achiral surfactants can be characterized with chiroptical spectroscopy using appropriate chiral probes. In addition, a chiral compound, fluorenyl methyloxy carbonyl l-leucine sodium salt (FLNa) is found for the first time to behave as a surfactant in water, with 205 ?(2) surface area per molecule at the air-water interface, critical micelle concentration (CMC) of 0.18 M, and Gibbs energy of micellization of -14 kJ/mol. The specific rotation of FLNa in water is found to increase with concentration beyond CMC, suggesting the formation of chiral aggregates. Different conformations of FLNa amenable to micellization have been identified using quantum chemical conformational analysis and their specific rotations calculated. The formation of lamellar aggregates of FLNa in water is suggested to be the cause for increase in specific rotation with concentration beyond CMC.     

Micellar electrokinetic capillary chromatography as a powerful tool for pharmacological investigations without sample pretreatment: a precise technique providing cost advantages and limits of detection to the low nanomolar range.

A number of pharmaceuticals (e.g., acetaminophen, salicylic acid, sulfamethoxazole, theophylline, tolbutamide and trimethoprim) have been determined in human plasma by micellar electrokinetic chromatography (MEKC), without sample pretreatment, using underivatized fused-silica capillaries. The total analysis time was only 10 min. A sodium dodecyl sulfate (SDS)-containing borate buffer (60 mM with 200 mM SDS) at pH 10 was used. Between runs, proteins adsorbed to the capillary wall are removed by rinsing with SDS buffer and either acetonitrile (e.g., 50% v/v) or isopropanol (e.g., 10% v/v). Other rinsing procedures are discussed (salts, enzyme-containing solutions, organic solvents, sodium hydroxide, hydrofluoric acid). The separation system is tested in a concentration range between 10 ng/mL and 100 microg/mL; a detection limit of about 20 ng/mL can readily be obtained. The sensitivity was substantially improved using isopropanol as buffer additive. A day-to-day precision for relative peak areas of 1-2% relative standard deviation (RSD, n > 40) was reached in the upper concentration range. Under repeatability conditions, these values could also be obtained for low microg/mL concentrations. Thus, not only drug monitoring but also pharmacokinetic investigations from blood plasma become possible without further sample pretreatment.     

Determination of short-chain carbonyl compounds in drinking water matrices by bar adsorptive micro-extraction (BAμE) with in situ derivatization

In this contribution, bar adsorptive micro-extraction using polystyrene-divinylbenzene sorbent phase and in situ derivatization with pentafluorophenyl hydrazine, followed by liquid desorption and high-performance liquid chromatography-diode array detection (BAμE(PS-DVB)(PFPH in situ)-LD/HPLC-DAD), was developed for the determination of six short-chain carbonyl compounds (formaldehyde, acetaldehyde, propanal, acetone, butanone, and 2-hexenal) in drinking water matrices. PFPH presented very good specificity as an in situ derivatization agent for short-chain ketones and aldehydes in aqueous media, allowing the formation of adducts with remarkable sensitivity, selectivity and the absence of photodegradation. Assays performed on 30-mL water samples spiked at the 25.0 μg L(-1) levels, under optimized experimental conditions, yielded recoveries ranging from 47.4 ± 3.8% to 85.2 ± 3.8%, in which the PS-DVB proved to be a convenient sorbent phase. The analytical performance showed good accuracy, suitable precision (RSD < 13.0%), detection limits in between 47 and 132 ng L(-1) and remarkable linear dynamic ranges (r(2) > 0.9907) from 1.0 to 80.0 μg L(-1). By using the standard addition methodology, the application of the present method to drinking water samples treated with different disinfectants, namely, chloride, ozone and both, allowed very good performances to monitor these priority compounds at the trace level. The proposed methodology proved to be a feasible alternative for polar compound analysis, showing to be easy to implement, reliable, sensitive and requiring a low sample volume to monitor short-chain aldehydes and ketones in drinking water matrices.     

Moisture induced solid phase degradation of l-ascorbic acid part 3, structural characterisation of the degradation products

The influence of moisture on the solid phase degradation of l-ascorbic acid and the chemical characteristics of the degradation products have been investigated previously [Shephard et al. (1998) (in press)]. Moisture induced degradation in the solid phase leads to severe discolouration. This paper describes the isolation of the compounds responsible for the discolouration and their partial chemical identification. Eight different degradation compounds were found to be present in a severely discoloured sample [Shepherd et al. (1998) (in press)]. Three of the compounds were present at levels above 1% of the total chromatography peak area with the major degradation peak present at 29% in a sample with 5% v/w moisture present when stored at 60 degrees C for 42 days. The major impurity was isolated and was found to exhibit a lambda(max) at 280 nm with further absorbance to 600 nm. This material was pyrolysed at 300, 500, and 600 degrees C. Amongst the volatile pyrolysates tentatively identified were furfural, 2-furancarboxylic acid, 1-(2-furanyl)-ethanone, tetrahydrofuran and 1-(2-furanyl)-1-propanone along with some aromatic compounds such as benzene and phenol. The periodate consumption of the major impurity was examined and the products of the reaction investigated. Estimation of hydroxyl and carbonyl group content by acetyl group determination of the acetate and reduced acetate showed that for every five repeating units there was one hydroxyl group and for every four repeating units there was one carbonyl group. Elemental analysis gave 46.26% carbon, 5.42% hydrogen and 48.32% oxygen giving an empirical formula of CH(2)O.     

Ionene-Bound Borohydrides: Efficient, Selective, and Versatile Polymer-Supported Reducing Agents

Summary. Reduction of structurally different carbonyl compounds, such as aldehydes, ketones, α,β-unsaturated enals and enones, acid chlorides, and imines was accomplished efficiently using high capacity ionene based borohydride reagents. Aldehydes and imines were reduced to the corresponding alcohols and amines in excellent yields in methanol at ambient temperature while ketones and acid chlorides were reduced in iso-propanol and THF-MeOH at reflux. Chemoselective reduction of aldehydes over ketones was achieved successfully with these reagents. Complete regioselectivity was also observed in the reduction of α,β-unsaturated aldehydes and ketones.     

An optimized method for the determination of volatile and semi-volatile aldehydes and ketones in ambient particulate matter

A method has been developed to measure aldehydes and ketones associated with atmospheric particles. Carbonyl compounds from particulate material collected on Teflon-coated glass-fiber filters were simultaneously extracted and derivatized with an appropriate 2,4-dinitrophenylhydrazine (2,4-DNPH) solution. The efficiency of this procedure utilizing various 2,4-DNPH concentrations and solvent compositions was studied for 13 carbonyl compounds of atmospheric importance. These include formaldehyde, acetaldehyde, acetone, dicarbonyls such as glyoxal and methylglyoxal, and biogenic carbonyls such as pinonaldehyde and nopinone. An extraction solution containing 3 × 10^?2 M 2,4-DNPH, in 60% acetonitrile/40% water, and pH 3 was most efficient in extracting and derivatizing these aldehydes and ketones (83-100% recovery). Improved sample enrichment and 2,4-DNPH purification methods were developed that afforded detection limits of 0.009-5.6 ng m^?3. The relative standard deviation for replicate analyses were 1.9-10.1%. Carbonyl compounds in ambient particulate samples were quantified during a recent field study. Median values for nine carbonyl species ranged from 0.01-33.9 ng m^?3 during the study.     

Die Aminoalkylierung von Carbonylverbindungen mit Hilfe der Wittig-Reaktion

The Aminoalkylation of Carbonyl Compounds by the Wittig-Reaction The Wittig reaction would be a very suitable way to replace the carbonyl group in aldehydes and ketones by a 2-amino-ethylidene group if a simple and convenient method could be devised for synthesizing (2-amino-ethyl)triphenylphosphonium bromides 3 . We have synthesized compounds of type like (2-dialkylaminoethyl)-, (2-morpholino-ethyl)-, (2-(1-imidazolyl)ethyl)-, and (2-(1-triazolyl)ethyl)-triphenylphosphonium bromides (cf. Table 1), by melting at 150° the hydrobromides of triphenylphosphine and of the appropriate 2-amino-ethanol. The phosphonium bromides of type 3 could be converted with ketones by the Wittig reaction into the desired amino-ethylidene compounds of type 2 , e.g. 18 – 22 (Table 2). In the case of the reaction with 4-chlorobenzaldehyde the steric course of the transformation was studied, and conditions were found favoring either cis or trans compounds (e.g. 27a or 27b in the reaction of the phosphonium bromide 11 , cf. Table 3).