Diacid Compounds Research Articles

Characterization of chemical components of fresh and aged aerosol from vehicle exhaust emissions in Hong Kong

The chemical properties of fresh and aged aerosol emitted during controlled vehicular exhaust emissions were characterized in the analysis. Pyrene (10417.1 ± 534.9 ng kg−1) is the most abundant of all analyzed compounds in total fresh emission and succinic acid (57359.8 ± 4000.3 ng kg−1) is for the total aged emission. The fresh emission factors (EFfresh) of all compounds in the n-alkanes group demonstrate higher average emissions for the two vehicles with EURO 3 standard compared to the other vehicles. The EFfresh for benzo [a]pyrene is in descending order: G1 (183.1 ± 144.7 ng kg−1) > G3 (103.4 ± 60.1 ng kg−1) > G4 (91.2 ± 80.1 ng kg−1) > G2 (88.6 ± 93.9 ng kg−1). Aged/fresh (A/F) emission ratios (>20) confirmed that these diacid compounds are generated by the photooxidation of primary pollutants that emitted from gasoline combustions. High A/F ratios (>200) in phthalic acid, isophthalic acid and terephthalic acid under idling mode imply relatively more intense photochemical reactions for their productions compared with other chemical groups. Strong positive correlations (r > 0.6) were observed between the degradation of toluene and formations of pinonic acid, succinic acid, adipic acid, terephthalic acid, glutaric acid and citramalic acid after the aging process, suggesting possible photooxidation of toluene that can lead to secondary organic aerosol (SOA) formation in the urban atmosphere. The findings demonstrate that vehicle emission standards for pollution in relation to the change of particulate matter chemical compositions and SOA formations. The results warrant a need for regulated reformulation for such vehicles.

Metal removal capability of two cyanobacterial species in autotrophic and mixotrophic mode of nutrition

BackgroundCyanobacteria are ecologically significant prokaryotes that can be found in heavy metals contaminated environments. As their photosynthetic machinery imposes high demands for metals, homeostasis of these micronutrients has been extensively considered in cyanobacteria. Recently, most studies have been focused on different habitats using microalgae leads to a remarkable reduction of an array of organic and inorganic nutrients, but what takes place in the extracellular environment when cells are exposed to external supplementation with heavy metals remains largely unknown.MethodsHere, extracellular polymeric substances (EPS) production in strains Nostoc sp. N27P72 and Nostoc sp. FB71 was isolated from different habitats and thenthe results were compared and reported.ResultCultures of both strains, supplemented separately with either glucose, sucrose, lactose, or maltose showed that production of EPS and cell dry weight were boosted by maltose supplementation. The production of EPS (9.1 ± 0.05 μg/ml) and increase in cell dry weight (1.01 ± 0.06 g/l) were comparatively high in Nostoc sp. N27P72 which was isolated from lime stones.The cultures were evaluated for their ability to remove Cu (II), Cr (III), and Ni (II) in culture media with and without maltose. The crude EPS showed metal adsorption capacity assuming the order Ni (II) > Cu (II) > Cr (III) from the metal-binding experiments.Nickel was preferentially biosorbed with a maximal uptake of 188.8 ± 0.14 mg (g cell dry wt) −1 crude EPS. We found that using maltose as a carbon source can increase the production of EPS, protein, and carbohydrates content and it could be a significant reason for the high ability of metal absorbance. FT-IR spectroscopy revealed that the treatment with Ni can change the functional groups and glycoside linkages in both strains. Results of Gas Chromatography-Mass Spectrometry (GC–MS) were used to determine the biochemical composition of Nostoc sp. N27P72, showed that strong Ni (II) removal capability could be associated with the high silicon containing heterocyclic compound and aromatic diacid compounds content.ConclusionThe results of this studyindicatede that strains Nostoc sp. N27P72 can be a good candidate for the commercial production of EPS and might be utilized in bioremediation field as an alternative to synthetic and abiotic flocculants.

Weak Interactions and Conformational Changes in Core-Protonated A2- and Ax-Type Porphyrin Dications.

Individual chemical motifs are known to introduce structural distortions to the porphyrin macrocycle, be it in the core or at the periphery of the macrocycle. The interplay when introducing two or more of these known structural motifs has been scarcely explored and is not necessarily simply additive; these structural distortions have a chance to compound or negate to introduce new structural types. To this end, a series of compounds with complementary peripheral (5,15-disubstitution) and core (acidification) substitution patterns were investigated. The single-crystal X-ray structures of 18 5,15-diphenylporphyrin, 5,15-diphenylporphyrindi-ium diacid, and related compounds are reported, including the first example of a 5,15-dialkylporphyrindi-ium. Normal-coordinate structural decomposition (NSD) analysis is used for a detailed analysis of the conformation of the porphyrin subunit within the crystal structures. An elongation of porphyrin macrocycles along the C5,C15- axis (B2g symmetry) is observed in all of the free base porphyrins and porphyrin dications; distance across the core is around 0.3 Å in the free base and diacid compounds, and more than doubled in 5,15-dipentylporphyrin and 5,15-dipentylporphyrindi-ium diacid. While the free base porphyrins are largely planar, a large out-of-plane distortion can be observed in 5,15-diphenylporphyrin diacids, with the expected “projective saddle” shape characteristic for such systems. The combination of these two distortions (B2u and B2g) from regular porphyrin structure results in a macrocycle best characterized in the chiral point-group D2. A rare structural type of a cis-hydrogen bond chelate is observed for 5,15-dipentylporphyrindi-ium diacid, which adopts an achiral C2v symmetry. Crystallographic data indicate that the protonated porphyrin core forms hydrogen bonding chelates (N-H⋯X⋯H-N) to counter-anions. Weaker interactions, such as induced intramolecular C-H⋯O interactions from the porphyrin periphery are described, with distances characteristic of charge-assisted interactions. This paper offers a conceptual framework for accessing porphyrin macrocycles with designable distortion and symmetry, useful for the selective perturbation of electronic states and a design-for-application approach to solid state porphyrin materials.

Reduction-responsive vesicles composed of dimethylaminopropyl octadecanamide and dithiodipropionic acid

ABSTRACTReduction-responsive vesicle was prepared by salt-bridging N-[3-(dimethylamino)propyl]-octadecanamide (DMAPODA, a cationic amphiphile) using 3,3′-dithiodipropionic acid (DTPA, a disulfide diacid compound). According to the transmission electron micrograph and the fluorescence quenching degree (53.2%), it could be said that vesicles were formed when the DMAPODA to DTPA molar ratio was 2:2. The DMAPODA/DTPA associate was considered to be a building block for vesicle formation because DTPA could electrostatically associate with DMAPODA and help the cationic amphiphile assemble into the vesicle. On a differential scanning calorimetric thermogram, the DMAPODA/DTPA vesicle showed two endothermic peaks at 50.6°C and 63.2°C. The peak found at the lower temperature was possibly due to the solid gel-to-liquid crystal phase transition of the vesicular membrane and the peak found at the higher temperature was considered to be due to the melting of DMAPODA, indicating that unassociated DMAPODA coexisted with DMAPODA/DTPA vesicles. The release of calcein enveloped in the vesicle was promoted by DL-dithiothreitol, possibly because DTPA can be broken by the reducing agent to form mercaptopropionic acids and the vesicle could be disintegrated and/or the vesicular membrane would become defective.

Synthesis of 3‐Substituted Tetrahydrofuran and 4‐Substituted Tetrahydropyran Derivatives by Cyclization of Dicarboxylic Acids with InBr3/TMDS

AbstractAn efficient reduction followed by cyclization of diacid compounds with the InBr3/TMDS system is reported. This system allows the formation of five‐ and six‐membered ring ethers substituted in the 3‐ or 4‐position.

Crystallization and Polymorphism of 1,3‐Acyl‐Palmitoyl‐rac‐Glycerols

AbstractCrystallization and melting behavior, small‐angle X‐ray scattering, X‐ray powder diffraction and infra‐red absorbance were measured for nine 1,3‐acyl‐palmitoyl‐rac‐glycerols (1,3‐acetoyl‐, ‐butyroyl‐, ‐hexanoyl‐, ‐octanoyl‐, ‐decanoyl‐, ‐lauroyl, ‐myristoyl‐ and ‐oleoyl‐palmitoyl‐rac‐glycerol and 1,3‐dipalmitoyl‐glycerol). All but one of the prepared 1,3‐diacylglycerols (1,3‐DAG) were β‐stable with 1,3‐acetoyl‐palmitoyl‐rac‐glycerol being the exception (β′‐stable). Small‐angle X‐ray scattering indicates that molecules in β‐tending diacid 1,3‐DAG adopt a herringbone‐type configuration similar to monoacid 1,3‐DAG. In this configuration acyl chains of the same length associate and regular chain‐end matching between terminal methyl groups delineate lamellae. In contrast, molecules in crystalline 1,3‐acetoyl‐palmitoyl‐rac‐glycerol are oriented similar to those of 1(3)‐monoacylglycerol. Interestingly, DSC curves indicate five of the nine diacid compounds have meta‐stable forms—suggesting these forms are quite common for diacid 1,3‐DAG. Meta‐stable forms are observed in the melting curve when the difference in length between acyl chains is large (1,3‐acetoyl‐, ‐butyroyl‐ and ‐hexanoyl‐palmitoyl‐rac‐glycerol), and in the crystallization curve when the difference is moderate (1,3‐decanoyl‐ and ‐lauroyl‐palmitoyl‐rac‐glycerol).

Face-to-Face Alignment of Porphyrin/Fullerene Nanowires Linked by Axial Metal Coordination

A general approach to construct one-dimensional face-to-face alignment of porphyrin/fullerene nanowires has been developed. This system uses extended trans-dihydroxotin(IV) porphyrin and trans-dicarboxylate-substituted [60]fullerenoacetic diacid compounds. The nanowires are arranged in regular one-dimensional linear arrays with lengths in the range 50–300 nm. In the nanowires, each fullerene unit is axially coordinated to the central metal ion of a Sn(IV) porphyrin unit via Sn-carboxylate coordination and forms a face-to-face aligned structure. The synthesis and the hierarchical structure of nanowires have been investigated. They could have potential applications for photoelectronic devices, organic solar cells and so on.

Organic aerosol characterization by complementary measurements of chemical bonds and molecular fragments

Organic aerosol chemical markers from normalized concentrations of independent measurements of mass fragments (using Aerosol Mass Spectrometry, AMS) are compared to bond-based functional groups (from Fourier Transform Infrared spectroscopy, FTIR) during eight field projects in the western hemisphere. Several field projects show weak correlations between alcohol group fractions and m/ z 60 fractions, consistent with the organic hydroxyl groups and the fragmentation of saccharides, but the weakness of the correlations indicate chemical differences among the relationships for ambient aerosols in different regions. Carboxylic acid group fractions and m/ z 44 fractions are correlated weakly for three projects, with correlations expected for aerosols dominated by di-acid compounds since their fragmentation is typically dominated by m/ z 44. Despite differences for three projects with ratios of m/ z 44 to m/ z 57 fragments less than 10, five projects showed a linear trend between the project-average m/ z 44 to m/ z 57 ratio and the ratio of acid and alkane functional groups. While this correlation explains only a fraction of the fragment and bond variability measured, the consistency of this relationship at multiple sites indicates a general agreement with the interpretation of the relative amount of m/ z 44 as a carboxylic acid group marker and m/ z 57 as an alkane group marker.

SYNTHESIS AND PROPERTIES OF ORGANO-SOLUBLE POLY (AMIDE IMIDE)S WITH HIGH REFRACTIVE INDICES

A series of novel poly(amide-imide)s(PAIs)containing sulfur elements were synthesized and characterized.The flexible sulfur-containing groups,either the linear thioether linkage or cyclic thianthrene group were introduced into the PAIs in order to increase the refractive indices and decrease birefringences of the polymers.Thus,an aromatic diacid compound 1,4-bis(4-trimellit-imidophenylenesulfanyl)benzene(BTPB)was first synthesized from a sulfur-containing diamine 1,4-bis(4-aminophenylenesulfanyl)benzene(2SPDA)and trimellitic anhydride(TMA).Then,BTPB was polymerized with two aromatic diamines with high sulfur contents,4,4'-thiobis[(p-phenylenesulfanyl)aniline](3SDA)and 2,7-bis(4-aminophenylenesulfanyl)-thianthrene(APTT),respectively to afford two PAIs.The obtained high-molecular-weight PAIs with the inherent viscosities of 1.06～1.17 dL/g are soluble in N-methyl-2-pyrrolidinone(NMP)at room temperature.The PAI films exhibit good thermal stability up to 440℃ and glass transition temperatures higher than 190℃.In addition,the PAI films show good optical transparency in the visible light region with the cutoff wavelengths around 400 nm and optical transmittances higher than 90% at 500 nm.The high sulfur contents and the flexible thioether linkages endow the PAI films with refractive indices higher than 1.73 and birefringences lower than 0.04 at 632.8 nm.

Photochemical reduction and reoxidation of aqueous mercuric chloride in the presence of ferrioxalate and air

In this study, ferric oxalate is used to represent the photosensitive Fe(III) complexes as well as the diacid compounds which are at significant concentrations in cloud and rain droplets. Because of the common carboxylate functional group; ferric oxalate is also used as a model to represent humic substances found in natural water. UVA irradiation of aqueous acidic mercuric chloride (pH 1–4) in the presence of an excess of ferrioxalate results in partial reduction of the mercuric ion to elemental mercury. The pseudo-first-order rate constant “ k obs” for the photoreduction reaction is pH-dependent as is the yield of residual Hg(II). When exposed to visible irradiation the rate is about 10 times slower and no reaction was observed in the dark. The inferred mechanism of photoreduction involves the reaction of Hg(II) with a secondary photoproduct, the strongly reducing radical anion CO 2 −•. In the presence of dissolved oxygen, competition for CO 2 −• between Hg(II) and O 2 reduces the rate and efficiency of mercuric ion reduction. The O 2 −•/HO 2 products do not reduce Hg(II). On the contrary, their disproportionation leads to the formation of H 2O 2 which causes a re-oxidation of Hg(0) at pH values of ≤ 4. Chloride ion decreases the rate of the reduction of Hg(II).

後発医薬品採用のための品質評価―マレイン酸エナラプリル錠における検討―

A comparative study was carried out to evaluate the quality of one brand name tablet (A) and five generic tablets (B∼F) containing 5 mg of enalapril maleate (ENA). Tablet quality was evaluated based on such characteristics as content, impurities, dissolution profile, hygroscopic properties, and stability. In the purity test, we measured the quantities of degradation products such as diacid compound (DA) and diketopiperazine compound (DKP) and in the hygroscopicity test, the weight and hardness of the tablets without blister packaging was measured initially and after 2 weeks and 4 weeks of storage at 0%, 43%, 75% and 93% relative humidity (RH). To test stability, we measured the quantities of ENA, DA, and DKP in tablets stored without blister packaging at 40°C and 75% RH for 12 weeks.The ENA content in all preparations was approximately equal to the indicated content. Initially, DA was not detected in any of the preparations. About 0.3% DKP was detected in preparation B and C. The dissolution profiles of all generic tablets were similar to those of the brand name tablet. For preparations A, B, and D, a marked increase in tablet weight and decrease in tablet hardness was observed with increasing RH. In the stability test, the remaining ENA content in preparations A, B, and D after 12 weeks was significantly lower than the initial content. The DA content in preparations A and D had increased markedly after 12 weeks and so had the DKP content in preparation B.Our study showed that the quality of the generic tablets C, E, and F was comparable to that of brand name tablet A with respect to stability and resistance to humidity. We conclude that if generic manufacturers continue to produce such high quality drugs, this will lead to greater confidence in their effectiveness and an increase in their use in the clinical setting.

Modeling aided design of potent glycogen phosphorylase inhibitors

Molecular modeling has been used to assist in the development of a novel series of potent glycogen phosphorylase inhibitors based on a phenyl diacid lead, compound 1. In the absence of suitable competitive binding assays, compound 1 was predicted to bind at the AMP allosteric site based on superposition onto known inhibitors which bind at different sites in the enzyme and analyses of the surrounding protein environment associated with these distinct sites. Possible docking modes of compound 1 at the AMP allosteric site were further explored using the crystal structure of rabbit muscle glycogen phosphorylase complexed with a Bayer diacid compound W1807 (PDB entry 3AMV). Compound 1 was predicted to interact with positively charged arginines at the AMP allosteric site in the docking model. Characterization of the binding pocket by a grid-based surface calculation of the docking model revealed a large unfilled hydrophobic region near the central phenyl ring, suggesting that compounds with larger hydrophobic groups in this region would improve binding. A series of naphthyl diacid compounds were designed and synthesized to access this hydrophobic cleft, and showed significantly improved potency

Photochemical production and loss of organic acids in high Arctic aerosols during long-range transport and polar sunrise ozone depletion events

Abstract Unique daily measurements of water-soluble organics in fine ( 2 μm) aerosols were conducted at Alert in the Canadian Arctic in winter to spring of 1992. They yield insight into photochemical production and loss of organics during long-range transport and ozone depletion events following polar sunrise. Comprehensive analyses of α, ω-dicarboxylic acids (C2–C12), ω-oxocarboxylic acids (C2–C9) and α-dicarbonyls (C2, C3) as well as pyruvic acid and aromatic (phthalic) diacid were conducted using GC and GC/MS techniques. Oxalic (C2) acid was generally the dominant diacid species in both fine and coarse fractions, followed by malonic (C3) and succinic (C4) acids. Concentrations of total diacids in the fine aerosol fraction (0.2–64 ng m−3) were 5–60 times higher than those in the coarse fraction (0.01–3 ng m−3). After polar sunrise in early-March, the total concentration of fine aerosol diacids increased by a factor of 3–5 while the coarse mode did not change significantly. From dark winter to sunlit spring, temporal changes in correlations and ratios of these water-soluble organics to vanadium and sulfate measured simultaneously suggest that atmospheric diacids and related organic compounds are largely controlled by long-range atmospheric transport of polluted air during winter, but they are significantly affected by photochemical production. The latter can occur in sunlight either during transport to the Arctic or during photochemical events associated with surface ozone depletion and bromine chemistry near Alert in spring. Conversion of gaseous precursors to particulate matter via photochemical oxidation was intensified at polar sunrise, resulting in a peak in the ratio of total diacids to V. During ozone depletion events, complex patterns are indicated in photochemical production and loss depending on the diacid compound. Unsaturated (maleic and phthalic) diacids were inversely correlated with particulate Br whereas saturated diacids (C2–C4) positively correlated with particulate Br. These results suggest that Br chemistry associated with ozone depletion leads to degradation of unsaturated diacids and to the production of smaller saturated diacids.

Synthesis and characterization of segmented copolymers of aromatic polyether sulfone with liquid crystalline polyesters containing flexible spacers

The synthesis of segmented copolymers of aromatic polyether sulfone and liquid crystalline polyester containing flexible spacers is presented. The segmented copolymers were prepared by solution condensation of hydroxy-terminated polyether sulfone with diacid compounds 1–5 and 4,4′-dihydroxybiphenyl in a mixture of triphenylphosphine, pyridine and hexachloroethane. The obtained polymers show a glass transition at around 160 °C which belongs to the segmental motion of polyether sulfone blocks, and one or two melting transitions which belong to the thermal transitions of LCP blocks. Optical polarized microscopy verifies that the obtained segmented copolymers present a nematic liquid crystalline phase at a temperature higher than their melting transitions.

Addition d'alkylmercaptans sur le vinyl et l'allylphosphonate de diéthyle et modifications chimiques

Diester phosphonoalkyl monomers with long hydrocarbon chains were synthesized. They were obtained by addition of alkylmercaptans on allyl- and vinyl-phosphonated compounds. For the synthesis of the desired monoadducts, it is better to use allyl compounds rather than vinyl ones. Chemical reactions of these diester homologues were performed in order to obtain monoacid and diacid compounds according to two methods: either by acid or basic hydrolysis, or by silylation. This second method involves first the dealkylation of the phosphonated ester by means of trimethyl halosilane, bromotrimethylsilane or chlorotrimethylsilane (less efficient but cheaper), followed by the hydrolysis of the obtained silyl ester.

Overview of Fosinopril

Fosinopril is a prodrug of the active diacid compound, fosinoprilat. Fosinopril is the first of a new chemical class of angiotensin-converting enzyme (ACE) inhibitors, the phosphinic acids, and is indicated for the once-daily treatment of mild-to-moderate essential hypertension.

A lamellar liquid crystal as an in situ surface balance. I. The conformation of 5- (and 6-)carboxy-4-hexyl-2-cyclohexene-1-yl octanoic acid and its monosoap

The interfacial conformation of a dicarboxylic acid, 5- (and 6-)carboxy-4-hexyl-2-cyclohexene-1-yl octanoic acid, and its monosodium soap was determined from the change of liquid crystal dimensions after introduction of the diacid compounds. The results showed that both functional groups of the monosoap form were present at the interface and that increased water content of the liquid crystal matrix had little effect on the conformation of the monosoap. On the other hand, the results indicated the conformation of the diacid as such to depend on the water content of the matrix. At low water content, the diacid form was in a conformation similar to that found for the monosoap. However, increasing the water content of the matrix resulted in a sharp decrease in the calculated partial molecular areas for the diacid, indicating an extended conformation for the diacid.