Estimation of the normal boiling point of organic compounds via group contributions

The normal boiling point is a fundamental thermo-physical property, which is important in describing the transition between the vapor and liquid phases. Reliable method which can predict it is of great importance, especially for compounds where there are no experimental data available. In this work, an improved group contribution method, which is second order method, for determination of the normal boiling point of organic compounds based on the Joback functional first order groups with some changes and added some other functional groups was developed by using experimental data for 632 organic components. It could distinguish most of structural isomerism and stereoisomerism, which including the structural, cis- and trans- isomers of organic compounds. First and second order contributions for hydrocarbons and hydrocarbon derivatives containing carbon, hydrogen, oxygen, nitrogen, sulfur, fluorine, chlorine and bromine atoms, are given. The fminsearch mathematical approach from MATLAB software is used in this study to select an optimal collection of functional groups (65 functional groups) and subsequently to develop the model. This is a direct search method that uses the simplex search method of Lagarias et al. The results of the new method are compared to the several currently used methods and are shown to be far more accurate and reliable. The average absolute deviation of normal boiling point predictions for 632 organic compounds is 4.4350 K; and the average absolute relative deviation is 1.1047 %, which is of adequate accuracy for many practical applications.

Chemical characterization of dissolved organic compounds from coastal sea surface microlayers (Baltic Sea, Germany)

The physicochemical properties of the sea surface microlayer (SML), i.e. the boundary layer between the air and the sea, and its impact on air-sea exchange processes have been investigated for decades. However, a detailed description about these processes remains incomplete. In order to obtain a better chemical characterization of the SML, in a case study three pairs of SML and corresponding bulk water samples were taken in the southern Baltic Sea. The samples were analyzed for dissolved organic carbon and dissolved total nitrogen, as well as for several organic nitrogen containing compounds and carbohydrates, namely aliphatic amines, dissolved free amino acids, dissolved free monosaccharides, sugar alcohols, and monosaccharide anhydrates. Therefore, reasonable analytical procedures with respect to desalting and enrichment were established. All aliphatic amines and the majority of the investigated amino acids (11 out of 18) were found in the samples with average concentrations between 53 ng/l and 1574 ng/l. The concentrations of carbohydrates were slightly higher, averaging 2900 ng/l. Calculation of the enrichment factor (EF) between the sea surface microlayer and the bulk water showed that dissolved total nitrogen was more enriched (EF: 1.1 and 1.2) in the SML than dissolved organic carbon (EF: 1.0 and 1.1). The nitrogen containing organic compounds were generally found to be enriched in the SML (EF: 1.9-9.2), whereas dissolved carbohydrates were not enriched or even depleted (EF: 0.7-1.2). Although the investigated compounds contributed on average only 0.3% to the dissolved organic carbon and 0.4% to the total dissolved nitrogen fraction, these results underline the importance of single compound analysis to determine SML structure, function, and its potential for a transfer of compounds into the atmosphere.

Sediment and organic matter properties, and molecular formula from sampling locations in the Northern Black Sea

Remineralization of organic matter in reactive marine sediments releases nutrients and dissolved organic matter (DOM) into the ocean. Here we focused on the molecular-level characterization of DOM by high-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) in sediment pore waters and bottom waters from contrasting redox regimes in the northern Black Sea with particular emphasis on nitrogen-bearing compounds to derive an improved understanding of the molecular transformations involved in nitrogen release. The number of nitrogen-bearing molecules is generally higher in pore waters than in bottom waters. This suggests intensified degradation of nitrogen-bearing precursor molecules such as proteins in anoxic sediments: No significant difference was observed between sediments deposited under oxic vs anoxic conditions (average O/C ratios of 0.55) suggesting that the different organic matter quality induced by contrasting redox conditions does not impact protein diagenesis in the subseafloor. Compounds in the pore waters were on average larger, less oxygenated, and had a higher number of unsaturations. Applying a mathematical model, we could show that the assemblages of nitrogen-bearing molecular formulas are potential products of proteinaceous material that was transformed by the following reactions: (a) hydrolysis and deamination, both reducing the molecular size and nitrogen content of the products and intermediates; (b) oxidation and hydration of the intermediates; and (c) methylation and dehydration.

Organic compounds in sediments and pore waters of ODP Sites 117-723 and 117-724

Total organic carbon, amino compounds, and carbohydrates were measured in pore waters and sediments of Pliocene to Pleistocene age from Sites 723 and 724 (ODP Leg 117) to evaluate (1) relationships between organic matter in the sediment and in the pore water, (2) the imprint of lithological variations on the abundance and contribution of organic substances, (3) degradation of amino compounds and carbohydrates with time and/or depth, and (4) the dependence of the ammonia concentration in the pore water on the degradation of amino compounds in the sediment. Total organic carbon concentrations (TOC) of the investigated sediment samples range from 0.9% to 8.7%, and total nitrogen concentrations (TN) from 0.1% to 0.5%. Up to 4.9% of the TOC is contributed by hydrolyzable amino acids (THAA) which are present in amounts between 1.1 and 21.3 µmol/g dry sediment and decrease strongly downhole. Hydrolyzable carbohydrates (THCHO) were found in concentrations from 1.3 to 6.6 ?mol/g sediment constituting between 0.1% and 2.0% of the TOC. Differences between the distribution patterns of monomers in Sites 723 and 724 indicate higher terrigenous influence for Site 724 and, furthermore, enhanced input of organic matter that is relatively resistant to microbial degradation. Lithologically distinct facies close to the Pliocene/Pleistocene boundary yield different organic matter compositions. Laminated horizons seem to correspond with enhanced amounts of biogenic siliceous material and minor microbiological degradation. Total amounts of dissolved organic carbon (DOC) in pore waters vary between 11 and 131 mg/L. Concentrations of DOC as well as of dissolved amino compounds and carbohydrates appear to be related to microbial activity and/or associated redox zones and not so much to the abundance of organic matter in the sediments. Distributions of amino acids and monosaccharides in pore waters show a general enrichment in relatively stable components in comparison to those of the sediments. Nevertheless, the same trend appears between amino acids present in the sediments from Sites 723 and 724 as well as between amino acids in pore waters from these two sites, indicating a direct relation between the dissolved and the sedimentary organic fractions. Different ammonia concentrations in the pore waters of Sites 723 and 724 seem to be related to enhanced release of ammonia from degradation of amino compounds in Site 723.

Contents of organic compounds in sediments from DSDP Legs 1 and 4

Fifteen sediment samples were studied from five drill sites recovered by the Glomar Challenger on Legs I and IV in the Gulf of Mexico and western Atlantic. This study concentrated on compounds derived from biogenic precursors, namely: (1) hydrocarbons, (2) fatty acids, (3) pigments and (4) amino acids. Carbon isotope (dC13) data [values <(-26)?, relative to PDB], long-chain n-alkyl hydrocarbons (>>C27) with odd carbon numbered molecules dominating even carbon numbered species, and presence of perylene proved useful as possible indicators for terrigenous contributions to the organic matter in some samples. Apparently land-derived organic matter can be transported for distances over 1000 km into the ocean and their source still recognized. The study was primarily designed to investigate: (i) the sources of the organic matter present in the sediment, (ii) their stability with time of accumulation and (iii) the conditions necessary for in situ formation of new compounds.

Concentration of organic compounds in the snow-ice cover of the Eastern Antarctic

This paper presents data on concentrations and composition of organic substances, lipids, and hydrocarbons, in the snow-ice cover of fast ices and continental lakes of Antarctic. It was shown that organic compounds were accumulated in layers with the most intense autochthonous processes (mainly at the snow-ice and ice-water boundaries). These zones remain active at a biogeochemical medium even at low temperatures. The maximum content of organic compounds (10-20 times that of the snow-ice cover of other regions) and a sharp change in the proportions of their migration forms in the ice volume were detected in the regions of penguin colonies (fast ice in the Buromsky Island and a lake in the Haswell Island). Contents and composition of hydrocarbons in Antarctic ices were compared with those of Arctic ices.

Concentrations of organic compounds in suspended matter from surface waters and surface layer bottom sediments of the Obskay Guba (Ob River estuary) and the Kara Sea

Data are presented on concentrations of aliphatic and polycyclic aromatic hydrocarbons (AHC and PAH) in interstitial waters and bottom sediments of the Kara Sea compared to distribution of particulate matter and organic carbon. It was found that AHC concentrations within the water mass (aver. 16 µg/l) are mainly formed by natural processes. Distribution of AHC represents variability of hydrological and sedimentation processes in different regions of the sea. The widest ranges of the concentrations occurred in the Obskaya Guba - Kara Sea section: in water (10-310 µg/l for AHC and 0.4-7.2 ng/l for PAH) and in the surface layer of the bottom sediments (8-42 µg/l for AHC and 9-94 ng/g for PAH). Differentiation of hydrocarbons (HC) in different media follows regularities typical for marginal filters; therefore no oil and pyrogenic compounds are supplied to the open sea. In sediments contents of HC depend on variations in redox conditions in sediments and on their composition.

Organic compounds in snow, ice, and sub-ice waters from the mouth of the Severnaya Dvina River and the Kandalaksha Gulf (White Sea)

The paper reports data on concentrations of organic compounds (organic carbon, lipids; aliphatic hydrocarbons, and polycyclic aromatic hydrocarbons) in snow, ice, and sub-ice waters from the mouth of the Severnaya Dvina River in March 2005-2007 and the Kandalaksha Gulf (Chupa Bay) in March 2004. It was established that organic compounds are accumulated in snow and the upper ice layer near Archangelsk city. Distribution of molecular markers indicates that pollutions were mainly caused by local fallouts. In the Chupa Bay organic compounds are concentrated in the lower ice layer; it is typical for Arctic snow-ice cover. High contents of organic compounds in the snow-ice cover of the White Sea are caused by pollution of air and water during the winter season.

Concentration of organic compounds in slush, under-ice water, and the snow-ice fast-ice cover of the southeast sector of the Antarctic in April 2008

Data are presented on concentration of hydrocarbons (HC) relative to concentrations of suspended matter, lipids, organic carbon, and chlorophyll a in surface waters and snow-ice cover of the East Antarctic coastal areas. It was shown that growth of concentrations of aliphatic HC (AHC) to 30 µg/l in surface waters takes place in frontal zones and under young ice formation. AHC concentration in snow increases with growth of aerosol concentration in the atmosphere. In the lower part of ice, at the boundary with seawater, despite low temperatures, autochthonous processes may provide high AHC concentrations (up to 289 µg/l). Within the snow-ice cover on fast ice, concentration co-variations of all the compounds considered take place.