Current Organic Chemistry - Volume 17, Issue 24, 2013

“Thus, the following things are by natural law common to all – the air, running water, the sea and consequently the seashore” [1]. The natural environment, including products derived from it such as food and water, can be subject to contamination from agriculture and industry. This has always been the case since chemicals have been employed to improve agricultural yields, control pests or in the manufacture of industrial products. Although a great deal has been done over the past half century to ameliorate such contaminations through improvements to practices and regulations governing the use and discharge of chemicals, contamination still occurs. This review seeks to provide an overview of the sources of contamination from both historic and current practices. By its nature, such a review cannot cover all potential sources but will use examples of how contaminations have been identified and dealt with. Past instances such as the consequences of the use of pesticides and fertilisers will be discussed briefly as will contamination from major industries such as mining, petrochemicals and automotive. The review will also consider possible contaminations from the use of modern practices such as 'fracking', nanotechnology and the use of waste materials as agricultural fertiliser that can lead to a range of potentially hazardous waste materials being discharged in to the environment and which may contaminate food and water.

Banana plantations in tropical humid regions require a high input of pesticides. Given the long history of this practice, a number of pesticides that are now banned have accumulated in these soils. Little is known about the sorption of two banned insecticides, chlordecone and cadusafos, which are known to cause adverse environmental and health effects. We studied the sorption-desorption characteristics (Freundlich sorption-desorption coefficient, Kf, and partition coefficient, Kd) of these two molecules in tropical volcanic soils with different soil properties. In particular, we observed the effect of the chemical nature of the soil organic carbon (SOC). The sorption of chlordecone (35.56<d<144.96 L kg^-1) and the desorption hysteresis (apparent hysteresis index, H<0.43) were very high. Sorption was significantly lower for cadusafos (1.47< Kd 19.94 L kg^-1) and less hysteretic (0.59< H< 1.08). The correlation between Kd and Kfsor values and SOC content was statistically significant for both molecules (p<0.01). KOC anged between 1218-2547 L kg^-1 for chlordecone and between 67 L kg^-1 and 167 L kg^-1 for cadusafos. The chemical composition of the soil organic matter was determined using cross-polarization magic-angle-spinning NMR spectroscopy (CP/MAS NMR). Chlordecone was found to display a higher affinity to soils with shorter alkyl chains and fewer carboxyl groups, while cadusafos had a higher affinity for soils with more oxidized OC (methoxy and carboxyl groups) and longer alkyl chains. This highlights the complex role of SOC chemistry on the sorption of chlordecone and the fact that soil practices, such as the addition of fresh organic amendments, may not efficiently enhance the sorption of chlordecone.

Soil organic matter (SOM) holds a prominent place among the many indicators that are studied in relation to soil function. Different viewpoints are reflected in characterizing SOM, depending on the study procedures used, or the focus of the researchers. There are many possibilities for the isolation and fractionation of SOM and this has led to a plurality of interpretations and conclusions. Transformations to organic materials that lead to the more recalcitrant components of SOM are outlined, and the associations which these materials can have in the soil environment, and aspects of their compositions are referred to. A review is given of the organic matter pools in soils, of their functions, and of the controls which they have in soil systems. A succinct review is given of physical fractionation procedures for SOM. This approach is highly relevant, though rarely used in modern studies of SOM. The merits and demerits of wet oxidation procedures, relative to dry combustion for determining soil organic carbon contents are discussed, and reference is made to the emerging chemometric techniques based on the use of Near (NIR) and Mid (MIR) infrared spectroscopy.

This review focuses on the chemical nature of that fraction of already dissolved organic matter into soil solution, or extracted by mild extractants, which is truly readily available for microbial activity and, consequently, more sensitive than total soil organic matter to changes in management and/or environmental conditions. In particular, we deal with low molecular weight compounds such as monosaccharides, amino sugars and amino acids. Soil sampling strategy and extraction procedure, prior to analyses, are crucial to make comparable results among laboratories. Although soil management and climatic conditions may cause large variability, extractable organic C and N may indicate the amount of substrates available to microbial biomass. Hot water extractable carbohydrates are among the most sensitive indicators of various factors such as tillage, cropping system, soil inundation frequency, seasonality and wildfires. Moreover, hot water extracts mainly microbial carbohydrates, i.e. those more involved to bind soil aggregates. The turnover rate of free amino acids in soils is very high, ranging from 1 h to about 30 hours. This explains the usually very low amino acid-N extractable from soils. The pHvariable charge of amino acids favours their adsorption on soil colloids. Amino sugars concentration in soils (mainly glucosamine, galactosamine, mannosamine and muramic acid) is more useful indicators of microbial necromass than microbial living biomass since they tend to stabilize and accumulate in soil. Moreover, their use as specific biomarkers is questionable due the widespread presence among microorganisms and plants.

Losses of soil organic carbon often occur because of intensive agricultural practices that lead to removal of organic carbon following harvest production and to insufficient inputs. Organic amendments can be very appropriate for enhancing organic carbon content in very stressed agricultural soils. By enhancing soil organic matter, they generally play an important role in environmental matrices due to their capacity in retaining water and in enhancing nutrient availability to plants. Therefore, understanding the mechanisms by which organic amendments interact with other chemicals in the environment is of paramount importance. The attention was focused on farms near Sele river (Campania region, Italy), an area characterized by intensive agriculture. Two farms, with contrasting geopedologic properties (clay vs. sandy), were selected in order to study the effect of different doses of organic amendments containing compost from municipal solid wastes and wood-wastes (scraps of poplars pruning) at different ratios. The organic fractions were extracted from soil, after one and twelve months from amendment, and were analysed in order to establish their elemental composition and properties by FTIR, CPMAS ¹³C NMR spectroscopy and FFC-NMR relaxometry. Results showed an important role of soil geopedologic characteristics and experimental time in the evolution of humic acids. In less aerobic conditions as occurs in clay soils, organic matter was more stable, rich in carbonyl groups belonging to aldehydes and ketones, whereas under more aerobic conditions, occurring in sandy soils, organic matter had undergone a faster degradation, due to oxidative conditions and more intensive microbial activity.

To effectively characterise and distinguish between different organic matter samples, multiple chemical characterisation techniques are often employed. Due to the structural complexity of organic matter and the unique information provided by different characterisation techniques, it is often difficult to compare and combine data obtained from different analytical methods. In this study, we show how non-parametric multivariate statistical approaches can be used to compare the relative pattern of similarity/dissimilarity between organic samples characterised by two common solid-state analytical techniques: ¹³C nuclear magnetic resonance (NMR) spectroscopy and flash pyrolysis-gas chromatography mass spectrometry (py-GCMS). These analytical methods were used to characterise a suite of plant residues including the leaf, flower, bark and wood of several species. Using non-parametric multivariate statistical approaches we identified similarities between the plant residue data using ordination plots, which enabled us to identify where NMR and py-GCMS distinguished between residues differently. A mantel-type test called RELATE showed that there was significant (P<0.05) similarity between the NMR and py-GCMS data in terms of their ability to differentiate between plant residues of different type; 61% of the sample discrimination was common to both profiling techniques, while 39% of discrimination was method specific. Further multivariate comparisons indicated that NMR was more sensitive to detecting differences in the organic composition of the plant residues.

High Resolution Magic Angle Spinning (HR-MAS) NMR spectroscopy is a versatile technique that provides high resolution NMR data on samples containing solutions, gels and swellable solids. In addition to providing structural information HR-MAS can also be used to investigate interfaces (for example organic structures at the solid-aqueous soil interface), processes such as swelling/ flocculation, kinetic transfer between gel/liquid phases, as well as conformation and molecular interactions in situ. As such, HRMAS has potential in a diversity of fields including organic, biological, environmental, and medical research. This manuscript focuses on the application of HR-MAS to intact natural samples. A range of 1D and 2D NMR experiments are reviewed and compared in terms of general performance on a range of samples. Therefore, this practical guide and review should be a useful reference and starting point for those wishing to apply HR-MAS NMR. While this article focuses on natural samples, common key 1D and 2D experiments are considered which may be of interest to readers with diverse research interests.

This review is a survey of recent advances in environment related aspects of organic photochemistry. Besides presenting general concepts, the manuscript is mainly focused on the photoreactivity of natural organic matter, and on the photochemistry of anthropogenic substances under natural light irradiation.

Protonation of local anesthetics, LA, and their inclusion complexes with cyclodextrins, CD, are the central issue of this review. The physicochemical properties of LA, such as acid-base character, are crucial to understand their behavior because their capacity to reach and to block sodium channels and act as anesthetics, depends on their protonation state. Consequently, different techniques that are used to determine acid-base equilibrium constants, together with the data published are reviewed. Potentiometry and spectrophometry, are by far the most used techniques. Although these are classical methods for this kind of determinations, the calibration procedure and the approximations used are not always described properly. Besides, the extent of complexation with cyclodextrins varies greatly with the protonation state of the involved molecules, an interesting fact in the administration of LA and in the determination of their inclusion constants. A great variety of experimental techniques have been used to achieve this goal, in fact, there is not a universal method and different properties that change with the inclusion process can be employed, but the system characteristics are of crucial importance in their choice. Several methods are discussed together with the values of constants gathered from the literature.

Hydrogen bonding facilitated self-assembly is an appealing strategy for constructing advanced molecular architecture. Arrays of quadruply hydrogen-bonding (QHB) modules are especially appealing due to the reason that it features extremely strong yet reversible and dynamic interactions. This review focus on the design and development of polymeric materials utilizing QHB arrays such as 2- ureido-4[1H]-pyrimidone (UPy), butylurea of guanosine (UG), deazapterin (DeAP), 2,7-diamido-1,8-naphthyridine (DAN) and 7- deazaguanine urea (DeUG). Investigating QHB interaction at molecular level and evaluate the physical and chemical properties of the resulting material in solution and bulk are discussed. Specific examples highlighted in this review demonstrate how QHB modules are used and incorporated into polymer matrix to yield stimuli-responsive functionalized polymer. It is discussed how QHB modules providing extra interactions which are responsive under mechanical stress. The interactions associated with QHB modules could be effective adhesion promoters and source of energy dissipater and can facilitate development of functional polymers and smart materials such as stimuliresponsive polymers, novel interpenetrating polymers, polymer blends and fiber/particle reinforced polymer nano-composite.

Herein, we describe the synthesis of a series of rac-N,N'-dibenzylpropane-2-aryl-substituted imidazolidines prepared from the corresponding aromatic aldehydes and two N,N'-dibenzylpropane-1,2-diamines, namely rac-N,N'-dibenzylpropane-1,2-diamine 3a and rac-2,2'-[propane-1,2-diylbis(iminomethanediyl)]diphenol 3b, produced by the NaBH4 reduction of the corresponding diimines of benzaldehyde and salicylaldehyde.

Porphyrins are tetrapyrrolic macrocycles with a fascinating and multifarious variegation of properties of essential significance in up-to-date and leading technologies. This class of compounds exhibits very attractive properties as for well established synthetic paths, advantageous photophysical characteristics, high sensitivity, selectivity, response and recovery times, and reproducibility in sensors. Porphyrins solution, porphyrin-based nanocomposites and porphyrin Langmuir–Blodgett films porphyrins in membranes as sensors for metal ions, gas, explosives, amine, acid, DNA and others has been reviewed in spectrophotometric (absorption, light scattering and fluorescence), electrochemical or chromatographic methods.

An ortho halogenation of arylurea derivatives has been developed via palladium-catalyzed C-H bond activation. The reactions were regio-selective, facile and afforded good to excellent product yields under mild conditions.