Other classes of organic compounds

As with all aromatic compounds, aromatic amines absorb relatively strongly in the UV region (see Chapter 11). A first study [33], based on the use of the deconvolution method, has been applied to the estimation of aniline derivative concentrations in industrial wastewater. For the purpose, a basis of reference spectra (see Chapter 2) has been defined by including characteristic average spectra for global and chlorinated aniline mixtures. 

Another study on aromatic amines from azo dye reduction gives a complete overview on the use of direct UV spectrophotometric detection in textile industry wastewater [34], 

Mercaptans (R-SH) [35] are weak acids (pKa around 10) and give rise to an equilibrium in aqueous solution. In basic media, bathochromic and hyperchromic shifts are observed in all cases. This effect is particularly marked with thiophenate ion because of a stabilisation of the negative charge with the n electrons of the aromatic ring. By adjusting the pH of sample to 11 after addition of sodium hydroxide solution 2.5 M, the spectra show a well-defined peak of absorbance at 238 nm for the alkylthiols or 263 nm for the thio-phenols. The application of the deconvolution method allows the estimation of the global concentration of mercaptans in wastewater. 

A major point is related to the need to adjust the sample pH to 11. At this value, all mercaptans are supposed to be under the thiolate form, which is known to be oxidised readily at high pH value in the presence of dissolved oxygen. Thus, the spectra acquisition must be carried out less than 15 min after pH adjustment. 

The UV/UV method allows the simple determination of overall sugar content. The procedure was applied successfully to food liquid products (soft drinks and commercial and natural fruit juices), with high sugar concentrations (between 40 and 500 g/L). The method could be extended to the determination of sugar (at lower concentrations) in industrial processes, as in wine production, for example. 

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Picrates, Many aromatic hydrocarbons (and other classes of organic compounds) form molecular compounds with picric acid, for example, naphthalene picrate CioHg.CgH2(N02)30H. Some picrates, e.g., anthracene picrate, are so unstable as to be decomposed by many, particularly hydroxylic, solvents they therefore cannot be easily recrystaUised. Their preparation may be accomplished in such non-hydroxylic solvents as chloroform, benzene or ether. The picrates of hydrocarbons can be readily separated into their constituents by warming with dilute ammonia solution and filtering (if the hydrocarbon is a solid) through a moist filter paper. The filtrate contains the picric acid as the ammonium salt, and the hydrocarbon is left on the filter paper. 

This reagent affords compounds (1 1) with aromatic hydrocarbons and other classes of organic compounds (heterocyclic compounds, aromatic ethers, etc.). 

The most common interfering substance, especially with alcohols of low mole cular weight, is water this may result in an inaccurate interpretation of the test if applied alone. Most of the water may usually be removed by shaking with a little anhydrous calcium sulphate,. though dry ethers (and also the saturated aliphatic and the simple aromatic hydrocarbons) do not react with sodium, many other classes of organic compounds do. Thus ... 

We first encountered nucleophilic substitution in Chapter 4, in the reaction of alcohols with hydrogen halides to fonn alkyl halides. Now we ll see how alkyl halides can themselves be converted to other classes of organic compounds by nucleophilic substitution. 

Aromatic substances, more than any other class of organic compounds, have acquired a large number of nonsystematic names. The use of such names is discouraged, but 1UPAC rules allow for some of the more widely used ones to be retained (Table 15.1). Thus, methylbenzene is known commonly as toluene hydroxybenzene, as phenol ami nobenzene, as aniline and so on. 

Establishing the elemental composition based on the isotopic peaks may be problematic if, for example, the sample contains impurities with the masses in the region of the molecular ion cluster. In the El mass spectra of amines, alcohols, acids, and some other classes of organic compounds there is often a peak of [M + H]+ ion. It distorts the isotopic picture. It is worth mentioning as well that in real experimental conditions the peak intensity may vary slightly in each... 

Other classes of organic compounds have been proposed and tested as HTL materials but have yet to gain wide acceptance. A few of the more interesting examples include isoindoles [112], bisphenol-acetophenone-polycarbonate [113], and polysilanes [114]. 

As CH-acids in the MCRs with aldehydes and aminoazoles, other classes of organic compounds were used as well. Cyanoacetic acid derivatives, acetoyl(aroyl) acetonitriles, ketosulfones, acetophenones, and other reagents were successfully introduced into these three-component heterocyclizations. For example, synthesis of pyrazolo[3,4-b]pyridine-5-carbonitriles 40 was carried out as the multicomponent treatment of 5-aminopyrazole, aldehyde, and benzoylacetonitriles solvent-free by fusion either in ammonium acetate at 120°C or in boiling ethanol with EtsN (Scheme 17) [69]. The second approach gave the worst results from the viewpoint of yields and purity of the target compounds. 

Analytical data for the other classes of organic compounds show normal fatty acids to be more than an order of magnitude greater than n-alkanes in modem sediments, typically 26 /Agrams/gram and 1.5 /Agram/ gram, respectively for ancient sediments, the abundances were found to... 

The melting points (more accurately termed the decomposition points) of sugars and some of their derivatives, e.g. osazones, are not so definite as those of other classes of organic compounds they vary with the rate of heating and the differences between individual members are not always large. There are, however, a number of reactions and derivatives which will assist in the characterisation of the simple sugars. 

Compared to other classes of organic compounds, ethers have relatively low toxicities. This characteristic can be attributed to the low reactivity of the C-O-C functional group arising from the high strength of the carbon-oxygen bond. Like diethyl ether, several of the more volatile ethers affect the central nervous system. Hazards other than their toxicities tend to be relatively more important for ethers. These hazards are flammability and formation of explosive peroxides (especially with di-isopropyl ether). 

Although alkanes are not as reactive as other classes of organic compounds, they have many of the same structural characteristics. We will use simple alkanes as examples to study some of the properties of organic compounds, including the structure of sjf hybridized carbon atoms and properties of C—C and C—H single bonds. 

Emphasis is placed on dyes presently in commerce and the industrial methods suitable for making them. Before doing so, we review the important principles that set dyes apart from other classes of organic compounds. 

The ASIS for many other classes of organic compounds have also been studied and plane rules for lactones, lactams, and acid anhydrides have been suggested cf reference [3] for a comprehensive selection of successful applications of ASIS. 

Hydrocarbons are compounds containing only carbon and hydrogen. Not only are hydrocarbons important in themselves, but they are the foundation of all the other classes of organic compounds. We must learn how to name and write formulas for the hydrocarbons and learn a few of their simple reactions. The number of such compounds is almost uncountable because carbon atoms can bond to other carbon atoms in seemingly limitless numbers. (An eight-carbon chain is shown in Figure 20.1. Compounds with extremely long chains are discussed in... 

Optically active cyanohydrins are synthetic precursors of a-hydroxy carboxylic acids, a-amino carboxylic acids, /1-hydroxy amines, and several other classes of organic compound of biological importance [146]. Several efficient catalysts have been developed by using titanium as the central metal. 

The most characteristic properly of the carboxylic acids is the one that gives them their name acidity. Their tendency to give up a hydrogen ion is such that in aqueous solution a measurable equilibrium exists between acid and ions they are thus much more acidic than any other class of organic compounds we have studied so far. 

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