Carboxylic acids and hydrocarbons

In addition to water, a variety of organic liquids, including amines, carboxylic acids, and hydrocarbons, have been used as solvents in the study of the homogeneous reactions of hydrogen with metal salts. In general, there is more uncertainty about the nature of the species present in such systems than in aqueous solution and, correspondingly, it is usually more difficult to elucidate the reaction mechanisms in detail. The most extensive solvent effect studies have been made on cupric, cuprous, and silver salts. A number of the more important results are considered below. 

Naraoka H., Shimoyama A., Komiya M., Yamamoto H., and Harada K. (1987) Carboxylic acids and hydrocarbons in Antarctic carbonaceous chondrites. In Twelfth Symposium on Antarctic Meteorites. National Institute of Polar Research, Tokyo, pp. 9 -11. 

For the Irati oil shale carboxylic acids and hydrocarbons total together 30% of the bitumen (porphyrins are present in very small amounts). Still, 70% of the bitumen remains to be characterized. 

The Maillard reaction and the oxidation of lipids are two of the most important reactions for the formation of aromas in cooked foods. Interactions between lipid oxidation and the Maillard reaction have received less attention, despite the fact that lipids, sugars, and amino acids exist in close proximity in most foods. Lipids, upon exposure to heat and oxygen, are known to decompose into secondary products, including alcohols, aldehydes, ketones, carboxylic acids, and hydrocarbons. Aldehydes and ketones produce heterocyclic flavor compounds reacting with amines and... 

The list of solutes that are known to be preferentially sorbed by cellulose acetate membranes includes many alcohols, phenols, un-lonlzed carboxylic acids and hydrocarbons ( ). Although solute preferential sorption is a common occurrence with a number of important aqueous organic systems little experimental or quantitative work has appeared in the literature. The purpose of the current work is to rectify this situation. 

Behar, F. Albrecht, P. 1984. Correlations between carboxylic acids and hydrocarbons in several crude oils. Alteration by biodegradation. Organic Geochemistry, 6, 597-604. 

The nitrosoamide reaction is a clean one, and only nitrogen, carboxylic acids and hydrocarbons are formed as by-products (equation 110) these compounds are usually readily removed from the substitution products. Two examples from the hterature will illustrate the use to which the reaction has been put. Alvarez has used the method recently in his conversion of pregnenolone acetate (28) into epitestosterone (29) (equation 111) . Based on our own stereochemical results it is certain that considerable testosterone acetate was formed in this reaction as well. Also in the steroid... 

Hydroperoxyhexane cleaves with formation of carboxylic acid and hydrocarbon radical (ethylene or propylene). These known examples show that the presence of even traces of solvents may change the chemistry and the rate of photooxidative processes because of formation of radicals. 

A further example is given below illustrating the use of a dibasic anhydride (succinic anhydride) the succinoylation reaction is a valuable one since it leads to aroyl carboxylic acids and ultimately to polynuclear hydrocarbons. This general scheme of synthesis of substituted hydrocarbons through the use of succinic anhydride is sometimes called the Haworth reaction. Thus a-tetralone (see below) may be reduced by the Clemmensen method to tetralin (tetrahydronaphthalene) and the latter converted into naphthalene either catal3d.ically or by means of sulphur or selenium (compare Section, VI,33). 

Electrolysis, under similar conditions, of a mixture of two carboxylic acids RCOOH and R COOH leads, in addition to normal coupling products R—R and R —R, to cross coupling R—R. If a mixture of a saturated carboxylic acid and a half ester of an ato-dicarboxylic acid is electrolysed, there are three main products, viz., a hydrocarbon (I), a mono-ester (II), and a di-ester (HI) and these are readily separable by distillation. Some unsaturated ester (IV) is often present in small quantity. 

FIGURE 19 6 Space filling model of a micelle formed by association of car boxylate ions derived from a long chain carboxylic acid The hydrocarbon chains tend to be on the inside and the carboxylate ions on the surface where they are in contact with water mole cules and metal cations... 

Participation of fluorocarbocations, derived from carboxylic acids and from halo acetones, in reactions of carbonyl compounds with sulfur tetrafluoride has been directly evidenced by trapping them with aromatic hydrocarbons [207, 20S],... 

The hydrocarbons are the basic framework for all organic compounds. Different classes of organic compounds have one or more of the hydrogen atoms replaced by other atoms or groups of atoms. All we need to be aware of at this stage are the three classes of compounds known as alcohols, carboxylic acids, and haloalkanes ... 

Most resolution is done on carboxylic acids and often, when a molecule does not contain a carboxyl group, it is converted to a carboxylic acid before resolution is attempted. However, the principle of conversion to diastereomers is not confined to carboxylic acids, and other groupsmay serve as handles to be coupled to an optically active reagent. Racemic bases can be converted to diastereomeric salts with active acids. Alcohols can be converted to diastereomeric esters, aldehydes to diastereomeric hydrazones, and so on. Even hydrocarbons can be converted to diastereomeric inclusion... 

Carboxylic acid and carboxylate were completely decarboxy-lated to the parent hydrocarbons. According to Brower, carboxylic acid is quite stable in glass apparatus, but decomposed completely in a stainless steel autoclave. 

As an example we may consider the Kolbe reaction, the oxidation of carboxylic acid and carboxylates of the form R-COOH or R-COO- to form coupled hydrocarbon products of the form R2. Investigation of this reaction in aqueous and non-aqueous solvents has revealed that the processes taking place are very complex indeed. In general, the product R2 is only formed at high current densities on smooth electrodes. At lower current densities, alkenes and non-dimeric products such as R-H are found, and, especially in alkaline solutions, the product R-OH can be formed in good... 

For most organic chemicals the solubility is reported at a defined temperature in distilled water. For substances which dissociate (e.g., phenols, carboxylic acids and amines) it is essential to report the pH of the determination because the extent of dissociation affects the solubility. It is common to maintain the desired pH by buffering with an appropriate electrolyte mixture. This raises the complication that the presence of electrolytes modifies the water structure and changes the solubility. The effect is usually salting-out. For example, many hydrocarbons have solubilities in seawater about 75% of their solubilities in distilled water. Care must thus be taken to interpret and use reported data properly when electrolytes are present. 

Each of these bond enthalpies is an average enthalpy, measured from a series of similar molecules. Values of AH, . for, say, C-H bonds in hydrocarbons are likely to be fairly similar, as shown by the values in Table 3.3. The bond energies of C-H bonds will differ (sometimes quite markedly) in more exceptional molecules, such as those bearing ionic charges, e.g. carbocations. AH, . values differ for the OH bond in an alcohol, in a carboxylic acid and in a phenol. 

High-performance liquid chromatography has, to date, only found limited applications in the analysis of sludges (aliphatic hydrocarbons, cationic and non-ionic surface active agents, carboxylic acids and cobalamin). 

The dianhydride of perylene tetracarboxylic acid is converted into the pigment form by preparing the corresponding alkali salt and then reprecipitating the compound with an acid. The dianhydride is formed after separating the acid by thermal aftertreatment at 100 to 200°C, possibly under pressure, with an organic solvent. The list of suitable media includes alcohols, ketones, carboxylic acid esters, hydrocarbons, and dipolar aprotic solvents. 

In contrast to the other large cats, the urine of the cheetah, A. jubatus, is practically odorless to the human nose. An analysis of the organic material from cheetah urine showed that diglycerides, triglycerides, and free sterols are possibly present in the urine and that it contains some of the C2-C8 fatty acids [95], while aldehydes and ketones that are prominent in tiger and leopard urine [96] are absent from cheetah urine. A recent study [97] of the chemical composition of the urine of cheetah in their natural habitat and in captivity has shown that volatile hydrocarbons, aldehydes, saturated and unsaturated cyclic and acyclic ketones, carboxylic acids and short-chain ethers are compound classes represented in minute quantities by more than one member in the urine of this animal. Traces of 2-acetylfuran, acetaldehyde diethyl acetal, ethyl acetate, dimethyl sulfone, formanilide, and larger quantities of urea and elemental sulfur were also present in the urine of this animal. Sulfur was found in all the urine samples collected from male cheetah in captivity in South Africa and from wild cheetah in Namibia. Only one organosulfur compound, dimethyl disulfide, is present in the urine at such a low concentration that it is not detectable by humans [97]. 

The general formula for an ester is RCOOR, where R is a hydrogen atom or a hydrocarbon, and R is a hydrocarbon. You can think of an ester as the product of a reaction between a carboxylic acid and an alcohol, as shown in Figure 1.26. 

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