Carboxylic acids, aromatic, olefinic

Naphthenic adds are a family of carboxylic acid surfactants, primarily consisting of cyclic terpenoids used in source and geochemical charaderisation of petroleum reserves (Brient, Wessner Doyle, 1995). The compwimd group is composed predominately of alkyl-substituted cycloaliphatic carboxyUc adds with smaller amounts of acyclic aliphatic (paraffinic or fatty) acids. Aromatic olefinic, hydroxyl and dibasic adds are also present as minor components of naphthenic adds. The cydoaliphatic adds include single rings and fused multiple rings. 

The fatty acids measured by these techniques have all been small monomeric molecules. Lamar and Goerlitz [ 125] studied the acidic materials in highly coloured water and found that most of the nonvolatile material was composed of polymeric hydroxy carboxylic acids, with some aromatic and olefinic unsaturation. Their methods included gas, paper, and column chromatography with infrared spectrophotometry as the major technique used for the actual characterisation of the compounds. 

Synthetic operations involving ozonolysis lead to formation of aldehydes, ketones or carboxylic acids, as shown in Scheme 16, or to various peroxide compounds, as depicted in Scheme 7 (Section V.B.5), depending on the nature of the R to R substituents and the prevalent conditions of reaction no effort is usually made to isolate either type of ozonide, but only the final products. This notwithstanding, intermediates 276 and 278 are prone to qualitative, quantitative and structural analysis. The appearance of a red-brown discoloration during ozonization of an olefin below — 180°C was postulated as due to formation of an olefin-ozone complex, in analogy to the jr-complexes formed with aromatic compounds however, this contention was contested (see also Section V1I.C.2). 

Oxidation of olefins 9-27 Oxidation of alkynes 9-65 Reductive condensation of aromatic carboxylic acids... 

On the pages which follow, general methods are illustrated for the synthesis of a wide variety of classes of organic compounds including acyl isocyanates (from amides and oxalyl chloride p. 16), epoxides (from reductive coupling of aromatic aldehydes by hexamethylphosphorous triamide p. 31), a-fluoro acids (from 1-alkenes p. 37), 0-lactams (from olefins and chlorosulfonyl isocyanate p. 51), 1 y3,5-triketones (from dianions of 1,3-diketones and esters p. 57), sulfinate esters (from disulfides, alcohols, and lead tetraacetate p. 62), carboxylic acids (from carbonylation of alcohols or olefins via carbonium-ion intermediates p. 72), sulfoxides (from sulfides and sodium periodate p. 78), carbazoles... 

Carboxylic acids contain the -C(0)0H functional group bound to an aliphatic, olefinic, or aromatic hydrocarbon moiety. This section deals with those carboxylic acids that contain only C, H, and O. Carboxylic acids that contain other elements, such as trichloroacetic acid (a strong acid) or deadly poisonous monofluoroacetic acid, are discussed in later chapters. Some of the more significant carboxylic acids are shown in Figure 14.6. 

Aluminum chloride is used in the petroleum industries and various aspects of organic chemistry technology. For example, aluminum chloride is a catalyst in the alkylation of paraffins and aromatic hydrocarbons by olefins and also in the formation of complex ketones, aldehydes, and carboxylic acid derivatives. 

Saturated hydrocarbons < olefins < aromatic hydrocarbons = organic halides < sulfides < ethers < nitro compounds < esters = aldehydes = ketones < alcohols = amines < sulfones < amides < carboxylic acids... 

Some variants of our central reaction have been discovered. Consistent with the notion that NHC ligands are stable in the absence of aromatic jr-stabilization, a non-aromatic N-heterocycle, 4,4-dimethyl-2-oxazoline (3), can be added to olefins in the presence of a rhodium catalyst [10]. The optimized reaction conditions are especially mild, making this an effective method for preparation of protected carboxylic acids. 

Olefins react with 4,4-dimethyl-2-oxazoline (3) much more efficiently (Table 3, azoline column) than they do with other (aromatic) substrates [10]. Rather than requiring reaction temperatures of 135-180 °C for the reaction to occur, addition of 3 to olefins is optimally conducted between 45 and 105 °C. The substrate scope of this reaction includes, for the first time, disubstituted alkenes (Table 3, azoline column, Entries 2 and 3). The coupling products of 3 with olefins can be depro-tected to reveal carboxylic acids or elaborated further using well-known methods [16]. 

In a process developed by Myers et al., aromatic carboxylic acids were directly employed as substrates for Heck olefinations, albeit in the presence of a large excess of silver carbonate [38]. This base both facilitates the decarboxylation step and acts as an oxidant, generating arylpalladium(II) intermediates. In related processes, arylphosphonic [39] and arylboronic acids [40] were used as aryl sources in the presence of an oxidant. 

Notable examples of general synthetic procedures in Volume 47 include the synthesis of aromatic aldehydes (from dichloro-methyl methyl ether), aliphatic aldehydes (from alkyl halides and trimethylamine oxide and by oxidation of alcohols using dimethyl sulfoxide, dicyclohexylcarbodiimide, and pyridinum trifluoro-acetate the latter method is particularly useful since the conditions are so mild), carbethoxycycloalkanones (from sodium hydride, diethyl carbonate, and the cycloalkanone), m-dialkylbenzenes (from the />-isomer by isomerization with hydrogen fluoride and boron trifluoride), and the deamination of amines (by conversion to the nitrosoamide and thermolysis to the ester). Other general methods are represented by the synthesis of 1,1-difluoro olefins (from sodium chlorodifluoroacetate, triphenyl phosphine, and an aldehyde or ketone), the nitration of aromatic rings (with ni-tronium tetrafluoroborate), the reductive methylation of aromatic nitro compounds (with formaldehyde and hydrogen), the synthesis of dialkyl ketones (from carboxylic acids and iron powder), and the preparation of 1-substituted cyclopropanols (from the condensation of a l,3-dichloro-2-propanol derivative and ethyl-... 

Tables 4 and 5 include several electron adducts of aromatic and olefinic carboxylic acids. The dissociation constants of these radicals are generally much higher than those of the parent acids because of the additional charge. It appears that one should not compare the value of 12-0 for the electron adduct (C6H5C02H) with pK = 4-2 for C6HsC02H. Instead, a comparison of the first pA = 5 3 for the conjugate acid of the electron adduct (C6HsC02H2)" seems more suitable. Similarly pK for the conjugate acid of the electron adduct of the C6HsC(OH)OCH3 (5-5) is comparable to that of the acid or...

The oxidation catalyst is believed to be ruthenium tetraoxide based on work by Engle,149 who showed that alkenes could be cleaved with stoichiometric amounts of ruthenium tetraoxide. Suitable solvents for the Ru/peracid systems are water and hexane, the alkene (if liquid) and aromatic compounds. Complex-ing solvents like dimethylformamide, acetonitrile and ethers, and the addition of nitrogen-complexing agents decrease the catalytic system s activity. It has also been found that the system has to be carefully buffered otherwise the yield of the resulting carboxylic acid drops drastically.150 The influence of various ruthenium compounds has also been studied, and generally most simple and complex ruthenium salts are active. The two exceptions are Ru-red and Ru-metal, which are both inferior to the others. Ruthenium to olefin molar ratios as low as 1/20000 will afford excellent cleavage yields (> 70%). vic-Diols are also... 

The classical method for making tert-butyl esters involves mineral acid-catalysed addition of the carboxylic acid to isobutene but it is a rather harsh procedure for use in any but the most insensitive of substrates [Scheme 6.33].80-82 Moreover, the method is hazardous because a sealed apparatus is needed to prevent evaporation of the volatile isobutene. A simpler procedure [Scheme 6.34] involves use of tert-butyl alcohol in the presence of a heterogeneous acid catalyst — concentrated sulfuric acid dispersed on powdered anhydrous magnesium sulfate. 3 No interna] pressure is developed during the reaction and the method is successful for various aromatic, aliphatic, olefinic, heteroaromatic, and protected amino acids. Also primary and secondary alcohols can be converted into the corresponding /erf-butyl ethers using essentially the same procedure (with the exception of alcohols particularly prone to carbonium ion formation (e.g. p-... 

The total unsaturation from Equation (7) can be apportioned into contributions from alicyclic structural moieties such as furanose and pyra-nose rings, aromatic structural moieties such as benzene rings, and carbonyl-containing moieties such as carboxylic acids, esters, amides, aldehydes, and ketones. Olefinic moieties such as the unsaturated alkyl chains of some lipids are thought to be of only minor importance. Equation (7) can thus be rewritten as... 

Assigning the peaks to individual carbons in a C SSNMR experiment is not always trivial, as peaks can vary by more than 10 ppm from their solution values. In a broad sense, peaks from 160 to 180 ppm are due to carbonyl groups of carboxylic acid derivatives, 200-220 ppm are due to ketone carbonyls, 100-160 ppm are from aromatic and olefinic carbons, 50-100 ppm are from sp -hydridized carbons attached to heteroatoms, and 10-40 ppm are typically aliphatic carbons attached to other carbons and/or hydrogens. These are purely estimates of the basic functionalities found in most organic molecules, and exceptions to these ranges are not uncommon. Many crystalline systems also possess more than one crystallographically inequivalent molecule per unit cell, which is also easily detectable in SSNMR experiments and can make interpretation of spectra more complicated. For instance, if two peaks exist in the C SSNMR spectrum for each carbon, there are two molecules in the unit cell, although not every peak in each inequivalent molecule is always resolved. 

In such olefin formation reactions, an electrodecarboxylation-deprotonation sequence is also involved. Electrochemical aromatization of the nonconjugated dienes (LXIV and LXVI) can be successfully performed by this method as in Eqs. (34) and (35) [154]. Decarboxylation of the y-lactone a- and )6-carboxylic acids (LXVIII and LXX) in a Py-H20-Et3N-(Pt or C) proceeds smoothly, yielding the corresponding bute-... 

A. Olefinic compounds Acetylenic compounds Aromatic compounds Carbonyl compounds F/c-Oxygen compounds Nitrogen compounds Sulfur compounds Halogen compounds Other heteroatom compounds Organometallic compounds Stereoselective and Stereospecific Electrooxidation A. Carboxylic acids Acetoxylation Methoxylation Acetamidation... 

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