Carboxylic adds, separation

Electrolysis, under similar conditions, of a mixture of two carboxyUc 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 add and a half-ester of an ouo-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. 

Groszek, A.J. (1985) Process for separating a carboxylic add of 1-8 carbon atoms from a mixture thereof with water and/or one or more other oxygenated aliphatic compounds. Eur. Patent 132,049. 

Access to racemic thiazolidine-2-carboxylic acid (3-thiaproline, 12) is obtained by reacting cysteamine (49) with glyoxylic acid ester (Scheme 9), 165>182>1831 whilst the reaction of (R)-cysteine with glyoxylic acid 184 1851 leads to (2/ /S,5/ )-thiazolidine-2-carboxylic acid. 185 The diastereomers of thiazolidine-2-carboxylic add (12) are rapidly interconverting and therefore cannot be separated. 185 In the presence of (2R,3R)- and (2S,3S)-tartaric acid, reaction of cysteamine with glyoxylic acid leads to the enantiomerically pure (2/ )- and (2S)-thia-zolidine-2-carboxylic acid salts. 186 The acids undergo fast racemization in acetic acid. 186 ... 

Schlosser, 5. (2002) Method of separation of carboxylic adds from aqueous and... 

Urea A is the starting material for preparing the carbodiimide C, which activates carboxylic acids according to the same mechanism and for the same reason as DCC, with which you are already familiar (Figures 6.15 and 6.26). If the carbodiimide C from Figure 7.5 were not so much more expensive than DCC, everybody would use the former instead of the latter for carboxylic acid activation. There is a practical reason for this. When a heteroatom nucleophile is acylated with the DCC adduct of a carboxylic acid, besides the desired carboxylic acid derivative one obtains dicyclohexyl urea (formula B in Figure 7.5). This (stoichiometric) by-product must be separated from the acylation product, which is relatively laborious when realized by chromatography or by crystallization. When a carboxylic add has been activated with the carbodiimide C and the subsequent acylation of a heteroatom nucleophile has been effected, one also obtains a urea as a stoichiometric by-product. It has the structure D and is therefore... 

A mixture of zwitterionic and cationic surfactants yielded superb separation of common anions on a C18 column, while a mixture of a zwitterionic and anionic modifiers proved valuable in the separation of carboxylic adds under reversed phase conditions. It reduced the chromatographic run time and improved peak shape [10]. 

An IPC-ESI-MS/MS method using volatile perfluorinated carboxylic adds as IPRs added directly to the sample solution (not incorporated into the mobile phase) was developed for the quantitative assay of methadone in human plasma. This cost-effective strategy enhanced the efficiency of separation and minimized ion suppression because no IPR was present in the eluent [103]. Table 13.1 lists other potential uses of IPC in the pharmaceutical and clinical analysis fields. 

Selective separation of strontium from calcium at significant SrCl2 concentration levels up to 2 g/L was obtained with KB-4 carboxylic add exchanger employed in a Higgins-type contactor [246]. The pilot unit for strontium recovery from seawater in the closed (and practically waste-free) processing scheme was constructed in the Okhotsk Sea region (Sakhalin power station). The data obtained with the new pilot plant have shown that several components will be recovered simultaneously from seawater. The unit is estimated to produce more than 150 kg of SrCOj, more than 5000 kg of KNOj, and about 2 kg of RbNOj [15]. However, recovery of strontium is still uneconomical. Its cost is expected to become comparable to that of strontium produced from traditional, land-based sources. 

Figure 8.1. Gradient separation of carboxylic adds with background correction with a 15 cm x 4.1 mm Hamilton PRP-X300 column of 0.17 mequiv/g exchange capacity. Gradient 1.0 mM sulfuric acid (pH 2.7) for 1.0 min, then a 0-20% acetonitrile linear gradient over 4.0 min. followed by a 5.0 min hold at 20 % acetonitrile. Other conditions were the same as in Fig. 1. Peaks I = oxalic acid, 2 = tartaric acid. 3 = maleic acid, 4 = citric acid, 5 = lactic add, 6 = acetic add, 7 = succinic add, 8 = glutaric acid, 9 = propionic acid, 10 = butyric acid, 11 = valeric add. From Ref. [7] with permission.

For GC or FIPLC quantification, or GC-MS identification, neutral compounds are of necessity analyzed without further chemical treatment. For compounds with functional groups such as hydroxyl, amino, carboxylic add, or reactive carbonyl groups, however, it may be convenient to prepare suitable derivatives. This has a long tradition in organic chemistry highlighted by the use of crystalline phenylosazones of carbohydrates to prepare and separate otherwise intradable mixtures of noncrystalline carbohydrates (Fischer 1909). In the present context, there are several advantages in using such procedures ... 

Complex formation between M " (M = Mg, Ca, Sr, or Ba) and l,3-diamino-2-hydroxypropane-JVN -dimalonic add, N-(carboxymethyl)aspartic add, NN-bis(carboxymethyl)aspartic acid, and thiophen-2-carboxylic add in aqueous solutions has been die subject of four separate investigations in general, the stability of the complexes decreases as the cationic radius is increased. ... 

Gif systems were originally designed to mimic non-heme enzymatic oxidation of alkanes. All of them involve a pyridine-acetic acid (or other carboxylic add) solution of the hydrocarbon being oxidized, an iron-based catalyst, and an electron source. However, Gif systems have a ploblem in the separation of catalyst because the homogeneous catalytic systems are employed. Thus, we have modified the GiflV system by using heterogeneous catalysts, iron oxide supported on silica, and then the results are reported in this paper. 

Supercritical fluids are known to posses several useful characteristics required to achieve efficient separation and enhanced reaction rates. It is also quite likely that the introduction of the additional supercritical phase can be beneficial in certain cases (Tab. 1.3). Suitable candidates are the reactions that involve components having their critical properties dose to the reaction conditions. The reaction pressure may be manipulated to fine-tune the required conditions. Hydration of ethylene, propylene, n-butenes and isobutylene, esterifications of carboxylic adds with these olefins, and even alkylations (e. g., cumene production, Cg alkylates from C4 streams) may be explored as potentially important reactions in this category. 

Lipids are long chain (C12-C30) biological hydrocarbons that have a single functional group, such as a carboxylic add, ester, or alcohol, at one end of the chain. Several methods can be considered for separating lipids from the plant or animal cells in which they are found. Candidate processes include these ... 

The process for the industrial production of permethric acid by Roussel-Uclaf starts from racemic trons-chrysanthemic acid, which is in turn accessed by the Martel synthesis (cf. 1,3-cycloelimination). After separation of the enantiomers with an amino-alcohol, the (IR)-enantiomer is subjected to ozonolysis. Basic epimerisation gives (IR)-cis-caronaldehyde hemiacetal. Water is added to the (IS)-enantiomer in the presence of a catalytic amount of sulfuric acid then the carboxylic add function is epimerised with the formation of a lactone. Magnesium bromide-catalysed ring-opening leads to (lR)-c s-chrysanthemic acid, which is converted into (IR)-ds-caronaldehyde hemiacetal by an analogous route. [105]... 

The nature of the chiral derivatization reagent is critical in achieving optimum resolution of the diastereomers, and for simple carboxylic add reagents containing a phenyl or other 7t-donating group close to the chiral centre are recommended to improve the resolution. This effect was particularly well demonstrated by Kaneda [59], who showed that the S(+)-2-butanol (20) or R(—)-2-octanol (21) esters of 2-methylbutyric add were unresolved by gas chromatography but the esters with R- -methylbenzyl alcohol (19) were readily separated. (See Section 4.2.2 for the numbered structures). 

If the catalyst is modified with titanium and phosphorus compounds it is possible under suitable reaction conditions, to use technical anthracene with a purity lower than 95%. The impurities in the technical anthracene are oxidized to the corresponding carboxylic adds, which can be separated from the anthraquinone with aqueous alkali Nihon lyoryu Kogyo). 

Umeh, E.O. Separation and determination of low molecular weight straight chain Ci g carboxylic adds by gas chro- 25. matography of their anilide derivatives. J. Chromatogr. 

The Hosomi-Sakurai-Prins reaction of the easily available enal 142 and allylsilane 143 was performed in the presence of Lewis acids to give the 4-methylene-tetrahydropyran with poor cis-trans selectivity ( 2 1), however, the pro tic acid provided only cis-144, which was converted into the aldehyde 145. The Takai iodoalkenylation, followed by desilylation and Sharpless asymmetric epoxidation, provided 146 with a 4 1 ratio of /Z, which was separable via the treatment of TBAE After protection of the primary alcohol, the alkenyllithium derived from the iodoalkene, reacted with aldehyde 147 to form 148, which was converted into epoxy-carboxylic add 149 in five steps. The key macrocyclization was performed by the treatment of 149 with Ti(Oi-Pr)4 [73] under high diluted conditions (2 mM) at 75 °C to provide the macrolactone 150 in moderate yield with 30% of the starting material recovery. After desilylation, the chemoselective oxidation of the allyl alcohol with 4-acetylamino-2,2,6,6-tetramethylpiperidine- 1-oxoammonium tetraflu-oroborate, followed by oxidative cleavage of the C20-C21 diol, produced (-)-dactyloUde (Scheme 30). 

Before starting a detailed discussion, some words have to be said about the approach taken here, especially with resped to the fatty acid salts. There is considerable scope for confusion and it has to be admitted that the situation is quite complex and by no means dearly resolved at present. The problems stem from the fad that salts such as caldum stearate are frequently used as additives in their own right and can influence compound properties without having any filler surface effeds. They are also often attraded to filler surfaces and may be formed when fatty acids read with filler surfaces. It is thus almost impossible to separate out the effects of surface and polymer modification, especially as filler surface treatments based on fatty acids may split off salts into the polymer phase, while salts initially in the polymer phase may become attached to the filler during processing. For consistency, the approach taken here is to discuss these additives in terms of filler surface attachment, but it is by no means dear that this is necessary for good effeds are to be obtained with fatty (and other carboxylic) adds and their salts [2]. 

L-ProNne, Pro pyrrolidine-2-carboxylic add, a pro-teogenic amino add. Pro is very soluble in water, but is also soluble in ethanol, so it can be separated from other amino adds by ethanol extraction. Being an imi-no add, it forms a yellow color with ninhydrin, rather than the purple color characteristic of a-amino acids... 

Organic acids or bases that have been extracted can be regenerated by neutralizing the extraction reagent. This would be done if the organic acid or base were a product of a reaction rather than an impurity. For example, if a carboxylic acid has been extracted with the aqueous base, the compound can be regenerated by acidifying the extract with 6 M HCl until the solution becomes just acidic, as indicated by litmus or pH paper. When the solution becomes acidic, the carboxylic add will separate from the aqueous solution. If the acid is a solid at room temperature, it will precipitate and can be purified by filtration and crystallization. If the acid is a liquid, it will form a separate layer. In this case, it would usually be necessary to... 

Based on earlier research on the separation of the lanthanides, ion exchange separations were also done using citric add as a complexant. Because the citrate eluent is plagued by relatively slow kinetics, other hydroxy-carboxylic adds were tested as elutriants for the higher actinide elements. Lactic add was among the first spedes tried, but better interactinide separations were observed using a-hydroxyisobutyric acid... 

Figure 5.15 Separation of aliphatic mono-carboxylic acids. Separator column lonPac ICE-AS1 eluent 1 mmol/L octanesulfonic add flow rate 1 mlVmin detection suppressed...

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