Isomerization acids

Naphthalene disulphonic acids are prepared by more prolonged sulphonation than in the preparation of the monosulphonic acids. Four isomeric acids are obtained. 

When treated with certain reagents, the ketoximes in particular undergo the Beckmann rearrangement to isomeric acid amides (p. 227). 

Amidation. Reaction of maleic anhydride or its isomeric acids with ammonia [7664-41-7] (qv), primary amines (qv), and secondary amines produces mono- or diamides. The monoamide derivative from the reaction of ammonia and maleic anhydride is called maleamic acid [557-24-4] (8). Another monoamide derivative formed from the reaction of aniline [62-53-3] and maleic anhydride is maleanilic acid [555-59-9] (9). 

Esterification. Both mono- and dialkyl maleates and fumarates are obtained on treatment of maleic anhydride or its isomeric acids with alcohols or alkoxides (25). An extensive review is available (59). Alkyl fumarates (18) often are made from isomeri2ation of the corresponding maleate (19) (60). 

Finally, the techniques of nmr, infrared spectroscopy, and thin-layer chromatography also can be used to assay maleic anhydride (172). The individual anhydrides may be analyzed by gas chromatography (173,174). The isomeric acids can be determined by polarography (175), thermal analysis (176), paper and thin-layer chromatographies (177), and nonaqueous titrations with an alkaU (178). Maleic and fumaric acids may be separated by both gel filtration (179) and ion-exchange techniques (180). 

Clay-catalyzed dimerization of unsaturated fatty acids appears to be a carbonium ion reaction, based on the observed double bond isomerization, acid catalysis, chain branching, and hydrogen transfer (8,9,11). 

Homolytic oxaziridine decomposition can be easily initiated by iron(II) ion in acidic media. Catalytic amounts are sufficient because chain reactions proceed. The reaction proceeds obviously in the case of 2-r-alkyloxaziridines like (56), where it yields the isomeric acid amide (111) (57JA5739). 

The use of the two isomeric acids yields an irregular chain inhibiting crystallisation. This has two consequences ... 

I b J per cent, alcohol. The I depended on. iccoi-ding to free acids, of which the at - la, and isomeric acid Wiiii also found ii... 

What spectroscopic method could you use to distinguish among the following three isomeric acids Tell what characteristic features you would expect for each acid. 

Hogeveen138 measured apparent acidity constants of substituted /i-phenylthio-, /J-phenylsulfinyl- and / -phenylsulfonyl-acrylic acids (cis and trans) in 50% v/v ethanol. The p values for transmission through SCH=CH, SOCH=CH and S02CH=CH were 0.531, 0.389 and 0.320 respectively for the cis acids and 0.652, 0.282 and 0.331 for the trans acids. These results were discussed in considerable detail and compared with those of pertinent related systems. Little importance was attached to the small differences between p values for cis/trans isomers, and the relative transmissions were taken as the mean p values 0.59,0.34 and 0.33. The superior transmission of SCH=CH was attributed to greater polarizability. The values for pKJtrans) — pKJcis) of isomeric acids were also discussed. For the sulfonyl acids this is almost constant at 0.1 unit for the sulfinyl adds there is some variation about a mean value of 0.26 unit, and for the thio adds there is also some variation about a mean value of — 0.15 unit. The differing behavior of the three systems in this respect was explained in terms of hypothetical conformations and electrostatic interactions therein. 

Figure 8 Separation of isomeric acids (maleic and fumaric acid) by controlled surface porosity anion exchange chromatography. Column Sulfonated fluoropolymer coated onto a 50-p glass bead. Average pore size about 1000 A. Flow rate 2.73 ml/min. Eluant 10 mM HN03. Temperature 60°C. Detection absorbance. (Reproduced from Kirkland, J. J., J. Chromatogr. Sci., 7,361,1969. By permission of Preston Publications, A Division of Preston Industries, Inc.)...

Care must be taken to use pure o-chlorotoluene in this preparation otherwise the o-chlorobenzoic acid may be contaminated with isomeric acids which are very difhcult to remove. The o-chlorotoluene therefore should be prepared from pure o-toluidine or o-chlorotoluenesulfonic acid. 

In the preceding chapter the formation of the less stable of two isomeric acids on rapid neutralization of an organometallic compound was explained in terms of a free ion or ion pair as the reagent. The compounds involved were the salts of comparatively strong acids, however, and the media were highly polar. The ion or ion pair would be less likely to be the reagent in the case of the salt of a very weak acid, such as an alkyl lithium compound, in a non-polar solvent. Salts of unsaturated but weak acids might exist in either of two partly covalent forms this possibility provides an alternative explanation for the formation of the less stable of the two isomeric acids on neutralization. Presumably the bulk of the covalent or partly covalent... 

This modification of the Curtius reaction has been used extensively in many laboratories and has been found to be generally applicable. Some examples from the literature include the stereoselective synthesis of a wide variety of cyclopropylamine derivatives from the corresponding acids,11-13 the stereoselective preparation of some substituted norbornylamines from easily isomerized acids,14 the preparation of some 1-aminocyelobutancearboxylic acids from the corresponding acid esters,18 the preparation of a substituted cyclobutanone from... 

Cyanogen produces, with hydroxyl, three isomeric acids and an isomerio neutral body —... 

In this series there sre three isomeric acids contahiing four atoms of carbon, viz. 

Wohler143 first described the formation, from concentrated aqueous thiocyanic acid, of a compound, C2H2N2S3 later named isoperthiocyanic acid, and now formulated as 3-imino-5-thiono-l,2,4-dithia-zolidine (144). Solutions of isoperthiocyanic acid in alkali deposit sulfur this redissolves presently giving a liquid containing144-147 the salt of an isomeric acid, later named perthiocyanic acid, for which the 3,5-dimercapto-l,2,4-thiadiazole structure is now accepted (see Section III, J, 1). This acid, isolated from its barium salt by treatment with mineral acid and ether extraction,144,145 readily reverts to isoperthiocyanic acid,144 but fairly stable specimens are obtainable under carefully controlled conditions.148 148... 

Tlic foregoing sulphonic acids are all known, at least in the form of their salts, and are obtainable, directly or indirectly, by the interaction of sulphurous and nitrous acids or their salts. Isomerides of some of the sulphonic acids are also known, for example, hydroxylaminc-iso-sulphonic acid, NH. O.SOo.OH,1 which is obtainable by the action of chlorosulphonic acid on hydroxylamine hydrochloride. As its constitution indicates, this isomeric acid is in reality a derivative of permono-sulphuric acid (see p. 192). 

The washings and mother liquors from crystallizations may be evaporated and esterified to separate the isomeric acids.3... 

Attempts to rearrange tne phenyl acid into the trane form by heating to 290° with fused alkali yielded a small amount of an isomeric acid. Tnis acid was unattacked by potassium permanganate and was probably the cls-phenyl cls-trans dlcarboxyllc acid not enough was at hand to Investigate its properties. 

Another isomeric acid Is obtained from bromtri-methyleuccinic anhydride It ie probably an unsaturated acid,the formula for the brom-anhydride perhaps being CH xc COjLH CH v... 

Free xanthic acids (83), also referred to as O-alkyl- and O-aryl-dithiocarbonic acids, are not well-characterized compounds. They are strong acids and stable only in an extremely pure state. The isomeric acids (84) are unknown. 

An alternative approach (1991JHC81) to the construction of the thieno[3,2-c] pyridine system is based on C(6)-C(7) bond formation (approach S). For example, heating carboxylic acid 279 in PPA resulted in its cyclization giving 9-oxo-4H, 9f/-pyrrolo[l,2-a]thieno[2,3-<7]pyridine (280) in low yield. An attempt to prepare this compound by an independent synthesis, viz., by cyclization of isomeric acid 281 under analogous conditions, failed. 

Grewe et al (29) synthesised the four possible isomeric acids by stereospecific routes, as also the corresponding piperidides, and determined their spectral and other physical characteristics. This cleared the confusion in earlier works on the supposed isolation of chavicinic acids from pepper. They also determined their pungency and showed that, excepting piperine, 5(3,4-dioxymethylene phenyl)-2-trans.4-trans-pentadienoic acid, all other isomers are poorly pungent. They concluded that neither chavicine nor the other two, cis-trans or trans-cis. isomers exist in natural pepper. They also showed that most of the isomers were unstable to light and were easily converted into the trans.trans piperine. 

In order to follow the catalytic recovering produced by the burning of coke, partially regenerated catalyst samples were submitted to standard reaction tests for benzene hydrogenation (metallic function) and normal pentane isomerization (acid function). Benzene hydrogenation was done at 423 K, 0.1 MPa, WHSV = 2 h 1, and molar ratio H2/Bz = 20. 200 mg of catalyst were loaded, which was reduced at 533 K with H2 for 2 h before the test. The isomerization of n-pentane was performed at 773 K, 0.1 MPa, WHSV = 2 h 1 and molar ratio H n = 6. 200 mg of catalyst were loaded, and were reduced with hydrogen at 773 K for 2 h before the test. 

The electrolysis of these three isomeric acids affords thus considerable qualitative differences in the results. Summing up the whole matter, it can be said that the electrolysis of a valeric acid gives octane, butyl valerate, butylene, butyl alcohol, and butyric aldehyde. 

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