Salt isomerism

Thiiranium chloride, 1,2,2,3,3-pentamethyl-formation, 7, 174 Thiiranium salts isomerization, 7, 163 reactions... 

Indolizines, aromatic heterocycles with 12-jr-elec-tron system salts, isomeric with indole and isoindole, are prepared in good yields from pyrylium salts with active a-methylene groups.215 216 Aromatics derived from pyrylium salts by substitution of one or two fi-CW group(s) with a heteroatom are also possible. 

Chromium in the trivalent state forms a variety of salts, the most important and the simplest being the violet salts, which liberate in aqueous solution chromium cation Cr" A green series of chromic salts, isomeric with the violet salts, liberate in aqueous solution some chromium cation, whilst part of the chromium is present as a complex ion. With weak acids, sulphurous, hydrocyanic, or thiocyanic acids, the chromic ion forms complex ions of great stability. Finally, a very large group of salts exists where chromium associated with ammonia forms the complex ion, the chromi-ammines. 

Z-I2 complex leads to the formation of (Z)- as well as ( )-radicals of 99. In the absence of iodine, the free 99 salt isomerizes reversibly upon direct irradiation [242]. 

Werner (34) has discussed an example of what he believes to be salt isomerism, namely [Co(en)2(NCS)2]Cl, in which the NCS group can be N-bonded or S-bonded. It seems, however, that true salt isomers involving the NCS groups are not yet known for Co(III) complexes. Recently, Basolo et al. (8, 9) have prepared them for the first time for Pd (II). 

This method is based on the potassium salts isomerization of phthalic adds. Developed to the industrial stage by Teijin and Kawasaki in Japan, it employs phthalic anhydride or its precursor, o-xylene, as the raw material. If the raw material is phthalic anhydride, the essential step is the potassium salts isomerization of phthalic adds. This reaction, conducted under carbon dioxide pressure at 2.106 Pa absolute and 400°C, in the presence of cadmium salts as catalyst, is followed by exchange reactions of the potassium salts. 

In fact, Werner played such a central and almost monopolistic role in coordination chemistry that his name is virtually synonymous with the field. Even today, almost 75 years after his death in 1919, coordination compounds, particularly metal-ammines, are still colloquially called Werner complexes. The coordination theory not only provided a logical explanation for known "molecular compounds, but also predicted series of unknown compounds, whose eventual discovery lent further weight to Werner s controversial ideas. He showed how ammonia could be replaced by water or other groups, and he demonstrated the existence of transition series between ammines, double salts, and hydrates. Werner recognized and named many types of inorganic isomerism such as coordination isomerism, polymerization isomerism, ionization isomerism, hydrate isomerism, salt isomerism, coordination position isomerism, and valence isomerism. He also postulated explanations for polynuclear complexes, hydrated metal ions, hydrolysis, and acids and bases. His view of the two types of chemical... 

COT is prepared by the polymerization of ethyne at moderate temperature and pressure in the presence of nickel salts. The molecule is non-planar and behaves as a typical cyclic olefin, having no aromatic properties. It may be catalytically hydrogenated to cyclo-octene, but with Zn and dil. sulphuric acid gives 1,3,6-cyclooclairiene. It reacts with maleic anhydride to give an adduct, m.p. 166 C, derived from the isomeric structure bicyclo-4,2,0-octa-2,4,7-triene(I) ... 

To isomerize safrole to isosafrole one would like to have pure safrole to start with. This, usually, is not the case. Quasi-pure safrole from sassafras oil is ok. Straight-up sassafras oil is probably ok too, though not recommended. The safrole is then refluxed (boiled under a condenser) in a saturated KOHyethanoI solution for about a day and that s it. The temperature of reflux is about 120-140°C owing to the fact that the ethanol (usually boiling around 65-70°C) is saturated with the halide salt. 

If two equivalents of the reagents are used, disubstitution to ECeC-CH(E)R occurs in most cases, but interestingly the reaction of LiCeCCH(Li)R with an excess of COj gives mainly the allenic dicarboxylic acids. These are probably the result of a rapid isomerization of the primary dilithium salt of the acetylenic diacid during the work-up or during the reaction of the dilithio compound with COj ... 

Tertiary acetylenic halides give unsatisfactory results owing to further isomerization of the allenic halide into a conjugated diene system under the influence of the copper salt. Bromo- and iodoallenes with the structures R R2C=C=CH-X can also be synthesized by an aqueous procedure, consisting of reaction between... 

Note 1. No cyanide was used to remove the copper salts, since the nitrile is probably very base-sensitive (isomerization to a conjugated diene). 

Imino-4-thiazolines are far more basic than their isomeric 2-aminothiazoles (see Table VI-1). They react with most electrophDic centers through the exocyclic nitrogen and are easily acylated (37, 477, 706) and sulfonated (652). The reaction of 2-imino-3-methyi-4-thiazoline (378) with a-chloracetic anhydride yields 379 (Scheme 217) (707). This exclusive reactivity of the exocyclic nitrogen precludes the direct synthesis of endocyclic quaternary salts of 2-imino-4-thiazolines. although this class of compounds was prepared recently according to Scheme 218 (493). 

Able to form Ag salt of lower solubility than AgQ in H2O. Therefore applications in photographic processes Inhibition of histidine decarboxylase activity Antifoggant for color films Anthelmintic activity Quenching for oil composition caialj si for the industrial isomerization of cis a, (3 unsaturaied carboxylic acids rubber vul-cankzate improver... 

The first identified complexes of unsubstituted thiazole were described by Erlenmeyer and Schmid (461) they were obtained by dissolution in absolute alcohol of both thiazole and an anhydrous cobalt(II) salt (Table 1-62). Heating the a-CoCri 2Th complex in chloroform gives the 0 isomer, which on standirtg at room temperature reverses back to the a form. According to Hant2sch (462), these isomers correspond to a cis-trans isomerism. Several complexes of 2,2 -(183) and 4,4 -dithiazolyl (184) were also prepared and found similar to pyridyl analogs (185) (Table 1-63). Zn(II), Fe(II), Co(II), Ni(II) and Cu(II) chelates of 2.4-/>is(2-pyridyl)thiazole (186) and (2-pyridylamino)-4-(2-pyridy])thiazole (187) have been investigated. The formation constants for species MLr, and ML -" (L = 186 or 187) have been calculated from data obtained by potentiometric, spectrophotometric, and partition techniques. 

With R] different from R2 two isomeric compounds (138 and 139) are possible, depending on the direction of ring closure (86). However, only one form is generally obtained. Finally, the trisubstituted thioureas such as N,N,N -trimethylthiourea react with chloroacetone to give a thiazolium salt, in a reaction identical to that of the N-monosubstituted thioamides (Scheme 67). 

In the presence of mercuric salts, butynediol rapidly isomerizes to 1-hydroxy-3-buten-2-one (62). 

Henkel Rearrangement of Benzoic Acid and Phthalic Anhydride. Henkel technology is based on the conversion of benzenecarboxyhc acids to their potassium salts. The salts are rearranged in the presence of carbon dioxide and a catalyst such as cadmium or zinc oxide to form dipotassium terephthalate, which is converted to terephthahc acid (59—61). Henkel technology is obsolete and is no longer practiced, but it was once commercialized by Teijin Hercules Chemical Co. and Kawasaki Kasei Chemicals Ltd. Both processes foUowed a route starting with oxidation of napthalene to phthahc anhydride. In the Teijin process, the phthaHc anhydride was converted sequentially to monopotassium and then dipotassium o-phthalate by aqueous recycle of monopotassium and dipotassium terephthalate (62). The dipotassium o-phthalate was recovered and isomerized in carbon dioxide at a pressure of 1000—5000 kPa ( 10 50 atm) and at 350—450°C. The product dipotassium terephthalate was dissolved in water and recycled as noted above. Production of monopotassium o-phthalate released terephthahc acid, which was filtered, dried, and stored (63,64). 

For many years oral xanthines, shown in Table 2, were the preferred first-line treatment for asthma in the United States, and if the aerosol and oral formulations of P2" go sts are considered separately, as they are in Table 1, this was still the case in 1989. Within this class of compounds theophylline (8), or one of its various salt forms, such as aminophylline [317-34-0] (theophylline ethylenediamine 2 l), have been the predominant agents. Theophylline, 1,3-dimethylxanthine [58-55-9], is but one member of a class of naturally occurring alkaloids. Two more common alkaloids are theobromine (9), isomeric with theophylline and the principal alkaloid in cacao beans, and caffeine, (10), 1,3,7-Trimethylxanthine [58-08-2], found in coffee and tea. 

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