Thiazole paper

Thiazole Paper (Mimosa Paper).—Used as an indicator for free alkali and is preferable to turmeric. Turned red by alkalis, but not influenced by ammonia even in high concentrations. 

Clayton yellow paper (thiazole paper) is paper impregnated with the dye formed by coupling diazotized primuline sulfonic acid with primuline sulfonic acid. The color change occurs at pH 11-12. If this paper is not available, a little less than the estimated amount of alkali should be used. The mixture is warmed to 85 and a small test portion is removed and warmed with more alkali. If any appreciable amount of the insoluble matter dissolves, more alkali is needed. 

The solution is then carefully neutralized by the dropwise addition of about 90 grams of concentrated hydrochloric acid to the point where the reaction to thiazole paper disappears. It is then heated to 80°, and 40 grams of zinc dust is added. If the solution is not decolorized in 5 minutes, more hydrochloric acid is dropped in slowly, keeping the tempera-... 

Thiazole yellow is changed by sodium hydroxide from a pure yellow to a bright red, and it can be used, therefore, as a reagent to test for alkali (thiazole paper). 

Thiazole Paper (Mimosa Paper). This indicator is used to test for free alkali. It is colored a pure red by alkalis and is far better for this purpose than Curcuma. The paper is prepared as described for Congo red paper, except that the acetic acid is omitted. Ammom a has no effect on this paper unless it is in very concentrated solution. 

Most of the spectroscopic properties of 2-imino-4-thiazolines have been treated in Section II. Paper chromatography and thin-layer chromatography are particularly suitable for distinguishing 2-atnino-thiazoles from 2-imino-4-thiazolines their RfS and characteristic reactions are different (148, 494. 705). 

The controversy seemed then to be closed. In 1890 Hantzsch had already started his work on the structure of oximes, and his synthetic work on heterocycles was practically ended. However, 27 years later, in July 1919, Tcherniac published a new paper entitled TTiiocyanoacetone and its derivatives as isomerides (33), where, after the description of improved and generalized methods for the preparation of thiocyanoacetone he came to the explosive conclusion that the substance which has been known since 1887 as hydroxymethylthiazole is not a thiazole at all. It might be called 2-imino-4-methylthioxole, but for the sake of simplicity, and in view of the now proved existence of two other isomerides of thiocyanoacetone, it seems preferable to adopt the generic... 

The first empirical and qualitative approach to the electronic structure of thiazole appeared in 1931 in a paper entitled Aspects of the chemistry of the thiazole group (115). In this historical review. Hunter showed the technical importance of the group, especially of the benzothiazole derivatives, and correlated the observed reactivity with the mobility of the electronic system. In 1943, Jensen et al. (116) explained the low value observed for the dipole moment of thiazole (1.64D in benzene) by the small contribution of the polar-limiting structures and thus by an essentially dienic character of the v system of thiazole. The first theoretical calculation of the electronic structure of thiazole. benzothiazole, and their methyl derivatives was performed by Pullman and Metzger using the Huckel method (5, 6, 8). 

Until the end of the forties, when the HMO method was first applied to thiazole, most of the experimental results concerning its chemical reactivity remained of a qualitative nature. Papers devoted to the subject... 

The infrared and Raman spectra of many alkyl and arylthiazoles have been recorded. Band assignment and more fundamental work has been undertaken on a small number of derivatives. Several papers have been dedicated to the interpretation of infrared spectra (128-134, 860), but they are not always in agreement with each other. However, the work of Chouteau (99, 135) is noteworthy. The infrared spectrum of thiazole consists of 18 normal vibrations as well as harmonic and combination bands. 

Papers dealing with this topic are exhaustively reviewed in Comprehensive Heterocyclic Chemistry I (84CHEC-I(6)235) and II (96CHEC-II(3)373). Nevertheless, little information is available on the 5-oxides. Recently, the heteroaromaticity of thiazole compared with isothiazole and thiadiazole 5,5-dioxide systems was studied (97MI1). Quantum-chemical calculations and X-ray studies were performed on 3,3 -di[l,3-thiazolidin-4-one] derivatives (95JCC(25)589) studied for their potential biological activity (97FA(52)43). 

The thiazolecarboxylic acid structure (40) was also guessed in a similar way, from tracer experiments. The unknown compound was converted into the thiamine thiazole by heating at 100°C and pH 2. On paper electrophoresis, it migrated as an anion at pH 4. Tracer experiments indicated that it incorporated C-l and C-2 of L-tyrosine, and the sulfur of sulfate. The synthetic acid was prepared by carboxylation of the lithium derivative of the thiamine thiazole, and the derivatives shown in Scheme 19 were obtained by conventional methods. Again, the radioactivity of the unknown, labeled with 35S could not be separated from structure 40, added as carrier, and the molar radioactivity remained constant through several recrystallizations and the derivatizations of Scheme 17. 

Since their commercial introduction during the 1940s as components of proprietary detergents and laundry preparations, these products have found extensive usage in the whitening of paper and textile materials. Disperse FBAs are available for whitening hydrophobic fibres and solvent-soluble FBAs impart fluorescence to oils, paints, varnishes and waxes. Approximately 75% of commercially established FBAs are stilbene derivatives with inherent substantivity for paper and cellulosic textiles, but the remainder come from about twenty different chemical classes. These include aminocoumarins (6%), naphthalimides (3%), pyrazoles and pyrazolines (each about 2%), acenaphthenes, benzidine sulphones, stilbene-naphthotriazoles, thiazoles and xanthenes (each about 1%). FBAs of these and other chemical types are discussed in detail in Chapter 11 of Volume 2. 

We reported in the previous papers [8, 9] that the effect of the operational factors such as temperature and solvents on the polymorphic crystallization of a thiazole derivative - 2-(3 -Cyano-4-(2-methylpropoxy)-phenyl)-4-methyl-thiazole-5-car-boxylic acid (BPT) - which is an enzyme inhibitor. In this paper, we synthesized the esters of BPT and studied the effect of the molecular structure on polymorphic nucleation systemically, and at the same time we also examined the solvent effect on the polymorphic nucleation of the ester. 

Two independent papers have reported the synthesis of nitrogen-heterocycle complexes of the type [RhCl3(py-X)3] (py-X = 3-Etpy, 3-CNpy, 4-Etpy, or 4-CNpy) and rr(ans-[RhY2L4] (Y = Cl or Br L = several substituted pyridines, isoquinoline, pyrimidine, pyrazole, thiazole, and substituted imidazoles). All the compounds were prepared catalytically by boiling RhCl3.3H20 with ethanolic solutions of L. It is interesting that 2-substituted... 

A number of papers have reported Stille couplings of either 2- or 5-stannylated thiazoles. The 2-stannylated thiazole 21 undergoes Stille couplings with the triflate 22 to give the aryldifluorophosphonate 23 which is useful as a building block for the... 

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