Лако-красочные материалы — производство

NMR spectroscopy is commonly used for the identification of isomeric tetrazolium salts. There are significant differences in the chemical shifts of C-methyl and ^-methyl protons as shown in Table 4 for compounds 128 (126)   (127)   Scheme 18   CH3 СНзСОСН^® ^CH3 N N I I N-=-N (128)   Compound О ffi N-CH3 C-CH3 […]

The fragmentation of tetrazolium salts under electron impact seems to follow characteristic paths. 5-Methy1-2,3-diphenyl tetrazolium (124) shows, in addition to the parent ion peak, peaks corresponding to the phenyl diazonium fragment and the complementary ion at m/z 132. At higher ionization energies, a strong peak at m/z 91 corresponding to the elimination of acetonitrile from […]

X-ray structure analysis of 2,3-diphenyl-5-thiomethyltetrazolium triio­dide (123) shows that the phenyl rings at the 2- and 3-positions are out of the plane of the tetrazolium ring by 69 and 58°, respectively. The bond distances in the tetrazolium ring are not equal. In contrast, 2,3-diphenyl-5- mercaptide shows extensive bond delocalization.209,2 1 0

Nineham1 proposed that tetrazolium salts exist as resonance hybrids forms (120) and (121) (shown for 2,3-substituted ones). However, UV- visible, IR, NMR, and differential calorimetric studies on unsymmetrically substituted 2,3,5-triaryl tetrazolium salts (with a substituted phenyl in the 5-position) indicate the existence of distinct isomers.197-206 Inversion at the trisubstituted nitrogen may be slowed down by […]

7.4.1. Physical Properties Depending on the substituent, and to a lesser extent on the counterion, tetrazolium salts are generally crystalline colorless, or yellowish to orange solids. Although their solubility depends on the substituent pattern and the counterion, they are generally slightly soluble in water. Thus, tetrazoliumsalts containing trimethylammonium groups on the aromatic substituents are very […]

As will be discussed later (Sections 7.4.2.1 and 7.4.2.2), tetrazolium salts are not stable under basic conditions. Depending on the substituent, however, acidic conditions may allow some transformations. Thus, 2,3,5- triphenyltetrazolium chloride can be converted to the disulfonic acid deriva­tive by the action of concentrated sulfuric acid or oleum.1

Some of the methods used for the preparation of either formazans or tetrazoles can lead directly to tetrazolium salts when appropriate substitu­ents are present. 7.3.3.1. From Nitrilium Salts Nitrilium salts (66) react with alkyl or aryl azides to give good yields of 1,4,5-trisubstituted tetrazolium salts (115) (Eq. 20).189,255 7.3.3.2. Oxidations Ferricyanide oxidation of 1,5-disubstituted thiocarbazones […]

Benson et al. 177 first reported the synthesis of tetrazolium salts by the alkylation of disubstituted tetrazoles. While selectivity is a major problem, alkylation can still be considered a viable method for the preparation of 1,3,5- and 1,4,5-trisubstituted as well as 1,5 and 2,5-disubstituted tetrazolium salts. Electronic effects of substituent, as well as reaction conditions […]

Oxidation of guanazyls (112) with nitric acid or preferably lead tetra­acetate leads to tetrazole (113) with the elimination of urea. The reaction proceeds well, with near-quantitative yields, with a variety of 1- or 3- substituents as well as with bisguanazyls, e. g., 114 (Scheme 16).23-25,176

1,5- Disubstituted tetrazoles are conveniently prepared from acyl hydrazines (98) and diazonium salts.166 The reaction proceeds through the intermediate tetrazenes (99) followed by cyclization to the tetrazole (100) (Scheme 13). The intermediate can be isolated under mildly basic conditions. Symmetrically 1,2-diacylated hydrazines yield 1-substituted tet­razoles through the elimination of one of the acyl groups.166 — […]