Лако-красочные материалы — производство

5.3.2.1. Via One-Carbon Synthons Triethyl orthoformate or chloroform can react with arene nucleophiles to give triphenylmethanes with three identical aryl groups.5’52’67 In addi­tion, dialkylarylamines, when treated with dialkoxycarbenium tetrafluoro — borates under thermodynamic conditions or with triethyl orthoformate/zinc chloride in ether under anhydrous conditions, give triarylmethanes.68 For example, 4-methoxycarbazole and triethyl orthoformate in the presence […]

5.3.1. Diphenylmethanes Diphenylmethanes that have two identical phenyl groups are syn­thesized by the condensation of formaldehyde or its equivalent with an arylamine in the presence of concentrated hydrochloric acid.47-51 However, it is usually difficult to stop the reaction at the diphenylmethane stage. Magnesium phenolates react with triethylorthoformate regiospecifically at the ortho position of the phenoxy […]

Like most dyes, substituents on di — and triphenylmethane dyes have a significant effect on the absorption spectra. Acetylation of the imino nitro­gen of auramine O (32) results in shift to longer wavelength (Eq. 3). A general rule for triphenylmethane dyes is that the greater the fraction of positive charge that is on the auxochromes, […]

Some dyes can be formed from triphenylmethane leuco materials by simple thermolysis. For example, when 28 is heated an irreversible intra­molecular alkylation reaction occurs to form the stable dye41 29 (Eq. 1). Scheme 5 Besides the formation of colored compounds, leuco dyes can undergo other chemical reactions. For example, leuco bases can be sulfonated42 or […]

The formation of color from triheteroarylmethanes differs from the methodology employed for triphenylmethane leuco dyes40 (Scheme 4). Dyes are initially formed by alkylation of the pyridyl nitrogen, followed by deprotonation at the central methine carbon. Thus, treatment of the colorless 3,3′-diindolyl-4-pyridylmethane 22 with excess methyl iodide pro­duces colorless compound 23. Subsequent treatment of 23 with […]

The formation of colored materials from leuco bases such as 4 and 5 is accomplished by treatment with acids such as acid clay, bisphenol A, acetic acid, or silica gel.39 For leuco base 4 the leaving group is hydroxy, alkoxy, or cyanide, or a nitrogen-containing heterocycle.

Direct oxidation of diphenylmethanes is of little practical value as color formers. In liquid sulfur dioxide, leuco diphenylmethane 12 (Scheme 2) undergoes hydride abstraction by triphenylcarbenium perchlorate at the benzylic amine position to form immonium ion7 13, whereas in acetonitrile (11) Scheme 1 diphenylmethane dye 14 is formed. This example demonstrates the influence that the […]

5.2.1. Color-Formation Reactions Colorless triarylmethane leuco materials 8 can be converted to carbon — ium ion (9)-colored materials, either by hydride abstraction or by chemical or photooxidation. In addition, some leuco compounds such as 11 can be converted to colored materials by treatment with an acid. The latter case is similar to the chemistry observed […]

RAMAIAH MUTHYALA and XIANGFU LAN 5.1. INTRODUCTION Di — or triarylmethane leuco dyes are those with electron-donating groups such as amino, or hydroxyl substituted at the para or less frequently at the ortho position of phenyl rings. To be of value as dye precursors, at least two amino groups or a combination of hydroxyl and […]

In analogy to the original preparation of Malachite Green lactone, pyromellitic anhydride has also been reacted with N, N-dimethylaniline in a zinc chloride melt to yield mixtures of the bisphthalides 29 and 30.109 However, far superior yields were obtained if reaction was carried out in two steps, as described in Scheme 12. The initial condensation […]