3- Dimethylaminobenzaldehyde

The dimethylformamide is available as technical grade DMF from the Grasselli Chemicals Department of E. I. du Pont de Nemours and Company. Dimethylformamide can be prepared by the method of Mitchell and Reid s from dimethylamine and formic acid. 

Dimethylaniline free from monomethylaniline (Eastman Kodak Company) is used. 

It is possible to neutralize the acid solution partially with sodium hydroxide before the sodium acetate is added, but it is more difficult to avoid localized heating by this method. It is important to keep the reaction mixture below 20° during the neutralization, by the addition of ice if necessary, since any excessive increase in temperature of the aqueous solution leads to the formation of greenish blue dyestuffs, which are very difficult to remove from the product. 

The mixture may turn orange-colored when allowed to stand overnight. 

If a purer product is desired, the aldehyde may be purified by the method described by Adams and Coleman.  

The long known reaction of the indole nucleus of tryptophan with aldehydes under strongly acidic conditions to give colored products (135,287,397) was employed by Spies and Chambers (379) in a colorimetric procedure for the determination of tryptophan. In this method, the tryptophan-containing compounds (peptides or proteins) are dissolved in concentrated sulfuric acid containing / -dimethylamino-benzaldehyde (DAB) and a blue color is obtained after a prescribed time by adding sodium nitrite solution. 

The nature of the chromophore obtained upon reaction of the tryptophan residue and DAB is so far not completely elucidated. Current evidence does not permit a choice between structures (205) (derived from 1 mole of tryptophan and 1 mole of DAB) and (206), but (206) seems more likely since its formation requires oxidation (135). 

Although the method of Spies and Chambers has been extensively used and normally gives reliable results, the method has some limitations. Variations in the absorption maximum (from a normal value of 590- 

600 nm to 545-460 nm) have been verified with different protein samples (379). Intense light, oxidizing and reducing agents, including HiS, bisulfite and chloride ions interfere with the method (135, 379). Interference has been eliminated to some extent by appropriate addition of silver sulfate to the assay mixture (379). Low tryptophan values are obtained due to reaction of sulfur amino acids, serine and threonine with the indole nucleus of tryptophan. The nature of these reactions remains to be established. 

Friedman et al 136) eliminate interference due to cysteine and cystine residues by reducing the protein disulfide bonds and alkylating the native and generated-SH groups with vinyl derivatives. Juneja et al. 219) evaluated in detail the interference by sulfur amino acids they estimated the tryptophan content of wool colorimetrically after hydrolysis with 6N Ba(OH)2 for 5 hours at 125° C followed by removal of liberated H2S and barium with silver sulfate and sulfuric acid respectively. 

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Dissolve 2 g 4-dimethylaminobenzaldehyde in 100 ml of a mixture of glacial acetic acid and 32% hydrochloric acid (85 + 15). 

Dimethoxytetrahydrofuran 4-Dimethylaminobenzaldehyde Acetic acid (glacial acetic acid)... 

Dimethoxytetrahydrofuran forms pyrrole derivatives with primary amines, these derivatives then condense with 4-dimethylaminobenzaldehyde in acid milieu to yield colored products [1] ... 

Methyl-6-aminobenzoselenazole when treated with 3-penten-2-one gave by a simple Doebner-Miller type reaction the 2,7,8-trimethylselenazoloquinoline 43 in 18.6% yield, that is the angular product and not the linearly annelated one was formed. Its structure was confirmed by the coupling constant in proton NMR (71JHC693). Selenazoloquinoline 43 can be converted via the 6-methylpyridium salt in the reaction with 4-dimethylaminobenzaldehyde to 2,6-dimethyl-7,9-bis(l-(4-dimethylaminophenyl)-2-ethenyl)selenazolo[5,4-/]quinolinium iodide 44 (Ar = 4-dimethylaminophenyl). This dye exhibited two absorption maxima between 500 and 600 nm (72MI2). 

When treated with 4-dimethylaminobenzaldehyde, diazonium salts, or phthalic anhydride, these salts produced the corresponding styryl or azamethine dyes derived from l,2,3-thiadiazolo[4,5-/] or [5,4-/]quinolines. The Xmax of azamethine... 

It is possible to replace the vanillin in the reagent by 4-dimethylaminobenzaldehyde, 4-hydroxybenzaldehyde, salicylaldehyde, /n-anisaldehyde, cinnamaldehyde, 4-hydioxy-benzoic acid or vanillic acid [3]. However, the range of colors obtained is not so broad. 

Dimethoxytetrahydrofuran — 4-Dimethylaminobenzaldehyde Reagent 265 4-Dimethylamino-cinnamaldehyde — Hydrochloric Add Reagent. 269... 

There are two main synthetic routes to Crystal Violet Lactone (CVL) and its analogues (Figure 1.23). The first involves the condensation of 4,4 -bismethyhydrol (1.73), also called Michler s Hydrol, with 3-dimethylaminobenzoic acid in dilute acid to give the leuco CVL, which is then oxidised to CVL. A wide variety of oxidants can be used but the preferred method uses hydrogen peroxide in basic solution. The oldest, and most versatile route starts by reacting 4-dimethylaminobenzaldehyde... 

Bis(dimethylamino)benzil has been made previously by heating a mixture of oxalyl chloride and N,N-dimethylaniline under a pressure of 300 atmospheres of carbon monoxide in a steel pressure vessel at 100°.4 The present method is simpler and gives better yields. As 4-dimethylaminobenzaldehyde cannot be converted to the corresponding benzoin,5 this common route to benzils cannot be used to prepare 4,4 -bis (dimethylamino) benzil. 

Vanillin and 4-dimethylaminobenzaldehyde (DMABA) react with hydroxyl groups in the Ko-marowsky reaction. These postcolumn reagents, prepared in methanolic sulphuric acid, react with the carboxylic acid PETs at elevated temperatures. The PETs decompose in a poorly understood reaction, to form colored products detected at ca. 520 nm. Typically, the extraction step consists of either LLE or SPE (98). 

The most important styryl dyes for textile dyeing are obtained by condensation of 4-aminobenzaldehydes with l,3,3-trimethyl-2-methyleneindoline and its derivatives. The dye 26, synthesized from 4-dimethylaminobenzaldehyde and l,3,3-trimethyl-2-methyleneindoline dyes polyacrylonitrile, a brilliant red shade. 

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