Phenols Color reactions

Fia. 3. Alkaline ferricyanide 4-aminoantipyrine phenol color reaction [according to Powell and Smith (P22)]. 

Note Color reactions occur even before application of spray solution II [6]. Tertiary aliphatic amines and phenols with blocked ortho and para positions and aromatic N-acylated amines, e.g. acetanilide, do not react [1],... 

Sulfur-containing samples show colored spots when sprayed with 2,6-dibromo-quinone-4-chlorimide Gibbs reagent). For preparation, 2 g of this compound is dissolved in 100 ml of acetic acid or ethanol. Heating to 110°C is necessary to give a reaction. This reagent also creates colored zones when samples contain phenols. For reactions with phenols, only the less-reactive 2,6-dichloroquinone-4-chlorimide can be used under the same conditions. 

In a 1-1. round-bottomed flask are placed 36.0 g. (0.132 mole) of 2-(/>-tolylsulfonyl)dihydroisoindole,1 2 36.0 g. (0.38 mole) of phenol, 270 ml. of 48% hydrobromic acid (Note 1), and 45 ml. of propionic acid. A few boiling chips are added, and the flask is fitted with a reflux condenser in the top of which is placed a T-tube connected to a source of low-pressure nitrogen and to a mercury bubbler. The mixture is heated under reflux for 2 hours in an atmosphere of nitrogen. The deeply colored reaction mixture is cooled to room temperature, transferred to a 1-1. separatory funnel, and washed with two 200-ml. portions of ether (Note 2). The aqueous phase is then added dropwise over a 1-hour period to a vigorously stirred (Note 3) solution of 200 g. of sodium hydroxide in 600 ml. of water in a 2-1. Erlenmeyer flask immersed in an ice bath. The solution is transferred to a 3-1. separatory funnel and extracted with five 300-ml. portions of ether. The ethereal extracts are combined, dried over anhydrous potassium carbonate (Note 4), and filtered. The solvent is distilled, and the dark residual oil is transferred to a distillation... 

Repeated TLC of active, pooled fractions from Red Flame grapes revealed major spots with Ry s corresponding to those of catechin and epi-catechin, identical color reaction with p-toluenesolfonic acid spray reagent, and coelution of trimethylsilane (TMS) derivatives by GC with reference samples of these flavans. However catechin and epicatechin were assayed with the bacterial strains described and no activity was detected. TMS-derivatized samples of active grape flavans were examined by GC-MS, but a search for the molecular ions of a number of known wr-inducing phenolics yielded negative results. 

IBX possesses a great selectivity for the reaction with alcohols and the interaction with other functional groups normally demands more severe experimental conditions. According to Santagostino et al.,83 phenols and anilines react with IBX producing complex and dark colored reaction mixtures. Nevertheless, it is possible to selectively oxidize alcohols in the presence of certain phenols that are not very electron rich.88b... 

The main phase of reaction of pine kraft lignin with formaldehyde proceeds at almost constant pH (Figure 3). The extent of Cannizzaro reaction is insignificant since it can be estimated from the formic acid content. The formation of phenol alcohols (as determined by FeCl3-color reaction) reached its peak after 2 hours, and the stability is rather high even after a day. 

As indicated in the schematic diagram in Fig. 1, AOD was mixed with HRP, 4-aminophenazone, and phenol in phosphate buffer (pH 7.0) solution, and the colored reaction occurred with the mixture flowing through a 100-cm-long coil. All tubes used had a 0.8-mm id and the 25-cm injection valve loop permitted injection of 0.185 mL of enzymes-reagents solution per analysis. After each analysis, the solution produced containing the enzymes was directed to waste. 

The metabolism of atropine (227) by rat and guinea pig liver microsomes has been studied (197-199). French workers noted the formation of nora-tropine (229), apoatropine (233), and a phenolic metabolite formulated as the ortho-phenol 230 (197, 198) by liver microsomes from the rat, and they reported that hydrolysis of the ester function of 227 did not occur with enzymes from this source (197, 198). The structure of 229 was determined by TLC comparisons of the metabolite with an authentic sample and by correlation of the formation of the metabolite with the release of formaldehyde in the incubation mixture. The structure of 233 was deduced by TLC and UV spectral comparisons of isolated metabolite with authentic sample, and the phenol 230 was identified by TLC color reactions and by comparison with a phenolic sample obtained by Udenfried oxidation of atropine. In the absence of more definitive data on the phenolic products of this reaction, the structure 230 proposed for the phenolic metabolite of atropine... 

A large number of phenols and aromatic amines exhibit color reactions with lignified tissue and certain lignin preparations (Brauns 1952, Brauns and Brauns... 

Table 2.1.1. Color reactions of lignin with phenols and amines...

Uncondensed phenolic units in lignin have been estimated by a color reaction based on oxidation with potassium nitrosodisulfonate (Fremy s salt) (Adler and Lundquist 1961) as illustrated below ... 

Pew JC (1951) Structural aspect of the color reaction of lignin with phenols. J Am Chem Soc 73 1678-1685... 

In the field, a quick test for the general level of total phenolics in a plant can be the starting point for a more detailed quantitative analysis of the nature and amounts of specific compounds. Various oxidation-reduction methods have been exploited to analyze total phenolics in plant extracts. Many, but not all, phenols form complexes with ferric chloride (FeCy. Ferric chloride gives a color reaction with phenolic compounds. While the phenolate ion is oxidized, the ferric ions are reduced to the ferrous state. 

Chemical Reactions. Perform the same phenolics test with twigs of both jnvenile and adult growth forms of the same species. Use whatever species are available in your area aspen, cottonwood, red oak, willow, basswood, ash, or others. Compare the color reaction in jnvenile shoots with those in shoots of the adnlt growth form. 

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