Phenolic, groups

Reactions of Picric Acid, (i) The presence of the three nitro groups in picric acid considerably increases the acidic properties of the phenolic group and therefore picric acid, unlike most phenols, will evolve carbon dioxide from sodium carbonate solution. Show this by boiling picric acid with sodium carbonate solution, using the method described in Section 5, p. 330. The reaction is not readily shown by a cold saturated aqueous solution of picric acid, because the latter is so dilute that the sodium carbonate is largely converted into sodium bicarbonate without loss of carbon dioxide. 

Phenol condenses with phthahc anhydride in the presence of concentrated sulphuric acid or anhydrous zinc chloride to yield the colourless phenolphthalein as the main product. When dilute caustic alkah is added to an alcoholic solution of phenolphthalein, an intense red colouration is produced. The alkali opens the lactone ring in phenolphthalein and forms a salt at one phenolic group. The reaction may be represented in steps, with the formation of a h3q)othetical unstable Intermediate that changes to a coloured ion. The colour is probably due to resonance which places the negative charge on either of the two equivalent oxygen atoms. With excess of concentrated caustic alkali, the first red colour disappears this is due to the production of the carbinol and attendant salt formation, rendering resonance impossible. The various reactions may be represented as follows ... 

Band 1, 3 OSyL (3242 cm.". ) Hydrogen bonded 0—H absorption of the phenolic group (Table II). 

Fig. 28. Traditional duv-resist design using derivatives of polyhydroxystyrene. Monomer (a) contributes hydrophilic character to the polymer, and its acidic phenol group enhances aqueous base solubiUty monomer (b) provides acid-labile pendent groups.

This reaction can also be utili2ed to prepare functionali2ed initiators by reaction of butyUithium with a substituted 1,1-diphenylethylene derivative. For example, polymers end functionali2ed with primary amine, tertiary amine, phenol, and bis(phenol) groups have been prepared in essentiaUy quantitative yield by using the reaction of butyUithium with the corresponding substituted (or protected) 1,1-diphenylethylene (87). 

Here X and Y are immobilizing groups. Fuji instant color films are based on a similar dye-release mechanism using the o-sulfonamidophenol dye-release compounds shown in Figure 8 (35). Similarly, immobilej -su1fonamidoani1ines, where Y is H and the phenol group is replaced by an NHR moiety, may be used as dye releasers. 

A 2-methoxyethoxymethyl ether was used to protect one phenol group during a total synthesis of gibberellic acid. 

An ether that would not undergo rearrangement to a 3-alkyl derivative during acid-catalyzed removal of — NH protective groups was required to protect the phenol group in tyrosine. Four compounds were investigated (9-cyclohexyl-, (9-isobomyl-, 0-[l-(5-pentamethylcyclopentadienyl)ethyl]-, and O-isopropyltyro-sine. 

Pivaloyl chloride reacts selectively with the less hindered phenol group. 

Catechols can be protected as diethers or diesters by methods that have been described to protect phenols. However, formation of cyclic acetals and ketals (e.g., methylenedioxy, acetonide, cyclohexylidenedioxy, diphenylmethylenedioxy derivatives) or cyclic esters (e.g., borates or carbonates) selectively protects the two adjacent hydroxyl groups in the presence of isolated phenol groups. 

A cyclic borate can be used to protect a catechol group during base-catalyzed alkylation or acylation of an isolated phenol group the borate ester is then readily hydrolyzed by dilute acid. ... 

Metal oxides. Magnesium oxide is used to cure polychloroprene by converting its few active allylic chloride from 1,2 addition into ether cross-links. There is a synergistic effect when magnesium oxide is used in combination with t-butyl phenolic resins in solvent-borne polychloroprene adhesives. When solvent is removed, the phenolic group in the resin reacts with the magnesium oxide to cross-link [49]. 

These results demonstrate some interesting chemical principles of the use of acrylic adhesives. They stick to a broad range of substrates, with some notable exceptions. One of these is galvanized steel, a chemically active substrate which can interact with the adhesive and inhibit cure. Another is Noryl , a blend of polystyrene and polyphenylene oxide. It contains phenol groups that are known polymerization inhibitors. Highly non-polar substrates such as polyolefins and silicones are difficult to bond with any technology, but as we shall see, the initiator can play a big role in acrylic adhesion to polyolefins. 

Synthesis of the remaining half of the molecule starts with the formation of the monomethyl ether (9) from orcinol (8). The carbon atom that is to serve as the bridge is introduced as an aldehyde by formylation with zinc cyanide and hydrochloric acid (10). The phenol is then protected as the acetate. Successive oxidation and treatment with thionyl chloride affords the protected acid chloride (11). Acylation of the free phenol group in 7 by means of 11 affords the ester, 12. The ester is then rearranged by an ortho-Fries reaction (catalyzed by either titanium... 

Reaction of pyroc techol with epichlorohydrin in the presence of base affords the benzodioxan derivative, 136, (The reaction may well involve initial displacement of halogen by phenoxide followed by opening of the oxirane by the anion from the second phenolic group.) Treatment of the alcohol with thio-nyl chloride gives the corresponding chloro compound (137). Displacement of halogen by means of diethylamine affords piper-oxan (138), a compound with a-sympathetic blocking activity. 

The methyl ether of eugenol, CjjHj 02, is found in calamus oil, cassie oU, betel oil, bay oil, and various other essential oils. It can be prepared artificially by the action of methyl iodide on eugenol sodium. Its constitution is identical with that of eugenol, except that the phenolic group, OH, has been replaced by the methoxy group, O. CHg. 

Phenolat, n. phenoxide, phenolate. Phenol-ather, m. phenol ether, -carbonsaure, /. phenolcarboxylic acid, -gruppe, /, phenol group,... 

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