Cryptophenol

The aromatic ring of alkylphenols imparts an acidic character to the hydroxyl group the piC of unhindered alkylphenols is 10—11 (2). Alkylphenols unsubstituted in the ortho position dissolve in aqueous caustic. As the carbon number of the alkyl chain increases, the solubihty of the alkah phenolate salt in water decreases, but aqueous caustic extractions of alkylphenols from an organic solution can be accomphshed at elevated temperatures. Bulky ortho substituents reduce the solubihty of the alkah phenolate in water. The term cryptophenol has been used to describe this phenomenon. A 35% solution of potassium hydroxide in methanol (Qaisen s alkah) dissolves such hindered phenols (3). 

Thalictine (60), C37H40N2O6, an amorphous, air-sensitive base, was isolated from Thalictrum thunbergii D.C. as its nitrate salt, mp 226-228°C. The alkaloid shows [a]D -15.8° (CHC13), -12.2° (MeOH), IR 3550 cm"1 (OH), and it gave a positive ammonium phosphomolybdate color test for a cryptophenol. The... 

Haplophytine is a very weak acid, but it is apparent from its behavior that it contains neither carboxylic acid nor simple phenolic groupings. For example, chloroform extracts haplophytine from its solution in 0.2 N sodium hydroxide, but normal sodium hydroxide removes haplophytine from its solution in chloroform. Evaporation of its solutions in baryta or ammonia yields only haplophytine (2). That the weakly acidic center is contained in a cryptophenolic grouping is established by the following observations. Haplophytine reacts slowly with diazomethane to give a nonacidic O-methyl ether, mp 288°-291°, [a] +12° (chloroform),... 

The data could be explained by several trimeric alternatives and a choice between them was made as follows Constitution CLVIII was selected on the basis of the results obtained by repetition of the potassium in liquid ammonia cleavage of 0-ethylpilocereine. A careful search for products revealed that the reaction yielded, besides compounds CLIX, CLX, CLXI, and CLXII identified previously, the cryptophenolic base CLXIII. Formation of this is compatible only with formula CLVIII. 

The decomposition temperature of various ROO-CHD s was followed by the differential scanning calorimetry (DSC). 2-tert-Butylperoxy-2-methyl-4,6-di-tert-butyl-2,5-cyclohexadiene-l-one LXXIV (R = tert-Bu, R1 = Me) decomposes at 75 °C 31, 128. According to119 121, this ROO-CHD is about thirty times less thermally stable than the analogous isomeric XXXVIa. Also129 mentioned the lower thermal stability of 2-tert-butylperoxy-2,4,6-tri-tert-butyl-3,5-cyclo-hexadiene-l-one in comparision to 4-tert-butylperoxy-2,4,6-tri-tert-butyl-2,5-cyclo-hexadiene-l-one. In accordance with the high sensitivity to heat, the compounds of type LXXIV initiate the oxidation of tetrahydronapththalene as low as 65 °C 31> 32> 94. It can be extrapolated from the thermal behaviour of LXXIV that 2-alkylperoxy-3,5-cyclohexadienones, formed from so called cryptophenolic antioxidants, accelerate the oxidation of some hydrocarbon substrates already near the ambient temperature. 

In this section the reactions of 2-tert-butylated and 2,6-di-tert-butylated phenols recently described are considered. The former, the cryptophenols are not completely hindered like the 2,6-di-tett-butylphenols although their reactions are different from those of 2-methylphenols. In both groups the reactions are comparatively straightfonward and comprise substitution or oxidation either at the phenolic oxygen or at the carbon in the 4-position. 

The difficulties mentioned above can be progressively overcome when an increased ratio of chips of Firms spp. is mixed with those of Cryptomeria japonica in advance of cooking (122). Apparently, the resin acids from pine chips behave as a surfactant and dissolve some of the neutral resins as well as the cryptophenols out of Cryptomeria japonica chips into the aqueous media (18). 

Most phenols are soluble in dilute sodium hydroxide solution (for test see p. 105). However, exceptions are known—the so-called cryptophenols. The hydroxy group of these phenols is situated on the aromatic nucleus between substituents with branched chains or between other substituents easily donating electrons. 

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