Trihydric phenols

An additional activating hydroxyl group on the phenolic ring allows resorcinol to react rapidly widi formaldehyde even in die absence of catalysts.8 Hiis provides a method for room temperature cure of resorcinol-formaldehyde resins or mixed phenol-formaldehyde/resorcinol-formaldehyde resins. Trihydric phenols have not achieved commercial importance, probably due to tiieir higher costs. 

With a 5.6% concentration of poly (vinyl alcohol), the proportion of gelling agents should be approximately as given below, on the basis of the weight of the poly(vinyl alcohol) dihydric phenols 40%, trihydric phenols 30%, 1-naphthols 8%, and dihydroxynaphthalenes 3.5%. 

In the rabbit, phenol gives rise to catechol and quinol. Hydroxyquinol is a minor metabolite of catechol but not of quinol, and neither quinol nor resorcinol is further oxidized to trihydric phenols.126 Aniline and its derivatives do not undergo meta substitution, but give rise to ortho- and para-directed hydroxylation products only.122... 

Other products that may be epoxidized in this way include dihydric and trihydric phenols, aliphatic polyols such as glycerol, and simple alcohols such as butanol or alyl alcohol. These products, especially the monofunctional glycidyl ethers, are used at relatively low percentages to reduce the viscosity of formulations containing DGEBA resins. In this way, they act as reactive diluents. 

Stone and Waters (1965) found that 4-methylcatechol, which cannot undergo condensation to give a dioxin derivative corresponding to that formed by catechol, gives, on aerial oxidation in alkaline solution, the semiquinone radical of the trihydric phenol (44), probably as follows ... 

There are three isomeric trihydric phenols or trihydroxy benzenes or benzenetriols, namely pyrogallol, phloroglucinol, and... 

The number of epoxy groups depends upon the number of OH groups in the starting material and the extent of substitution on those groups with the chloroepoxypropane. Alkyl substituted phenols such as o-cresol can also be used to produce epoxies, and esterified novolac resins can be used in polyester coatings. 2,3-epoxypropyl ethers can also be produced fiom di- and trihydric phenols. 

Mono-, di-, and trihydric phenols easily yield readily crystallizable esters with phenylnitrocinnamic or phenylcinnamic acid, in presence of phosphoric anhydride and a neutral solvent. The reaction increases in energy with the number of hydroxyl groups and therefore a solvent of high boiling point, such as toluene, should be employed with tri- and dihydric phenols. If the latter are in excess they yield only monocsters. ... 

Boehm, E., and Williams, R. 1943. Study of the inhibiting actions of propyl gallate and certain other trihydric phenols on the autoxidation of animal and vegetable oils. Qiiart. J. Pharm. and Pharmacol. 16, 232. 

Trihydric phenols have only played a minor role because of their high price. Bisphenol A [2,2 -Z /5(hydroxyphenyl)propane] is still being used to a small extent in phenolic resin production. However, there is renewed interest in some specialty phenols such as chlorinated and brominated types as a result of legislation regarding flame retardancy. 

This test is given by a number of phenols. In general monohydric phenols tend to give a red color but with di- and trihydric phenols the colors tend to be yellow-orange or brown. With vanillin and vanillic acid a characteristic purple color is obtained which appears to be specific for these two compounds (88). 

---