PROPERTIES OF PHENOLS

It is important to analyze the fact that the phenoxide ion s negative charge is stabilized by the delocalization of the electrons into the benzene ring This is one of the reasons for phenols increased acidity compared to alcohols. In alkoxide ions negative charge is localized in the oxygen atom (not delocalized). 

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One of the characteristic properties of phenol is the ease with which it gives substitution products, this property being particularly well shown by the ready nitration, sulphonation and bromination which the benzene ring in the phenol molecule undergoes. 

The observation of nitration nitrosation for mesitylene is important, for it shows that this reaction depends on the reactivity of the aromatic nucleus rather than on any special properties of phenols or anilines. 

Many of the properties of phenols reflect the polarization implied by the resonance description The hydroxyl oxygen is less basic and the hydroxyl proton more acidic in phenols than m alcohols Electrophiles attack the aromatic ring of phenols much faster than they attack benzene indicating that the ring especially at the positions ortho and para to the hydroxyl group is relatively electron rich... 

The most characteristic property of phenols is their acidity Phenols are more acidic than alcohols but less acidic than carboxylic acids Recall that carboxylic acids have s of approximately 5 whereas the pK s of alcohols are m the 16-20 range The pK for most phenols is about 10... 

At room temperature phenol is a white, crystalline mass. Phenol gradually turns pink if it contains impurities or is exposed to heat or light. It has a distinctive sweet, tarry odor, and burning taste. Phenol has limited solubiUty in water between 0 and 65°C. Above 65.3°C phenol and water are miscible in all proportions. It is very soluble in alcohol, ben2ene, chloroform, ether, and partially disassociated organics in general. It is less soluble in paraffinic hydrocarbons. The important physical properties of phenol are Hsted in Table 1. 

Beside being acidic, a significant industrial chemical property of phenol is the extremely high reactivity of its ring toward electrophilic substitution. If steric conditions permit, the substitution leads first to the formation of the 2- or 4-mono derivative, then to the 2,4- or 2,6-diderivative, and finally to the 2,4,6-triderivative. The halogenation of phenol produces mono-, di-, and tribal ophenols. 

Table 15. Strength Properties of Phenolic—Carbon-Fiber Composites...

Table 23.3 Average physical properties of phenolic resin-based laminates...

Cresylic acid is a commercial mixture of phenolic compounds including phenol, cresols, and xylenols. This mixture varies widely according to its source. Properties of phenol, cresols, and xylenols are shown in Table 4-5 Cresylic acid constitutes part of the oxygen compounds found in crudes that are concentrated in the naphtha fraction obtained principally from naphthenic and asphaltic-based crudes. Phenolic compounds, which are weak acids, are extracted with relatively strong aqueous caustic solutions. 

Important properties of phenolic resins are their hardness, corrosion resistance, rigidity, and resistance to water hydrolysis. They are also less expensive than many other polymers. 

Imai, Y., et al. (2001). Fluorescence properties of phenolate anions of coe-lenteramide analogues the light-emitter structure in aequorin bioluminescence. J. Photocbem. Photobiol., A Chemistry 146 95-107. 

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