Preparation and Uses of Phenols

The outbreak of World War I provided a stimulus for industrial preparation of large amounts of synthetic phenol, which was needed as a raw material to manufacture the explosive, picric acid (2,4,6-trinitrophenol). Today, more than 2 million tons of phenol are manufactured each year in the United States for use in such products as Bakelite resin and adhesives for binding pl3Wood. 

For many years, phenol was manufactured b the Dow process, in which chlorobenzene reacts with NaOH at high temperature and pressure (Section 16.9). Now, however, an alternative synthesis from isopropylbenzene (cumene) is used. Cumene reacts with air at high temperature by a radical mechanism to form cumene hydroperoxide, which is converted into phenol and acetone by treatment with acid. This is a particularly efficient process because two valuable chemicals are prepared at the same time. 

Mechanism of the formation of phenol by acid-catalyzed reaction of cumene hydroperoxide. 

Protonation of the hydroperoxy group on the terminal oxygen atom gives an oxonium ion. .. 

Nucleophilic addition of water to the carbocation yields another oxonium ion... 

Elimination of phenol from the protonated hemiacetal gives acetone as coproduct. 

In the laboratory, simple phenols can be prepared from aromatic sulfonic acids by melting with NaOH at high temperature (Section 16.2). Few functional groups can survive such harsh conditions, though, and the reaction is therefore limited to the preparation of alkyl-substituted phenols. We ll see a better method of phenol preparation from aromatic amines in Section 24.8. 

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Polymer stabilization has been realized by generating a highly reactive carbene species that can insert into the polymer chain. Kaplan et al. described the preparation and use of a phenolic diazooxide that generates a carbene upon heating and that attaches the phenolic group to... 

Recently, Porter and Waisbrot demonstrated that azidoformyl compounds containing a hindered phenolic antioxidant moiety decomposed thermally to form carbalkoxynitrene intermediates that insert into a natural rubber matrix (9). This chapter describes the preparation and use of antioxidants containing the sulfonyl azide group, that decomposes to liberate nitrogen and the sulfonyl nitrene species when heated either in a vulcanization process or in an extruder. 

Today, phenol-formaldehyde resins, using prepolymers such as novolaks and resols, are widely used in industry, mainly because they demonstrate excellent toughness and thermal-resistant properties. There is, however, a general concern regarding the toxicity of formaldehyde, and this has resulted in hmitations on the preparation and use of these materials. Consequently, an alternative process for the synthesis of phenolic polymers which would avoid the use of formaldehyde, has long been sought. 

The samples preparation and extraction of phenolics from source materials is the first step involved in their analysis. While colorimetric methods are used for determination of different classes of phenolics, chromatographic and... 

How does the benzene ring modify the behavior of neighboring reactive centers This chapter takes a closer look at the effects exerted by the ring on the reactivity of alkyl substituents, as well as of attached hydroxy and amino functions. We shall see that the behavior of these groups (introduced in Chapters 3, 8, and 21) is altered by the occurrence of resonance. After considering the special reactivity of aryl-substituted (benzylic) carbon atoms, we turn our attention to the preparation and reactions of phenols and benzenamines (anilines). These compounds are found widely in nature and are used in synthetic procedures as precursors to substances such as aspirin, dyes, and vitamins. 

Brominated Phenols. Tribromophenol [75-80-9] and dibromophenol [615-58-7] are both prepared through bromination of phenol. These are not actually used as reactive flame retardants, but rather as starting materials for other flame retardants such as BTBPE [37853-59-1] and epoxy oligomers. 

Ethyleneamines are used in certain petroleum refining operations as well. Eor example, an EDA solution of sodium 2-aminoethoxide is used to extract thiols from straight-mn petroleum distillates (314) a combination of substituted phenol and AEP are used as an antioxidant to control fouling during processing of a hydrocarbon (315) AEP is used to separate alkenes from thermally cracked petroleum products (316) and TEPA is used to separate carbon disulfide from a pyrolysis fraction from ethylene production (317). EDA and DETA are used in the preparation and reprocessing of certain... 

In addition lo its use in making resins and adhesives, phenol is also the starting material for the synthesis of chlorinated phenols and the food preservatives BHT (butylated hvdroxytoiuene) and BHA (butylated bydroxyanisole). Penta-chlorophenol, a widely used wood preservative, is prepared by reaction of phenol with excess CI2- The herbicide 2,4-D (2,4-dichlorophenoxyacetjc acid) is prepared from 2,4-dichlorophenol, and the hospital antiseptic agent hexa-chlorophene is prepared from 2,4,5-trichlorophenol. 

An 8000-member library of trisamino- and aminooxy-l,3,5-triazines has been prepared by use of highly effective, microwave-assisted nucleophilic substitution of polypropylene (PP) or cellulose membrane-bound monochlorotriazines. The key step relied on the microwave-promoted substitution of the chlorine atom in monochlorotriazines (Scheme 12.7) [35]. Whereas the conventional procedure required relatively harsh conditions such as 80 °C for 5 h or very long reaction times (4 days), all substitution reactions were found to proceed within 6 min, with both amines and solutions of cesium salts of phenols, and use of microwave irradiation in a domestic oven under atmospheric reaction conditions. The reactions were conducted by applying a SPOT-synthesis technique [36] on 18 x 26 cm cellulose membranes leading to a spatially addressed parallel assembly of the desired triazines after cleavage with TFA vapor. This concept was later also extended to other halogenated heterocycles, such as 2,4,6-trichloropyrimidine, 4,6-dichloro-5-nitropyrimidine, and 2,6,8-trichloro-7-methylpurine, and applied to the synthesis of macrocyclic peptidomimetics [37]. 

Phenol is both a man-made chemical and produced naturally. It is found in nature in some foods and in human and animal wastes and decomposing organic material. The largest single use of phenol is as an intermediate in the production of phenolic resins. However, it is also used in the production of caprolactam (which is used in the manufacture of nylon 6 and other synthetic fibers) and bisphenol A (which is used in the manufacture of epoxy and other resins). Phenol is also used as a slimicide (a chemical toxic to bacteria and fungi characteristic of aqueous slimes), as a disinfectant, and in medicinal preparations such as over-the-counter treatments for sore throats. Phenol ranks in the top 50 in production volumes for chemicals produced in the United States. Chapters 3 and 4 contain more information. 

This paper, then, describes the preparation and characterization of a solvolysis lignin prepared under conditions that are very different to previous solvolytic lignin preparations. In particular, no water, acid or base is used in this process during the delignification step. The lignin is then acid precipitated and hydrolyzed in dilute aqueous solution to produce monomeric substituted phenols. 

DEPC-treated water should be used for all RNA preparation solutions, gloves should be worn at all times, and RNase-free tips and tubes used. It is not necessary to purify mRNA, since total RNA prepared from freshly isolated or even frozen (liquid nitrogen or-80°C) lymphocytes is pure enough to carry out the RT-PCR reactions. A number of commercial kits are now available for RNA isolation (e.g., Stratagene), and use of one of these is recommended. Alternatively the single-step guanidimum thiocyanate/phenol extraction method of Chomczynski and Sacchi (23), on which most kit protocols are based, should be employed. If the lymphocyte numbers are low (<5 x 106), carrier RNA (100 pg of 16S ribosomal RNA) can be added at the start of this procedure to aid recovery. The preparation ends with a precipitation step using isopropanol, and the RNA may stored at -20°C in this form until required. 

EC (2003) Restrictions on the marketing and use of certain dangerous substances and preparations, nonyl phenol, nonyl phenol ethoxylates and cement. Official Journal ofthe European Communities, L178 (17 July 2003), 24-7. 

Early attempts to use mimosa tannin in particleboard adhesives involved high-temperature alkaline treatment of the extract to reduce viscosity of the 40% solids level needed (43,44) Subsequent improvements followed the same course as with plywood, namely the use of phenol-formaldehyde or phenol-resorcinol-formaldehyde as crosslinking agents (45) and the use of catalysts or mix modifications to reduce press temperature requirements and to extend pot life. Recent work (46) has shown that exterior chipboard adhesives can also be prepared by crosslinking of mimosa tannins with 4,4-diphenylmethane diisocyanate. 

The use of supramolecular interactions to bind a pharmaceutically active drug noncovalently to a polymer in order to achieve slow release was presented by Puskas et al. [96]. Here, a side-chain functionahzed poly(styrene) bearing thymine moieties (Fig. 20) was prepared and complexed with phenol as a complexing agent. The release of the bound phenol was studied in aqueous buffer solution, revealing a slow desorption within 4.5 hours from the polymer. Thus, this system is adaptable for slow release of drugs from polymeric matrices. 

Bromination ofarenes. NBS in DMF is useful for monobromination of reactive arenes and also of phenols and anilines. The reaction is not useful for monobromination of o- and p-hydroxyphenols or for dianilines. Some compounds (and the yields) prepared in this way are listed. ... 

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