Phenols, alkylation table

Carlier32,33 used various functional alkylsilane groups on silica as co-monomer, transfer agent or initiator for grafting of a functional polymer. These functional polymers may be used to anchor a catalyst. The polymer polyphenylsilsesquioxane was grafted onto porous silica and sulfonated, to obtain catalysts of high stability with enhanced site accessibility and increased number of sites, as well as high acidity level.34 This catalyst is used for esterification and phenol alkylation. Other catalysts have been reviewed by Pinnavaia,35 and are summarized in table 8.5. 

Let us now examine the antioxidant test results for the various phenols alkylated by a-olefins. They have been evaluated in several tests, but data are presented in Table III for only four different test procedures, chosen to illustrate the effect of increasing severity of test conditions. The least severe of these is the 140°C. stress-crack life test using a 65-mil thick molded bar. The 160 °C. oven-life test using the same molded bar is somewhat more severe. Increasing severity is shown by the 140°C. oven-life test and the 160°C. oven-life test using 5-mil film test pieces. The relatively thick bars used in the first two tests provide a reservoir of antioxidant to replace that lost from the surface. These tests probably measure the inherent effectiveness of the antioxidant. In the tests using... 

The activity and selectivity of aluminas used depend on the added ion and its concentration. It is seen from the data of Table 1 that activity increases with the decrease in surface basicity. This is in agreement with previous work regarding the reaction of phenol alkylation with methanol over oxides [5-10,16],... 

Peroxide Decomposers as Processing Stabiiizers. Alkyl and aryl phosphite esters (see Scheme 12) are effective melt stabilizers. They are often used in combination with hindered phenols (see Table 6). Phosphites generally function by a stoichiometric peroxidolytic mechanism (PD-S) Table 7 illustrates the benefits of using the commercial phosphites TNPP (AO 15) and Irgafos P-EPQ (AO 17, Table 3) for melt stabilization (95). The unique phosphite AO 37 and its phosphate transformation products AOs 38 and 39, (Table 7), which were shown (104,133-135) to operate by a catalytic mechanism (PD-C), are particularly effective at low concentration of the parent stabilizer molecule (see AO 37, Table 7) (95). Phosphites are, however, generally susceptible to hydrolysis. For example, hydrolysis of aryl phosphites leads to the formation of low molecular mass phenol and a... 

Instructions for the TLC of the phenols expected as products of thermolysis were abundantly available already Preliminary experiments owed that the phenol mixtures to be expected were best separated by double development using benzene in a run of IS cm. For speed and reproducibility this solvent gives the best results although superposition of phenol with m- and p-cresols and also some higher alkyl-phenols (cf. Table 8) is unavoidable. Partition-TLC on layers impregnated with formamide has been used successfully to separate these critical homolc ous or isomeric phenols 3°). We have studied thoroughly the scope of application and... 

Substituted Phenols. Phenol itself is used in the largest volume, but substituted phenols are used for specialty resins (Table 2). Substituted phenols are typically alkylated phenols made from phenol and a corresponding a-olefin with acid catalysts (13). Acidic catalysis is frequendy in the form of an ion-exchange resin (lER) and the reaction proceeds preferentially in the para position. For example, in the production of /-butylphenol using isobutylene, the product is >95% para-substituted. The incorporation of alkyl phenols into the resin reduces reactivity, hardness, cross-link density, and color formation, but increases solubiHty in nonpolar solvents, dexibiHty, and compatibiHty with natural oils. 

Of course, the physical properties of alkylphenols are comparable to phenol. The properties are strongly influenced by the type of alkyl substituent and its position on the ring. Alkylphenols, like phenol, are typically soflds at 25°C. Their form is affected by the size and configuration of the alkyl group, its position on the ring, and purity. They appear colorless, or white, to a pale yellow when pure (Table 1). 

Methylphenol is converted to 6-/ f2 -butyl-2-methylphenol [2219-82-1] by alkylation with isobutylene under aluminum catalysis. A number of phenoHc anti-oxidants used to stabilize mbber and plastics against thermal oxidative degradation are based on this compound. The condensation of 6-/ f2 -butyl-2-methylphenol with formaldehyde yields 4,4 -methylenebis(2-methyl-6-/ f2 butylphenol) [96-65-17, reaction with sulfur dichloride yields 4,4 -thiobis(2-methyl-6-/ f2 butylphenol) [96-66-2] and reaction with methyl acrylate under base catalysis yields the corresponding hydrocinnamate. Transesterification of the hydrocinnamate with triethylene glycol yields triethylene glycol-bis[3-(3-/ f2 -butyl-5-methyl-4-hydroxyphenyl)propionate] [36443-68-2] (39). 2-Methylphenol is also a component of cresyHc acids, blends of phenol, cresols, and xylenols. CresyHc acids are used as solvents in a number of coating appHcations (see Table 3). 

Production of a-methylstyrene (AMS) from cumene by dehydrogenation was practiced commercially by Dow until 1977. It is now produced as a by-product in the production of phenol and acetone from cumene. Cumene is manufactured by alkylation of benzene with propylene. In the phenol—acetone process, cumene is oxidized in the Hquid phase thermally to cumene hydroperoxide. The hydroperoxide is spHt into phenol and acetone by a cleavage reaction catalyzed by sulfur dioxide. Up to 2% of the cumene is converted to a-methylstyrene. Phenol and acetone are large-volume chemicals and the supply of the by-product a-methylstyrene is weU in excess of its demand. Producers are forced to hydrogenate it back to cumene for recycle to the phenol—acetone plant. Estimated plant capacities of the U.S. producers of a-methylstyrene are Hsted in Table 13 (80). 

Commercial Antioxidants Table 4 includes the main classes of antioxidants sold in the United States and the suppHer s suggested apphcations. Some of these are mixtures rather than single substrates. This is especially tme of alkylated amines and alkylated phenols. The extent of alkylation and the olefins used for alkylation can vary among manufacturers. Table 4 is not a complete listing of available antioxidants in the United States. 

Irg 1076, AO-3 (CB), are used in combination with metal dithiolates, e.g., NiDEC, AO-30 (PD), due to the sensitized photoxidation of dithiolates by the oxidation products of phenols, particularly stilbenequinones (SQ, see reaction 9C) (Table 3). Hindered piperidines exhibit a complex behavior when present in combination with other antioxidants and stabilizers they have to be oxidized initially to the corresponding nitroxyl radical before becoming effective. Consequently, both CB-D and PD antioxidants, which remove alkyl peroxyl radicals and hydroperoxides, respectively, antagonise the UV stabilizing action of this class of compounds (e.g.. Table 3, NiDEC 4- Tin 770). However, since the hindered piperidines themselves are neither melt- nor heat-stabilizers for polymers, they have to be used with conventional antioxidants and stabilizers. 

Alkyl-substituted phenols have different reactivities than phenol toward reaction with formaldehyde. Relative reactivities determined by monitoring the disappearance of formaldehyde in phenol-paraformaldehyde reactions (Table 7.3) show that, under basic conditions, meta-cresol reacts with formaldehyde approximately three times faster titan phenol while ortho- and para-cresols react at approximately one-third the rate of phenol.18 Similar trends were observed for the reactivities of acid-catalyzed phenolic monomers with formaldehyde. 

Sulfur cross-links have limited stability at elevated temperatures and can rearrange to form new cross-links. These results in poor permanent set and creep for vulcanizates when exposed for long periods of time at high temperatures. Resin cure systems provide C-C cross-links and heat stability. Alkyl phenol-formaldehyde derivatives are usually employed for tire bladder application. Typical vulcanization system is shown in Table 14.24. The properties are summarized in Tables 14.25 and 14.26. 

The most common hydrophobes used as the basis for surfactants are those containing eight to eighteen carbon atoms, such as those listed as carboxylates in Table 9.1. Some hydrophobes are aromatic (benzene or naphthalene) moieties, often containing lower alkyl substituents dodecylbenzene (9.1) is a common example. Alkyl-substituted toluenes, xylenes and phenols, and mono- and di-alkylated naphthalenes (9.2 and 9.3), are also used. 

In addition to this reaction, quinones and other alkyl radical acceptors retard polymer oxidation by the reaction with alkyl radicals (see earlier). As a result, effectiveness of these inhibitors increases with the formation of hydroperoxide groups in PP. In addition, the inhibiting capacity of these antioxidants grows with hydroperoxide accumulation. The results illustrating the efficiency of the antioxidants with cyclic chain termination mechanisms in PP containing hydroperoxide groups is presented in Table 19.12. The polyatomic phenols producing quinones also possess the ability to terminate several chains. 

Table 1.2. Yield of Products in Alkylation Reaction of Phenol by Styrene...

Predictably, 1,2,4-triazole is alkylated preferentially at the 1-position [36, 38,39]. Specific alkylation at the 4-position can be achieved by the initial reaction with dibromomethane to form the bis-triazol-l-ylmethane (see below), followed by quat-emization of the triazole system at the 4-position and subsequent C-N cleavage of the 1,1 -methylenebistriazolium salts [40]. 1,2,3-Benztriazole yields a mixture of the isomeric 1- and 2-alkylated derivatives [41]. The 1-isomer predominates, but the ratio depends on whether the reactions are conducted in the presence, or absence, of a nonpolar organic solvent (Table 5.33). Higher ratios of the 1-isomer are obtained under solidrliquid two-phase conditions. Thus, alkylation of 1,2,3-benztriazole with benzyl chloride produces an overall yield of 95% with the l- 2-isomer ratio of ca. 5.7 1 similar reactions with diphenylmethyl and triphenylmethyl chlorides gives overall yields of 95% (9 1 ratio) and 70% (100% 1-isomer), respectively [38], 6-Substituted purines are alkylated at the N9-atom and reaction with 1-bromo-3-chloropropane yields exclusively the 9-chloropropyl derivative (cf. reaction wi phenols) [42]. 

The optical yield was found to be very sensitive to structural modifications of the achiral agent. For example, use of the more bulky FV or Bu substituents in the 3,5-positions of phenol resulted in lower optical yields. In some cases a reversal of the sense of asymmetric induction was observed. Systematic variation of reaction conditions using the best achiral component, 3,5-xylenol, established that optimum results were obtained in ether solvent at about - 15°C. There was also a minor but definite influence of the rate of addition of ketone as well as an effect of concentration on optical yield, with a slower rate being advantageous. The results of reduction of aryl alkyl ketones are shown in Table 9, along with comparative results of reduction with similar chiral auxiliary reagents. 

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