Reaction of Phenols and Benzyl Alcohols

Benzanilides also undergo ortho-arylahon (Equahon 10.11) [26]. Eor this reachon, aryl triflates as arylahng reagents are more effechve than aryl bromides. Here, the reachon is considered to proceed via coordinahon of amide ardon to ArPd(II) as that of benzyl phenyl ketone, since no reachon takes place with secondary 

Benzylamines themselves (Equation 10.15) [31] and 2-pyridylbenzenes (Equation 10.16) [29] are direcdy arylated with aryl iodides or PI12IBE4 by Pd(II)-Pd(IV) catalytic cycles. In the presence of oxone as oxidant, 2-pyridylbenzenes undergo regioselective homocoupling (Equation 10.17) [32]. It is worth noting here that pyridyl nitrogen also acts as an anchor for regioselective aliphatic C—H aryla-tion (Equations 10.18 and 10.19) [33, 34]. 

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Reactions. Saligenin [90-01-7] undergoes the typical reactions of phenols and benzyl alcohol. When heated above 100°C, it transforms into a pale yellow resinous material. Amorphous condensation products are obtained when saligenin reacts with acetic anhydride, phosphoms pentachloride, or mineral acids. Upon boiling with dilute acids, saligenin is converted into a resinous body, saliretin, a condensed form of saligenin. Condensation reactions of saligenin with itself in the absence of any catalysts and in the presence of bases have also been studied. 

COMPARISON OF TERTIARY AMINE (DMCHA) WITH ORGANOTIN (DBTDL) CATALYSTS IN THE REACTION OF PHENOL AND BENZYL ALCOHOL WITH PHENYL ISOCYANATE IN DIOXANE AT 25°C... 

Chapter 1 examines the phenomenological principles involved in the modeling of photocatalytic reactions including the photo-adsorption of chemical species. This chapter proposes a method to quantify photo-adsorbed species onto irradiated TiOi. The technique is applied to the oxidation of phenol and benzyl alcohol. 

The effect of type of catalyst on the reactivity of phenol and benzyl alcohol with phenyl isocyanate can be seen in Table III. In the case of tertiary amine (DMCHA), there is a relatively small difference in the reactivity of both the phenol and benzyl alcohol with phenyl isocyanate. Using DBTDL as catalyst, benzyl alcohol was found to be 26 times more reactive than phenol in the reaction with phenyl isocyanate. 

Some preservatives can cause injection site reactions, which is another factor that needs consideration when choosing a preservative. In clinical trials that focused on the evaluation of preservatives and buffers in Norditropin , pain perception was observed to be lower in formulations containing phenol and benzyl alcohol as compared to a formulation containing m-cresol (69). Interestingly, among the commonly used preservatives, benzyl alcohol possesses anesthetic properties (70). 

The reactivity of the model phenols and benzyl alcohols with phenyl isocyanate was determined in the presence of a tertiary amine (DMCHA) and a tin catalyst (DBTDL) by measurement of the reaction kinetics. The experimental results based on initial equal concentrations of phenyl isocyanate and protic reactants showed that the catalyzed reactions followed second order reaction with respect to the disappearance of isocyanate groups (see Figure 1). It was also found that a linear relationship exists between the experimental rate constant kexp, and the initial concentration of the amine catalyst (see Figure 2). In the case of the tin catalyst, the reaction with respect to catalyst concentration was found to be one-half order (see Figures 3-4). A similar relationship for the tin catalyzed urethane reaction was found by Borkent... 

The action of the tin catalyst was found to be quite different from the action of the tertiary amine catalyst. In the presence of the amine catalyst the reactivity of the phenol and benzyl alcohol was approximately equal (see Table IV). In the case of DBTDL, the reactivity ratio was similar to that of the non-catalyzed reaction, which indicates that the polarization of the isocyanate by the tin catalyst due to complex formation presumably played an important role in the reaction catalysis (see Table VI). 

BOX 18.6 Examples of reactions of ethanol. phenol and benzyl alcohol... 

The availability of Nafion on silica has not only lowered the cost of the resin but also has made it versatile (Sun et al., 1997 Harmer et al., 1998). A number of industrially important reactions have been attempted, with considerable success, with these catalysts. Consider the Fries rearrangement of phenyl acetate to p-acetyl phenol (/t-hydroxy acetophenone). This has been accomplished by Hoelderich and co-workers (Heidekum, 1998). In the ca.se of alkylation of benzene with benzyl alcohol, Amberlyst-15 and p-toluene sulphonic acid are ineffective and Nafion on silica works well at 80 °C. 

Benzene-l,4-diols are oxidized to quinones by benzyltrimethylammonium tribromide under mild conditions in almost quantitative yields [6]. With an excess of the tribromide further reaction produces the 2-bromo-l, 4-quinones. This oxidation is in contrast to the analogous reaction of phenols, which produces bromophenols (see Section 2.3). Hindered 4-methyl-phenols are oxidized to the corresponding benzyl alcohols, benzaldehydes, bromomethyl derivatives and 4-bromo-4-methylcyclo-hexa-2,5-dien-l-ones [7]. Benzylic alcohols are oxidized under neutral or basic conditions to yield the corresponding aldehydes (>70%) oxidation with an excess of the reagent produces the benzoic acids (>90%) [8],... 

A number of compounds react rapidly with DDQ at room temperature. They include allylic and benzylic alcohols, which can thus be selectively oxidized, and enols and phenols, which undergo coupling reactions or dehydrogenation, depending on their structure. Rapid reaction with DDQ is also often observed in compounds containing activated tertiary hydrogen atoms. The workup described here can be used in all these cases. 

Consistent with the results of this study is the outcome of the oxidation of 4-X-substituted phenols by use of PINO, generated from HPI with Pb(OAc)4 at 25 °C in MeCN containing 1% AcOH . The reactivity (fcn) of PINO towards phenolic O—H bonds (BDE 85-90 kcal moC ) was about one order of magnitude higher than that measured towards the C—H bond of benzyl alcohols (cf. Table 4). A p value of —3.1 was obtained from plotting log kn vs. for this reaction, where removal of H-atom from the phenolic O—H bond (which is weaker than the O—H bond of aliphatic or benzyl alcohols) induces an oxidative phenolic coupling with the PINO moiety. In view of the low redox potential of the substituted phenols (in the 0.8-1.1 V/NHE range), and of the substantial value of the kinetic isotope effect = 3.1-3.7 measured, ... 

HA compounds is not necessary for the formation of a polyester. Nevertheless, an acceleration effect of HA compounds on the rate of copolymerization was detected later 36 57 74), even for systems in which proton donors are directly bound to monomers 67). This effect is not the sum of the contributions from the tertiary amine and the proton donor but even stronger. Hence, proton donors display a cocatalytic effect. Concerning the effect of HA compounds Tanaka and Kakiuchi 36) established a linear correlation between Hammett s ct constants and the logarithm of the gelation time for various substituted derivatives of benzoic acid, benzyl alcohol and phenol, and positive reaction parameters q were found in all cases. This means that electron-withdrawing substituents increase the effect of HA compounds, or their effect becomes more pronounced with increasing hydrogen atom acidity. 

Bakelite, the first synthetic polymer, is an example of a thermoset polymer. It is prepared by the polymerization of phenol and formaldehyde in the presence of ail acid. Carbocations produced by protonation of formaldehyde bond to the ortho and para positions of the highly reactive phenol molecules in a Friedel-Crafts alkylation reaction. The benzylic alcohols that are produced in this step react to produce carbocations that then alkylate additional phenol molecules. A mechanism for the first few steps of this polymerization process is shown in Figure 24.4. 

Utilization of this principle for the synthesis of the target tree-like (dendritic) macromolecule is shown in Scheme 4.31. The basic reaction chosen was again very simple, namely the formation of benzyl ethers from phenols and benzylic halides. It was found that the coupling of benzylic bromide 91 with 2 equivalents of 3,5-dihydroxybenzyl alcohol 92 could be carried out without affecting the... 

The instability of some compounds under further irradiation is especially remarkable. We found that at first the secondary photo roduct is formed from the primary product and therefore has to be considered as a final product. Under these conditions benzaldehyde, the primary photoqrroduct of toluene, produces benzyl alcohol in the presence of H2O2. The addition of oxygen considerably accelerates the degradation rate, whereas the formation of phenols and hydroxylated biphenyls as well as the dimerization reactions under extended irradiation will increase. At X> 290 nm under normal conditions, we found in experiments with xylenes in aqueous H2O2, transformation rates up to 60% whereas in the corresponding reaction in dark no transformation occurred (Table 2). 

To tubes containing 1 ml of the following hydroxy compounds, add a very small piece of sodium and note the rate of reaction ethanol, 1-butanol, benzyl alcohol, tert-bviyl alcohol, and -phenol. Arrange these in the order of increasing reactivity towards sodium. 

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