Phenolysis reactions

Functionality Measurement of Phenolated Lignin. It is important to have knowledge of the functionality of the phenolated lignin from the point of view of further chemical modification. The amount of bound phenol in the phenolysis reaction has been measured by titrating the phenol extracted from the reaction mixture (15). This indirect method measures the unreacted phenol and determines bound phenol as the difference between the initial charge and the titrated phenol. This is sometimes misleading. 1H NMR spectroscopy is another candidate for the determination of the amount of bound phenol. However, this calculation is difficult since the number of protons before and after the phenolysis reaction is unknown. 

Figure 1. Gel permeation chromatograms of phenolysis reaction mixtures— Phenol mixtures reacted for (A) 10 min, (B) 60 min, (C) 120 min, and (D) 240 min.

Choice of the Lignin Modification Reaction. The phenolysis reaction was selected as a means of modifying the structure and reactivity of the ammonium lignin sulfonate for three main practical reasons. First, because this lignin derivative is soluble in (and will ultimately be used in conjunction with) liquid phenol itself second, because unreacted phenol, unlike other reaction solvents, would not have to be removed from the phenolated product after reaction and before conversion to the adhesive resin and third, because lignins and carbohydrates are known to react with phenols under acidic conditions (6,7). 

Phenolysis Reaction Procedure. To explore the concept of phenolation, mixtures of a commercial spray-dried softwood ammonium lignin sulfonate (10 g, Orzan A, 60% ammonium lignin sulfonate (MW0 = 228), 28% sugars, 6.2% sulfur, 2.5% ash, ITT-Rayonier, Shelton, Washington available in bulk at 17 cents a pound (<9) and commercial grade phenol (15 mL, Reichhold Chemicals Inc., Tacoma, Washington) contained in small pressure bombs (30 mL, Parr Instrument Company, Moline, Illinois) were heated by suspension in a hydraulic... 

The data in the table demonstrate that about half of the water-soluble ammonium ion content is converted into some new form of nitrogen, the nature of which has yet to be determined. Concurrent total nitrogen analyses by the use of a modified Kjeldahl procedure (0) capable of cleaving heterocyclic structures confirmed that no detectable amount of nitrogen had been lost from the phenolysis reaction system. 

Degradation of Lignin Molecular Weight. In addition to these transformations of the water-sensitive carbohydrates, the phenolysis reaction also affects... 

Kinetic Study of the Phenolysis Reaction. With the demonstration that all of the already outlined deficiencies of ammonium lignin sulfonates as a phenol replacement can be reduced by phenolysis, attention was turned to consideration of the construction of a pilot plant scale continuous tube reactor. This is needed in order to prepare the large amounts of phenolyzed lignin sulfonates required for resin synthesis and testing under plywood production conditions. 

The effect of heating time on the extent of phenolysis in this larger reactor was also studied at 220 °C, and the resulting data secured are summarized in Table V. It was necessary to use a heating time correction because the exother-micity of the phenolysis reaction at 200 °C increased the temperature of the reactants as the time of reaction progressed. 

With this demonstration that the kinetics of the phenolysis reaction are second order in nature, an Arrhenius rate constant model... 

Reactions. Although both C-alkylsulfinyl- and C-alkylsulfonylquinoxalines have great potential as versatile intermediates, especially for displacement reactions, they have seldom been used as such in recent years for example, their hydrolysis, alcoholysis, and phenolysis have been totally ignored. However, an example of the conversion of an arylsulfonyl-into a halogenoquinoxaline has been given in Section 3.1.5, and some other reported reactions are illustrated in the following examples. 

In a few cases, SnI reactions have been found to proceed with partial retention (20-50%) of configuration. Ion pairs have been invoked to explain some of these. For example, it has been proposed that the phenolysis of optically active a-phenyl-ethyl chloride, in which the ether of net retained configuration is obtained, involves a four-center mechanism ... 

The reaction of a carboxylic acid with N,Af -carbonyldiimidazolellH33 (abbreviated as CDI), forming an imidazolide as the first step followed by alcoholysis or phenolysis of the imidazolide (second step), constitutes a synthesis of esters that differs from most other methods by virtue of its particularly mild reaction conditions.t41,[5] It may be conducted in two separate steps with isolation of the carboxylic acid imidazolide, but more frequently the synthesis is carried out as a one-pot reaction without isolation of the intermediate. Equimolar amounts of carboxylic acid, alcohol, and CDI are allowed to react in anhydrous tetrahydrofuran, benzene, trichloromethane, dichloromethane, dimethylformamide, or nitromethane to give the ester in high yield. The solvents should be anhydrous because of the moisture sensitivity of CDI (see Chapter 2). Even such unusual solvent as supercritical carbon dioxide at a pressure of 3000 psi and a temperature of 36-68 °C has been used for esterification with azolides.[6]... 

Reactions of alkylsulfinyl- and alkylsulfonylpyrazines also have limited representation in recent literature. Their alcoholysis or phenolysis is covered in Section 5.3.1 other reactions are illustrated in the following examples ... 

From the data in Table II, it seems that the pressures involved in carrying out the phenolysis modification do not pose any special engineering problems since the maximum encountered is only 45 psi. Subsequently, however, in another set of experiments that were carried out for longer heating periods, the pressures observed rose to much higher levels (cf. Table VIII). This may be due to the presence of water generated by dehydration reactions. 

Solubility of Phenolated Lignin Sulfonates. Since the presence of ammonium sulfonate moieties tends to confer water solubility, their disappearance should be reflected in a reduction of this characteristic. The extent of this effect was assessed by measuring the solubility of a stirred aliquot (1-4 g) of the 200 °C phenolysis product in water (200 mL). The resultant suspension was filtered and the residue dried for about 2 days at 22 °C to constant weight. The results obtained under a variety of reaction conditions are summarized in Table III. 

Phenolysis of Carbohydrates. The carbohydrates are also modified by reaction with phenol under comparable conditions as has been demonstrated by Mathur (11) Among the products identified were levulinic acid, furfural, and hydroxymethylfurfural. All are capable of forming carbon-carbon bonds with phenol. 

Table IV. Effect of Reaction Temperature on Extent of Phenolysis and Degree of Water Insolubility Conferred upon a Commercial Ammonium Lignin Sulfonate Admixed with Phenol (61.5%) and Heated for 2 Hours...

As a prelude to the design of the tube reactor (10), a kinetic study of the phenolysis procedure as a function of temperature was carried out on a larger scale. The equipment used was a stainless steel pressure reactor (Model 4501, Parr Instrument Company, Moline, Illinois). This reactor is fitted with an internal stirrer, an external electric heater, and a continuous sampling device. A mixture of the commercial ammonium lignin sulfonate (668 g) and molten phenol (1000 mL) was sealed into the reactor and heated to the designated temperatures. Approximately 3 hours were needed to heat the reactor from room temperature to 200 °C. A similar period of time was required to cool the reactor and its contents back to 22 °C after completion of a run. After a reaction period nominally lasting 2 hours, the unreacted phenol was steam distilled from the reaction mixture and the amount measured by comparative UV spectroscopy. The results obtained and summarized in Table IV show that a substantial amount of phenol becomes chemically combined with the renewable resource feedstock. 

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