Alkylation of solvent

Alkylation of solvent represents still another pathway for changing the properties of a recycle solvent. If we consider alkylation in terms of the transfer to methyl groups from coal to solvent components, then there are several structural and physical changes that occur to the solvent. Alkylation will increase the hydrogen content of the solvent at the expense of coal since the solvent molecule will have a C-H replaced by C-CH. This represents an increase in the aliphatic content and conversely a decrease in the aromatic content of the solvent. Kleinpeter (7) has indicated that alkylation of condensed aromatics is a problem. High aliphatic character will decrease the ability of the solvent to act as a physical solvent for coal liquefaction products. 

Three processes were found to be important in considering the self sufficiency of solvent in liquefaction technology cracking of the solvent to form gases (which is < 3.6% of solvent used), condensation of solvent components, and alkylation of solvent by coal (Figure 9 ). 

Alkvl Azides from Alkyl Bromides and Sodium Azide General procedure for the synthesis of alkyl azides. In a typical experiment, benzyl bromide (360 mg, 2.1 mmol) in petroleum ether (3 mL) and sodium azide (180 mg, 2.76 mmol) in water (3 mL) are admixed in a round-bottomed flask. To this stirred solution, pillared clay (100 mg) is added and the reaction mixture is refluxed with constant stirring at 90-100 C until all the starting material is consumed, as obsen/ed by thin layer chromatographv using pure hexane as solvent. The reaction is quenched with water and the product extracted into ether. The ether extracts are washed with water and the organic layer dried over sodium sulfate. The removal of solvent under reduced pressure affords the pure alkyl azides as confirmed by the spectral analysis. ... 

Direct alkylation of esters can be carried out by forming the enolate with LDA fol lowed by addition of an alkyl halide Tetrahydrofuran (THF) is the solvent most often used m these reactions... 

Semipermanent hair color products are formulated at an alkaline pH, usually between 8.5 and 10. At this pH the cuticle of the hair lifts away from the hair a Httie, allowing for easier penetration of dye. An alkyl amine buffered with an organic acid normally is used to obtain the desired pH. The formulations contain a mixture of solvents and surfactants to solubilize the dyes and a thickening agent is added so that the product stays on the hair without mnning or dripping. A 20—30 min appHcation time is normal for this type of product. A representative formula for a semipermanent dye product is given in Table 7. 

Isopropylnaphthalenes produced by alkylation of naphthalene with propjdene have gained commercial importance as chemical intermediates, eg, 2-isopropylnaphthalene [2027-17-OJ, and as multipurpose solvents, eg, mixed isopropylnaphthalenes. Alkylation of naphthalene with alkyl haUdes (except methyl hahdes), acid chlorides, and acid anhydrides proceeds in the presence of anhydrous aluminum chloride by Friedel-Crafts reactions (qv). The products are alkylnaphthalenes or alkyl naphthyl ketones, respectively (see Alkylation). 

Isopropylnaphthalenes can be prepared readily by the catalytic alkylation of naphthalene with propjiene. 2-lsopropylnaphthalene [2027-17-0] is an important intermediate used in the manufacture of 2-naphthol (see Naphthalenederivatives). The alkylation of naphthalene with propjiene, preferably in an inert solvent at 40—100°C with an aluminum chloride, hydrogen fluoride, or boron trifluoride—phosphoric acid catalyst, gives 90—95% wt % 2-isopropylnaphthalene however, a considerable amount of polyalkylate also is produced. Preferably, the propylation of naphthalene is carried out in the vapor phase in a continuous manner, over a phosphoric acid on kieselguhr catalyst under pressure at ca 220—250°C. The alkylate, which is low in di- and polyisopropylnaphthalenes, then is isomerized by recycling over the same catalyst at 240°C or by using aluminum chloride catalyst at 80°C. After distillation, a product containing >90 wt % 2-isopropylnaphthalene is obtained (47). 

The solvent is 28 CC-olefins recycled from the fractionation section. Effluent from the reactors includes product a-olefins, unreacted ethylene, aluminum alkyls of the same carbon number distribution as the product olefins, and polymer. The effluent is flashed to remove ethylene, filtered to remove polyethylene, and treated to reduce the aluminum alkyls in the stream. In the original plant operation, these aluminum alkyls were not removed, resulting in the formation of paraffins (- 1.4%) when the reactor effluent was treated with caustic to kill the catalyst. In the new plant, however, it is likely that these aluminum alkyls are transalkylated with ethylene by adding a catalyst such as 60 ppm of a nickel compound, eg, nickel octanoate (6). The new plant contains a caustic wash section and the product olefins still contain some paraffins ( 0.5%). After treatment with caustic, cmde olefins are sent to a water wash to remove sodium and aluminum salts. 

Kinetics are slow and many hours are requited for a 95% conversion of the reactants. In the case of the subject compound, there is evidence that the reaction is autocatalytic but only when approximately 30% conversion to the product has occurred (19). Reaction kinetics are heavily dependent on the species of halogen ia the alkyl haHde and decrease ia the order I >Br >C1. Tetrabutylphosphonium chloride exhibits a high solubiHty ia a variety of solvents, for example, >80% ia water, >70% ia 2-propanol, and >50% ia toluene at 25°C. Its analogues show similar properties. One of the latest appHcations for this phosphonium salt is the manufacture of readily dyeable polyester yams (20,21). 

Gumylphenol. -Cumylphenol (PGP) or 4-(1-methyl-l-phenylethyl)phenol is produced by the alkylation of phenol with a-methylstyrene under acid catalysis. a-Methylstyrene is a by-product from the production of phenol via the cumene oxidation process. The principal by-products from the production of 4-cumylphenol result from the dimerization and intramolecular alkylation of a-methylstyrene to yield substituted indanes. 4-Cumylphenol [599-64-4] is purified by either fractional distillation or crystallization from a suitable solvent. Purification by crystallization results in the easy separation of the substituted indanes from the product and yields a soHd material which is packaged in plastic or paper bags (20 kg net weight). Purification of 4-cumylphenol by fractional distillation yields a product which is almost totally free of any dicumylphenol. The molten product resulting from purification by distillation can be flaked to yield a soHd form however, the soHd form of 4-cumylphenol sinters severely over time. PGP is best stored and transported as a molten material. 

Dimethjlphenol (2,6-xylenol) is produced by the gas phase alkylation of phenol with methanol using modified alumina catalysis. The cmde product contains 2-methylphenol, 2,6-dimethylphenol, a minor amount of 2,4-dimethylphenol, and a mixture of trimethylphenols. The 2,6-dimethylphenol is purified by fractional distillation. The mixture of di- and trimethylphenols is sold as cresyHc acid for use as a solvent. 2,6-Dimethylphenol [576-26-1] is available in 55-gal dmms (208-L) and in bulk shipments in tank wagons and railcars. 

N-Alkylpyrroles may be obtained by the Knorr synthesis or by the reaction of the pyrrolyl metallates, ie, Na, K, and Tl, with alkyl haUdes such as iodomethane, eg, 1-methylpyrrole [96-54-8]. Alkylation of pyrroles at the other ring positions can be carried out under mild conditions with allyhc or hensylic hahdes or under more stringent conditions (100—150°C) with CH I. However, unless most of the other ring positions are blocked, poly alkylation and polymerisation tend to occur. N-Alkylation of pyrroles is favored by polar solvents and weakly coordinating cations (Na", K" ). More strongly coordinating cations (Li", Mg " ) lead to more C-alkylation. 

Hydroxyl Group. Reactions of the phenohc hydroxyl group iaclude the formation of salts, esters, and ethers. The sodium salt of the hydroxyl group is alkylated readily by an alkyl hahde (WiUiamson ether synthesis). Normally, only alkylation of the hydroxyl is observed. However, phenolate ions are ambident nucleophiles and under certain conditions, ring alkylation can also occur. Proper choice of reaction conditions can produce essentially exclusive substitution. Polar solvents favor formation of the ether nonpolar solvents favor ring substitution. 

Short-chain alkylated biphenyls are the principal biphenyl derivatives in commercial use. They are generally produced by Hquid-phase Friedel-Crafts alkylation of biphenyl with ethylene, propylene, or mixed butenes. A series of mixed ethylated biphenyl heat-transfer fluids (trademarked Therm S-600, 700, 800) is marketed by Nippon Steel. A mixed diethylbenzene—ethylbiphenyl heat-transfer fluid is also available from Dow (63). Monoisopropylbiphenyl [25640-78-2] largely as a mixture of meta- and para-isomers is produced by Koch Chemical Co. Monoisopropylbiphenyl (MIPB) was selected by Westinghouse (64,65) as a PCB replacement in capacitors and this is its primary appHcation today. For a time MIPB was also employed as a PCB replacement in pressure sensitive copy paper, but this outlet has since given way to other dye solvents. A similar product consisting of a mixture of j -butylbiphenyl isomers [38784-93-9] (66) is currently the favored dye solvent for pressure sensitive copy paper (67) manufactured in the United States. 

Organic Halides. Alkyl halides and aiyl halides, activated by election withdrawing groups (such as NO2) in the ortho or para positions, react with alkyleneamines to form mono- or disubstituted derivatives. Product distribution is controlled by reactant ratio, metal complexation or choice of solvent (16,17). Mixing methylene chloride [75-09-2J and EDA reportedly causes a mnaway reaction (18). 

Pyrroles do not react with alkyl halides in a simple fashion polyalkylated products are obtained from reaction with methyl iodide at elevated temperatures and also from the more reactive allyl and benzyl halides under milder conditions in the presence of weak bases. Alkylation of pyrrole Grignard reagents gives mainly 2-alkylated pyrroles whereas N-alkylated pyrroles are obtained by alkylation of pyrrole alkali-metal salts in ionizing solvents. 

TABLE 15-6 Settling of Aqueous Uranium Leach Liquors with Kerosine-Alkyl Phosphate Solvent ... 

Alkylation of enamines can take place on carbon or on nitrogen (see Section I). The theoretical considerations and reaction conditions which determine whether C or N alkylation takes place have already been studied extensively 26-32). These studies have shown that the facility with which alkylation takes place depends on the basicity of theenamine, on the ease of formation of a trigonal atom in the transition state, and on the nature of the enamine, the alkylating agent, and the solvent. 

Vinylogous amides, which have an enamine function in conjugation with a carbonyl group, constitute tridentate systems and thus open the possibility of alkylation on carbon, nitrogen, or oxygen. It has been found that the pyrrolidine enamine of acetylacetone gives rise to a carbon mcthylation but an oxygen ethylation product 41). The alkylation of cyclic 1,3-diketone-derived enamines has been studied 41,283). O Alkylation was found in alcohol solvents and predominant C alkylation in nonprotonic solvents. 

The alkylation of enamines with nitroolefins, which gives intermediates for reductive cyclization (6S2), also provided an example of a stable cycliza-tion product derived from attack of the intermediate imonium function by the nitro anion (683). A previously claimed tetrasubstituted enamine, which was obtained from addition of a vinylsulfone to morpholinocyclohexene (314), was shown to be the corresponding cyclobutane (684). Perfluoro-olefins also gave alkylation products with enamines (685). Reactions of enamines with diazodicarboxylate (683,686) have been used diagnostically for 6-substituted cyclohexenamines. In a reaction of 2-penten-4-one with a substituted vinylogous amide, stereochemical direction was seen to depend on solvent polarity (687). 

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