Toluene, selective methylation

Effect of physico-chemical properties of ZSM-5 on shape selective methylation of toluene. 215 National Meeting, American Chemical Society at Dallas, Texas, March 1998. 

Xie, Y., Zhao, B., Long, X., and Tang, Y. (2000) Dispersion of oxides on H-ZSM-5 and tlireshold effect on shape selective methylation of toluene. ACS Symp. Sen, 738 (Shape Selective Catalysis), 188-200. 

The model monosaccharides just listed were prepared from common precursor IV.l (Scheme 39), which was readily obtained by azidonitration of 3,4,6-tri-O-acetyl-D-galactal followed by deacetylation with sodium methoxide. Treatment of IV.l with acetone and toluene p-sulfonic acid monohydrate at room temperature led to predominant formation of the thermodynamically favored 3,4-O-isopropylidene (IV.2) in 61% yield while also producing 27% of the 4,6-O-isopropylidene derivative IV.3. The position of the isopropylidene IV.2 was verified by the use of NMR chemical shift analysis to confirm the position of the acetate group in the resultant acetylated adduct IV.4. Synthesis of the 4-O-sulfate derivative (IV.7) from IV.2 utilized a step that differentiated the 3-OH and 4-OH positions after benzylation and de-isopro-pylidination of IV.2, a selective methylation at the 3-OH of diol IV.5 was achieved via a tin procedure [91] to give methyl glycoside IV.6. Conversion of the azide into... 

Diaryl-2,4-dithiohydantoins, when refluxed with BF3 dimethyl etherate or mixtures of the former reagent with BF3 in toluene or chlorobenzene, are selectively methylated at the S2 atom and/or undergo the above-mentioned rearrangement to yield imidazole derivatives (89).226... 

The effect of the content of alkali earth oxides MgO and BaO on the catalytic and basic properties of NaX zeolites have also been investigated by Kovacheva ct al. (32. 46]. For the MgO-modified NaX zeolites, the best catalytic properties were obtained by NaX zeolite impregnated with a maximum of 13 wt. % MgO. The significant improvement in the catalytic properties was attributed to the presence of a moderate amount of strong basic sites. The catalytic activity was found to depend on the temperature and the MgO content. It was demonstrated that the catalysts possess well preserved crystal structure and low amount of MgO crystal phase. It was reported that the amount of basic active sites but not the strength is dependent on the content of MgO in the zeolite. BaO/NaX was also found to be an effective catalyst for the oxidative methylation of toluene with methane. The catalytic properties of this zeolite was reported to be superior to those of the MgO/NaX zeolite. It was demonstrated that an increase in the barium content leads to an increase in the amount of basic sites and a corresponding increase in catalytic activity. The catalysts were found to possess a preserved crystal structure and the existence of differently dispersed BaO and formation of BaC03 were detected in the catalysts. The conversion of toluene, selectivity and the yield of ethylbenzene plus styrene were reported to depend on (i) the content of barium in the zeolite, (ii) the reaction temperature, (iii) the time of catalytic use, (v) the state of the zeolite crystal structure and (vi) the state of barium in the zeolite lattice. 

Acrylic sealants are water-based but they may also contain ethylene and propylene glycols, mineral spirits and mineral oil. There are also solvent-based acrylic sealants which contain substantial amounts of solvents such as mineral spirits, toluene and xylene. Polysulfide sealants usually contain toluene but methyl ethyl ketone is also used. The group of class B sealants contains substantially more solvents (up to 40% by volume) but there are some exceptions. PVC sealants are based on plastisols and they can be made without solvents. Butyl rubber based sealants usually contain hydrocarbons (Q-C,2). Styrene-buta-diene-styrene based sealants usually have a large amoxmt of solvents selected from a group including toluene, heptane, hexane, methyl ethyl ketone, isobutyl isobutyrate, n-amyl acetate, n-amyl ketone. They are usually processed in solvent mixtures. Polychloroprene is usually dissolved in a mixture of solvents including ketones or esters, and aromatic and aliphatic hydrocarbons. The list includes naphtha, hexane, acetone, methyl ethyl ketone, benzene, and toluene. 

The selective monochlorination of the methyl group in toluene to give benzyl chloride with SO2CI2 is possible with catalysis by Pd(Ph3P)4[124],... 

Membranes and Osmosis. Membranes based on PEI can be used for the dehydration of organic solvents such as 2-propanol, methyl ethyl ketone, and toluene (451), and for concentrating seawater (452—454). On exposure to ultrasound waves, aqueous PEI salt solutions and brominated poly(2,6-dimethylphenylene oxide) form stable emulsions from which it is possible to cast membranes in which submicrometer capsules of the salt solution ate embedded (455). The rate of release of the salt solution can be altered by surface—active substances. In membranes, PEI can act as a proton source in the generation of a photocurrent (456). The formation of a PEI coating on ion-exchange membranes modifies the transport properties and results in permanent selectivity of the membrane (457). The electrochemical testing of salts (458) is another possible appHcation of PEI. 

Because much toluene is demethylated for use as benzene, considerable effort has been expended on developing processes in which toluene can be used in place of benzene to make directiy from toluene the same products that are derived from benzene. Such processes both save the cost of demethylation and utilize the methyl group already on toluene. Most of this effort has been directed toward manufacture of styrene. An alternative approach is the manufacture of i ra-methylstyrene by selective ethylation of toluene, followed by dehydrogenation. Resins from this monomer are expected to displace... 

Rapid, simple, quaUtative methods suitable for determining the presence of benzene in the workplace or surroundings have been utilized since the 1930s. Many early tests offered methods for detection of aromatics but were not specific for benzene. A straightforward test allowing selective detection of benzene involves nitration of a sample to y -dinitrobenzene and reaction of the resultant ether extract with an ethanoHc solution of sodium hydroxide and methyl ethyl ketone (2-butanone), followed by the addition of acetic acid to eliminate interferences from toluene and xylenes. Benzene imparts a persistent red color to the solution (87). The method is claimed to be sensitive to concentrations as low as 0.27 ppm benzene from 10 mL air samples. 

In contrast to the hydrolysis of prochiral esters performed in aqueous solutions, the enzymatic acylation of prochiral diols is usually carried out in an inert organic solvent such as hexane, ether, toluene, or ethyl acetate. In order to increase the reaction rate and the degree of conversion, activated esters such as vinyl carboxylates are often used as acylating agents. The vinyl alcohol formed as a result of transesterification tautomerizes to acetaldehyde, making the reaction practically irreversible. The presence of a bulky substituent in the 2-position helps the enzyme to discriminate between enantiotopic faces as a result the enzymatic acylation of prochiral 2-benzoxy-l,3-propanediol (34) proceeds with excellent selectivity (ee > 96%) (49). In the case of the 2-methyl substituted diol (33) the selectivity is only moderate (50). 

Procedure has been proposed for the P(V) and As(V) determination based on the selective extraction of ionic associate of Crystal Violet with reduced molybdophosphate with mixture of inert (toluene) and active (methyl isobutyl ketone) solvents. Extraction of reagent is negligible. After concentration determination lower than 10 mol/1 of P(V) and As(V) is possible. 

Aromatic solvents or polycyclic aromatic hydrocarbons (PAFI) in water, e.g. can be detected by QCM coated with bulk-imprinted polymer layers. Flere, the interaction sites are not confined to the surface of the sensitive material but are distributed within the entire bulk leading to very appreciable sensor responses. Additionally, these materials show high selectivity aromatic solvents e.g. can be distinguished both by the number of methyl groups on the ring (toluene vs. xylene, etc.) and by their respective position. Selectivity factors in this case reach values of up to 100. 

The conclusion of Brown et a/.346,347 viz. that the increased reactivity along a series of alkyl halides is due to the increased polarisation of the carbon-halogen bond has been challenged by Allen and Yats348, who found constant meta para isomer ratios for methylation, ethylation, and isopropylation of toluene, and since this ratio reflects the selectivity and hence reactivity of the electrophile they con-... 

Lipases from C. antarctica and P. cepacia showed higher enantioselectivity in the two ionic liquids l-ethyl-3-methylimidazolium tetrafluoroborate and l-butyl-3-methylimidazolium hexafluoroborate than in THE and toluene, in the kinetic resolution of several secondary alcohols [49]. Similarly, with lipases from Pseudomonas species and Alcaligenes species, increased enantioselectivity was observed in the resolution of 1 -phenylethanol in several ionic liquids as compared to methyl tert-butyl ether [50]. Another study has demonstrated that lipase from Candida rugosa is at least 100% more selective in l-butyl-3-methylimidazolium hexafluoroborate and l-octyl-3-nonylimidazolium hexafluorophosphate than in n-hexane, in the resolution of racemic 2-chloro-propanoic acid [51]. 

On the other hand, the oxidation of the alkyl substituent in alkyl aromatic compounds can be carried out by various methods efficiently. For example, CAN has been used to oxidize substituted toluene to aryl aldehydes. Selective oxidation at one methyl group can be achieved (Eq. 7.19).44 The reaction is usually carried out in aqueous acetic acid. 

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