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Aromatization preferential

Aromatics can be separated from non-aromatics preferentially by adsorption on certain solids. This type of process gives rise to cyclic operations which, schematically speaking, comprise a preliminary adsorption of the aromatics, followed by their desorption (by an eluant, heat or both). The dnant is then separated from the effluents by distillation, fondxampie. [Pg.240]

Dealkylation of EB and cracking of non-aromatics preferentially occurs in the top bed. The bottom bed promotes isomerization of xylenes, while minimizing loss of xylenes from side reactions. The reactor effluent is cooled by heat exchange, and the resulting liquid and vapor phases are separated in the product separator (3). The liquid is then sent to a fractionator (4) for recovery of benzene and toluene from the isomerate. [Pg.284]

In 1998 Harrison reported the synthesis and characterization of water-soluble, dynamic, cobalt-coordinated carcerand 16 (Fig. 9.7) [64]. A follow-on study 7 years later found that 16 can entrap a range of guests [65]. Competition studies revealed that anisole and p-xylene were the strongest binders both had an encapsulation preference 20,000 times stronger than the poorest guest, m-xylene. Harrison extended this work using the same cavitand complexed with Fe (II) [66]. The resulting carcerands were also water-soluble and were found to contain six waters. In the presence of bromobenzene-saturated water, the aromatic preferentially bound. [Pg.203]

The electronic theory provides by these means a description of the influence of substituents upon the distribution of electrons in the ground state of an aromatic molecule as it changes the situation in benzene. It then assumes that an electrophile will react preferentially at positions which are relatively enriched with electrons, providing in this way an isolated molecule theory of reactivity. [Pg.127]

In this model, reaction is considered to occur preferentially at that position in the aromatic molecule to which the approach of the electrophile causes the smallest increase in zero energy. In molecules possessing polar or dipolar groups, long range electrostatic forces will initially be the most important. [Pg.130]

The (thermal) decomposition of thiazol-2-yldiazonium salts in a variety of solvents at 0 C in presence of alkali generates thiazol-2-yl radicals (413). The same radicals result from the photolysis in the same solvents of 2-iodothiazole (414). Their electrophilic character is shown by their ability to attack preferentially positions of high rr-electron density of aromatic substrates in which they are generated (Fig. 1-21). The major... [Pg.111]

If the Lewis base ( Y ) had acted as a nucleophile and bonded to carbon the prod uct would have been a nonaromatic cyclohexadiene derivative Addition and substitution products arise by alternative reaction paths of a cyclohexadienyl cation Substitution occurs preferentially because there is a substantial driving force favoring rearomatization Figure 12 1 is a potential energy diagram describing the general mechanism of electrophilic aromatic substitution For electrophilic aromatic substitution reactions to... [Pg.476]

Notice too that the most shielded carbons of the aromatic ring are the ones that are ortho and para to the hydroxyl group m keeping with our experience that the OH group donates electrons preferentially to these positions... [Pg.1015]

The Gattermann-Koch synthesis is suitable for the preparation of simple aromatic aldehydes from ben2ene and its substituted derivatives, as well as from polycychc aromatics. The para isomers are produced preferentially. Aromatics with meta-directing substituents cannot be formylated (108). [Pg.559]

These reversible reactions are cataly2ed by bases or acids, such as 2iac chloride and aluminum isopropoxide, or by anion-exchange resias. Ultrasonic vibrations improve the reaction rate and yield. Reaction of aromatic aldehydes or ketones with nitroparaffins yields either the nitro alcohol or the nitro olefin, depending on the catalyst. Conjugated unsaturated aldehydes or ketones and nitroparaffins (Michael addition) yield nitro-substituted carbonyl compounds rather than nitro alcohols. Condensation with keto esters gives the substituted nitro alcohols (37) keto aldehydes react preferentially at the aldehyde function. [Pg.100]

Both 2- and 3-methyl groups in pyrido[2,3-Z ]pyrazines are acylated by ethyl oxalate (71TH21500). They give (preferentially 3-) styryl derivatives with aromatic aldehydes and oximes with pentyl nitrite. [Pg.253]

Primary and secondary aliphatic and aromatic amines react readily with thiiranes to give 2-mercaptoethylamine derivatives (Scheme 76) (76RCR25, 66CRV297). The reaction fails or gives poor yields with amines which are sterically hindered e.g. N,iV-dicyclohexylamine) or whose nitrogen atom is weakly basic e.g. N,A/ -diphenylamine). Aromatic amines are less reactive and higher reaction temperatures are usually required for them. The reaction mechanism is Sn2 and substituted thiiranes are attacked preferentially at the least hindered... [Pg.158]

Impurities can sometimes be removed by conversion to derivatives under conditions where the major component does not react or reacts much more slowly. For example, normal (straight-chain) paraffins can be freed from unsaturated and branched-chain components by taking advantage of the greater reactivity of the latter with chlorosulfonic acid or bromine. Similarly, the preferential nitration of aromatic hydrocarbons can be used to remove e.g. benzene or toluene from cyclohexane by shaking for several hours with a mixture of concentrated nitric acid (25%), sulfuric acid (58%), and water (17%). [Pg.60]

This is nicely illustrated by members of the chymotrypsin superfamily the enzymes chymotrypsin, trypsin, and elastase have very similar three-dimensional structures but different specificity. They preferentially cleave adjacent to bulky aromatic side chains, positively charged side chains, and small uncharged side chains, respectively. Three residues, numbers 189, 216, and 226, are responsible for these preferences (Figure 11.11). Residues 216... [Pg.212]

Lube oil extraction plants often use phenol as solvent. Phenol is used because of its solvent power with a wide range of feed stocks and its ease of recovery. Phenol preferentially dissolves aromatic-type hydrocarbons from the feed stock and improves its oxidation stability and to some extent its color. Phenol extraction can be used over the entire viscosity range of lube distillates and deasphalted oils. The phenol solvent extraction separation is primarily by molecular type or composition. In order to accomplish a separation by solvent extraction, it is necessary that two liquid phases be present. In phenol solvent extraction of lubricating oils these two phases are an oil-rich phase and a phenol-rich phase. Tne oil-rich phase or raffinate solution consists of the "treated" oil from which undesirable naphthenic and aromatic components have been removed plus some dissolved phenol. The phenol-rich phase or extract solution consists mainly of the bulk of the phenol plus the undesirable components removed from the oil feed. The oil materials remaining... [Pg.231]

Process for Using Alkyl Substituted C8-C10 Aromatic Hydrocarbons as Preferential Physical Solvents for Selective Processing of Hydrocarbon Gas Streams, U.S. Patent 4,692,179, Sep. 8, 1987. [Pg.331]

Complications often arise in the use of 1,3-diketones under the above reaction conditions. This is primarily due to the lack of regioselectivity with regard to formation of the intermediate thioacetal. However, when benzoyl acetone derivatives are employed, the thioketal forms preferentially with the aromatic ketone. ... [Pg.189]

Benzannulated furans are coordinated preferentially at the aromatic ring (Ti -mode). [Pg.51]


See other pages where Aromatization preferential is mentioned: [Pg.172]    [Pg.206]    [Pg.207]    [Pg.120]    [Pg.436]    [Pg.229]    [Pg.285]    [Pg.854]    [Pg.172]    [Pg.206]    [Pg.207]    [Pg.120]    [Pg.436]    [Pg.229]    [Pg.285]    [Pg.854]    [Pg.49]    [Pg.341]    [Pg.431]    [Pg.81]    [Pg.775]    [Pg.29]    [Pg.552]    [Pg.557]    [Pg.162]    [Pg.39]    [Pg.30]    [Pg.36]    [Pg.36]    [Pg.63]    [Pg.173]    [Pg.560]    [Pg.229]    [Pg.182]    [Pg.775]    [Pg.392]    [Pg.201]    [Pg.15]    [Pg.8]    [Pg.3]   
See also in sourсe #XX -- [ Pg.2 ]




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