Alkyl groups substituted benzenes

The monoaromatics consist of benzene rings substituted with a number of alkyl groups. The major reaction taking place in the catalytic cracker will be removal of alkyl groups. Since benzene has a boiling point of 176°F, it is also anticipated that the monoaromatics will be cracked to products other than slurry oil and coke.(4)... 

In this contribution, we will describe the basic approach to construct the retention prediction system in reversed-phase LC for alkyl-benzenes, polycyclic airomatic hydrocau bons (PAHs) aind polau group substituted benzenes, baised on the use of sudi established relationships between retention and physicodiemlcal parameters of these compounds. The system has been constructed on a 16—bit microcomputer, and the application for optimization of sepairation conditions will be demonstrated. 

Some benzo-fused, eight-membered ring, methyl-substituted sulfur ylides can show methyl resonance at unusually low values d 1.8-2.0 if the ylide methyl group can be shielded by the benzene ring in a predominant conformation <82CC1060,84CPB4360>. This would be expected to extend to other alkyl group substituted, benzo-fused ylides. 

The hydrogen-bonding energy seemed to contribute to the retention on the graphitized carbon (Hypercarb ) column, but not to the retention on another carbon BioTechnologyResearch (BTR ) column. Therefore, only alkyl-group-substituted compounds were selected and their log k values were correlated with MI values. The correlation coefficient was 0.718 for log A ref- The log A ref values of benzene, toluene, o- grlene, m- ylene,p- g lene, o-te/t-butylphenol, 4-ethylphenol,... 

However, other studies on the nitration of a series of 3-methyl- and 3-ethyl-1,2-benzisoxazoles have shown that a mixture of the 5-nitro and 5,7-dinitro derivatives is formed (77IJC(B)1058, 77IJC(B)1061). The effect of substituents in the benzene ring is also of interest. If the 5-position is blocked, e.g. by a chloro group or by alkyl groups, nitration then occurs at the 4-position. 3-Alkyl-7-chloro and 3,7-dialkyl derivatives result in the formation of the appropriate 5-nitro derivative. The isomeric 3-alkyl-6-chloro- and 3,6-dialkyl-1,2-benzisoxazoles yield a mixture of the 5-nitro and 5,7-dinitro compounds. Both H NMR measurements and alternate syntheses were used in establishing the structures of these substitution products. 

One example of substituent replacement involves cleavage of a highly branched alkyl group. The alkyl group is expelled as a carbocation, and for this reason, substitution is most common for branched alkyl groups. The nitration of l,4-bis(i-propyl)benzene provides an example ... 

The general rule has been formulated (P) that the less substituted enamine is formed from unsymmetrical ketones such as the 2-alkylcyclohexanones. In enamine 21 the R, group and the N-alkyl groups would interfere with one another if overlap is to be maintained between the nitrogen unshared electrons and the double bond. There would be less repulsion if the isomeric enamine (22) were formed. 2-Phenylcyclohexanone and pyrrolidine with p-toluenesulfonic acid as catalyst in refluxing benzene gave enamine... 

Among the most useful electrophilic aromatic substitution reactions In the laboratory is alkylation—the introduction of an alkyl group onto the benzene ring. Called the Friedel-Crafts reaction after its discoverers, the reaction is carried out... 

Aromatic hydrocarbons substituted by alkyl groups other than methyl are notorious for their tendency to disproportionate in Friedel-Crafts reactions. This tendency has previously limited the application of the isomerization of para- or ortho-) m ky -benzenes to the corresponding meta compounds. At the lower temperature of the present modification, disproportionation can be minimized. 

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