Friedel-Crafts Isomerization. II.¹ Aluminum Chloride-Catalyzed Isomerization of Chlorofluorobenzenes and Dichlorobenzenes. The Effect of Aluminum Chloride on Difluorobenzenes

Abstract

Individual peaks were identified by the retention times of pure halobenzenes and dihalobenzene isomers. Identification of separated fractions in a number of preparative scale runs waa made by infrared spectroscopy. Components were separated from the reaction mixture using a 3 m. X 1 in. aluminum preparative-scale column packed with polypropylene glycol supported on diatomaceous earth. Samples of up to 5 ml. were separated by this method.Acknowledgment.-The authors are indebted to D~. E. B, ~~k~~ for the n.m.r, andThe water-promoted, aluminum chloride-catalyzed isomerization of chlorofluorobenzenes takes place by an intramolecularThe equilibrium isomer mixture is composed of 470 ortho, 64% meta, and 327, paraIsomerization of ortho-chlorofluorobenzene is much slower than that of the meta and para isomers Halogen exchange and electrophilic arylation in this case overtake Isomerization of dichlorobenzenes also takes The equilibDifluorobenzenes are Halogen exchange and electrophilic arylation are the only reactions taking 1,Zshift of the chlorine substituent. chlorofluorobenzene. (because of the ortho deactivating effect of fluorine). isomerization, so that equilibrium cannot be reached from the ortho isomer.place by a predominantly intramolxular 1,2-shift mechanism (disproportionation is generally less than 1 %). rium mixture for dichlorobenzene was found to contain 8% ortho, 60% meta, and 32% para isomer. unable to undergo Friedel-Crafts isomerization. place. The mechanism of the investigated reactions is discussed based on the obtained experimental data.

Tetrabutylammonium Salts of Aluminum(III) and Gallium(III) Phthalocyanine Radical Anions Bonded with Fluoren‐9‐olato− Anions and Indium(III) Phthalocyanine Bromide Radical Anions

“…Given that isomerically pure o ‐dichlorobenzene was used in the synthesis, it is most plausible that Al III Cl(Pc 2− ) and Ga III Cl(Pc 2− ) act as catalysts for the isomerization of o ‐dichlorobenzene. It is known also that AlCl 3 isomerizes o ‐dichlorobenzene into p ‐dichlorobenzene . It is seen that Ga III ClPc is less effective than Al III ClPc for the isomerization of o ‐dichlorobenzene, whereas In III ClPc is ineffective for this isomerization, as in the case of 2 , a mixture of p ‐ and o ‐dichlorobenzene molecules is formed but only o ‐dichlorobenzene molecules are found in 3 .…”

“…It is known also that AlCl 3 isomerizes o-dichlorobenzene into p-dichlorobenzene. [26] It is seen that Ga III ClPc is lesse ffective than Al III ClPc for the isomerization of o-dichlorobenzene, whereas In III ClPc is ineffective for this isomerization, as in the case of 2,amixture of p-and o-dichlorobenzenemolecules is formed butonly o-dichlorobenzene molecules are found in 3.O ther metal phthalocyanine [M(PcC 3À )]C À salts( M= Sn II ,P b II ,T i IV O, Sn IV Cl 2 )h ave also been reported to contain only o-dichlorobenzene molecules. [6][7][8] The geometric parameters of the aluminum(III) and gallium(III) phthalocyanines in 1 and 2 are listed in Ta ble 1.…”

Thermodynamic Analysis of Isomerization Equilibria of Chlorotoluenes and Dichlorobenzenes in a Biphasic Reaction Systems Containing Highly Acidic Chloroaluminate Melts

“…However, it is well established that the meta -isomers are the thermodynamically most stable compounds in their respective isomeric mixtures. , As a consequence, a promising route to produce the meta -isomer efficiently is the isomerization of p -dichlorobenzene or p- chlorotoluene. This highly selective reaction can be carried out under typical Friedel–Crafts conditions with water promoted aluminum chloride. , However, these classical catalysts have an important drawback: the product isolation procedure demands for the hydrolysis of the reaction system, which leads to the complete destruction of the catalyst. This makes the reuse of the catalyst impossible and the isomerization protocol not sustainable and not economic.…”

“…It is well established, that catalytic reactions in alkylbenzenes and chlorobenzenes (see Figure S1 in the Supporting Information) are usually limited by the equilibrium of isomerization and disproportionation reactions. ,,, However, relative rates of these chemical reactions are significantly different and they are crucially dependent on the temperature of experiment. For example, as shown by Olah and Meyer, starting from mixtures with different amount of ortho -, meta- , and para -isomers, the distribution of isomers approximates equilibrium only after 50 h at 373 K. Therefore, reactions given in Figure , have to be considered both under kinetic and under thermodynamic control.…”

Dihalobenzene Shape Sorting by Nonporous Adaptive Crystals of Perbromoethylated Pillararenes

“…[1] Particularly, DCB isomers are widely used as organic solvents,r aw materials,a nd intermediates for organic synthesis,e specially pesticides and drugs.I nt he chemical industrial production process,D CB isomers are usually obtained by direct chlorination of benzene. [2] Thes ynthesized chlorination solution needs to be subjected to multi-step deep processing such as dehydrogenation, crystallization, rectification, and purification to obtain high-purity DCB products,w hich accounts for most of the energy consumption in industrial processes. [3] oDCB, mDCB and pDCB have similar boiling points (Table S1).…”