Benzoylation of benzene

Brown and Young410,411 studied the benzoylation of benzene and toluene by benzoyl chloride catalysed by aluminium chloride at 25 °C in nitrobenzene as solvent. For a given concentration of reagents, the rate equation was... 

The method was also applied to the benzoylation of other aromatic compounds (Tab. 7.7). The benzoylation of benzene itself, volatile and less reactive, seemed more difficult to perform (Tab. 7.7, entry 4). Silyl-substituted aromatics reacted by ipso Si-substitution [77], and were less volatile. With trimethylsilylbenzene, benzoylation occurred with an overall yield higher than for benzene, but the competitive H-substitu-tion was also observed (entry 5). 

Benzoylation of benzene and other aromatic compounds by benzoyl chloride over H-BEA zeolite modified by indium oxides has been investigated.191 We report in Table 4.2 the time required for half reaction (L/2) f°r a series of aromatic substrates used in the above reaction. The benzoylation reaction rate (via L /2 value) depends strongly on the substituent group present in the aromatic substrate and increases due to the presence of the electron-donating group, depending upon its electron-donating ability. The activity order is as follows benzene toluene < p-xylene < anisole. 

Figure 5 The benzoylation of benzene (0.5 mol) using benzoyl chloride (0.05 mol) at 85 °C catalysed by sulfated zirconia (lOg)...

Diarylketones are also the important fine chemical intermediates, which could be prepared by the acylation of aromatic hydrocarbon with benzoyl chloride and benzoic anhydride. The ionic liquids have also been used to catalyze the synthesis of diarylke-tone. Earle et al. [105] have reported the benzoylation of benzene, derivants of benzene (toluene, anisole, isobutyl benzene, phenyl chloride and fluoride) to synthesize the diarylketone by use of chloroindate (III) ionic liquids as the green dual catalysts and solvents. As a result, good yields (75-96%) were obtained under proper conditions with the ionic liquids as the clean reaction medium and recyclable catalysts. 

A dramatic acceleration of benzene acylation is also observed by using a similar catalyst consisting of a combination of hafnium triflate and triflic acid. While in the benzoylation of benzene with BC, low yields of benzo-phenone (BP) (5%-10%) are obtained in the presence of hafnium triflate (5% mol) or triflic acid (5% mol), a 77% yield is obtained when combining hafnium triflate (5% mol) with triflic acid (5% mol). The yield is improved to 82% when hafnium triflate and triflic acid are used in higher quantity (10% mol) a further increase of the catalyst amount does not improve the... 

BEA zeolites are very efficient catalysts in the benzoylation of benzene with The catalytic activity of I5EA in comparison with ZSM-12 and REY zeolites is 5.76,0.25, and 0.27 mmol x g i x h h The higher activity of the BEA may be attributed to its stronger acid sites and possible contribution of the mesoporous system that minimizes catalyst decay by coke deposition, with corresponding improvements in activity and time of catalyst use. The conversion of BC to benzophenone (BP) significantly increases with increase in the reaction time, temperature, BEA BC ratio, and benzene BC ratio. When these parameters rise to 18 h, 80°C, 0.33 w/w ratio, and 5 mol/mol ratio, respectively, the BP yield is 54%. 

The preparation and use of indium trichloride, gallium trichloride, and zinc chloride supported on MCM-41 as Lewis acids in the Friedel-Crafts acylation of aromatics with acyl chlorides was investigated. The support itself shows no catalytic activity in the benzoylation of benzene with BC, whereas the highest activity is showed by the supported indium trichloride. The order for acylation activity of the supported metal chloride (indium trichloride > gallium trichloride zinc chloride) is quite similar to that of the redox potential of the metals [E , +/, (-0.34 V) > E°Ga /Ga ( 0.53 V) > E 2n +/zn ( 0.74 V)] and confirms a possible relationship between the redox potential and the catalytic activity of the supported metal chloride. The reaction can be efficiently applied to a variety of aromatic compounds, including toluene, para-xylene, mesitylene, anisole, and 2-MN (70%-90% yield), confirming the moisture insensitivity of the catalyst. ... 

Aluminum-chloride-grafted MCM-41 shows high catalytic activity in the benzoylation of benzene and toluene with leading to 55% and 63% BC conversion, respectively. The catalyst can be reused in the subsequent experiments but with somewhat reduced activity this is most probably due to its momentary exposure to the atmosphere during its reuse. When the catalyst is exposed to the atmosphere for a longer period (>2-3 min), its activity is totally killed and, also, its color changes from brown to white due to the adsorption of moisture from the atmosphere. 

A similar trend is observed in the benzoylation of benzene with parfl-chlorobenzoyl chloride over SZ catalyst prepared from zirconium(IV) oxychloride and calcined at 650°C for 3 h (Scheme 4.33)i° ... 

Benzoylation of benzene, toluene, and ortho-xylene at the corresponding refluxing temperatures for 1 h over iron SZ (2% iron) follows the expected order benzene (15%) < toluene (80%) < ortho-xylene (96%). In the model reaction between BC and toluene, the truly heterogeneous nature of the catalyst as well as its resistance to deactivation during reuse is confirmed. 

Singh, A. P. and Bhattacharya, D. 1995. Benzoylation of benzene to benzo-phenone over zeolite catalysts. Catal. Lett. 32 327-333. 

Choudhary, V. R. and Jana, S. K. 2002. Benzoylation of benzene and substituted benzenes by benzoyl chloride over InjOj/Si-MCM-ll catalyst. /. Mol. Catal. A Chem. 184 247-255. 

Nishamol, K., Rehna, K. S., and Sugunan, S. 2004. Liquid-phase Friedel-Crafts benzoylation of benzene using CuxMn(i x)Fe204 spinel catalysts. React. Kinet. Catal. Lett. 81 229-233. 

TABLE 8.23 Kinetic Data for Benzoylation of Benzene and Derivatives in Benzoyl Chloride Solution at 25°C... 

Rate constants reported for the AlCla-catalyzed benzoylation of benzene and its... 

Acylations were also catalyzed by bismuth(III) triflate. This property has been well demonstrated in the case of the benzoylation of benzene, toluene, and chlorobenzene [34], The mechanistic investigations confirmed BzOTf as active species of the benzoylation. Again, the activity of Bi(OTf>3 was much higher than that of other metallic triflates, and was comparable with that of TfOH. It has also the advantage that the triflate moieties are more easily recoverable. Other acylations of activated or deactivated benzenes such as fluorobenzene also proceeded in high yields in the presence of cataljdic amounts of Bi(OTf)3 [35]. 

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