Phthalic anhydride, formation

Phthalic anhydride is the most important product in the oxidation of o-xylene, which has become competitive with naphthalene as a feedstock for the industrial production of this component. This process is carried out at 350— 400°C and the industrial catalysts consist of doped V2Os or V2Os—Ti02 mixtures, pure or supported. Maximum yields of 70—75 mol. % (95—105 wt. %) are reported. Carbon oxides are the main by-products, besides minor amounts of tolualdehyde and maleic anhydride. Tolualde-hyde is the main product at low conversion and an essential intermediate in the phthalic anhydride formation, while maleic anhydride is mainly formed as a side-product directly from o-xlyene. 

It may favour bimolecular condensation reactions which are not acid-catalyzed, but which are accelerated by the proper geometry of sites at which the molecules are adsorbed. This property likely plays an important role in the mechanism of phthalic anhydride formation from w-pentane (19). 

Juusola el at. (1970) reported a study on V20 IK2S04lSi02 get catalyst at low conversions of o-Xylene and otolualdehyde. They used the same catalyst as Mann and Downie (1968), and both workers identified p-benzoquinone as a reaction product. These appear to be the only reported findings of this compound as a product of the oxidation of rvXylene on Vanadia catalysts. Juusola et at. (1970) network shows phthalic anhydride formation by a consecutive mechanism via o-tolualdehyde, (Moluic acid and phthaiide. Carbon dioxide is thought to be formed from o-tolualdehyde and phthaiide in addition to the direct path from o-Xylene p-berizoquinone is formed solely from o-Xylene. 

Boag et al. (1975) studied the reaction on a silica supported catalyst of similar composition to that of Juusola et al. (1970). the scheme is similar to that postulated by Herten and Froment (1968) with the exception that phthalide is considered to be a final product and not an intermediate one in the phthalic anhydride formation. 

Phthalein formation Fuse together carefully in a dry test-tube a few crystals of salicylic acid or of a salicylate with an equal quantity of phthalic anhydride rnoistened with 2 drops of cone. HjSO. Cool, dissolve in water and... 

The fluorescein test for succinic acid (p. 349) and the phthalein and fluorescein tests for phthalic acid (p. 351) are obviously given also by succinic anhydride and phthalic anhydride, as these tests depend upon the initial formation of the anhy dride in each case. 

The oxidation of dimethyl 3-methyl-3//-3-benzazepine-2,4-dicarboxylate (1) with potassium permanganate in acetone solution brings about destruction of the azepine ring and formation of phthalic anhydride (2).24... 

Phthalic anhydride derivatives are also not typical precursors in phthalocyanine formation. Their use is of interest in cases where the substituents prohibit conversion of the anhydride to nitrogen-containing derivatives like phthalimides or phthalonitriles. 

Note The exothermic nitration of phthalic acid or phthalic anhydride by a fuming nitric acid-sulfuric acid mixt may give mixts of the potentially expl phthaloyl nitrates or nitrites or their nitro derivatives. Formation of these compds can be avoided if the nitrating mixt is... 

The effect of sodium nitrite on phthalic anhydride when it was hot ended with a violent detonation of the medium. It was explained by the formation of a derivative containing the following unstable group CO-ONO. 

In the preparation of the polyester, you will react ethylene glycol, a diol, with phthalic anhydride. In this activity, phthalic anhydride will react similarly to the way phthalic acid (1,2-benzenedicarboxylic acid) reacts, resulting in the formation of a polyester. Phthalic acid and ethylene glycol are the A and B units of the A-B polymer phthalic anhydride + ethylene glycol —> polyester. 

Phenyl indandiones With an acidic hydrogen often interfere with clot formation. When electron withdrawing groups are present in the p-position, acidity is increased and activity goes up. The opposite effect is seen with electron-donating substituents. Synthesized in the usual way, the anticoagulant bromindione (15) results from sodium acetate-catalyzed condensation of phthalic anhydride and p-a-bromophenyl-acetic acid. ... 

The pyrolysis of a number of compounds at temperatures around 600— 800° and at pressures of the order of 10 2 mm. has been shown to give rise to benzyne. These compounds include for example indanetrione 29>, and phthalic anhydride 30 38>. The dimerisation of benzyne to yield biphenylene has been used preparatively 31 33>, an(j the pyrolysis of tetrafluorophthalic anhydride 34>, and tetrachlorophthalic anhydride 3i-33) gave the corresponding octahalobiphenylenes. In the case of the pyrolysis of tetrachlorophthalic anhydride some hexachlorobenzene is also formed, while the pyrolysis of tetrabromophthalic anhydride results in the formation of hexabromobenzene but no octabromobiphenylene. The disproportionation of tetrabromobenzyne to form carbon and bromine is a function of the high temperature involved and, as we shall see later, both tetrabromo- and tetraiodo-benzyne behave normally in solution. 

Fluidized bed reactors were first employed on a large scale for the catalytic cracking of petroleum fractions, but in recent years they have been employed for an increasingly large variety of reactions, both catalytic and non-catalytic. The catalytic reactions include the partial oxidation of naphthalene to phthalic anhydride and the formation of acrylonitrile from propylene, ammonia, and air. The noncatalytic applications include the roasting of ores and Tie fluorination of uranium oxide. 

Yet another method of avoiding PCB formation in the solvent process is to dispense with the need for urea as a reactant by using the more expensive phthalonitrile instead of phthalic anhydride. 

Although anthraquinone is the starting point for the preparation of many derivatives, involving substitution and replacement reactions, certain compounds are obtained directly by varying the components in the above synthesis. Thus, for example, replacement of benzene with methylbenzene (toluene) leads to the formation of 2-methylanthraquinone. A particularly important variation on the phthalic anhydride route is the synthesis of 1,4-dihydroxyanthraquinone (6.6 quinizarin) using 4-chlorophenol with sulphuric acid and boric acid as catalyst (Scheme 6.3). The absence of aluminium chloride permits hydrolysis of the chloro substituent to take place. 

The phthalonitrile process has the particular advantage over the phthalic anhydride process of forming ring-substituted chloro-copper phthalocyanines. Using copper(I)chloride produces so-called semi-chloro Copper Phalocyanine Blue, a pigment which possesses a statistical average of 0.5 chlorine atoms per copper phthalocyanine molecule. Copper(II)chloride, on the other hand, affords a product which comprises an average of one chlorine atom per copper phthalocyanine molecule. A prerequisite for the formation of the chloro substituted compound, however, is the absence of ammonia or urea in the reaction mixture. 

A. 1 Equilibrium data for anhydride formation from succinic, maleic and phthalic acidsa... 

The direct formation of A-substituted phthalimides from phthalic anhydride and alkyl azides, via the intermediate RN=PPh, compound, is catalysed by the presence of tetra-n-butylammonium cyanide [34],... 

The influence of temperature on the ortho effect has been evaluated in the alkaline hydrolysis in aqueous DMSO solutions of ortho-, meta- and para-substituted phenyl benzoates (26). The alcoholysis of phthalic anhydride (27) to monoalkyl phthalates (28) occurs through an A-2 mechanism via rate-determining attack of the alcohol on a carbonyl carbon of the anhydride (Scheme 4). Evidence adduced for this proposal included highly negative A 5 values and a p value of 4-2.1. In the same study, titanium tetra-n-butoxide and tri-n-butyltin ethanoxide were shown to act as effective catalysts of the half-ester formation from (27), the mechanism involving alkoxy ligand exchange at the metal as an initial step. ... 

The gas-phase reaction of N2O5 and naphthalene in an environmental chamber at room temperature resulted in the formation of 1- and 2-nitronaphthalene with approximate yields of 18 and 7.5%, respectively (Pitts et ah, 1985). The reaction of naphthalene with NOx to form nitronaphthalene was reported to occur in urban air from St. Louis, MO (Randahl et ah, 1982). The gas-phase reaction of naphthalene with OH radicals yielded phthalaldehyde, phthalic anhydride, phthalide, 1,4-naphthoquione, cis- and rra/J5-2-formylcinnamaldehyde, and 2,3-epoxy-1,4-naphthoquinone. 

The formation of phthalic anhydride is highly exothermic, and even with the most careful design the heat removal from packed bed reactors can become uncheckable, leading to temperature runaways, meltdowns, and even explosions. If the chief engineer of those reactors had been required to sit on the reactor during start up, there would be fewer chief engineers about. ... 

In a study of the formation and reactions of arynes at high temperatures. Fields and Meyerson plyrolyzed a thiophene solution of phthalic anhydride at 690° by mass spectrometry and gas chromatography they found benzene, naphthalene, benzo[b]thiophene, phenylthiophenes, bithienyls, thienothiophene 1, and naphthothiophene in the pyrolysis products. Pyrolysis of thiophene itself produced benzo-[Z lthiophene, thienothiophene 1, phenylthiophene, and bithienyl. The... 

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