Sulfuric acid synthesis

Primary steam reforming Secondary steam reforming Carbon monoxide conversion Carbon monoxide methanation Ammonia synthesis Sulfuric acid synthesis Methanol synthesis Oxo synthesis Ethylene oxide Ethylene dichloride Vinylacetate Butadiene Maleic anhydride Phthalic anhydride Cyclohexane Styrene Hydrodealkylation Catalytic reforming Isomerization Polymerization (Hydro)desulfurization Hydrocracking... 

Tamaddon, F. and Farahi, M. 2012. A new three-component reaction catalyzed by silica sulfuric acid Synthesis of tetrasubstituted pyrroles. Synlett 23 1379-1383. 

A new three-component reaction catalyzed by silica sulfuric acid synthesis of tetrasubstituted pyrroles. 

The nitration of the 2-anilino-4-phenylselenazole (103) is much more complicated. Even careful nitration using the nitrate-sulfuric acid method leads to the formation of a mixture of variously nitrated compounds in an almost violent reaction. By the use of column chromatography as well as thin-layer chromatography a separation could be made, and the compounds could be partly identified by an independent synthesis. Scheme 33 shows a general view of the substances prepared. Ring fission was not obser ed under mild conditions. 

When applied to the synthesis of ethers the reaction is effective only with primary alcohols Elimination to form alkenes predominates with secondary and tertiary alcohols Diethyl ether is prepared on an industrial scale by heating ethanol with sulfuric acid at 140°C At higher temperatures elimination predominates and ethylene is the major product A mechanism for the formation of diethyl ether is outlined m Figure 15 3 The individual steps of this mechanism are analogous to those seen earlier Nucleophilic attack on a protonated alcohol was encountered m the reaction of primary alcohols with hydrogen halides (Section 4 12) and the nucleophilic properties of alcohols were dis cussed m the context of solvolysis reactions (Section 8 7) Both the first and the last steps are proton transfer reactions between oxygens... 

The most widely used industrial synthesis of phenol is based on isopropylbenzene (cumene) as the starting material and is shown m the third entry of Table 24 3 The eco nomically attractive features of this process are its use of cheap reagents (oxygen and sulfuric acid) and the fact that it yields two high volume industrial chemicals phenol and acetone The mechanism of this novel synthesis forms the basis of Problem 24 29 at the end of this chapter... 

Alkali Fusion of /u-Benzenedisulfonic Acid. Even though this process like the previous one is a very ancient one, it is still the main route for the synthesis of resorcinol. It has been described in detail previously and does not seem to have drastically evolved since 1980. It involves the reaction of benzene with sulfuric acid to form y -benzenedisulfonic acid which is then converted to its disulfonate sodium salt by treatment with sodium sulfite. In a second step, this salt is heated to 350°C in the presence of sodium hydroxide yielding the sodium resorcinate and sodium sulfite. 

The synthesis of 2,4-dihydroxyacetophenone [89-84-9] (21) by acylation reactions of resorcinol has been extensively studied. The reaction is performed using acetic anhydride (104), acetyl chloride (105), or acetic acid (106). The esterification of resorcinol by acetic anhydride followed by the isomerization of the diacetate intermediate has also been described in the presence of zinc chloride (107). Alkylation of resorcinol can be carried out using ethers (108), olefins (109), or alcohols (110). The catalysts which are generally used include sulfuric acid, phosphoric and polyphosphoric acids, acidic resins, or aluminum and iron derivatives. 2-Chlororesorcinol [6201-65-1] (22) is obtained by a sulfonation—chloration—desulfonation technique (111). 1,2,4-Trihydroxybenzene [533-73-3] (23) is obtained by hydroxylation of resorcinol using hydrogen peroxide (112) or peracids (113). 

Reactions and Uses. The common reactions that a-hydroxy acids undergo such as self- or bimolecular esterification to oligomers or cycHc esters, hydrogenation, oxidation, etc, have been discussed in connection with lactic and hydroxyacetic acid. A reaction that is of value for the synthesis of higher aldehydes is decarbonylation under boiling sulfuric acid with loss of water. Since one carbon atom is lost in the process, the series of reactions may be used for stepwise degradation of a carbon chain. 

Examples of polymers which form anisotropic polymer melts iaclude petroleum pitches, polyesters, polyethers, polyphosphaziaes, a-poly- -xyljlene, and polysdoxanes. Synthesis goals iaclude the iacorporation of a Hquid crystal-like entity iato the maia chaia of the polymer to iacrease the strength and thermal stabiHty of the materials that are formed from the Hquid crystal precursor, the locking ia of Hquid crystalline properties of the fluid iato the soHd phase, and the production of extended chain polymers that are soluble ia organic solvents rather than sulfuric acid. 

Synthesis. Hydroxyhydroquiaone is not produced on a large scale, but many uses for it are being developed. The most convenient preparation of hydroxyhydroquiaone is the reaction of -benzoquiaone with acetic anhydride ia the preseace of sulfuric acid or phosphoric acid. The resultant triacetate (29) can be hydrolyzed to hydroxyhydroquiaone (86). 

The earliest reported reference describing the synthesis of phenylene sulfide stmctures is that of Friedel and Crafts in 1888 (6). The electrophilic reactions studied were based on reactions of benzene and various sulfur sources. These electrophilic substitution reactions were characterized by low yields (50—80%) of rather poorly characterized products by the standards of 1990s. Products contained many by-products, such as thianthrene. Results of self-condensation of thiophenol, catalyzed by aluminum chloride and sulfuric acid (7), were analogous to those of Friedel and Crafts. 

Fig. 2. Synthesis of uma2enil (18). The isonitrosoacetanihde is synthesized from 4-f1iioroani1ine. Cyclization using sulfuric acid is followed by oxidization using peracetic acid to the isatoic anhydride. Reaction of sarcosine in DMF and acetic acid leads to the benzodiazepine-2,5-dione. Deprotonation, phosphorylation, and subsequent reaction with diethyl malonate leads to the diester. After selective hydrolysis and decarboxylation the resulting monoester is nitrosated and catalyticaHy hydrogenated to the aminoester. Introduction of the final carbon atom is accompHshed by reaction of triethyl orthoformate to...

Oxidation. The synthesis of quinolinic acid and its subsequent decarboxylation to nicotinic acid [59-67-6] (7) has been accompHshed direcdy in 79% yield using a nitric—sulfuric acid mixture above 220°C (25). A wide variety of oxidants have been used in the preparation of quinoline N-oxide. This substrate has proved to be useful in the preparation of 2-chloroquinoline [612-62-4] and 4-chloroquinoline [611 -35-8] using sulfuryl chloride (26). The oxidized nitrogen is readily reduced with DMSO (27) (see Amine oxides). 

Conra.d-Limpa.ch-KnorrSynthesis. When a P-keto ester is the carbonyl component of these pathways, two products are possible, and the regiochemistry can be optimized. Aniline reacts with ethyl acetoacetate below 100°C to form 3-anilinocrotonate (14), which is converted to 4-hydroxy-2-methylquinoline [607-67-0] by placing it in a preheated environment at 250°C. If the initial reaction takes place at 160°C, acetoacetanilide (15) forms and can be cyclized with concentrated sulfuric acid to 2-hydroxy-4-methylquinoline [607-66-9] (49). This example of kinetic vs thermodynamic control has been employed in the synthesis of many quinoline derivatives. They are useful as intermediates for the synthesis of chemotherapeutic agents (see Chemotherapeuticsanticancer). 

A variation involves the reaction of benzylamines with glyoxal hemiacetal (168). Cyclization of the intermediate (35) with sulfuric acid produces the same isoquinoline as that obtained from the Schiff base derived from an aromatic aldehyde and aminoacetal. This method has proved especially useful for the synthesis of 1-substituted isoquinolines. 

Most current industrial vitamin C production is based on the efficient second synthesis developed by Reichstein and Grbssner in 1934 (15). Various attempts to develop a superior, more economical L-ascorbic acid process have been reported since 1934. These approaches, which have met with htde success, ate summarized in Crawford s comprehensive review (46). Currently, all chemical syntheses of vitamin C involve modifications of the Reichstein and Grbssner approach (Fig. 5). In the first step, D-glucose (4) is catalytically (Ni-catalyst) hydrogenated to D-sorbitol (20). Oxidation to L-sotbose (21) occurs microhiologicaRy with The isolated L-sotbose is reacted with acetone and sulfuric acid to yield 2,3 4,6 diacetone-L-sorbose,... 

Later, a completely different and more convenient synthesis of riboflavin and analogues was developed (34). It consists of the nitrosative cyclization of 6-(A/-D-ribityl-3,4-xyhdino)uracil (18), obtained from the condensation of A/-D-ribityl-3,4-xyhdine (11) and 6-chlorouracil (19), with excess sodium nitrite in acetic acid, or the cyclization of (18) with potassium nitrate in acetic in the presence of sulfuric acid, to give riboflavin-5-oxide (20) in high yield. Reduction with sodium dithionite gives (1). In another synthesis, 5-nitro-6-(A/-D-ribityl-3,4-xyhdino) uracil (21), prepared in situ from the condensation of 6-chloro-5-nitrouracil (22) with A/-D-ribityl-3,4-xyhdine (11), was hydrogenated over palladium on charcoal in acetic acid. The filtrate included 5-amino-6-(A/-D-ribityl-3,4-xyhdino)uracil (23) and was maintained at room temperature to precipitate (1) by autoxidation (35). These two pathways are suitable for the preparation of riboflavin analogues possessing several substituents (Fig. 4). 

The latter method typically requires less severe conditions than the former because of the labile nature of the organic anhydride (87,137). Both of these reactions can result in explosions and significant precautions should be taken prior to any attempted synthesis of a peracid (87). For soHd peracids the reaction mixture can be neutralized with sodium hydroxide and the resulting fUtercake washed with water. In the case of the sulfuric acid mediated reaction the peracid has sodium sulfate incorporated in the cake (135). The water of hydration present in the sodium sulfate is desirable to prevent detonation or deflagration of the soHd peracid when isolated in a dry state (87,138,139). 

---