Sulfuric acid as catalyst for

Thiele reaction. BF,-etherate is more satisfactory than sulfuric acid as catalyst for the Thiele reaction of a-naphthoquinone, for with sulfuric acid the yield is only... 

Ohle and Koller, Slobodin and Klimov, Bell, and Brady showed that low concentrations ( 0.5%) of sulfuric acid as catalyst for 1-3 days at room temperature lead to the formation of 1. Slightly higher concentrations of catalyst and shorter reaction times (3-24 hours) favor an increase in the proportion of 2, and lead to the isolation of mixtures of diacetals 1 and 2. However, at high concentrations of acid ( 4%), or after prolonged reaction, compound 2 was found to be the preponderant product. Evidently (see also Section III,2 p. 218), the diacetal 1 is the product of kinetically controlled condensation of D-fructose with acetone, but it rearranges, at a rate proportional to the concentration of the sulfuric acid catalyst, to the diacetal 2, which is thermodynamically more stable than 1, and thus preponderates at equilibrium. The use of zinc chloride as the catalyst is known to favor the formation of 1. 

Paushkin and Topchiev also used H3P()4-BF3 at room temperature to alkylate benzene with olefins (287,402). For alkylation of benzene with alcohols, temperatures of 90-97° and a feed mole ratio of 0.5 alcohol 1.0 benzene 0.5 catalyst were recommended (394). In a recent study (400a) these authors supplemented their previously published views (396) concerning the properties of boron fluoride complexes with phosphoric acid, alcohols, and sulfuric acid as catalysts. Data on the electroconductivity of these catalysts was correlated with their activity in alkylation of isobutane and it was concluded (400a) that the acid ion concentration did not affect the alkylation or polymerization reactions over these catalysts, and therefore the carbonium ion mechanism was not applicable. 

In Table 1.3.2 a method for the analysis of nitrates and nitrites for a wide variety of samples is given Aqueous nitrate ions are converted to nitrobenzene by reaction with benzene in the presence of concentrated sulfuric acid as catalyst. The special methods for the different materials are described. To stabilize samples against bacterial action, which can reduce nitrate concentrations, phenylmercuric acetate is added after collection ° Other inorganic compounds in the trace levels for gas-chromatographic determination are, for example, water and carbon monoxide, which were determined in organic solvents or air in the ppb-range ... 

ROH— RBr. The preferred procedure for the preparation of primary alkyl bromides calls for use of a small amount of sulfuric acid as catalyst. 2-Bromo-... 

Wirth ° has described a high-yield procedure for iodination with iodic acid as oxidant and sulfuric acid as catalyst ... 

Formylation of amines and alcohols. Behai,8 discoverer of the reagent, found that it reacts unidirectionally with simple alcohols to produce alkyl formates free from acetates. Hurd et al. J found that acetic-formic anhydride (prepared from formic acid and ketene) reacts quantitatively with aniline to give formanilide. Another study10 established that acetic-formic anhydride mixes endothermally with 2-nitro-2-methyl-l-propanol, exothermally with 2-nitro-2-methyl-l,3-propanediol, and displays no appreciable temperature effect with either 2-nitro-l-butanol or tris-(hydroxymethyl)-nitromethane. Formic esters are favored by avoiding a high reaction temperature and by not using sulfuric acid as catalyst. The mixed anhydride has been used for the preparation of formyl fluoride.11... 

In 1934, Hudson and his group observed that treatment of a number of methyl D-aldohexopyranoside tetraacetates gave the a-D-aldohexopyranose pentaacetates on acetolysis with sulfuric acid as catalyst. Three years later, they observed that methyl jS-D-arabinopyranoside 2,3,4-triacetate gives 56% of alde%do-D-arabinose hexaacetate and 11% of /3-D-arabino-pyranose 1,2,3,4-tetraacetate the optical rotation of the mixture decreased steadily during the reaction. However, for the a-D-arabinoside, the rotation rose very sharply during the first minute and then fell more slowly. At the end of the reaction, the products were essentially those from the jS-D-glycoside at the point of maximum rotation, a 14% yield of methyl jS-D-arabinopyranoside was isolated, showing that anomerization can occur under these conditions, followed by subsequent acetolysis to the peracetate. 

Another route to coumarins is the Pechmann condensation of phenols with (3-ketoesters. The reaction proceeds via transesterification and intramolecular hydroxyalkylation, followed by dehydration, and is conventionally conducted using sulfuric acid as catalyst. Resorcinol and ethyl acetoacetate reacted sol vent-free over H-beta at 150 °C to give 7-hydroxy-4-methylcoumarin (78 % isolated yield) [85J. This is another perfumery ingredient which is also an intermediate for the insecticide I Iymecromone. 

Methyl esters of carboxylic acids cannot be prepared by the usual method of azeotropic esterification. In a process for production of methyl esters, Clinton and Laskowski803 heated a carboxylic acid with methanol for 6-15 h in the presence of methylene dichloride or 1,2-dichloroethane and with sulfuric acid as catalyst, without removing the product water then they separated the organic phase containing the ester, washed it with sodium hydrogen carbonate solution, and worked it up as usual. 

Finally, by employing the CMR, with sulfuric acid as catalyst (2.5% wjv relative to MeOH), at 80 °C and with a residence time of 6 min in the microwave zone, the methyl p and a-O-glucofuranosides comprised nearly 80% of the product mixture (52 and 27% respectively). These conditions were suitable for large-scale preparation of the furanosides. When the residence time was extended to 12 min, the selectivity was reversed, with the methyl p and a-O-glucopyranosides being obtained in 23 and 54% yield, respectively (Scheme 3.12). 

The raw material for CTA is wood pulp oreotton lintersof high -eellulose content. The term -cellulose refers to the portion of the cellulosic raw material which is insoluble after treatment with an aqueous solution of sodium hydroxide of 17-18%. The acetylation, at least initially, is heterogeneous and topochemical wherein successive layers of cellulose fibers react and are solubilized in the reaetion medium, thus exposing new surfece for reactions. The cellulose fibers are mixed with sulfuric acid as catalyst and suspended in a mixture of aeetic anhydride and acetic acid. The anhydride is used in slight excess compared to the acetic acid. The sulfuric acid reacts with acetic anhydride to form acetylsulfiiric acid. 

Khodaei, M.M., Khosropour, A.R. and Fattahpour, R 2005. A modified procedure for the Dakin-West reaction An efficient and convenient method for a one-pot synthesis of P-acetamido ketones using silica sulfuric acid as catalyst. Tetrahedron Lett. 46(12) 2105-2108. 

Isopropylbenzene is an imp>ortant intermediate for the production of phenol. There are two main industrial methods for the synthesis of isopropylbenzene from benzene and propylene. One is the liquid-phase process using sulfuric acid as catalyst and the other is the vapor-phase process using phosphoric acid (or PiOs) supported on silica or kieselguhr, the content of P2O5 and SiOi being 62 — 65% and 25%, respectively. In the latter process, UOP process,the reaction is carried out at 570 — 640 K and 17 — 30 bar with a benzene-to-propylene ratio of 5 — 7. Isopropylbenzene yield of 96 — 97% of the theoretical value based on benzene and 91—92% based on propylene is typical. The formation of isopropylbenzene in the alkylated products is more than 90%. This process has also been applied to the alkylation of benzene with ethylene. 

In general ketones are more stable than their enol precursors and are the products actually isolated when alkynes undergo acid catalyzed hydration The standard method for alkyne hydration employs aqueous sulfuric acid as the reaction medium and mer cury(II) sulfate or mercury(II) oxide as a catalyst... 

---