Sulfur trioxide, addition compounds

See also Sulfuryl chloride) Sulfur trioxide, addition compounds with pyridine, dimethylaniline, and dioxane, 2 173, 174 for synthesis of deuterosulfuric acid, 6 121... 

The powerful oxidizing action of sulfur trioxide can be overcome by using the sulfur trioxide addition compounds mentioned above (page 612) their activity in sulfonation depends on their stability.167 Disulfur hexaoxide or its adducts to mineral acids (e.g., H2S207) are more powerful sulfonating agents than the stable adducts to dioxan55,101 or tertiary amines very mild conditions can be used with the latter 172 compounds that are especially sensitive to acids can be sulfonated by the pyridine-sulfur trioxide adduct without decomposition. 

In this case history, the control of the TMRaa (adiabatic Time-to-Maximum-Rate) is to be achieved in a semi-continuous reactor process by the dynamic optimization of the feed rate. Here it is desired to have the highest possible space-time-yield STY and it is necessary to achieve a thermally safe process (Keller, 1998). The reaction involves the addition of a sulfur trioxide on a nitro-aromatic compound... 

Tellurium Halides. Tellurium forms the dihalides TeCl and TeBi, but not Tel2. However, it forms tetrahalides with all four halogens. Tellurium decafluoride [53214-07-6] and hexafluoride can also be prepared. No monohalide, Te2X2, is believed to exist. Tellurium does not form well-defined oxyhalides as do sulfur and selenium. The tellurium halides show varying tendencies to form complexes and addition compounds with nitrogen compounds such as ammonia, pyridine, simple and substituted thioureas and anilines, and ethylenediamine, as well as sulfur trioxide and the chlorides of other elements. 

Fuming sulfuric acid and sulfur trioxide are more reactive than sulfuric acid, frequently leading to polysulfonation. Formation of addition compounds of sulfur trioxide with suitable Lewis bases (nitromethane, pyridine, 1,4-dioxane), however, moderates its reactivity allowing clean monosulfonation. 

Pyridine /V-oxide is unreactive toward iron-catalyzed bromination at 110°C (55JA2902), but silver sulfate-catalyzed bromination in sulfuric acid at 200°C gives a 10% yield of 2- and 4-bromination in the ratio 1 2 (6ITL32). With bromine in oleum the main product is 3-bromopyridine /V-oxide (60%) together with the 2,5-dibromo (—35%), and 2,3- and 3,4-dibromo compounds (—5%) (62T227). Presumably the N-oxide function is here complexed with sulfur trioxide, which causes deactivation and 3-orientation. Bromination in acetic anhydride also gives 3-substitution (35%) an addition-elimination mechanism has been proposed (65JPJ62). 

Barium 4Z- and 4 -2-Sulfo-2,3,4,6-tetrahydroxyhexa-2,4-dienoate-8-lac-tone. The procedure of Cousins et al. (36) was used to prepare L-ascorbyl 6-valerate (mp 89-92°C). The valerate ester (15 g, 57.6 mmol) was dissolved in pyridine (250 mL) at 25°C and pyridine-sulfur trioxide complex (25 g, 2.5 equivalents) was added. After stirring 18 h at room temperature, water (500 mL) was added, and the mixture was placed in a water bath at 70°C. The pH of the mixture was maintained at 9-9.5 by periodic addition of saturated barium hydroxide solution. The elimination reaction at 65°C was complete in 4-6 h, as evidenced by the constancy of the reaction pH. The reaction mixture was adjusted to pH 10 by addition of saturated barium hydroxide, and at that point the total volume of the mixture was 1.5 L. Pyridine was removed by evaporation under vacuum to 300 mL, and the evaporation step repeated twice after addition of water (250 mL). The mixture was adjusted to pH 2 by addition of sulfuric acid (1 M), and barium sulfate was removed by filtration. The filtrate was extracted with ethyl ether (3 X 500 mL) to remove valeric acid, and the aqueous layer (300 mL) was adjusted to pH 7 by addition of barium hydroxide. After evaporation to 50 mL, barium sulfate was removed, and an equal volume of acetonitrile was added to the filtrate. The desired compound crystallized in the cold to give 12.0 g (55% ) of crude material with mp 215-225°C. The crystals were dissolved in water (30 mL) and were decolorized with charcoal after addition of acetonitrile, analytically pure crystals were obtained [yield, 5 g with mp 220-225°C (decomposed)]. 

As pointed out, hydrogen chloride in itself is not an acid, but only becomes one when it forms a compound of a higher order, or in other words, an addition compound. Hydrogen chloride is able to form compounds of higher orders with the compounds of the first order, ammonia, platinic chloride, sulfur trioxide, auric chloride, water, etc., the compounds of the second order which are formed being. 5... 

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