Pyridine-SO3 complex

A disaccharide is added to a pyridine SO3 complex solution, which is prepared by reacting 5 to 6 times the molar amount of liquid SO3 as much as that of disaccharide with 5 to 10 times the amount of pyridine as that of the disaccharide at 0°C to 5°C, for sulfation at 50°C to 70°C for 3 to 7 hours. After the completion of sulfation, the greater part of pyridine Is removed by decantation. The obtained solution exhibits an acidity that is so strong that it is improper to apply the reaction with aluminum ion and, therefore, sodium hydroxide is added for neutralization. After the remaining pyridine is removed by concentration, 100 unit volumes of water per unit volume of the residue is added thereto. To the solution is then added aluminum ion solution mainly containing aluminum dihydroxychloride, the pH of which is 1.0 to 1.2, in such an amount that the aluminum ion Is present in an amount of 4 to 6 molar parts of the amount of disaccharide to provide a pH of 4 to 4.5. The mixture is reacted under stirring at room temperature and the formed disaccharide poly sulfate-aluminum compound is allowed to precipitate. After filtration, the residue is washed with water and dried. 

Pyrrole reacts with A-chlorosuccinimide to give 2-chloropyrrole. However, with SO2CI2 or aq. NaOCl, one obtains 2,3,4,5-tetrachloropyrrole. A-Bromosuccinimide forms 2-bromopyrrole, and bromine forms 2,3,4,5-tetrabromopyrrole. Pyrroles are nitrated with HNO3 in acetic anhydride at -10°C to yield 2-nitropyrroles. Concentrated sulfuric acid causes polymerization of pyrroles, but at 100°C, pyridine-SO3 complex provides the corresponding pyrrole-2-sulfonic acids [35 a]. 

Sulfonation of pyrrole with pyridine-SO3-complex leads mainly to pyrrole-3-sulfonic acid. This is in contrast to earher reports, which claim the formation of the 2-sulfonic acid the same is due to N-methylpyrrole [102]. 

Microwave heating was also used to prepare inorganic derivatives of starch. Potato starch was sulfated with pyridine. SO3 complex in a microwave-assisted soUd state process, and a maximum DS of 1.05 was obtained (Staroszczyk et al., 2007a). Although conventional oven... 

By use of adduct deactivated SO3 more readily controlled reaction of SO3 can be performed. Sulfur trloxlde forms adducts with Lewis bases such as DMF, pyridine, trlalkylamlnes and dioxane. These adducts are commercially available or conveniently synthesized (79). The reactivity of the SO3 complex Increases with decreasing base strength. Thus, the derivatized ascorbic acid 2-sulfate described above could also be synthesized from... 

The DMF-SO3 complex has been shown to have greater ability for sulfation than the commonly used pyridine-SOs complex [211]. 

The reaction of olefins with SO3 is exothermic, and often only secondary reaction products are isolated. Attempts to control the cycloaddition reaction involve the use of dioxane- or pyridine-S03 complexes. However, to generate the monomer from the cyclic trimer, freshly distilled SO3 at low temperatures is more effective. Also, oleum seem to have an advantage over the pure sulfur trioxide in [2+2] cycloaddition reactions. ... 

Another important example of a redox titration for inorganic analytes, which is important in industrial labs, is the determination of water in nonaqueous solvents. The titrant for this analysis is known as the Karl Fischer reagent and consists of a mixture of iodine, sulfur dioxide, pyridine, and methanol. The concentration of pyridine is sufficiently large so that b and SO2 are complexed with the pyridine (py) as py b and py SO2. When added to a sample containing water, b is reduced to U, and SO2 is oxidized to SO3. 

In sulfamation, also termed IV-sulfonation, compounds of the general structure I NSC H are formed as well as their corresponding salts, acid halides, and esters. The reagents are sulfamic acid (amido—sulfuric acid), SO3—pyridine complex, S03—tertiary amine complexes, aliphatic amine—S03 adducts, and chlorine isocyanate—S03 complexes (3). 

Reduction of Met(O) residues may also be performed prior to the acid deprotection step by use of the SO3/DMF complex in pyridine in the presence of a thiol.The reduction proceeds with the initial formation of a sulfonium ion and subsequent nucleophilic attack of the thiol (Scheme 2). The reaction is performed at room temperature and is generally completed within one hour. 

Sulfur trioxide (SO3) is an industrially important compound key to the production of sulfuric acid. It tends to polymeric forms both in the solid and liquid states. As a gas, the molecules have a planar triangular structure in which the sulfur atom has a high affinity for electrons. This explains its action as a strong Lewis acid towards bases that it does not oxidize. It can thus crystallize complexes with pyridine or trimethy-lamine. It has a very strong affinity for water and hence rapidly associates with water in the environment. 

Maximum reaction rate is attainable with the strongest reagent, namely, SO3, and its use is increasing. As a consequence of the increased production of sulfonates, there is a compelling interest in more efficient and more rapid and especially continuous processes. The use of SO is subject to limitations, however, as noted in Table 7-3. It reacts virtually instantaneously with many compounds, for example, hydrocarbons or alcohols, even at low temperatures. In other cases, however, it first forms a complex with the compound being sulfonated, and rearrangement to the desired sulfonic acid requires time and heat, as with benzoic acid, benzenesulfonic acid, and pyridine. 

Lewis acids such as BF3, SO3, AICI3, etc., readily react with pyridine to form Lewis salts (Scheme 6.5), and many coordination complexes have been prepared with metallic ions. 

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