Sulfur trioxide pyridine complex

Sulfur trioxide pyridine complex is the compound with the formula C₅H₅NSO₃. It is a colourless solid that dissolves in polar organic solvents. It is the adduct formed from the Lewis base pyridine and the Lewis acid sulfur trioxide. The compound is mainly used as a source of sulfur trioxide, for example in the synthesis of sulfate esters from alcohols:^[1]

ROH + C₅H₅NSO₃ → [C₅H₅NH]⁺[ROSO₃]⁻

Sulfur trioxide pyridine complex

Identifiers
CAS Number	26412-87-3 Y
3D model (JSmol)	Interactive image
ChemSpider	147422 Y
ECHA InfoCard	100.043.334
PubChem CID	168533
CompTox Dashboard (EPA)	DTXSID50885349
InChI InChI=1S/C5H5N.O3S/c1-2-4-6-5-3-1;1-4(2)3/h1-5H; Y Key: UDYFLDICVHJSOY-UHFFFAOYSA-N Y InChI=1/C5H5N.O3S/c1-2-4-6-5-3-1;1-4(2)3/h1-5H; Key: UDYFLDICVHJSOY-UHFFFAOYAG
SMILES O=S(=O)=O.n1ccccc1
Properties
Chemical formula	C5H5NSO3
Molar mass	159.16 g/mol
Appearance	white solid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) Infobox references

It also is useful for sulfamations:

R₂NH + C₅H₅NSO₃ → C₅H₅N + R₂NSO₃H

The compound is used for sulfonylation reactions, especially in the sulfonylation of furans.^[2] It is also an activating electrophile in a Parikh-Doering oxidation.^[3]