Synthesis: Carbon With One Heteroatom Attached by a Single Bond
Ring-opening of cyclic sulfamates by acylamine or mercaptan results in the formation of sulfamic acid salts (equation (39)) <2003OL811>. This method has been used in the synthesis of thiomorpholine and piperazine derivatives. Antimicrobial agent <2000T5571> and oligosaccharide derivative <2003OBC2253> are recently described bioactive compounds containing sulhamic acid.
SO3 is produced primarily by the combustion of carbon-based fuels, which are key intermediates in the atmosphere and react with water, 17 ammonia, 18 alcohols, 19 and organic acids 20 to contribute to the formation of sulfuric acid, sulfamic acid, methyl hydrogen sulfate and sulfate-carboxylic anhydride in the atmosphere. Of these reactions, the so3-h2o reaction is considered the most important due to the following factors :(1) the concentration of H2O in the atmosphere is high, up to 1017 molecules /cm3, 21 and (2) the product of this reaction is H2SO4, which is a key substance for nucleation and new particle formation, 22-24 accounts for nearly half of the aerosol nuclei. 4 FIG. 1A depicts the reaction of SO3 with monomer H2O. The reaction involves a single proton transfer process in which the protons of H2O are transferred to the O atom of SO3. At the same time, the hydroxyl of H2O reacts with the S atom of SO3 to form H2SO4. At the CCSD(T)/CBS//MP2/ A (T + D) level, the calculated free energy barrier relative to the prereactive complex is 25.1 kcal/mol, and MP2/a(T + D) thermal correction 25. The high energy barrier indicates that SO3-(H2O)1 reaction hardly occurs at ambient atmospheric temperatures. Thus, the abundance of H2SO4 in the atmosphere cannot be explained by this approach, and its source has long puzzled researchers.
Many researchers have studied the kinetics of vapor reaction of SO3 with water vapor. 26 Each of these studies measured SO3 concentrations at a range of H2O vapor pressures, yielding data consistent with the reaction of gaseous SO3 and H2O as a bimolecular process.
Theoretical calculations by Hoffmann and Schleyer25 and Morokuma and Muguruma17 show that experimental observations 29,30 cannot be explained by the reaction of SO3 with a single water molecule. Kolb et al. 31 showed that SO3 consumption may involve a reaction with dimer water. Morokuma and Muguruma17 show that the reaction takes place through a six-center transition state with very small activation energy.