A kinetic study of S-nitrosothiol decomposition.

Area of Science:

• Organic Chemistry
• Chemical Kinetics
• Biochemistry

Background:

• S-nitrosothiols (RSNOs) are key signaling molecules involved in various biological processes.
• Understanding the decomposition pathways of RSNOs is crucial for their application and interpretation in biological systems.

Purpose of the Study:

• To investigate the thermal decomposition mechanisms of S-nitrosothiols under anaerobic and aerobic conditions.
• To determine the kinetic parameters and activation energies for these decomposition reactions.
• To elucidate the role of nitric oxide, dioxygen, and steric effects in RSNO stability.

Main Methods:

• Kinetic measurements of S-nitrosothiol decomposition in refluxing alkane solvents at various temperatures.
• Determination of rate constants (k(t)) and activation energies (E#) using the Arrhenius equation.
• Investigation of aerobic decomposition pathways, including the role of N2O3 and antioxidants.

Main Results:

• Under anaerobic conditions, S-nitrosothiols decompose via reversible homolytic cleavage of the S-N bond, yielding nitric oxide and sulfanyl radicals.
• Tertiary S-nitrosothiols decompose faster than primary ones, with determined rate constants and activation energies.
• Aerobic decomposition proceeds via an autocatalytic chain process catalyzed by N2O3, inhibited by antioxidants and influenced by the steric bulk of the alkyl group.

Conclusions:

• The decomposition mechanism of S-nitrosothiols is highly dependent on oxygen availability.
• Steric hindrance plays a significant role in the aerobic decomposition pathway, affecting the rate of the chain reaction.
• These findings provide insights into the stability and reactivity of S-nitrosothiols in chemical and biological contexts.