Due to the increasing energy demand and the related environmental issues, combustion effi-ciency and reduction of pollutants emission have become a major concern for combustion ap-plications. In combustion, pollutant formation and fuel ignition are controlled by chemical kinetics, therefore, the design and optimization of combustion systems heavily relies on an accurate understanding of the underlying chemical processes. While combustion processes are governed by an interaction of chemical kinetics and transport processes, for gaining funda-mental understanding it is beneficial to separate both processes. To this end, shock tubes are frequently applied to generate a uniform gas phase environment for a wide range of tempera-tures and pressures that is suited for initiating reactions with subsequent time-resolved detec-tion. The combination of shock tube technique and laser absorption spectroscopy provides the platform for accurate chemical kinetic studies. Infrared laser absorption diagnostics have been widely applied in combustion research for example for in situ, fast, and sensitive measure-ments of temperature, pressure, and species concentrations. In the present study, laser absorption spectroscopy of carbon monoxide (CO) near 4.7 µm has been developed for the sensing of temperature and CO concentration behind the reflected shock wave. The sensor was further developed to enable fiber-based thermometry for more flexible applications in harsh environments. The oxidation of fuel-rich CH4/O2 mixtures, the thermal decomposition of anisole (C6H5OCH3), and the pyrolysis of acetylene (C2H2) and benzene (C6H6) were investigated by monitoring the CO concentration and temperature based on two-line absorption thermometry. The experimental data were applied for validation of reaction mechanisms covering different kinetics conditions such as single elementary reaction, partial oxidation, and soot formation. The oxidation of fuel-rich CH4/O2 mixtures was investigated to validate reaction mechanisms for reaction conditions that are important for polygeneration processes where partial oxidation allows to convert natural gas to higher-value chemicals. With the presences of dimethyl ether (DME) and n-heptane, the initial reaction temperature is significantly reduced because they promote the production of additional OH radicals. Anisole has recently been identified as fluorescence tracer for fuel/air mixing studies, but its decomposition kinetics were not yet fully understood. In the investigation of thermal decom-position of anisole at elevated temperatures, the literature model was found to strongly under-estimate the CO formation. As main reaction path for CO formation, the unimolecular decom-position of phenoxy radical (C6H5O) was investigated independently and new rate constants were determined. Soot formation from combustion is of high scientific interest. The temperature dependence as well as the influence of H2, O2, and CH4 on soot formation in the pyrolysis of C2H2 and C6H6 were investigated. The temperature dependence of the soot yield and the particle formation induction time were found to be in a good agreement with literature data. The presence of H2 led to a depletion of the particle formation in both systems whereas the opposite trend yield was observed in the presence of CH4 and O2.