This thesis presents the results of phenyl pyrolysis experiments conducted in a high pressure single pulse shock tube using nitrosobenzene as the phenyl radical source. The experiments were conducted at pressures of 25 bar and 50 bar, over a temperature range of 750 to 1400 K. The stable product species formed were detected and analyzed using a gas chromatograph and mass spectrometer apparatus. A rate for the nitrosobenzene dissociation reaction yielding phenyl radical and nitric oxide has been obtained from the experimental data. The ability of three different chemical kinetic models to simulate this data was tested using the CHEMKIN software. Sensitivity analysis was performed on these models and the result has been presented. The objective of this work is to explore the significant role phenyl radical plays in the combustion of aromatic hydrocarbons.