4.0 Discussion:4.1 HypothesisThe hypothesis of the reaction, there was a similarity in comparing the compound in the case where the nitrogen was neutral and protonated. Table (1) illustrates that there was clearly an energy difference between two cases of this compound of 119 kJ/mole with the basis set 6-311+G(d,p) and 128 kJ/mole with the basic set 6-31 G(d) and similarly at the theoretical level (B3LYP). Therefore, the protonated nitrogen of the HALS molecule had a higher energy than the neutral nitrogen due to the potential energy of the reaction. As a result, the reported hypothesis becomes incorrect compared to the calculation result found from the Gaussian program.4.2 The aim of calculating the activation energyThe aim of this report is to calculate the activation energy of the HALS reaction molecule using GAUSSIAN 09 via WebMO. interface. It was assumed that the transition state could be obtained by the reaction as in (Scheme 3). Using the program and format (opt=(TS,calcfc,noeigen) freq=noraman), the structure was optimized and formed into a ring shape so that it could transfer the hydrogen from carbon to nitrogen in the molecule . It was also attempted to redraw some lengths/angles of the NO and OC bonds to try to bring this final H closer to the N. Therefore, the result of transferring hydrogen directly to nitrogen was slightly very low, due to the frequency output (the first is negative) given a fairly low number of -252 (cm-1). Beside that, the molecule was animated from the program and did not look like a transfer from H to N (Figure 3(A)). Indeed, the significant effect of the methyl group located around both sides of the nitrogen did not lead to...... middle of paper ...... The aim of this report was to calculate the activation energy of the HALS molecule. Based on this, the transition state was not determined correctly in the steps taken using a different format. Additionally, the energy of the protonated nitrogen in the molecule was higher than where it was neutral. There were also different values ​​in the reaction enthalpy depending on the level of theory and the changing basis set (R = H). It can be suggested that modifying the mechanism of the HALS molecule may contribute to stabilization and achieving a transition state.6.0 Acknowledgments I would like to thank my supervisor, Dr. Stephen Blanksby, for the advice and support available that he gave me in writing this report. I would also like to thank my demonstrator David Marshall for his encouragement and guidance in achieving the transition status of my report..