## 2 Results and Discussion
### The Formation of Maleimide and Succinimide Products: Mechanism of Polymerization-Rupture
#### 2.1.1 Optimization and Thermodynamic Properties  
The structures of all transition states (TS) and all stationary points (including reactive R, intermediates INT, products P, byproducts H\({}_{2}\)O and NH\({}_{3}\), and residues, Res) were optimized, and frequency calculations were performed to obtain the corresponding thermal properties of each structure. Finally, the program Goodvibes v2.0.3 [14] was used to obtain the quasi-harmonic corrected Gibbs free energies presented in Table 1 and plotted in Figure 1. An average difference of 14 kJ/mol was obtained when comparing to the non-corrected Gibbs free energies obtained by default in Gaussian16. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**T** & \(i\) & **X** & **Y** & \(\Delta G_{i}\)\(G_{Y}^{ab}-G_{X}^{ab}\) **(k) mol\({}^{-1}\))** & \multicolumn{2}{c}{**Normalized Gibbs Free Energy,**} \\ \(\mathbf{(^{c}C)}\) & & & & & \(G_{Y}\) **(k) mol\({}^{-1}\))** \\ \hline
300 & – & – & 2 R & – & 0* \\  & 1 & 2 R & TS1 & 272 & 272 \\  & \(-1\) & TS1 & INT1 & \(-153\) & 119 \\  & 2 & INT1 & TS2 & 104 & 223 \\  & \(-2\) & TS2 & INT2 + H\({}_{2}\)O & –200 & 24 \\  & 3 & INT2 & TS3 & 171 & 195 \\  & \(-3\) & TS3 & INT3 & \(-91\) & 104 \\  & 4 & INT3 & TS4 & 135 & 239 \\  & \(-4\) & TS4 & INT4 + NH\({}_{3}\) & \(-233\) & 5 \\  & 5 & INT4+R’ & TS5 & 264 & 270 \\  & \(-5\) & TS5 & INT5 & \(-170\) & 100 \\  & 6 & INT5 & TS6 & 141 & 241 \\  & \(-6\) & TS6 & INT6 + H\({}_{2}\)O’ & \(-244\) & \(-4\) \\  & 7 & INT6 & TS7 & 181 & 177 \\  & \(-7\) & TS7 & INT7 & \(-96\) & 81 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Thermodynamic parameters for the mechanism of polymerization-rupture of asparagine obtained through DFT calculations: wb97 xd/6-31 lg(d,p). A quasi-harmonic correction was additionally applied using the program Goodvibes v2.0.3. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**T** & \(i\) & **X** & **Y** & \(\Delta G_{i}\)\(G_{Y}^{ph}\)-\(G_{X}^{ph}\) **(k) mol-1)** & \multicolumn{2}{c}{**Normalized Gibbs Free Energy,**} \\ \multicolumn{1}{c}{**(\({}^{\circ}\)C)**} & \multicolumn{1}{c}{} & & & \(G_{Y}\) **(k) mol-1)** \\ \hline  & 8 & INT7 & TS8 & 135 & 216 \\  & \(-\)8 & TS8 & INT8 + NH\({}_{3}\) & \(-\)248 & \(-\)32 \\  & 9 & INT8+R\({}^{\star}\) & TS9 & 270 & 238 \\  & \(-\)9 & TS9 & INT9 & \(-\)161 & 77 \\  & 10 & INT9 & TS10 & 151 & 228 \\  & \(-\)10 & TS10 & INT10 + H\({}_{2}\)O\({}^{\prime}\) & \(-\)242 & \(-\)14 \\  & 11 & INT10 & TS11 & 143 & 129 \\  & \(-\)11 & TS11 & INT11 & \(-\)96 & 33 \\  & 12 & INT11 & TS12 & 167 & 200 \\  & \(-\)12 & TS12 & INT12 + NH\({}_{3}\)\({}^{\prime}\) & \(-\)259 & \(-\)59 \\
625 & \(-\)12 & TS12 & INT12 + NH\({}_{3}\)\({}^{\prime}\) & \(-\) & \(-\)59 * \\  & 13 & INT12 & TS13 & 336 & 276 \\  & \(-\)13 & TS13 & INT13 + Res1 & \(-\)301 & \(-\)24 \\  & 14 & INT13 & TS14 & 214 & 189 \\  & \(-\)14 & TS14 & INT14 & \(-\)325 & \(-\)135 \\  & 15 & INT14 & TS15 & 225 & 89 \\  & \(-\)15 & TS15 & INT15 + Res2 & \(-\)245 & \(-\)156 \\  & 16 & INT15 & TS16 & 146 & \(-\)10 \\  & \(-\)16 & TS16 & INT16 & \(-\)222 & \(-\)232 \\  & 17 & INT16 & TS17 & 246 & 14 \\  & \(-\)17 & TS17 & INT17 + P1 & \(-\)241 & \(-\)228 \\  & 18 & INT17 & TS18 & 145 & \(-\)83 \\  & \(-\)18 & TS18 & P2 & \(-\)224 & \(-\)307 \\
1 & 2 R & 7.02 \(\times\) & & & \\  & 10 \({}^{-4}\) & & TS1 & \(1.97\times 10^{-4}\) & \\
2 & INT1 & 5.70 \(\times\) & & & \\  & 10 \({}^{-11}\) & & TS2 & \(2.93\times 10^{-7}\) & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: _Cont._  
Figure 1: Gibbs free energy profile for the formation of maleimide (P1) and succinimide (P2) products through polymerization (at 300 \({}^{\circ}\)C) and rupture (at 625 \({}^{\circ}\)C) of the polymer during pyrolysis of asparagine. The colored bands (white and grey) separate the three additions of monomer during polymerization (with four elementary steps for each one), and the three individual ruptures during the entire rupture process of the polymer (with two elementary steps each one).