## 1 Introduction  
Pyrolysis is defined as the chemical reactions occurring exclusively by the input of thermal energy to a reactant during heating processes above certain temperatures [1]. There is a wide range of applications for the pyrolysis techniques, which are normally grouped in the following two approaches: (i) applied pyrolysis, which is more concerned with the yields of pyrolysates [2] and has many large-scale industrial uses, such as the synthesis of raw materials from the petroleum refining industry [1], and the pyrolysis of biomass to produce fuels and chemicals [3]; and (ii) analytical pyrolysis, which is applied to the characterization of a particular analyte, the study of thermal reactions of simple organic molecules, or as a basis for mechanistic interpretations [2, 4, 5, 6, 7]. For instance, pyrolysis-gas chromatography/massspectrometry (Py-GC/MS) is one of the most used analytical pyrolysis techniques [1; 8], and, among the wide range of molecules that have been studied with this experimental procedure, the pyrolysis of amino acids has become a topic of interest for several authors [8; 9; 10]. Since the production of fuels from the pyrolysis of biomass is considered a sustainable alternative to the conventional fuels [11], revealing the reaction mechanisms for the degradation of biomass components during this pyrolytic processes has received considerable attention in the past few decades [3; 11]. Thus, as amino acids are essential constitutive units of various organic macromolecules, such as proteins and humic substances [8], studying their pyrolysis is related to that objective.  
Concerning the pyrolysis of asparagine (Asn), several studies have been reported: [PERSON] et al. [10] identified two main fragments in the mass spectrum after the Py-GC/MS of asparagine at 600 \({}^{\circ}\)C. The first peak at \(m/z=97\) was identified as a maleimide molecule (with a relative percentage of 51.8%), and a second peak at \(m/z=99\) corresponded to a succinimide molecule (with a comparable rate of 15.8%). [PERSON] et al. [9] reported negligible yields of low-temperature tar (LTT) at 300 \({}^{\circ}\)C, but a yield of 12% of high-temperature tar (HTT) at 625 \({}^{\circ}\)C, which mainly consists on maleimide and succinimide. [PERSON] et al. [8] mixed the amino acid with silica and a methylating agent to avoid unexpected secondary reactions of pyrolysis at 400-900 \({}^{\circ}\)C. Under those experimental conditions, they obtained a more favorable production of five-membered ring pyrolysates (\(m/z=99\), succinimide; and \(m/z=97\), maleimide), but also six-membered ring products (\(m/z=126\) and \(m/z=140\)) not reported previously. The latter was assumed to consist of fragments obtained through a diketopiperazine (DKP) species that are formed only with these specific experimental conditions. Although the formation of succinimide and maleimide had been related to a dimerization reaction and its subsequent rupture [8; 9], in 2004, with new experimental evidence, [PERSON] et. al. [12] mentioned the possibility of the formation and breakdown of a polypeptide instead, justifying the assumption due to the lack of volatile products in the LTT (a less volatile species than the dimer of asparagine might have been forming at that stage).  
Although a deep understanding of the mechanisms of reactions is not essential for its application in industrial activities, the full analytical potential of this technique is realized when the different products of pyrolysis identify and associate to the original analyte by a plausible mechanism [13]. Theoretical studies, such as the present work, can complement the experimental data, and contribute with specific information focused on the mechanisms of reactions that are outlined by experimental results.