Influence of Substituent on Thermal Decomposition of 1H-1,2,4-Triazole

Size: px

Start display at page:

Download "Influence of Substituent on Thermal Decomposition of 1H-1,2,4-Triazole"

Luke Weaver
6 years ago
Views:

1 01 th International Conference on Biology, Environment and Chemistry IPCBEE vol.58 (01) (01) IACSIT Press, Singapore DOI: /IPCBEE. 01. V58. 1 Influence of Substituent on Thermal Decomposition of 1-1,,-Triazole Shizuka Tagomori, Yusuke Kuwahara, iroshi Masamoto, Mikiji Shigematsu, and Wasana Kowhakul Faculty of Engineering, Fukuoka University, Fukuoka , Japan Abstract. The thermal decomposition of 1-1,,-triazole (1tri) and its derivatives with different substituents were studied by sealed-cell differential scanning calorimetry (SC-DSC). Molecular orbital calculations (MO) were used to clarify thermal and chemical properties. The thermal decomposition temperature (T DSC ) increased as (1tri-O ) < (1tri- ) < (1tri-C ) < (1tri-COO) < (1tri). The activation energy (ΔEa) was determined using the Kissinger and Ozawa approaches. The ΔEa increased as (-O ) < (- ) < (-C ) < (-COO) and corresponded with the order of the T DSC. The MO indicated that the 1tri- and 1tri-C decompose at 1- and C-, while 1tri-COO and 1tri-O decompose at -1 and C-. Keywords: substituent, 1-1,,-triazole, thermal decomposition temperature 1. Introduction An azole is a class of five-membered nitrogen and carbon heterocyclic ring compounds. Its application in gaseous form is expected to increase as it generates minimal toxic substances and has a low environmental impact. Since more than 50 wt% of triazole consists of nitrogen and a large amount of nitrogen gas is generated during its decomposition, this compound could be used as a gas generating agent by coordination with an appropriate substituent or metal [1 ]. owever, the effect of the substituent on the characteristic energy generation has not yet been clarified. If these effects were understood, it would be possible to expand and control the application of these energy-providing materials. The effect of nitrobenzene substituents has been reported on in terms of the relationship between the thermal decomposition temperature (T DSC ) and substituent constant [5]. The T DSC is higher for electron-withdrawing substituents such as (-O ), (-COO) and (-Cl) and lower for electron-donating substituents such as (- ), (-O), (-OC ) and (-C ) as p-substituted nitrobenzene. In this study, the influence of the (-O ), (-COO), (-C ) and (- ) substituents on the thermal decomposition of 1-1,,-triazole was determined. The molecular structures of 1tri and its derivatives are shown in Fig O C Fig. 1: Molecular structures of 1tri and its derivatives. 1 5 COO Corresponding author. Tel.: ; fax: address: kowhakulw@fukuoka-u.ac.jp. 66

2 The T DSC of 1tri, -amino-1,,-triazole (1tri- ) and -nitro-1,,-triazole (1tri-O ), -methyl-1-1,,-triazole (1tri-C ) and -carboxylic acid-1,,-triazole(1tri-coo) was determined by SC-DSC. To obtain an improved understanding of the thermal behaviour of 1tri and its coordination with the substituent, molecular orbital calculations (MO) were used to clarify compounds thermal and chemical properties.. Experimental.1. Materials 1tri, 1tri- and 1tri-O (all 98.0%, Tokyo Chemical Industry ), 1tri-C (95%, Wako Pure Chemical Industries) and 1tri-COO (Wako Pure Chemical Industries) were used in the test work... Thermal Analysis To investigate the thermal decomposition, SC-DSC (60 SII nanotechnology) was carried out in a stainless steel cell at a heating rate of 10 K min -1 from 0 to 500 C under a steady state flow of air using a 1.0 mg sample... Molecular Orbital Calculations To obtain an understanding of the thermal and chemical properties of 1tri when coordinated with a substituent, MO were conducted using the Spartan 08 and Gaussian 09 programs. Geometric optimization of the structures and vibration analyses were achieved using unrestricted BLYP/6-1+G* density functional theory (DFT). The influence of substituent on (1) electrostatic charge, Mulliken charge and natural charge, () dipole moment and () bond distance were determined.. Results and Discussion.1. Thermal Decomposition The SC-DSC results are summarized in Table 1. The T DSC of 1tri, (1tri- ), (1tri-O ), (1tri-C ) and (1tri-COO) was 8, 96, 79, 10 and C, respectively. The T DSC of the substituted 1tri increased as (1tri-O ) < (1tri- ) < (1tri-C ) < (1tri-COO) < (1tri). The influence of substituent on thermal decomposition increased as (-COO) < (-C ) < (- ) < (-O )... Activation Energy from SC-DSC The activation energy (ΔEa) was determined using the Kissinger [6] and Ozawa [7] approaches with formulae given in (1) and (), respectively. β is the heating rate [K min -1 ], T p is the exothermic peak temperature [K] and R is the gas constant [J K -1 mol -1 ]. The results are shown in Table. The values calculated by the Kissinger method are similar tothose obtained using the Ozawa method. The ΔEa decreases with substitution of the 1tri with (- ), (-O ), (-C ) and (-COO). The ΔEa and T DSC show good agreement (see Fig. ). Table 1: Summary of SC-DSC results. Sample 1tri 1tri- 1tri-O 1tri-C 1tri-COO Step Thermal effect Temperature range [ C] 1 endothermic 10-1 exothermic - 1 endothermic exothermic endothermic 18- exothermic endothermic -8 exothermic endothermic exothermic 7-89 T DSC [ C] T p [ C]

3 Table : ΔEa obtained by Kissinger and Ozawa approaches. 1tri 1tri- 1tri-O 1tri-C 1tri-COO ΔEa[kJ/mol] Kissinger 76 Ozawa 7 Kissinger 16 Ozawa 16 Kissinger 16 Ozawa 19 Kissinger 1 Ozawa 17 Kissinger 161 Ozawa 16 Fig. : Relationship between ΔEa and T DSC. Kissinger, Ozawa O C COO Fig. : Electrostatic charge at carbon and nitrogen of 1tri with each substituent. RA Ea 1 ln ln T p Ea R T p (1) A Ea Ea log log RF RT ().. Molecular Orbital Calculations The thermal and chemical properties of 1tri and its derivatives were studied using MO. We simulated the influence of substituent on (1) electrostatic charge, Mulliken charge and natural charge [8], () dipole moment and () bond distance. (1) electrostatic charge, Mulliken charge and natural charge The influence of the substituent at C of 1tri with regards to electrostatic charge is shown in Fig.. The electrostatic charge of 1tri at and shows a large negative charge relative to the other atoms in 1tri. The charges of 1tri at and are ( 0.50) and ( 0.5), respectively. The 1tri shows preferable coordination at and with cationic molecules [9]. The and became more negatively charged with (- ) and (-C ) substituents. The negative values at the and of the 1tri- were ( 0.56) and ( 0.56), respectively. For 1tri-C, the and values were ( 0.56) and ( 0.56), respectively. p 68

4 Dipole moment [D] C C C 1tri-COO 1tri-C 1tri-O 1tri- 1tri 1tri-COO 1tri-C 1tri-O 1tri- 1tri tri-COO 1tri-C 1tri-O 1tri- 1tri Electrostatic charge Mulliken charge atural charge Fig. : Comparison of charge at each atom for electrostatic, Mulliken and natural charge Melting point [ ] [ C] Fig. 5: Dipole moment versus melting point. 1tri, 1tri-, 1tri-O, 1tri-C, 1tri-COO For the 1tri coordinated with (-O ), and became slightly positively charged with values of ( 0.8) and ( 0.97) for and, respectively. A comparison of the electrostatic, Mulliken and natural charge at each atom is shown in Fig.. There was no effect on electrostatic charge at and regardless of the electron-donating and electron-withdrawing substituents. For the coordinating substituents (- ), (-O ), (-C ) and (-COO), C became more positively charged than 1tri. There was no effect on electrostatic charge on 1. For the coordinating substituents (- ), (-O ), (-C ) and (-COO), became more positively charged than 1tri. The coordinating electron-donating substituents (- ) and (-C ) made C more positively charged than 1tri. There was no effect on 1,, and and C became more positively charged than 1tri for the natural charge. () dipole moment The dipole moments of 1tri and when coordinated with the substituent (- ), (-O ), (-C ) and (-COO) are.96 [D],.16 [D], 7. [D],. [D] and.59 [D], respectively. The dipole moments versus melting point have a proportional relationship as shown in Fig. 5. () bond distance The bond distance of 1tri and its derivatives are summarized in Table. The bond distance of 1tri at 1- and -1 is 1.57 [Ǻ] and 1.5 [Ǻ], respectively. For the electron-donating substituents (- ) and (-C ), 1- became longer and -1 became shorter compared with 1tri. For the electron-withdrawing substituents (-COO) and (-O ), 1- became shorter and -1 became longer than 1tri. The single bonds 1-, C- and -1 are possible to be the cleavage bond. Therefore, degradation products of the lower molecules may be produced by disconnecting two single bonds at 1- and C- or 69

5 -1 and C- [10]. We consider that there is a relationship between bond distance and decomposition and assume that long bonds tend to become disconnected. The 1- bond of 1tri is longer than -1 and it is therefore expected that 1tri decomposes at 1- and C-. For the electron-donating substituents (- ) and (-C ), decomposition is expected to occur at 1- and C-. For the electron-withdrawing substituents coordinating as (-COO) and (-O ), it is expected that decomposition will occur at -1 and C-. Table : Summary of bond distance of 1tri coordinated with substituent.. Conclusion Distance [Å] 1- =C C- = -1 1tri tri tri-O tri-C tri-COO A study of the influence of substituent on the thermal decomposition of 1tri was studied by SC-DSC. MO were used to study compound thermal and chemical properties. The T DSC of the 1tri coordinated with substituents was lower than that of the 1tri. The ΔEa decreased when the 1tri was coordinated with (- ), (-O ), (-C ) and (-COO) substituents. 1tri- and 1tri-C decompose at the 1- and C- bonds, while 1tri-COO and 1tri-O decompose at -1 and C-. 5. References [1]. Kiuchi, W. Kowhakul, M. Arai, M. Tamura, Y. Wada, M. Kumasaki. A study on thermal behavior of triazoles. 6nd Japan Explosives Society Conference. Tokyo: 00, pp.5-8. [] W. Kowhakul, M. Kumasaki, M. Arai. Study on thermal behavior of 1-1,, triazole-copper complex with substituents. Science and Technology of Energetic Materials. 005, 66 (6): 5-0. [] W. Kowhakul, R. Miyazaki, M. Kumasaki, Y. Wada, M. Arai, M, Tamura. A study on the characteristics of azole-metal complexes. Kayaku Gakkaishi. 00, 6 (6): [] T. Masoumeh, S. Mahboubeh A., G. Mitra, S. Mahmoud. 1,-Sigmatropic hydrogen shift in -amino-1-1,,-triazole during the complexation of this ligand with cobalt (II) ion, single crystal structure of a new trinuclear Co(II) 1,,-triazole complex. Journal of Chemical Crystallography. 011, 1 (): [5] M. Tamura, M. Arai, and Y. Akutsu. Energy material and safety. Asakura Publishing, 1999, pp.1. [6]. E. Kissinger. Reaction kinetics in differential thermal analysis. Analytical Chemistry. 1957, 9 (11): [7] T. Ozawa. A new method of analyzing thermogravimetric data. Bulletin of the Chemical Society of Japan. 1965, 8 (11): [8] M. Shigematsu,. Masamoto. Suitable Calculation model and basis set for molecular orbital calculation of coniferyl alcohol radicals. Fukuoka University Review of Technological Sciences. 007, 79: [9] T. Tsutsui, Y. Kuwahara, W. Kowhakul,. Masamoto, M. Shigematsu. Computational simulation on the molecular structure of 1-1,,-triazole metal complexes. The 5th International Symposium on Chemical Engineering (ISCE-01). Okinawa: 01, PE-10. [10] S. Tagomori,. Masamoto, M. Shigematsu, W. Kowhakul. The molecular orbital analysis for the thermal decomposition of the triazole derivatives. Annual Meeting of the Society of Computer Chemistry, Japan. Fukuoka: 01 Oct. 70

electronic reprint Masanari Hirahara, Shigeyuki Masaoka and Ken Sakai Crystallography Journals Online is available from journals.iucr.

electronic reprint Masanari Hirahara, Shigeyuki Masaoka and Ken Sakai Crystallography Journals Online is available from journals.iucr. ISSN 1600-5368 Inorganic compounds Metal-organic compounds Organic compounds Acta Crystallographica Section E Structure Reports Online ISSN 1600-5368 Editors: W.T. A. Harrison, J. Simpson and M. Weil Bis(2,2