Theoretical analysis of atomic Si (3P) with 1-butyne (C4H6) reaction is necessary to be investigated for the interstellar chemistry of silicon. The interest of chemical bonding Silicon to Carbon grows significantly. Because of its low polarity and high bond strength, it is stable thermodynamically and kinetically. The objective of this research is to investigate the reaction between atomic Si (3P) and 1-butyne. The objective will be accomplished by,(1)determining the probable intermediates, transition states and the products,(2) proofing the transition states by calculation of Intrinsic reaction coordinates (IRCs),(3) calculating the reaction rate by Rice-Ramsperger-Kassel-Marcus (RRKM) Theory, and (4) Determining the concentration of products by branching ratio. The complex of C1 with lowest energy (-310.6 kJ/mol) and its isomer C1’ (-310.1 kJ/mol). The most probable products are obtained by dissociation of H2. The open chain products, such as 1p150+ H2( k = 2.70 x106 ) , 1p127+ H2( k = 2.70 x106 ), and 1p69+ H2 (4.82 x106) has calculated by RRKM. The concentration of those products has determined by calculating the branching ratio in various energy 0 kJ/mol, 25kJ/mol, and 30 kJ/mol. The fastest reaction in energy 30kJ/mol, the concentration of each product has determined, such as 1p150 (0.78), 1p127 (7.8 x 10-2), and 1p69 (0.15). There are nine most probable intermediates also has discussed clearly. The Intrinsic reaction coordinates (IRCs) has proved the reaction mechanism from complex to intermediates, intermediates to intermediates, complex to products, and intermediates to products. All the reactions are conducted in the singlet ground state potential energy surfaces for the stability.

ABSTRACT........................................................... i
I. INTRODUCTION.................................................... 1
I.1 Background..................................................... 1
I.2 objective ..................................................... 2
II. THEORITICAL METHODS............................................ 2
II.1 Reaction Path calculation .................................... 2
II.1.1 Rice-Ramsperger-Kassel-Marcus (RRKM) Theory................. 2
II.1.2 Complete Basis Set (CBS).................................... 3
III RESULT AND DISCUSSION.................................. 4
III.1 Reaction Paths on Singlet Potential Surface ................. 4
III.2 The most probable products .................................. 7
III.3 Products .................................................... 7
III.3The evolution of concentration with time...................... 8
IV CONCLUSION ............................................. 9
REFERENCES ....................................................... 10
APPENDICES ....................................................... 11
Table 1 .......................................................... 12
Table 2 .......................................................... 20
Table 3 .......................................................... 24
Figure 1 ......................................................... 25
Figure 2 ......................................................... 26
Figure 3 ......................................................... 27
Figure 4 ......................................................... 28
Figure 5 ......................................................... 29
Figure 6 ......................................................... 30
Figure 7 ......................................................... 31
Figure 8 ......................................................... 32
Figure 9 ......................................................... 33
Figure 10.a ...................................................... 72
Figure 10.b ...................................................... 74
Figure 11 ........................................................ 76
Figure 12 ........................................................ 77
Figure 13 ........................................................ 87
Figure 14 ........................................................ 96

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Gaussian 09, Revision E.01,
M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria,
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