TAP CHI HOA HOC
DOI. 10.15625/0866-7144.2014-0052
T. 52(6) 672-676 THANG12NAM2014
NGHIEN CLFU U THUYET SU" HINH T H A N H C3H6, XICLO.C3H6 VA C3HN TRONG PHAN U'NG GIU'A C2H VQI C3H7CN
Tran Quoc Tri'*, Nguyin Thi Minh Hue' 'Khoa Hod hoc Trucmg Bgi hoc Ddng Thap
^Khoa hda hgc vd Trung tdm tinh loan, Trudng Dgi hgc Suphgm Hd Ndi Din Tda sogn 6-01-2014; Chap nhan dang 4-12-2014 Abstract
Mechanisms of the addition, elimination, and migration of ethynyl radical (C2H) with n-propylcyanua (C3H7CN) have been studied by using Density-Functional Theory. The BHandHLYP functional was carried out with the 6- 311 -H-G(d,p) and 6-311 -H-G(3df,2p) basis sets. Geometry optimizations were performed with the former basis set while single-point calculations were done with the latter basis set in order to improve the energies. The relative energies were corrected with zero-point energy (ZPE). Based on the computational results, we constructed the potential energy surface for the reaction of C2H with C3H7CN. This potential energy surface, in combined with the thermodynamic quantities, allows predicting the high ability to form C3H6, C3HN, and cyclo-CsHg in the title reaction. Particularly, the computational results show that the formation of product PR19 (C3H7 + HCCCN) is the most favorable channel of this reaction. These results are usefiil to understand the reactivity of ethynyl radical with n-propylcyanua and also with other nitrile derivatives.
Keywords. Ethynyl radical. Density Functional Theory, n-propylxianua, potential energy surface, xiclopropane.
1. GIOI THIEU
Khi khao sat ca ehe phan ling ciia phan ling tach true tiep nguyen tii hidro va phan ifng the cua gdc etinyl (C2H) vdi cac hgp chit nitril R-CN (R: H, CH3,..) [4-7]. Ket qua nghien ciiu cho thay, ddi vdi hai nhdm phan ling nay, su tach hidro de tao nen C2H2 la im thi hon so vdi sy tao thanh H2CC. trong khi dd, cac phan ling the la nhiing phan ifng khd khan nhit nhung su khac biet giiia la khdng Idn. Ket qua nay phu hgp vdi cac ket qua nghien ciiu cua mdt sd tac gia khac [1-3]. Ddi vdi he phan ling C2H -i- R- CN, ngoai cac phan ling tach true tilp nguyen tii hidro va phan img thi, he chit nay cdn cd kha nang tham gia cac phan ling cdng, phan ling chuyen vj va phan ling phan hiiy. Do dd, viec tiep tuc khao sat mgt each day du hon ca ehe phan ifng ciia he chit nay la mgt viec lam cin thiet. Ket qua thu dugc tir nghien cuu nay cd the la ca sd de giai thich, du doan kha nang hinh thanh mdt sd san pham hda hgc trong khi quyen.
2. PHU'ONG PHAP TINH
c i u triic hinh hgc ciia cac chat phan ling, san phin trung gian, trang thai chuyen tiep va cac san
phim dIu dugc tdi uu theo phucmg phap philm ham mat do d mifc BHandHLYP/6-311-H-g(d,p). Trong dd trang thai chuyen tilp dimg dugc xac thuc bing viec phan ti'ch tin sd dao dgng, ciu tnic hinh hgc va do nhiem spin (S ). Nang lugng diem dan dugc cai thi?n d miic tinh cd bg ham ca sd cao hon so vdi ciu triic hinh hgc BHandHLYP/6-311-H-g(3df,2p) [9].
Tir cac kit qua nhSn dugc se thiet lap dugc bl mat thi nang va tinh dugc cac thdng so nhiet ddng hgc ciia he phan ifng. Cac phep tinh, cac diuat toan dugc tiln hanh tren ca sd phin mim Gaussian 03 [8].
3. KET QUA VA T H A O LUAN
3.1. Cau true hinh hoc
c i u true hinh hgc chi tilt cua san phim trung gian va mdt sd trang thai chuyin tilp dugc trinh bay chi tilt h-ong hinh 1.
3.2. Be mat the nang
Ket qua tinh hda hgc lugng tif cho cac phan irng trong he dugc trinh bay tren be mat thi nang trong hinh 2.
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TCHH, T. 52(6), 2014
Quan sat bl mgt thi nang cua he phan ung cho thay, khi gdc C2H tin cdng vao nguyen hi N va C lien ket ba, h? chat trai qua trang thai chuyen tiep TS16 va TS17 ung vdi phan ling cdng vao lien ket ha C=N trong phan tir C3H7CN dl tgo nen cac san pham trung gian ISl va 1S3. Khoang each C-N ling vdi sy hinh thanh lien kit mdi C-N la 1,874 A (dai hem so vdi 1,140 ciia lien kit ba C=N) trong TS17 va cac gia trj tuang ifng trong TS18 la C-C bang 2,317 A; C-N bing 1,152 A. Dg nhiem spin cua hai trang thai chuyen tiep nay lan lugt cd gia tri la 0,79 va 0,82. Cac thdng sd ve cau tnic va dg nhiem spin khang dinh cac TS16 va TS17 la cac trang thai chuyen tiep cua phan ling cgng vao N va C de tao nen cac san phim trung gian ISl (-140,5 kJ/mol) va IS3 (-197,4 kJ/mol). Hang rao nang lugng cua cac phan ling cgng nay cd gia tri tucmg ifng la 8,7 va 2,6 kJ/mol, cac gia trj nay hai cao hon so vdi TSl va TS2, tuong ducmg vdi TS3 va deu thap hem so vdi cac TS4 den TS15. Nhu vay, phan ling cgng la mdt
Trdn Qudc Tri vd cgng su trong nhung phan ifng rat dl xay ra ddi vdi h? chat nay.
Tir hgp chat trung gian ISl qua trang thai chuyen tilp TSl/2 de hinh thanh nen hgp chat hung gian IS2. Trgng thai chuyen tiep nay ifng vdi sy chuyen nguyen tii hidro tu nhdm CH2 sang nguyen tif C Hen kit ddi vdi nguyen tir N, khoang each ling vdi s^^
hinh thanh va cit diit lien kit C-H la 1,333 va 1,424 A. Hang rao nang lugng cua qua trinh chuyen vj nay la 32,0 kJ/mol, nang lugng ciia san pham IS2 tren bl mat thi nang la -148,6 kJ/mol va do nhiem spin ciia trgng thai chuyen tiep bang 0,78.
D I hinh thanh nen cac san pham PR16 (C3H6 + HCCNCH), PR17 (H + CH2CHCH2CHNCCH) va PR18 (H + HCCCNCHCHCHCH3) tir IS2 qua cac trang thai chuyin tilp TS2/16, TS2/17 va TS2/18, day la nhiing trgng thai chuyen tiep ciia phan ling tach. Trong do, TS2/16 img vdi su tach phan tir CjHj khoang each ifng vdi sy cat dirt lien ket C-C la 2,281 A, nang lugng tuong ddi ciia trang thai chuyen ISl
<tp 1.055
'T^'1.192 1 3 0 . 1 ^ ^ - 3 2 9 i.232yr
y ^ y 129.8 1.089 1-^81
1 . 0 8 7 * ^ I 1.520
© ^ " ^ 1-087 1,035
120.4 f \
\ 1.497
. ^ • ^ t v - ^ . ® 1-1189
^•™ ^ S . 4 8 5 ^ 1.077 1.085
I S 3
-C
191 ,057119.8 1.249
r 1.4.0
1.520 ~
1.077 «J 7 c _^^
Hinh I: Cau true chat trung gian va mgt sd trang thai chuyen tiep trong phan ling ciia C2H va C3H7CN [Dg dai lien ket (A), gdc lien ket ("), diu eham thay cho diu phay chi phin thap phan]
TCHH, T. 52(6), 2014 Hmh 1 (tiep Iheo)
Nghien ciu ti thuyet su hinh thanh...
K
^ ^ 1.874 057 1.20 1.202 122.9 ' 1.D86 1 1 2 ^ 14S41.S20 1-OS'
^^
1.266 > 1, 1.054 195
1.333
1.083 A ® ^ ^ ' ^ 0 1^82 1-™° 1 ^ 1
TS2/16
f
1 1.055 1.193 1.335 1.089 © . ^ 1.23S l.OBO ' 2.281
•- I-S'IS to 1.078
/ i
1.085TS3/19
^1.057
T 1,389 1.079 , icn ^152.2
1.085 , 1.087
1,086 ' " > i !•«<=
V 1,531® 1,086 TS3/4
f
1.05S Ji 1.1.9:2 1.430
121.6 -. 1.511
4fe T.522 1.365 j ^ 1.5G0
* » 1.091
/y?«/i 7: Cau true chat trung gian va mgt s6 trang thai chuyen tiep trong phan ijng_ cua C2H va C3H7CN [Dp dai lien ItSt (A), goe lien ket (°), diu chSm thay cho dSu phay chi phjn thjp phan]
tijp nay la -0,2 kj/mol. Trong TS2/I7 va 2/18, rao nang luong cua ba phan ung eho thay trat t\r tit khoang each ung voi su c5t dut lien kat C-H tucmg dl dSn kho khi tao thanh cac san phjm PRI6 > PRl 8 ling la 2,129 va 2,028 A. Hang rao nang luong cho .> PR17. Qua trinh tao thanh san phjm PR16, PR17 hai phan ung nay la 14,1 va 3,5 kj/mol. Gia tri hang va PR18 dugc thitc hien theo so d6 sau: RA - • TS
674
T C H H , T 52(6), 2 0 1 4 - > IS 1 ^ T S ^ IS2 ^ T S - » P R .
Trdn Qudc Tri vd cgng su
E(kJ/mo[)
TS)6 l.'TS4/(5
\ i
H C C ^ C C H 2 C H 2 C H 3
14 I TS2/17 3 5
C r t ^ C H C H i C H N C C H ;
IS4 C H 2 C H 2 C H 3 C ( N H ) C C H ;
I : IS4 .197^'' CH3CHCH2C(NH)CCH
-1405 PRI9
CHjCH^CHiCCN )CCH
! -214 i IS5 CH3CH2CHCCNH)CCH
Hinh 2: B e m a t t h e n a n g cua cac phan u n g giiJa C2H v a C3H7CN
Tir chat trung gian IS3 q u a t r a n g thai chuyen tiep TS3/19 tao nen P R I 9 (C3H7 + H C C C N ) , hang rao nang lugng t u o n g u n g la -87,2 kJ/mol. Tren be mat the nang cho thay, T S 3 / 4 la trang thai chuyen tiep ciia phan ling chuyen vi n g u y e n t u hidro tir n h d m CH2 sang nguyen t u nito d e hinh thanh nen hffp c h i t trung gian IS4 (-160,1 kJ/mol). K h o a n g each u n g vdi s u c i t dut lien ket la 1,365 A va s u hinh thanh lien k6t N - H trong T S n a y b i n g 1,268 A. H a n g rao nang l u g n g ciia phan ling la - 82,8 k J / m o l , gia tri nay thap hon nhieu so vdi h a n g rao n a n g l u g n g cua cac phan u n g the. Vi vay, p h a n u n g chuyen vi nay ve nguyen tac de xay ra hon c a c p h a n irng t h e . San p h i m PR20 ( H + H C C C ( N H ) C H 2 C H C H 2 ) d u g c hinh thanh tii IS4, n a n g l u g n g cua t r a n g thai chuyen tiep TS4/20 cd gia tri b i n g -13,5 kJ/mol. C u n g tir c h i t trung gian IS4 qua c a c trang thai chuyen tiep TS4/5 va T S 4 / 6 la n h u n g t r a n g thai chuyen t i l p u n g vdi s u chuygn vi n g u y e n t u hidro de hinh thanh nen 1S5 (-214,1 kJ/mol) va IS6 (-156,5 kJ/mol). H a n g rao
n a n g l u g n g t u o n g u n g la -41,6 va 5,5 kJ/mol. So v d i T S 3 / 4 cac T S 4 / 5 , T S 4 / 6 cd gia tri hang rao n a n g lugng cao h o n nen c a c phan u n g nay x a y ra se k h d khan h o n .
Tir 1S5 b a n g cac phan iing phan h u y se thu d u g c cac san p h i m P R 2 ] (H + H C C C ( N H ) C H C H C H 3 ) . H a n g rao n a n g l u g n g cCia phan u n g nay la -22,6 kJ/mol. San p h i m P R 2 2 (xiclo.C3H6+HCCCNH) c h u a hidro c a c b o n m a c h v d n g n o C3H6 d u g c hinh thanh n h d p h a n u n g phan hiiy IS6 khi di q u a t r a n g thai chuyen tiep T S 6 / 2 2 T r o n g t r a n g thai c h u y e n tiep nay, d d n g thdi vdi s u cat dirt lien ket C-C la s u hinh thanh lien ket C-C m d i , day la diem khac biet cua phan u n g nay vdi c a c phan u n g phan hiiy da xet.
H a n g rao n a n g l u g n g u n g vdi trang thai chuy8n ti6p nay la 66,3 kJ/mol v a la phan img rat cd k h a n a n g x a y ra. S u hinh thanh cac san p h a m P R 2 1 v a P R 2 2 d u g c m d ta t h e o s o dd sau: R A —• T S —»IS3 - ^ T S -^ IS4 ^ T S -^ IS5 -^ T S - ^ 1 S 6 -^ PR.
TCHH, T. 52(6), 2014 3.3. Thong so nhiet dong hgc
Ket qua tinh cac tham sd nhiet ddng d dieu kien tieu chuan cho bien thien thS dang nhiet-dang ap ciia cac phan ung cho thay: Trong sd cac san pham dugc hinh thanh do phan ung cdng va chuyen vj, sd cac phan irng cd bien thien the dang nhiet dang ap am bao gom PR16, PR19 va PR21 gia tri tuong ung la - 40,7; -136,9 va -11,6 kJ/mol. Cac phan img cd the dang nhiet dang ap duong hao gdm PR17, PR18, PR20, PR22 gia tri tuong img la 28,1; 5,6; 6,0 va 63,5 kJ/mol. Trong sd dd, phan ung tao thanh san pham PR17 la phan ung hoan toan khdng cd kha nang xay ra ve mat nhiet ddng hgc do bien thien entanpi cd gia tri duong cdn bien thien entropi cd gia tri am. Cac phan img cdn lai deu cd kha nang xay ra nhung d nhiet do thap do bien thien entanpi va bien thien entropi deu cd gia tn am. Trong cac tai lieu tham khao chung tdi cd dugc khdng tim thay gia tri ckc tham sd nhiet dgng hgc de so sanh va ddi chieu.
Hy vgng kit qua tinh ly thuyet se phii hgp tdt vdi cac ket qua thuc nghiem nhu cac cdng bd trudc day [4,6].
4. KET LUAN
1. Ket qua tinh b8 mat the nang va tham sd nhiet ddng hgc cho thiy, trong sd bay phan iing dugc khao sat trii phan umg tao thanh PRl 7 tit ca deu cd kha nang xay ra. Sv hinh thanh san pham CsH^, xiclo. C3H6 va HC3HN la mgt trong sd cac san pham cd kha nang dugc hinh thanh trong he phan ung nay va thu tu uu tien theo tt-attuCsHN > C3H6 > xiclo.CsHg.
2. So sanh toan bg cac phan irng trong he C2H va C3H7CN, ket qua cho thiy nhdm phan ung tach true tiep nguyen tir hidro, nhdm phan img cgng, chuyen vi va phan hiiy la nhiing nhdm thuan Igi hon, nhdm phan ung thi la khd khan nhit.
3. Cac thdng sd cau tnic, nhiet ddng hgc kem theo ciing duoc nghien ciiu chi tiet theo ly thuyet phi€m
Nghien cuu li thuyit sir hinh thanh...
ham mat do BHandHLYP vdi bg ham 6-311 ++g(d,p) va6-311-H-g(3df,2p).
TAI LIEU THAM K H A O
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8. M. J. Frisch, G. W. Trucks, H. B. Schlegel,.., J. A.
Pople; Gaussian, Inc., Pittsburgh PA.
9. Frank Jensen. Introduction to Computational Chemistry, Second edition, John Wiley & Sons, Ltd (2007).
Lien hi: Tran Quoc Tri
Bd mdn Hda li - Huu ca, Khoa Su pham Hda - Sinh - KTNN Trucmg Dai hgc Ddng Thap
Sd 783 Pham HiJu Lau, Thanh phd Cao Lanh, Tinh Ddng Thap E-mail: [email protected].
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