T A P C H i H O A H O C T. 5 1 ( 1 ) 7 - 1 2 T H A N G 2 N A M 2013
NGHIEN c i r u LY THUYET SU TAO THANH CAC SAN P H A M
C2H2, H2, H V A H C C O T U P H A N LCNG CCIA B E N Z I N V d l NGUYEN TO" 0X1
N g u y e n T h j M i n h H u e ' " , P h a n T h j T h u y ^
Khoa Hda hgc va Trung tarn Khoa hgc Tinh loan. Trudng Dgi IIQC Suphgm Hd Noi
^Khoa Hda hgc. Truwig Dai hgc Vinh D e n T d a s o ^ n 13-10-2011
A b s t r a c t
The reaction mechanism of the oxyzen (O) atom and benzyne (C6H4) has been studied by the Density Functional Theory (DFT) using the B3LYP functional combined with the 6-311 ++G(d,p) and 6-311 +G(3df,2p) basis sets We have mapped out the potential energy surfaces (PES) for the Ct,lly^O system and our results show that energetically allowed paths lead to the product sets of CsHj+CO. CsHi+H;, C J l,-i 11, HCCO+C^Hj and C2II2+C4H2O. However, the formation of C5H4+CO IS the most favorable process, with no exit barrier. The predicted barrier free channel indicates this reaction to be a fast process.
Keywords: C^Hj+O reaction, benzyne, potential energy surface (PES), Density Functional Theory (DFT).
1. GIOI T H I E U
Trong cac san pham c h e xuat tir d a u m d va than da, benzen va c a c dan xuat ciia benzen la mot trong nhiJng nguyen lieu quan trgng nhat ciia nganh cdng nghiep h u u c a nhu: polyme, t a , sgi, chat d e o , d u n g mdi, c a o su, thudc nhugm, d u g c pham, thudc trir djch hai... N h u ta d a biet goc phenyl la mdt chat trung gian quan trgng trong q u a trinh dot chay benzen [1], M d t sd cong trinh da chi ra benzin (C6H4) la mot san p h a m thu^n lgi ve nhiet dgng trong qua trinh phan h u y nhiet phenyl [2-4]. Hien nay, tren the gidi d a c d nhCrng c d n g trinh khac nhau ca t h y c nghiem v a ly thuyet nghien ciru ve benzin va cac isome ciia n d [5-7]. O x i nguyen t u cd m a t rat nhieu trong cac qua trinh ddt chay.
N h u vay, benzin v a oxi nguyen lir c d m a t dong thdi trong cac q u a trinh chuyen hda c u a benzen. Vi vay viec nghien c u u phan u n g gi&a chiing cd vai trd quan trgng trong viec tim hieu c a c qua trinh chuyen hda CLia benzen. T r o n g nghien c u u t r u d c day ve he phan ling nay [8] chiing tdi d a c u n g c a p n h u n g thdng tin v^ be m^t th6 nang t a o thanh c a c san pham C O , H2O. D6 hoan thien c a c h e phan irng cung n h u be mat th§ nang cua he n a y mot each d a y du va chi tiet chung tdi ti8p t u c nghien ciru he phan irng nay, Trong ngi d u n g bai bao nay c h u n g tdi se trinh bay s y hinh thanh c a c san p h i m H2, C2H2 v a c a c gde H, H C C O m a trong bai b a o t r u d c chiing tdi c h u a d e cap.
2. P H U O N G P H A P N G H I E N C U U
Tat ca c a c tinh toan d u g c t h u c hien bang phan mem Gaussian 03 [ 9 ] . C a u true hinh hgc ciia cac chat deu d u g c tdi uu hda bang phirang phap phiem ham m a t d o theo mire B 3 L Y P / 6 - 3 ] 1++G(d,p). S u xac dinh diing mot trang thai chuyen tiep lim d u g c ngoai viec phan tich tan sd d a o d g n g cijng cd t h e d u g c kiem chirng them bang each tinh toa d d ngi phan irng (IRC). N a n g l u a n g diem d a n d u g e tinh tdt ban d mire B 3 L Y P / 6 - 3 1 1 + G ( 3 d f , 2 p ) . D y a tren c a c ket qua thu d u g c cho phep thiet lap be mat the nang day dil tir d d rut ra d u g c thir t y uu lien ciia mdi d u d n g phan irng. Hi^u irng nhiet, the dang nhiet dang a p ciia cac phan irng tao thanh san phcm ciia he d u a c tinh d dieu kien nhiet d o 2 9 8 K, ap suat 1 atm [10].
3. K E T Q U A V A T H A O L U A N
Tren be mat the nang ciia he C6H4 va O (hinh 1), he chat tham gia gia phan irng ban dau ki hieu la RA; 3 san pham t a o thanh d u g c ky hieu la P , (x = 4-^14); cd 10 cau triic c u e lieu trung gian d u g c ky hieu la ly (y = I, 3 ^ 6 , 8, 10-^13) va 11 cau true trang thai chuyen tiep d u g c ky hieu la x/y vdi x, y la c a c e y e tieu, san p h a m va phtic t u o n g irng; c d I phirc trung gian d u g c k y hieu la Co-p^ t u a n g irng v d i san pham P^. Tir ket q u a tinh n a n g l u g n g dao d g n g diem khong va n a n g l u g n g diem d a n x a c djnh d u g c c a c
TCHH,T. 51(0,2013
mire nang lugng tuang quan cua cac cau triic so vdi muc nang Iugng ciia h? chat tham gia phan irng ban dau C6H4+O (RA) dugc qui udc bang 0.
Budc dau tien trong phan irng gde O khdng di qua hang rao nang lugng ma tan cdng true tiep vao C2, C3 ciia phan tu CfiH4 hinh thanh vdng ba C-O-C, tuang irng hgp chat trung gian I| (-334,1 kJ/mol).
Tuang ty cac phan irng ciia goc oxi vdi goc phenyl [II], Dieu nay cung cd the ly giai ve rngt djnh tinh.
Nguyin Thj Minh Hu? va cpng sir goc O d dang triplet b6n cd cac AO chira electron dgc than, trong khi dd phan tur C6H4 cd chira lien kk ba C2^C} cd mgt dg electron cao. Do dd C6H4 de chuyen djch electron sang goc O. Cung ket hgp vdi viec kiem tra ve ti'nh doi xiing ciia cac MO [8].
Tir be mat the nang ta nhan thay I| cd the hinh thanh cac san pham tach goc H qua cac dudng phan irng sau:
L- - ^ / M
_Z2LL^/
- ^ / s -
->/,
^P,{CJI,(} + H) (1)
>P,{CJI,O^II) (2) , ^ / , 2 >P,{CJip-\-H) (3)
r<. -38 3
l/p, UiCa'
:
•L-^M..^^
• C0-P7
-1075 l o / s :
-90.4 :s/i3 ', ,-1108 i.'j/n
« -
-2017;
i' 1/10',
4 2 1 . 6 ; I4
,/f37.4 ','ll/lZ,-'
-105 '.
-- /i06g Pr„+C,Hj . • P r , j t l l \ V ,'•123.1 X , \ i
• "u+»i rX- / ^
,' -- -424.3.- '.-383 %
III
• 6 1 2 . 3 ' 1|
'-V^" '<}
Hinh T Be mat the nang Tir cac dudng phan liiig tren, chat trung gian I5 dugc hinh thanh tir I| thdng qua hai trang thai chuyen tiep va I]o cd nang lugng tuang quan la -383,4 (kJ/mol) kha th§p. Xu^t phat tir I5 cd thi di qua cac trang thai chuyen tiep khac nhau dk hinh thanh cac hgp chat trung gian. Trong dd I12 (-404,3 kJ/mol) cd nang lugng tuang quan th^p nhSt, cac hgp chat nay tach true tiep gde hidro tao ra cac san pham P4, P5, Ps tuang ung. San pham cd bin nhSt la Ps vdi nang lugng tuang quan la -72,8 kJ/mol. Nhu v|y dudng phan irng sd 3 dugc uu lien do thuan lgi ve mat nang lugng.
(PES) he phan irng CsHj+O
Mat khac cac san pham tach goc cung dugc tao thanh tir cac hgp chat trung gian I^ tach gde H lien ket vdi O tao thanh san pham P,o (-88,3 kJ/mol).
Nhu vay su tach goc H deu xay ra d cac hgp chSt trung gian chua nhdm OH. Do kha nang dirt iien ket O-H dl xay ra hon lien kit C-H. Pio la san ph5m co nang lugng th3p nhSt, vi v^y phan ung tach H uu lien xay ra theo dudng phan irng nay. Ben canh do goc HCCO va C4H3 cung dugc tach ra tir I3, tuang ling san phSm Ps (-47,9 kJ/mol).
Ngoai ra, san pham H2 cung dugc tao ra qua nhieu dudng phan irng khac nhau.
TCHH, T. 51(1), 2013 Nghien ciru ly thuyet sic Igo thanh.
Bang 1: Gia trj nang lugng diem don HF (hartree), nang lugng dao dgng diem khdng ZPE (J/mol), nang lugng tuang quan E (kJ/mol)
Cau true RA(C(H,+0)
Pr4+H(P,) Pri+H(P,) Pr6-fHCCO(P6)
Pr,+H,(P,) Pr.+H(P,) Pr,+H2(P,) Prio+H(P,„) Pr„+H2(P„) Pr,2+CiHi(Pi2)
Prij+H!(Pi3) Pr|4+H2(P|4)
Im III l|2 l|3 Cp4 1/10 10/5 5/11 11/12 5/13 1/P, 4/P|3 4/C«
8/Pii 8/P|4 3/P,2
SP -306,0804067 -306,0836186 -306,1035331 -306,181546 -306,085486 -306,0893468 -306,0981532 -306,1048856 -306,1055407 -306,1116275 -306,1097093 -306,1166635 -306,2302984 -306,229978 -306,2385728 -306,215676 -306,0965161 -306,1543732 -306,118994 -306,119847 -306,131 -306,112409 -306,0945204 -306,0893003 -306,0936337 -306,0928797 -306,1106906 -306,110416
ZPE 196972,8 168146,1 186120,9 187395,8 171998,2 173167,9 166814,7 172978,9 168877,9 173342,9 167088,2 169093,1 207108,8 205675,4 207962,8 203435,8 172893,5 189468,1 190761,5 189685,5 192447,7 190556,5 176538,7 179286,9 173234,1 175941,8 176325,9 181396,8
E 0,0 -37,3 -38,3 -47,3 -53,9 -72,8 -76,7 -88,2 -94,1 -105,6 -106,8 -123,1 -383,4 -383,9 -404,3 -348,7 -66,4 -201,7 -107,5 -110,8 -137,4 -90,4 -57,5 -41,0 -58,5 -53,8 -100,2 -94,4
h^^P,(C,Hfi + H,) (4) h^^Co-P, >P,(C,Hfi+H,)(5) h^ijt^PiAC,Hfi + H,) (6) h-i^PiAC,HfO + H,) (7) L^^^PAC,H,CO + HA (8)
San pham H: dugc hinh thanh qua I4 thdng qua hai dudng phan u-ng 5 va 6, Dac biet san pham P7 (-55,3 kJ/mol), tao thanh bing each tach hai nguyen tir H lien kit vdi Ct va Ce trong I4, thdng qua TS4/C0 (-58,5 kJ/mol) va phirc trung gian C0-P7 (-66,4 kJ/mol). Khi thyc hien qua trinh tach H2 dg dai lien
kit H-C| tang manh tir 1,721 A trong TS4/C0 len 2,767 A trong cau triic phirc. Mat khac khi tach H2 tir hai H lien ket vdi Co va C5 qua TS4,i3 tao ra san pham P|., (-106,8 kJ/mol) gdm H2 va CeHjO.
Qua trinh tao ra san pham H2 cd the di tu I| va Ig thdng qua cac trang thai chuyen tiep tuang ung va tao ra cac san pham P9, P| 1, va PH deu cd nang lugng thap hon nhieu so vdi he cac chat tham gia phan u"ng ban dSu RA. Ket hgp vdi cac gia trj trong bang 2 ta thSy cac gia tri hieu ung nhiet (AH), the dang nhiet dSng ap (AG) deu am nen cac qua trinh cd the xay ra, Trong dd san pham PM (-123,1 kJ/mol) cd nang lugng thap nhat tren hk mgt thi nang nay. Ngoai ra Ig (-612,3 kJ/moI) la hgp chat trung gian ben nhat ciJa he phan iimg vi vay san pham P]j de hinh thanh
TCHH, T. 51(1), 2013 han so vdi cac san pham khac.
Sy hinh thanh san pham CjHj tir I3, ed the xay ra qua trinh djch chuyen H lien ket vdi C4 ve phia C3 ddng thdi vdi qua trinh dut lien ket C3-C4 thong qua TS3/P12 (-94,4 kJ/mol) hinh thanh san pham Pi2 (-105,6 kJ/mol).
Nhu vay ket hgp vdi nghien ciru trudc [8] chirng tdi da cung cSp day dii thdng tin ve ca che phan irng cung nhu be mat the nang ciia he. Trong h? phan irng giira goc O+C6H4 cd the hinh thanh 14 san pham khac nhau, 13 hgp chat trung gian va 25 trang thai chuyen tiep. Tir be m^t the nang day dii ciia h?
ta nhan thay tat ca cac hgp chat trung gian, cac Irang thai chuyen tiep va cac san phiim deu cd
nang lugng Ihap han hg chat ban dau chirng Id cac hudng phan irng nay deu cd the xay ra. Trang
Nguyin Thf Minh Hu? vd cpng sir thai chuyen tiep cd nang lugng cao nhat la TS5/P2 (-3,8 kJ/mol), hgp chat trung gian cd nang lugng thap nhat la Ig (-612,3 kJ/mol) chirng td Ig la mgt trong nhirng tr^ng thai ben cua h^ nay.
M§t, khic cac san pham d6u cd nang lugng thap han nhieu so vdi h? chat ban dau. Trong 14 san pham cd the t^o thanh thi cac san phSm tao ra CO (cacbonoxit) deu cd nang lugng thap, P3 C0+ C5H4 (vdng) cd nang lugng tuong del la -275,2 (kJ/mol) cd gia tri thap nhat. Chirng td P3 la san pham dugc uu tien nhat ve ni^t nang lugng. Ben canh dd gia trj hi?u irng nhi^t (AH), the dSng nhi?t dang ap (AG) ciia cac san pham P|, Pd-Pi2, P\4 6eu am vi vay cac san pham iiiiy dugc uu tien ve m^t nhi^t dgng han so vdi P2, ^i, 1*13 chi cd mgt gia tri am. Nhu vay, co Ihl thay hau het cac dudng phan iing deu cd the xay ra.
Bdng 2 Gia trj hieu ling nhigt (AH) va thi dang nhiet dang ap (AG) Phan ling
0 + C „ H 4 ->
->
—>
->
-+
-+
-i
^
-+
—>
-+
CsHi-O-H-l CsHj-O+H C j H i - m C C O CsHj + H;
C 6 H 3 - 0 + H CiHj-i-H;
C 6 H 3 - 0 + H CsHi-i-H, C4H2(ha)-fC2H2 Q H 2 + H 2 C(H2-1-H2
Ky hieu san pham P4 P5 P . P7 Ps P, P|0 Pll P|2 P|3 PlJ
AH, kJ/mol -25,9 -22,8 -12,1 -19,6 - 2 1 , 7 -19,1 -21,6 -86,0 -10,4 -19,1 -15,4
AG, kJ/mol -34,8 -30,4
•83,6 -66,6 -29,8 -64,2 -29,8 -56,9 -77,0 28,1 -64,3 Cac thdng sd nhiet dgng nhu hieu irng nhiet
(AH) va the dang nhiet dang ap (AG) ciia mgt phan irng cung cd the duac xac dinh bang ly thuyet [10].
Theo bang 3 thi cac san pham P4-HP14 ciia phan irng 0+C(iH4 deu cd hieu irng nhiet va the dang nhiet dang ap am, nggai trir san pham P13. Nhu vay, hudng lao ra san pham nay se khd xay ra.
4. KET LUAN
1. Ket hgp vdi cac ket qua trong ngien ciru trudc [8] la thu dugc be mat the nang day dii ciia he O+CeHj va cac ca che hinh thanh cac san phSin H2 C2H3, CO, H3O, gde H, goc HCCO ....
2. Khi goc Otan cdng vao phan tir CsHj hinh thanh tryc tiep chat trung gian I| chira vdng ba canh
C-O-C khdng qua mgt hang rao nang lugng, tuong ty vdi phan irng cua gde C(,Hs-^02 da dugc nghien cuu [10].
3. Thdng qua be mat the nang day dii ciia he budc dau cho thay cac hgp chat trung gian, trang thai chuyen tiep va san pham d§u cd nang lugng thap han so vdi chat ban dau. Cac san pham hau het deu cd gia trj hieu irng nhiet (AH), the dSng nhiet dang ap (AG) am. Vi vay cac san phSm deu cd the hinh thanh, hudng phan ung t^o san pham C5H4 (vdng) va CO la hudng uu tien vl mat nang lugng.
Ldi cam an: Trdn trong cam mi Nafosted Viet Nam^
lai tra cho cong trinh nay thong qua de tai. ma so 104.03.2010.29.
TCHH, T. 51(1), 2013 Nghien cuu ly thuyet sir tao thdnh TSi/io
TS,,,,
Hinh 3: Hinh hpc cac tr^ng thai chuyin tiep, circ tieu trung gian (Do dai lien ket (A), goc lien ket f))
II
T C H H , T. 51(1), 2 0 1 3 T A I L I E U T H A M K H A O
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Lien he: N g u y e n T h i M i n h H u e Bd mdn Hda ly, K h o a Hda hgc, T r u d n g Dai hgc S u pham Ha Ndi Sd 136 Xuan Thiiy, Cau Giay, H a N g i E-mail: H u e . N g u y e n @ h n u e . e d u . v n .
