Nghiên cứu lí thuyết phản ứng của gốc propargyl (C3H3) và nước bằng phương pháp phiếm hàm mật độ

TAP CHI HOA HOC

DOI: 10.15625/0866-7144.2015-0078

T. 53(1)6-12 THANG 2 NAM 2015

NGHIEN CLPU LJ THUYET PHAN U'NG CUA G6 C PROPARGYL (C3H3) VA

NU'O'C BAN G PHU'aNG PHAP PHI^M HAM MAT DO

Tran Hiru HuTig'*, Pham Van Tien^Nguyen Thi Minh Huf'

'BQ mon Hod, Truang Dgi hqc Kiin triic Hd Noi

^Vien Ky thudl Hoa hoc, Tnrang Dgi hoc Bach khoa Hd Noi

^Khoa Hod hgc va Trung tdm Khoa hoc Tinh todn- Tnrdng DHSP Ha Ngi

Din Tda soan 22-5-2014; Chip nhin dang 13-2-2015

Abstract

The reaction mechanism of the propargyl radical (C3H3') and water (H2O) has been studied by the Density

Functional Theory (DFT) using the B3LYP fimctional and the aug-cc-pvtz basis set. The potential energy surface (PES)

for the C3H3 and H2O system was also established. Calculated results indicate that products of this reaction can be

(HOCH2CCH -H H), (CH^CCHj + OH), (CH2=CH-CH0 -*- H), (C2H4 -i- HCO), (C2H5 + CO), (CH2-C-CH2 + OH),

(C2H2 + CHjOH), (CHCHCHO + H2), (CHCHCHOH + H), (CH3 + CH2CO), (CHj^C-CHOH+H). However, the

formation of (CH2=C=CH2 + OH) is the most favorable.

Keywords. Reaction mechanism, propargyl radical, water, density fiinctional theory.

1. MO DAU

Trong he ddt chay hidrocacbon cung nhu nhien

lieu hda thach da hinh thanh cac hidrocacbon thorn

da vdng va gdc propargyl (C3H3) dugc cho la cd vai

trd quan trgng trong qua trinh hinh thanh cac

hidrocacbon thorn dd [1]. Hien nay cd mgt so cdng

trinh nghien curu thuc nghiem phan iing cua C3H3

vdi C3H3, O, NO2 [1-3]. va mdt sd cdng trinh nghien

ciiu ly thuyet co che phan iing cua gdc C3H3 [4, 5]

da dugc cdng bd. Cac ket qua deu chi ra ring gdc

C3H3 cd kha nang phan img cao va da dang. Nude la

hgp chit phd blln trong khi quyln va dupe hinh

thanh trong hiu hit ciia qua trinh ddt chay cac chit

hiru CO. Da cd nhieu nghien ciru cua nude vdi cac

goc tu do nhu: CCb, CH, C2H, CCI, CjF... [6-9]

nhung chua thiy cdng trinh nao cdng bd kit qua

nghien cuii If thuylt ciing nhu thuc nghiem phan

ling cua gdc C3H3 vdi H2O. Do vay vi?c nghien ciiu

ly thuylt CO chi phan ihig ciia C3H3 vdi H2O khdng

nhihig md r^ng hieu biit vl kha nang phan iing goc

(C3H3) ma cdn giai thich dugc s\r hinh thanh cac san

phim trong qua trinh chuyln hda tir C3H3.

2. PHUONG PHAP TINH

ciu true hinh hpc cua cac chit phan iing, cac

chit trung gian, trang thai chuyln tilp va cac san

pham diu dugc tdi uu theo phuang phap phiim ham

mat dg d mirc B3LYP/aug-cc-pvtz [10]. Trong dd

trang thai chuyen tiep dung dugc xac thuc bing viec

phin tieh tan sd dao ddng, tpa dp thuc (IRC) cua

phan ling, tan sd dao ddng va tga do thy:c ciia phan

ling se cho biit su thay ddi vl ciu true hinh hpc tiit

chat dau den chit cudi, tren co sd dd rut ra ket lu?n

trang thai chuyln tilp can tim cd chinh xac hay

khdng. Ngoai ra dp nhiem spin (s^) cimg dugc xem

xet. Nang lugng dilm don cung dugc tinh vdi bp

ham CO sd B3LYP/aug-cc-pvtz, day la bp ham co

tinh chinh xac dd tin cay cao. Tu cac kit qua nhan

dupe se xac djnh ciu tnic, nang lugng, tinh cac

thdng sd nhiet dpng d 298 K, ap suit I atm [11] va

thiet lap be mat the nang cua he. Cac tinh toan dugc

thuc hien tren phin mlm Gaussian 03 [12].

3. KET QUA VA THA O LUAN

3.1. DUT doan kha nang phan irng

De so bd du doan hudng phan iing uu tien trong

he C3H3 va H2O (can cii vao gia tri nang lugng

tuong ddi AE), chiing tdi da tinh va phan tich nang

Iugng cua cac obitan phan tu (MO), mgt sd kit qua

dugc dua ra d bang 1.

Ap dung li thuylt obitan phan tii bien FMC

(frontier molecular orbital) va kit qua tinh d bang

cho thay, gia trj AE nhd nhat img vdi mirc nang

lugng LUMOa cua H2O va HOMOa cua gdc C3H3

[14]. Do dd, khi phan iing xay ra thi miit dp electron