Double.... H-atom Transfer, and of Alkoxy Radicals from Isoprene Prompt Chemistry Intramolecular......
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Transcript of Double.... H-atom Transfer, and of Alkoxy Radicals from Isoprene Prompt Chemistry Intramolecular......
![Page 1: Double.... H-atom Transfer, and of Alkoxy Radicals from Isoprene Prompt Chemistry Intramolecular... Hydrogen Bonding, T. S. Dibble Chemistry Department,](https://reader036.fdocuments.us/reader036/viewer/2022062308/56649ef95503460f94c0add4/html5/thumbnails/1.jpg)
Double . . . .H-atom Transfer, and of Alkoxy Radicals
from Isoprene
Prompt Chemistry
Intramolecular. . . Hydrogen Bonding,
T. S. DibbleChemistry Department, SUNY-ESF
![Page 2: Double.... H-atom Transfer, and of Alkoxy Radicals from Isoprene Prompt Chemistry Intramolecular... Hydrogen Bonding, T. S. Dibble Chemistry Department,](https://reader036.fdocuments.us/reader036/viewer/2022062308/56649ef95503460f94c0add4/html5/thumbnails/2.jpg)
OH O2
OH O2, NO O3
HOOH
Global Organic compound emissionsCH4 530 Tg/yearIsoprene 500 Tg/yearOther 650 Tg/year
Importance of Isoprene in the Atmosphere
(Oxidizes SO2 to sulfuric acid)
(Health Hazard)
(“Vacuum cleaner of the atmosphere”)
![Page 3: Double.... H-atom Transfer, and of Alkoxy Radicals from Isoprene Prompt Chemistry Intramolecular... Hydrogen Bonding, T. S. Dibble Chemistry Department,](https://reader036.fdocuments.us/reader036/viewer/2022062308/56649ef95503460f94c0add4/html5/thumbnails/3.jpg)
OH..
O2
OH
OO.OH.
OH
.OH
OH
OH
O.OHOH
.OH
OH
.O2
NO
.
OHOH
OO iso
*
(E)-1 (Z)-1
(Z)-V.
OHOH
ONO
Chemistry Forming Second Generation Radicals(Paulson and Seinfeld, 1992)
Note many branching pathways are not shown above!!
VIIO VIIOO VII
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Second Generation Alkoxy Radicals Expected to Decompose(Paulson and Seinfeld, 1992)
(Dibble, 2002)
OH
O
+ CH2OHVIIO
OHOH
O.
.
But double hydrogen bonding of (Z) isomerinhibits decomposition, unlike single H-bond (Dibble 1999) in first generation alkoxy radicals.
![Page 5: Double.... H-atom Transfer, and of Alkoxy Radicals from Isoprene Prompt Chemistry Intramolecular... Hydrogen Bonding, T. S. Dibble Chemistry Department,](https://reader036.fdocuments.us/reader036/viewer/2022062308/56649ef95503460f94c0add4/html5/thumbnails/5.jpg)
0 Kcal/mole
(4)
-19 Kcal/mole
Unexpected Chemistry
Double H-atom Transfer
Unexpected ChemistryUnexpected ChemistryUnexpected Chemistry
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OH
OH
O.
OH
O
OH
.
OH
O
OH
.
NomenclatureWe identify oxygen atoms by the number (in isoprene) of the
carbon atom to which it is bound. The O atom acting as ahydrogen bond donor is to the left of an arrow, the acceptor
is to the right.
(Z) VIIO(14, 4 3)
1
3
4
(Z) VII’OH (34, 4 1)
1
3
4
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Multiple Hydrogen bonding Arrangements(zero, one, or two hydrogen bonds)
(Z)-VII’OH (41)
(Z)-VII’OH (43,31)
(Z)-VII’OH (43) (Z)-VII’OH (none)
(Z)-VII’OH (31) (Z) VII’OH (34, 4 1)
1
3
4
![Page 8: Double.... H-atom Transfer, and of Alkoxy Radicals from Isoprene Prompt Chemistry Intramolecular... Hydrogen Bonding, T. S. Dibble Chemistry Department,](https://reader036.fdocuments.us/reader036/viewer/2022062308/56649ef95503460f94c0add4/html5/thumbnails/8.jpg)
5
-10
-15
10
0
-5
-20
(Z)-VII’OH (none) (Z)-VII’OH
(3 4)(Z)-VII’OH (4 3)
(Z)-VII’OH (4 3,3 1)(Z)-VII’OH (3 4,4 1)
(Z)-VII’OH (4 1) (Z)-VII’OH (3 1)
(Z)-VIIO (1 4,4 3)
(Z)-VIIO (1 3)’
Kca
l/m
ol
Relative Energies, H-atom transfer, and H-bonding
![Page 9: Double.... H-atom Transfer, and of Alkoxy Radicals from Isoprene Prompt Chemistry Intramolecular... Hydrogen Bonding, T. S. Dibble Chemistry Department,](https://reader036.fdocuments.us/reader036/viewer/2022062308/56649ef95503460f94c0add4/html5/thumbnails/9.jpg)
5
-10
-15
10
0
-5
-20
OHO
+CH2OH
OH
O
+ CH2OH
(Z)-VII’OH (none) (Z)-VII’OH
(3 4)(Z)-VII’OH (4 3)
(Z)-VII’OH (4 3,3 1)(Z)-VII’OH (3 4,4 1)
(Z)-VII’OH (4 1) (Z)-VII’OH (3 1)
(Z)-VIIO (1 4,4 3)
(Z)-VIIO (1 3)’
Kca
l/m
ol
Part of the Potential Energy ProfileThermal Decomposition of VII’OH is slow...
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0 5 10 15 20 250.00
0.25
0.50
0.75
1.00
F
ract
ion
Pro
mpt
Dec
ompo
tion
Initial Energy (Kcal/mol)
10 Torr
760 Torr
298 K
… But Prompt Decomposition of VII’OH is Extensive!
OOH
+ CH2OH
OHO
OH.
OHO
OH. M
*
* OHO
OH.
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Consequences for Atmospheric Chemistry?
OH
O
+VIIO
OHOH
O.
CH2OH.
CH2OH.
OHO
OH.VII'OH
O
OH
+
OHO
OH.
O2,NO
OHO
OHO.
O
O.
OH
OH
+
MGLY
O2
OH
O
+ HO2VII'OH
*
Decomposition of VIIO same as Prompt Decomposition of VII’OH!
But quenched VII’OH results in different chemistry
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Theodore S. [email protected]
Chemistry DepartmentState University of New York - Environmental Science and Forestry
Syracuse, NY 13210http://www.esf.edu/chemistry/faculty/dibble.htm
AcknowledgementsNSF-Atmospheric SciencesNCSA - University of KentuckyWei Deng, Katherine Kitney, Lei Zhang
J. Phys. Chem A, (2004) 108, 2199 and 2208.