This document summarizes research on the ozonolysis of 2,3-dimethyl-2-butene using a flow reactor with cavity ring-down spectroscopy (CRDS) for analysis. The goal is to detect carbonyl oxide (CI) intermediates produced during ozonolysis. Adding sulfur dioxide (SO2) as a scavenger reveals additional peaks in difference spectra that are attributed to a CI-SO2 adduct. Increasing initial SO2 concentrations results in larger changes to difference spectra, supporting assignment of the new peaks. Future work includes addressing SO2 flow fluctuations and searching for spectra of the SO2 adduct directly.

1. Ozonolysis of
2,3-dimethyl-2-butene
Group Meeting
Winter 2015

2. Outline
Motivation
Experimental Setup
Results
Future Work

3. Motivation
One of the most important processes of Volatile Organic
Carbons (VOCs) in the atmosphere is oxidation.
One of the main oxidation reactions of VOCs is
ozonolysis.

4. Carbonyl oxides, also know as Criegee Intermediates
(CIs), are produced by ozonolysis through the breaking
of a primary ozonide (POZ).

5. CIs are formed with a energy distribution that results in
only a fraction undergoing reactions or rearrangements.
Resulting in short lifetimes.

6. Rearrangement, decomposition, or reaction of carbonyl
oxides in the atmosphere produces secondary organic
aerosols, OH radicals, peroxy radicals, etc.

7. Experimental Setup
Ozonolysis of alkenes is done using a flow reactor:
Reaction products are measured using cavity ring-down
spectroscopy (CRDS).
Spectra of the main products is subtracted in order to look for CI
features.

8. CRDS:
Suitable for atmospheric measurements due to:
Long sample path (high sensitivity).
Real time measurements.
Portability (in situ measurements).

9. Spectra analysis:
   
   






n
i
ii N
L
dc
L
dc

 0
11

10. 318 320 322 324 326
0.15
0.20
0.25
0.30
0.35
0.40
0.45


Exp
Synth
   
      )(
11
0


fNNN
L
dc
acacformformozoz 







11. + O3
+

12. Simulation of the reaction in a flow reactor.
The system of ODEs is solved using
an approximation method by the
kinetic simulator KINTECUS.

13. # k Reaction Comments
1.13E-15 C6H12+O3==>CH3COCH3+0.85CH3COOCH3+0.15CH3CO2CH3 1
2.50E+05 CH3COOCH3==>CH3+CH3+CO2 18
7.80E+05 CH3COOCH3==>CH3COCH2+OH 19
5.00E+04 CH3COOCH3==>CH3OCOCH3 20
1.70E+05 CH3COOCH3==>CH3O+CH3+CO 21
4.40E+05 CH3COOCH3==>CH3O+CH3CO 22
1.10E+05 CH3COOCH3==>CH3OCO+CH3 23
9.13E-13 CH3+O3==>CH2O+H+O2 2
4.50E-11 CH3+CH3O==>CH2O+CH4 3
1.49E-15 CH3O+O2==>CH2O+HO2 4
2.49E-11 CH3O+CH3O==>CH2O+CH3OH 5
4.98E-11 CH3O+OH==>CH2O+H2O 6
1.19E-10 OH+C6H12==>C6H12OH 7
1.39E-11 OH+CH2O==>H2O+HCO 8
1.49E-13 OH+CO==>CO2+H 9
3.82E-13 H+C6H12==>C6H13 10
2.66E-11 H+O3==>OH+O2 11
5.65E-12 HO2+HO2==>H2O2+O2 12
7.97E-11 HO2+OH==>H2O+O2 13
1.66E-12 HO2+CH3O==>CH3OH+O2 14
4.90E-20 CH3CO2CH3 + C6H12 ==> CH3COCH3+C6H12O 15
1.00E-12 CH3CO2CH3 + O3 ==> CH3COCH3+O2+O2 16
3.00E-11 CH3CO2CH3+CH3==>CH3COCH3+CH3O 17
4.00E-11 CH3CO2CH3 + CH3CO2CH3 ==> CH3COCH3+CH3COCH3+O2 C1
5.00E-12 CH3CO2CH3+HO2==>CH3COOCH3HO2 C2 - DUMMY

14.    
        

fNNN
L
dc
acacformformozoz 






0
11
Results

15. Difference spectrum
           
n
i
iiacRacCOOCHCOOCH NNNf  ,2323

16. Scavenging with HFA
             
n
i
iiHFARHFAacRacCOOCHCOOCH NNNNf  ,,2323

17. ∆[Difference spectra]

18. Scavenging with SO2
   
          

fNNNN
L
dc
acacSOSOformformozoz 





 22
0
11

19. Difference spectrum
     
n
i
iiacRac NNf  ,

20. Why?
# k Reaction Comments
1.13E-15 C6H12 + O3  CH3COCH3 + 0.85CH3COOCH3 + 0.15CH3CO2CH3 1
4.90E-20 CH3CO2CH3 + C6H12  CH3COCH3 + C6H12O 15
1.00E-12 CH3CO2CH3 + O3  CH3COCH3 + O2 + O2 16
3.00E-11 CH3CO2CH3 + CH3  CH3COCH3 + CH3O 17
4.00E-11 CH3CO2CH3 + CH3CO2CH3  CH3COCH3 + CH3COCH3 +O2 C1
5.00E-12 CH3CO2CH3 + HO2  Products C2
5.00E-12 CH3CO2CH3 + OH  Products C3
4.00E-14 CH3CO2CH3 + CO  CH3COCH3 + CO2 C4
6.00E-13 CH3CO2CH3 + CH3COCH3  CH3CO2CH3CH3COCH3 C5
3.50E-11 CH3CO2CH3 + SO2  CH3CO2CH3SO2 C6

21. C6H12 O3 CH3COCH3 CH3COOCH3 CH3CO2CH3 CH2O CH3CO2CH3CH3COCH3 SO2 CH3CO2CH3SO2
no SO2 2.71E+16 8.26E+13 5.87E+14 5.96E+07 3.45E+10 2.37E+14 6.35E+13 0 0
with SO2 2.71E+16 8.26E+13 6.10E+14 5.87E+07 9.58E+08 2.41E+14 1.83E+12 5.45E+14 8.90E+13
∆1/t change
1.21E-03
sCI-SO2 adduct contributes to the signal
Initial SO2 Final SO2 Simulation SOZ
2.90E+14 2.20E+14
4.20E+14 3.50E+14
5.50E+14 3.60E+14
6.60E+14 5.00E+14
7.90E+14 6.00E+14

22. Measuring SO2

23. Scavenging with different amounts of SO2

24. Difference Spectra

25. Change in difference spectra with different initial SO2

26. Future Work
Fix flow fluctuations of SO2
Try more initial SO2 concentrations
Search for SOZ spectra
Try ethene ozonolysis using SO2 as scavenger