1. Possible Reaction Pathways and Species Identified
via Mass Spectrometry
Results
Investigation of Low Temperature Oxidation Reactions of
2-Phenylethanol Using Photoionization Mass Spectrometry
Anthony Medrano,1 Magaly Wooten,1 Joseph Czekner,1 David L. Osborn,2 Craig A. Taatjes,2 Giovanni Meloni1,*
1) Department of Chemistry, University of San Francisco, San Francisco, CA 94117; 2) Combustion Research Facility, Sandia National Laboratories, Livermore, CA 94551
Abstract
In search of economical, alternative biofuels, current research investigates the combustion
properties of 2-phenylethanol (2PE). Oxidation reactions of 2-phenylethanol are initiated using
248 nm photolysis of Cl2 in a quartz reaction chamber at temperatures of 298 and 550 K and a
pressure of 4 Torr. Products are identified using the multiplex photoionization mass
spectrometer coupled to the synchrotron radiation from the Advanced Light Source (ALS) in
Berkeley, CA. The reaction is compared at the two temperatures and preliminary results are
presented.
Introduction
• Concerns in global energy and environment lead to interest in finding alternative fuel produced
from renewable resources1-4
• Compared with ethanol, 2-phenylethanol offers advantages as a gasoline substitute because of its
higher energy density and lower hygroscopicity2
• 2-Phenylethanol is soluble in water and therefore may be washed out of the atmosphere by rain5
• 2-Phenylethanol is readily biodegradable6, has a low toxicity level,7 and is commonly used in
fragrances7
Conclusions
• The aromatic ring remains intact.
• All chemistry occurs on the side chain.
• Phenylacetaldehyde and 2-phenylethenol undergo decomposition, which explains the occurrence
of products with lower mass-to-charge ratios.
• For reactions with oxygen at 550 K compared to those at 298 K, there is a decrease in products
with lower a m/z and an increase in products with a higher m/z.
• For reactions without oxygen at 550 K compared to those at 298 K, products with a lower m/z
show no formation or similar concentration and for products with a higher m/z, there is a
significant increase in concentration at 550K.
• Branching fractions will be determined after more products have been identified.
References
1. Conner, M.; Liao, J. Appl. Envir. Microbiol. 2008, 74, 18, 5769–5775.
2. Conner, M.; Cann, A.; Liao, J. Appl. Microbiol. Biot. 2010, 86, 1155-1164.
3. Atsumi, S; Hanai, T; Liao, J. Nature. 2008, 451, 86-89.
4. Lee, S; Chou, H; Ham, T; Lee, T; Keasling J. Curr Opin Biotech. 2010, 19, 556-563
5. Daubert TE, Danner RP; Data Compilation Tables of Properties of Pure Compounds NY, NY: Amer Inst for Phys Prop Data (1989) -vp
6. Chemicals Inspection and Testing Institute; Biodegradation and bioaccumulation data of existing chemicals based on the CSCL Japan. Japan Chemical Industry
Ecology-Toxicology and Information Center. p. 5-21, ISBN 4-89074-101-1 (1992)]
7. Etschmann, M. M. W.; Bluemke, W.; Sell, D.; Shrader, J. Biotechnological production of 2-phenylethanol, Appl. Microbiol. Biotechnol. , 2002, 59, 1-8.
8. Klasinc, L.; Kovac, B.; Gusten, H., Photoelctron spectra of acenes. Electronic structure and substituent effects, Pure & Appl. Chem., 1983, 55, 289-298.
9. Dallinga, J.W.; Nibbering, N.M.M.; Louter, G.J., Formation and structure of [C8H8O]+ ions, generated from gas phase ions of phenylcyclopropylcarbinol and 1-phenyl-1-
(hydroxymethyl)cyclopropane, Org. Mass Spectrom., 1981, 16, 4.
10. Gaussian 09, Revision A.1, Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson,
G. A.; Nakatsuji, H.; Caricato, M.; Li, X.; Hratchian, H. P.; Izmaylov, A. F.; Bloino, J.; Zheng, G.; Sonnenberg, J. L.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.;
Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Montgomery, Jr., J. A.; Peralta, J. E.; Ogliaro, F.; Bearpark, M.; Heyd, J. J.; Brothers, E.;
Kudin, K. N.; Staroverov, V. N.; Kobayashi, R.; Normand, J.; Raghavachari, K.; Rendell, A.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Rega, N.; Millam, J. M.;
Klene, M.; Knox, J. E.; Cross, J. B.; Bakken, V.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.;
Martin, R. L.; Morokuma, K.; Zakrzewski, V. G.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Dapprich, S.; Daniels, A. D.; Farkas, Ö.; Foresman, J. B.; Ortiz, J. V.;
Cioslowski, J.; Fox, D. J. Gaussian, Inc., Wallingford CT, 2009.
Acknowledgments
We want to thank Joseph Czeckner and Magaly Wooten, graduate students in the Chemistry Master’s program at the
University of San Francisco, for their continued assistance. We acknowledge the American Chemical Society – Petroleum
Research Fund Grant # 51170 UNI6, the University of San Francisco Faculty Development Fund for financial support,
the usage of the chemistry computer cluster at the University of San Francisco supported by professors Claire Castro
and William Karney. The Advanced Light Source is supported by the Director, Office of Science, Office of Basic Energy
Sciences, Materials Sciences Division, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231 at
Lawrence Berkeley National Laboratory.
Apparatus
Data was collected in the 298-550 K temperature range using a laser photolysis reactor coupled to
multiplexed chemical kinetics photoionization mass spectrometer, which allows simultaneous
detection of the formation and depletion of multiple species during photolytically initiated
reactions. Oxidation is initiated by chlorine radicals produced by 351 nm photolysis of chloride.
(351 nm)
Reaction species were ionized by the tunable VUV synchrotron radiation produced at the
Advanced Light Source of Lawrence Berkeley National Laboratory8.
Figure 1. Schematic view of the reactor tube and time-resolved mass spectrometer using the
tunable VUV radiation of the Advanced Light Source at Lawrence Berkeley National Laboratory.
m
Dm
~ 2000
50 kHz
repetition
rate
Excimer laser
photolysis
hn
+150 V
-150 V
-4,000 V
R
E
A
Detector Detector
hν
0 V
0 V
+150 V
-150 V
-4,000 V
DC ion
optics
Dv⊥ ~ 0
P = 1 – 10 torr
T = 300 – 1000 K
push
pull
Ion
Formation
Ion
Extraction
Figure 2. (a) Mass-to-charge ratio (m/z) vs. photon energy (eV) 2D-slice for 2PE + Cl· + O2.
(b) m/z vs time (ms) 2D-slice for 2PE + Cl· + O2. (c) Experimental PIE curve of m/z = 106 with
benzaldehyde spectrum superimposed. (d) Experimental PIE curve of m/z = 120 with
phenylacetaldehyde spectrum superimposed. (e) Kinetic time traces of 2PE (multiplied by -1), m/z =
106, and m/z = 120. The data were collected from the experiments which occurred at 298 K with
oxygen at the ALS in November of 2011.
(a)
(b)
(c) (d)
Specific Aims
• To determine the products of 2PE and chlorine with and without oxygen at 298 and at 550 K:
+ O2 + Cl· → ?
+ Cl· → ?
2-Phenylethanol
M/Z Product Structure
Observed with O2 at
Specified Temperatures
(K)
Observed without O2 at
Specified Temperatures
(K)
30 Formaldehyde 298 / 550 298 / 550
32 Methanol Not observed 298
44 Acetaldehyde 298 / 550 298
46 Ethanol 298 Not observed
78 Benzene 298 / 550 298 / 550
92 Toluene 298 / 550 298 / 550
104 Styrene 550 298 / 550
106 Benzaldehyde 298 / 550 298 / 550
120 Phenylacetaldehyde 298 / 550 298 / 550
(e)
+
O2
O2O2
2O2
O2
Decomposition
O2
O2
+
+
+
+
+
+ +
+
+
O2
Decomposition
H shift
H shift
O2
O2
+
+
Decomposition
+
x 2