Measuring Heterogeneous Reaction Rates with ATR-FTIR Spectroscopy To Evaluate Chemical Fates in an Atmospheric Environment: A Physical Chemistry and Environmental Chemistry Laboratory Experiment

Abstract

This paper reports an undergraduate laboratory experiment to measure heterogeneous liquid/gas reaction kinetics (ozone-oleic acid and ozone-phenothrin) using a flow reactor coupled to an attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectrometer. The experiment is specially designed for an upper-level undergraduate Physical Chemistry laboratory course and may be incorporated in environmental chemistry and toxicology laboratory courses as well. From the experiment, students can measure heterogeneous reaction rates, calculate reactive uptake coefficients, and evaluate the lifetime of chemicals in an atmospheric environment, which is conducive to their understanding of several important concepts related to physical chemistry and environmental chemistry.

Kinetics study of heterogeneous reactions of ozone with unsaturated fatty acid single droplets using micro-FTIR spectroscopy

“…Such a good agreement demonstrates the pseudo-rst-order condition again, and the overall kinetics parameter is suitable for the whole reaction process. 39,40 Oxygen is also a common oxidizing gas in atmosphere. Richaud et al 41 studied the oxidation kinetics of unsaturated fatty esters at temperatures ranging from 90 to 150 C by using chemiluminescence.…”

“…The efficiency of uptake of ozone by a particle can be described by the uptake coefficient, g, which is the fraction of gas-particle collisions with the surface that results in loss. 12,21,22,26,31,39 In general, g is related to two limit uptake: chemical reaction and reactant diffusion. 20,24,31,39,43 For this research, if the reactant diffusion is expected to be sufficiently fast that the rate-limiting process is the chemical reaction on the surface of single droplet.…”

“…12,21,22,26,31,39 In general, g is related to two limit uptake: chemical reaction and reactant diffusion. 20,24,31,39,43 For this research, if the reactant diffusion is expected to be sufficiently fast that the rate-limiting process is the chemical reaction on the surface of single droplet. The overall uptake coefficient, g, can be measured by the following equation: 12,21,22,26,31,39,44…”

“…27 It has long been recognized that reactant diffusion is an important step for heterogeneous reaction of gas-phase species with the liquid or solid. 31,39,43 In order to conrm the ratelimiting of O 3 /fatty acid single droplet, it is necessary to evaluate the importance of diffusion process of the single droplet for observed reaction kinetics on the reaction systems. Assuming that the fatty acid diffusion is the rate-limiting rate, the UFA diffusion constant (D) within the single droplet can be measured by the following equation: 24,31,43…”

Applications of Infrared Spectroscopy in Analysis of Organic Aerosols

“…1710 -1680 Aromatic polycarboxylic acids (C=O) [12] 1706 C=O in aldehydes and ketones [55] 1700 Carbonyl (C=O) [54] 1690 -1680 Hydrogen bonded (O-H) [8] 1680 -1665, 1660 -1630 Aliphatic hydrocarbons (C=C) [12] 1680 -1630 C=O stretch in amide [44] 1680 -1620 Unsaturated aliphatic (C=C) [48] 1650 -1620 Alkenyl double bond stretch (C=C) [10] 1650 -1590 Amino (C-NH 2 ) [48] 1644, 1281, 849 O-N groups [31] 1640 -1560 N-H bend in primary amines [44] 1640 -1550 Primary and secondary amide N-H bend [44] 1440 -1220 Alcohol and phenol (C-O-H bend) [44] 1400 -1390 C-H deformation of CH 3 groups [52] 1400 OH in carbohydrates [12] 1400 C-H in carbohydrates [12] 1350 -1340 Nitro-aromatic (NO 2 ) [42] 1350 -1000 C-N stretch in amines [44] 1340 -1250 Aromatic (C-N) [48] 1320 -1210 Aliphatic carboxylic acids (CO) [12] 1320 -1210 Amino acids/Amines (CO) [12] 1300 -1100 Ketone C (C=O)C bend [44] 1300-1000 C-O stretch in ether, ester [44] 1298 -1200 Organonitrates [46] 1286, 1249, 1222 -CH 2 wagging [50] 1280 Organonitrate [41] 1280 -1278, 1631 Organonitrate [53] 1280 -1270 Organonitrate (ONO 2 ) [42] 1280 -1210 Esters/ethers/phenols (C-O) [7] 1280 -1137 C-O stretching of esters, ethers and phenols [52] 1280 Symmetric NO 2 stretch in organonitrate [44] G. 1260 -700 Alkane skeletal vibration (C-C) [38] 1220 C-O stretching and O-H bending vibrations of COOH [5] 1210 -1160, 1100 -1030 Esters/Lactones (C-C-O) [12] 1200 -900 Carbohydrates (C-O-C) [12] 1182 C-O-C stretching …”