Kinetics and Products of Gas-Phase Reactions of Ozone with Methyl Methacrylate, Methyl Acrylate, and Ethyl Acrylate F. Bernard, G. Eyglunent, V. Dae ¨le, and A. Mellouki* ICARE-CNRS, 1C AVenue de la Recherche Scientifique, 45071 Orle ´ans, Cedex 02, France ReceiVed: May 16, 2010; ReVised Manuscript ReceiVed: July 1, 2010 The kinetics and products of the gas-phase reactions of ozone with methyl methacrylate, methyl acrylate, and ethyl acrylate have been investigated at 760 Torr total pressure of air and 294 ( 2 K. The rate coefficients obtained (in cm 3 molecule -1 s -1 units) were as follows: k(methyl methacrylate) ) (6.7 ( 0.9) × 10 -18 , k(methyl acrylate) ) (0.95 ( 0.07) × 10 -18 , and k(ethyl acrylate) ) (1.3 ( 0.1) × 10 -18 . In addition to formaldehyde being observed as a product of the three reactions, the other major reaction products were methyl pyruvate from reaction of ozone with methyl methacrylate, methyl glyoxylate from reaction of ozone with methyl acrylate, and ethyl glyoxylate from reaction of ozone with ethyl acrylate. Possible reaction mechanisms leading to the observed products are presented and discussed. 1. Introduction Acrylate esters are volatile liquids, soluble in most organic solvents but only slightly soluble in water. Containing a double bond and a functional carboxylic group, they are highly reactive chemicals and, therefore, used mainly as intermediates in the production of other materials. For example, individual molecules of acrylic acid or esters, monomers, readily combine with themselves or other monomers to form long chains of repeating units to constitute polymers which have chemical and physical properties different from the constituent monomers. They are used in formulating paints and dispersions for paints, inks, and adhesives. They are also used in making cleaning products, antioxidant agents, surfactants for making aqueous resins, and dispersions for textiles and papers. Part of these compounds may escape into the atmosphere, where they can play a role in the atmospheric chemistry and air quality at local and regional scales. Acrylate esters contain a vinyl group, which makes them more reactive than simple esters in the gas phase toward the main atmospheric oxidants such as hydroxyl radicals (OH), nitrate radicals (NO 3 ), ozone (O 3 ), and chlorine atoms (Cl). Although numerous studies were conducted on the atmospheric degrada- tion of saturated esters 1-3 and unsaturated esters initiated by reactions with OH radicals 4-7 and Cl atoms, 8-12 fewer kinetic and mechanistic investigations have been performed on the unsaturated esters through reaction with ozone 13-17 and NO 3 radicals. 18-20 In this work, we report kinetic and mechanistic studies on ozone reactions with three acrylates: methyl methacrylate (MMA, CH 2 dC(CH 3 )C(O)OCH 3 ), methyl acrylate (MA, CH 2 dCHC(O)OCH 3 ), and ethyl acrylate (EA, CH 2 dCHC- (O)OCH 2 CH 3 ). Methyl methacrylate is the monomer to make polymethyl methacrylate acrylic plastics (PMMA), used as a shatterproof replacement for glass (this application consumes approximately 80% of the MMA). Methyl methacrylate is also used for production of the copolymer methyl methacrylate- butadiene-styrene (MBS), used as a modifier for PVC. In addition, MMA is a key ingredient in a number of products. Polymers and copolymers of methyl methacrylate are also used in undissolved surface coatings, adhesives, etc. Methyl acrylate can be used as a copolymer in the process of polymerization of polyanionic cellulose (PAC) polymers to reduce the glass- transition temperature of PAC polymers. It is also used in making vitamin B1. Ethyl acrylate is used in the production of polymers including resins, plastics, etc. In this work, the reaction rate coefficients of ozone with the three acrylates have been measured using both absolute and relative rate methods The mechanisms of these reactions have been also investigated using in situ FT-IR spectroscopy, which enabled us to determine the product formation yields. The results obtained are compared with previous studies on reactions of ozone with unsaturated esters. To date, only Grosjean and Grosjean 15,21 reported reaction product formation yields from reaction of methyl acrylate with ozone while Grosjean et al. 14 and Grosjean and Grosjean 16 reported the single kinetic studies of O 3 with methyl methacry- late and methyl acrylate, respectively. 2. Experimental Section Experiments were carried out in a 7300 L Teflon chamber in the dark at 294 ( 2 K and 760 Torr total pressure of purified air (<5% of relative humidity). Rapid mixing of reactants was ensured within 1-2 min using a set of two fans made of Teflon fitted into the chamber. After each experiment, the chamber was flushed with purified air for at least 12 h. Reactants were introduced into the chamber either via the liquid phase by streaming purified air or as a gas using a calibrated cylinder with a known volume (0.9 L) equipped with two pressure sensors (0-10 and 0-100 Torr, MKS Baratron). The temper- ature and relative humidity data were recorded by a combined * To whom correspondence should be addressed. E-mail: mellouki@ cnrs-orleans.fr. CH 2 dCH(CH 3 )C(O)OCH 3 + O 3 f products k 1 CH 2 dCHC(O)OCH 3 + O 3 f products k 2 CH 2 dCHC(O)OCH 2 CH 3 + O 3 f products k 3 J. Phys. Chem. A 2010, 114, 8376–8383 8376 10.1021/jp104451v  2010 American Chemical Society Published on Web 07/22/2010