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Criegee intermediates, which are the result of ozonolysis of alkenes, play a key role in many chemical and physical processes in the Earth's atmosphere. Their reactions with various atmospheric compounds are responsible for formation of hydroxyl radicals, atomic oxygen and hydrogen, sulfuric and nitric acids, and other chemically active radicals and molecules. In this work we have considered collisional-induced chemical reactions between three simple Criegee intermediate molecules: CH2OO, CH3CHOO, and (CH3)2COO with methane, which is a well-known active greenhouse gas. Methane concentration rapidly growths last decades that causes serious concern to the global scientific community. It was established that reactions between methane and Criegee Intermediates can follow through two main routes. One of them occurs over exchange of oxygen and hydrogen atoms upon collision and leads to the formation of methanol. Another one pass through the formation of an intermediate complex with a deep energy minimum, and produces OH radicals and a variety of other products, among which are acetone, acetaldehyde, formaldehyde, propaldehyde, methanol, water molecules, and others. In this work, the both kinds of the reactions have been studied, and the relative reaction rates of both pathways have been compared. [ABSTRACT FROM AUTHOR]

The increase in the concentration of methane in the atmosphere as a result of anthropogenic activity, melting of permafrost, and decomposition of gas hydrates on the seabed has attracted close attention of the scientific community in recent decades due to the potentially dangerous effect of methane on the ozone layer and the Earth's climate. According to various estimates, the greenhouse effect from methane is dozens of times stronger than the similar effect from carbon dioxide; therefore, the processes of methane transfer to the upper layers of the Earth's atmosphere, as well as its lifetime and interaction with other substances present in the stratosphere, mesosphere and ionosphere are of great scientific interest. In this study, we consider the chemical reactions occurring during collisions of methane molecules with methyl carbonyl oxide CH3CHOO in the upper atmosphere. It is shown that this process initiates the formation of the OH radical and starts a cascade of chemical reactions, the products of which are CH3, atomic hydrogen, acetone, acetaldehyde, propaldehyde, methyl alcohol, and water. These compounds are able to actively influence the composition of the atmosphere and its physicochemical properties. [ABSTRACT FROM AUTHOR]