Recombination processes cyclic reactions

The net reaction for this two-step mechanism is the conversion of an O3 molecule and an oxygen atom into two O2 molecules. In this mechanism, chlorine atoms catalyze ozone decomposition. They participate in the mechanism, but they do not appear in the overall stoichiometry. Although chlorine atoms are consumed in the first step, they are regenerated in the second. The cyclical nature of this process means that each chlorine atom can catalyze the destruction of many O3 molecules. It has been estimated that each chlorine atom produced by a CFC molecule in the upper stratosphere destroys about 100,000 molecules of ozone before it is removed by other reactions such as recombination CF2 Cl -b Cl CF2 CI2... 

Chemiluminescence can occur when a thermal (dark) reaction is so exothermic that its energy exceeds that of the electronically excited state of one of the product molecules. The major pathway for these reactions is the decomposition of cyclic peroxides, and this is at the basis of most bioluminescence processes. There are some other physico-chemical processes which can lead to the formation of excited states and thereby to the emission of light these are based on the bimolecular recombination of high-energy species such as free radicals and radical ions. 

The Baeyer-Villiger oxidation reaction is especially interesting for the oxidation of cyclic ketones into their corresponding lactones. One of the best-characterized BVMO is the cyclohexanone monooxygenase (CHMO) firom Acinetobacter calcoaceticus. The recombinant expression of this enzyme was successful in Saccharomyces cerevisiae (Stewart et al. 1998) and Escherichia coli (Doig et al. 2001 Mihovilovic et al. 2001). A major limitation of the industrial implementation of BVMOs is the need for efficient recycling of the cofactor NADPH (Baldwin and Woodley 2006). Therefore, the process development has been... 

The intramolecular photoinduced hydrogen abstraction of carbonyl compounds, known as the Norrish type 11 reaction, is one of the most important primary photochemical processes, usually giving the corresponding cyclic alcohols via hydrogen abstraction of the excited triplet carbonyl oxygen followed by radical recombination. 

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