Irradiation efficiency

Theory Ti02 acts as photocatalyst due to generation of photoexcited electrons and holes which were involved in decomposition of KI. Under ultrasonic irradiation efficiency of iodine release increased almost linearly with irradiation time. 

Much higher efficiencies can be obtained if the product can be handled in bulk rather than in packages. Thus, for a bulk grain irradiator or for liquid irradiations, efficiencies in the 40-70% region can be obtained. 

Among the configurations described in that paper, the irradiation carried out on the recirculation batch seems very promising since it allows high irradiation efficiency and high membrane permeate flow rate to be obtained and also it is possible to select the membrane type depending on the photocatalytic process under study. 

Based on literature precedent, the batch reactor was irradiated for 2 h, affording only 8% of 156 however, on employing a residence time of 2 h within the micro reactor and a flow rate of 8.3 pi min-1, the authors obtained adduct 156 in 88% yield. The enhanced irradiation efficiency obtained within the flow reactor therefore allowed a dramatic increase in reaction yield, coupled with a reduction in the overall reaction time required. With this in mind, the authors investigated the generality of the technique and, as Table 6.15 illustrates, moderate to good yields were obtained for a range of substituted cyclohex-2-enones and vinylic compounds. 

Sadek and coworkers [29] reported two-component domino reactions of l,l,3-tricyano-2-aminopropionitrile 29 with nitroolefins 30 in 1,4-dioxane under microwave irradiation, efficiently providing poly-substituted diaminobenzonitriles 31 in 70-73% yields (Scheme 12.11). 

The kinetic profiles of monomer conversion were obtained by FTIR monitoring of the photosensitive formulations exposed in solvent-free condition in the form of thin liquid films cast between two NaCl plates. Under 365 nm irradiation, efficient initiator photolysis induced the decay of specific bands of each monomer (at 775 cm of butenedioates and 815 cm for vinylic double bond or 930 cm for allylic unsaturation), as shown in Fig. 1 for a blend of the vinylated ribose (VIR) and diethyl fumarate (DEF). 

Microwave-assisted tandem Witting intramolecular Diels-Alder cycloaddition of ester tethered 1,3,9-decatrienes to give 3,4,4a,7,8,8a-hexahydroisochromen-1-ones was reported with high yields (53-89%) (Wu et al., 2011). Three consecutive carbon-carbon bonds in the end product were formed rapidly during this tandem process under the microwave irradiation efficiently. 

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