Hydrogen reagent

A basic process flow diagram for the SNCR TDN process is shown in Figure 17.3. Anhydrous or aqueous ammonia is vaporized and mixed with a carrier gas of air or steam for transport to injection/distribution modules. The injection distribution modules distribute ammonia and/or hydrogen reagent and carrier gas to proprietary spray nozzles or injection lances. Reagent flow control can be controlled and trimmed by outlet NOx signals or ammonia slip measurements. 

The carbocation subsequently is quenched by a hydride donor or hydrogen to yield the saturated product. A sufficient stability of the intermediate carbocation and proper choice of the hydrogenating reagent pair are prerequisites to a successful ionic hydrogenation. 

Fig. 6.6 COSY spectrum of C3v C6QH18 produced in high yield using diethylenetriamine as both solvent and hydrogenation reagent (Briggs et al. 2005). The weak cross-peak between protons A and B corresponds to a SJHH of 3 Hz. Asterisks indicate residual solvent (quartet) and a minor impurity (singlet)...

Scheme 16. Domino hydroformylation-Wittig olefination-hydrogenation. Reagents and conditions 1.5 Equiv.

Scheme 17. Domino hydroformylation-Knoevenagel condensation-hydrogenation. Reagents and conditions 1.1 Equiv. CH2EWG2, 1.2 equiv. piperidinium acetate, 0.7 mol% [Rh(CO)2acac], 2.8 mol%...

Figure 20. Stereoselective synthesis of naproxen and ibuprofen by hydrogenation. Reagents a, C02, electrolysis b, H30 + c, H +, -H20 d, H2, Ru(acac)2/BINAP.

Cleavage protocols for the release of aliphatic molecules are very common [273,274]. There exist, for example, procedures for photolabile linkers, linkers that are thermally cleavable and linkers that release target structures upon addition of hydrogenating reagents. Linkers for these methodologies are of a different nature as a result of their need to fulfil special demands. 

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