Self-supported gold/chitosan nanocatalyst for chemoselective hydrogenation in π-conjugated C C C O system

Immobilization of pectinase on chitosan-magnetic particles: Influence of particle preparation protocol on enzyme properties for fruit juice clarification

“…The band around 2900 cm −1 is due to C–H stretching of chitosan [54]. The broad band around 1620 cm −1 has contribution of N-H 2 bending (1653 cm −1 ) and N—H deformation of amide (1558 cm −1 ) typical of chitosan [55]. The broad band with maximum at 1070 cm −1 was assigned to skeletal vibration of C–O stretching of chitosan [55].…”

Tunneling effects in confined gold nanoparticle hydrogenation catalysts

“…Interestingly, the C=O double bond was hydrogenated only when conjugated to the C=C group, probably by means of the η 4 adsorption mode. 32,33 In this scenario, an ionic hydrogenation mechanism could occur in which γ-Al2O3 cooperates with the Au surface sites, generating the heterolytic activation of H2 and the transference of one proton to the carbonyl group of 1 with formation of the Au-hydride (Scheme 3a). 34,35 Moreover, higher amounts of 2-d2 3,4 using the Au nanocatalysts confined in the IL Au/M1 and Au/M2 (87-94%) (Table 3, entries 4 and 6 and Figures S12-S15 in the ESI) indicate the following two possible hydrogenation pathways: (i) the occurrence of 1,4-addition of H2 followed by isomerization of the enol formed, or (ii) a 3,4-addition directly to the ethylenic double bond.…”

“…As in the case of Au/γ-Al2O3, these facts indicate that adsorption pathway. 32,33 Here, there is the possible presence of dissociative chemisorption of the H2 mechanism with the formation of H atoms in bridge positions, which share the low coordinated Au surface atoms without substantially affecting the Au-Au distances (Scheme 3b). 36,37 These higher KIE values and higher amounts of 2-d2 3,4 could suggest the possible involvement of a tunneling mechanism in these restricted and confined spaces.…”

Selective Catalytic Oxidation of Ethylbenzene to Acetophenone: A Review of Catalyst Systems and Reaction Mechanisms

“…The biopolymer conformation accords it structural flexibility that enables conditioning of the support in various forms such as fibers, membranes, colloids, flakes, and gel beads . The available amines and hydroxyl groups on the chitosan surface enables wide range of physical and chemical modifications that expanded its applicability in many disciplines, including the field of heterogeneous catalysis such as coupling reactions, , hydration, , hydrogenation , and oxidation. , Huang and co-workers grafted cobalt tetrakis­( p -sulfophenyl) porphyrin and manganese tetrakis (4-sulfonatophenyl) porphyrin via acid–base reaction and chemical ligation of the H 2 N–C group with a central metal ion. Although the central metal ions in the complexes bind covalently with the chitosan that result in excellent stability and recyclability, the overall catalyst activity and selectivity is considerably low.…”