Peroxodicarbonate as a Green Oxidizer for the Selective Degradation of Kraft Lignin into Vanillin.

Lignin, the world's largest resource of renewable aromatics, with annually roughly 50 million tons of accruing technical lignin, mainly Kraft lignin, is highly underdeveloped regarding the production of monoaromatics. We demonstrate the oxidative depolymerization of Kraft lignin at 180 °C to produce vanillin 1 in yields up to 6.2 wt % and 92 % referred to the maximum yield gained from the quantification reaction utilizing nitrobenzene. Using peroxodicarbonate (C2 O6 2- ) as "green" oxidizer for the degradation, toxic and/or harmful reagents are prevented. Also, the formed waste can serve as makeup chemical in the pulping process. Na2 C2 O6 is synthesized in an ex-cell electrolysis of aqueous Na2 CO3 at BDD anodes, achieving a yield of Na2 C2 O6 with 41 %. At least, the oxidation and degradation of Kraft lignin is analysis via UV/Vis and NMR spectroscopy.

Crystal structure of rubidium methyl-diazo-tate.

The title compound, Rb+·H3CN2O-, has been crystallized in liquid ammonia as a reaction product of the reductive ammonolysis of the natural compound streptozocin. Elemental rubidium was used as reduction agent as it is soluble in liquid ammonia, forming a blue solution. Reductive bond cleavage in biogenic materials under kinetically controlled conditions offers a new approach to gain access to sustainably produced raw materials. The anion is nearly planar [dihedral angle O-N-N-C = -0.4 (2)°]. The Rb+ cation has a coordination number of seven, and coordinates to five anions. One anion is bound via both its N atoms, one by both O and N, two anions are bound by only their O atoms, and the last is bound via the N atom adjacent to the methyl group. The diazo-tate anions are bridged by cations and do not exhibit any direct contacts with each other. The cations form corrugated layers that propagate in the (-101) plane.

Crystal structure of rubidium peroxide ammonia disolvate.

The title compound, Rb2O2·2NH3, has been obtained as a reaction product of rubidium metal dissolved in liquid ammonia and glucuronic acid. As a result of the low-temperature crystallization, a disolvate was formed. To our knowledge, only one other solvate of an alkali metal peroxide is known: Na2O2·8H2O has been reported by Grehl et al. [Acta Cryst. (1995), C51, 1038-1040]. We determined the peroxide bond length to be 1.530 (11) Å, which is in accordance with the length reported by Bremm & Jansen [Z. Anorg. Allg. Chem. (1992), 610, 64-66]. One of the ammonia solvate molecules is disordered relative to a mirror plane, with 0.5 occupancy for the corresponding nitrogen atom.

Tetra-ammineplatinum(II) dichloride ammonia tetra-solvate.

The title compound, [Pt(NH3)4]Cl2·4NH3, was crystallized in liquid ammonia from the salt PtCl2. The platinum cation is coordinated by four ammonia mol-ecules, forming a square-planar complex. The chloride anions are surrounded by nine ammonia mol-ecules, either bound within the platinum complex or solvent mol-ecules. The solvent ammonia mol-ecules are packed in such a way that an extended network of N-H⋯N and N-H⋯Cl hydrogen bonds is formed. The structure is isotypic with [Pd(NH3)4]Cl2·4NH3 [Grassl & Korber (2014). Acta Cryst. E70, i32].

Tetra-amminepalladium(II) dichloride ammonia tetra-solvate.

The title compound, [Pd(NH3)4]Cl2·4NH3, was crystallized in liquid ammonia from the salt Pd(en)Cl2 (en is ethylenediamine) and is isotypic with [Pt(NH3)4]Cl2·4NH3 [Grassl & Korber (2014 ▶). Acta Cryst. E70, i31]. The Pd(2+) cation is coordinated by four ammonia mol-ecules, exhibiting a square-planar geometry. The chloride anions are surrounded by nine ammonia mol-ecules. These are either bound in the palladium complex or solvent mol-ecules. The packing of the ammonia solvent mol-ecules enables the formation of an extended network of N-H⋯N and N-H⋯Cl inter-actions with nearly ideal hydrogen-bonding geometry.

Acetyl-ene-ammonia-18-crown-6 (1/2/1).

The title compound, C(2)H(2)·C(12)H(24)O(6)·2NH(3), was formed by co-crystallization of 18-crown-6 and acetyl-ene in liquid ammonia. The 18-crown-6 mol-ecule has threefold rotoinversion symmetry. The acteylene mol-ecule lies on the threefold axis and the whole mol-ecule is generated by an inversion center. The two ammonia mol-ecules are also located on the threefold axis and are related by inversion symmetry. In the crystal, the ammonia mol-ecules are located below and above the crown ether plane and are connected by inter-molecular N-H⋯O hydrogen bonds. The acetyl-ene mol-ecules are additionally linked by weak C-H⋯N inter-actions into chains that propagate in the direction of the crystallographic c axis. The 18-crown-6 mol-ecule [occupancy ratio 0.830 (4):0.170 (4)] is disordered and was refined using a split model.