Poly selective hydrogenation

A polystyrene-poly(ethylene,l-butene)-polystyrene triblock copolymer is produced by the selective hydrogenation of the corresponding triblock copolymer in which the center block consists of random placements of 1,2-poly(1,3-butadiene) and 1,4-poly (1,3-butadiene) units. 

Partial hydrogenation of acetylenic compounds bearing a functional group such as a double bond has also been studied in relation to the preparation of important vitamins and fragrances. For example, selective hydrogenation of the triple bond of acetylenic alcohols and the double bond of olefin alcohols (linalol, isophytol) was performed with Pd colloids, as well as with bimetallic nanoparticles Pd/Au, Pd/Pt or Pd/Zn stabilized by a block copolymer (polystyrene-poly-4-vinylpyridine) (Scheme 9.8). The best activity (TOF 49.2 s 1) and selectivity (>99.5%) were obtained in toluene with Pd/Pt bimetallic catalyst due to the influence of the modifying metal [87, 88]. 

Kohler, J.U. and Bradley, J.S., A kinetic probe of the effect of a stabilizing polymer on a colloidal catalyst accelerated enantio selective hydrogenation of ethyl pyruvate catalyzed by poly(vinylpyrroli-done)-stabilized platinum colloids, Langmuir, 14, 2730,1998. 

Therefore It seems to be interesting to study such effects in the selective hydrogenation of a poly-unsaturated molecule as carvone. It was reported that the partial hydrogenation of this molecule is very sensitive to different homogeneous catalysts organometallic compounds (refs. 8-10), Zn/OH (ref. 11), NaBH (ref.12), and Zn-NiCl (ref. 13) as examples. 

Liu R, Cheng H, Wang Q et al (2008) Selective hydrogenation of unsaturated aldehydes in a poly(ethylene glycol)/compressed carbon dioxide biphasic system. Green Chem 10(10) 1082-1086... 

In addition to this we have several examples of which the polymer conformation of the polymeric complex leads the asymmetrical selectivity Hydrogenation reactions of 1-methylcinnamic acid and 1-acetamidocinnamic acid by several poly(L-amino acid)-Pd complexes are observed (142-144). Poly(L-valine) (/3-form) and poly(/3-benzyl-L-aspartate) (a-helix, sinistral) give dextrorotative products, and poly(L-leucine) and poly( 3-benzyl-L-aspartate) (a-helix, dextral) do levo-rotatory products. Also, optical active poly-/3-hydroxyl esters-Raney Ni catalyst (145) and Ion-exchange resin modified by optical active amino acid-metal complex (146,147) are observed in asymmetrically selective hydrogenations. 

Ruthenium complexes generated from the amphiphilic phosphines 24 (see also Section 7.5) were used for the selective hydrogenation of 3-methyl-2-butenal (pre-nal) to 3-methyl-2-butenol (prenol) in isopropanol/water mixtures [49]. High conversions of up to 100% and selectivities of 90-96% were achieved with ligands of the type 24 containing long poly ether chains [49]. 

The selective hydrogenation of an olefinic bond in crotonaldehyde gives n-butyraldehyde in presence of a suitable catalyst n-butyraldehyde reacts with poly (vinyl alcohol) to form poly (vinyl butyral) which is used as an interlayer for safety glass as well as for coating fabrics and for injection-moulding compositions. Butyraldehyde also finds use in making oil-soluble and alcohol-soluble resins. Butyraldehyde is a raw material for the manufacture of butyric acid and butyric anhydride... 

PREPARATIVE TECHNIQUE H-H polystyrene has never been obtained directly from styrene monomer. It is synthesized by the selective hydrogenation of l,4-poly(2,3-diphenyl-1,3-butadiene) (PDPB) using potassium/ethanol. PDPB is prepared by the free radical polymerization of 2,3-diphenyl-l,3-butadiene to give a 45% cis, 55% trans structure. H-H PS is then given in the Scune ratio of erythro and threo linkages after the chemical reduction of the internal double bond of the PDPB. ... 

N. (1981) Selective hydrogenation of cyclooctadienes catalyzed by colloidal palladium in poly(N-Vinyl-2-pyrrolidone). Makromol. Chem., Rapid Commun., 2, 99-103. 

Hameed N, Guo Q. Selective hydrogen bonding and hierarchical nanostructures in poly(hydroxyether of bisphenol A)/poly(e-caprolactone)-block-poly(2-vinyl pyridine) blends. Polymer 2008 49(4) 922-933. 

In this paper we present a comparative stu of two types of nanoparticulate catalysts based on amphiphilic block copolymers (polystyrene-b-poly(4-vinyl pyridine) (PS-b-P4VP) and poly(ethylene oxide)-b-poly(2-vinyl pyridine) (PEO-b-P2VP)) and HPS. The catalytic properties of these nanocomposites were studied in selective hydrogenation of a triple bond of dehydrolinalool (DHL) and direct selective oxidation of monosaccharides L-sorpbose and D-glucose. 

The selective hydrogenation of propyne to propene has been studied over porous ultraflltration polymeric membranes of polyacrylonitrile (PAN), polyetherimide (PEI) or polyamideimide (PAI) or over poly(acrylic acid) membranes, treated with palladium acetate. Similarly, porous PVDF membranes, also loaded with palladium particles, were used in hydrogenation flow-through experiments of methylenecyclohexane to methylcy-clohexanone. The hydrogenation of viscous liquids such as vegetable oils could also be performed in flow-through experiments over porous polymeric membranes loaded with palladium or platinum particles. " ... 

ADMET polymers are easily characterized using common analysis techniques, including nuclear magnetic resonance ( H and 13C NMR), infrared (IR) spectra, elemental analysis, gel permeation chromatography (GPC), vapor pressure osmometry (VPO), membrane osmometry (MO), thermal gravimetric analysis (TGA), and differential scanning calorimetry (DSC). The preparation of poly(l-octenylene) (10) via the metathesis of 1,9-decadiene (9) is an excellent model polymerization to study ADMET, since the monomer is readily available and the polymer is well known.21 The NMR characterization data (Fig. 8.9) for the hydrogenated versions of poly(l-octenylene) illustrate the clean and selective nature of ADMET. 

---