Carbohydrates resins

Natural rubber is harvested as latex by tapping trees in a manner similar to maple syrup. Tree latex contains about 35 wt% rubber solids, as well as small quantities of carbohydrates, resins, mineral salts and fatty acids. Ammonia should be immediately added to the latex to avoid coagulation by these other ingredients and to prevent bacterial degradation. After collection, the latex can be concentrated to 60-70% solids if the latex product is required for end-use. Otherwise, the latex is coagulated, washed, dried, and pressed into bales for use as dry rubber. 

Synthetic Resin Industry Liquid resin stabilizer, molding powder, carbohydrate resins, vulcanization of vinyl resins and copolymers, aniline shellac resins... 

It is clear from Equation (19.4) that saturated fat, not cholesterol, is the single most important factor that raises serum cholesterol. Some cases of hyperlipoproteinemia type IV (high VLDL) respond to low-carbohydrate diets, because the excess of VLDL comes from intestinal cells, where it is produced from dietary carbohydrate. Resins, such as cholestyramine and cholestipol, bind and cause the excretion of bile salts, forcing the organism to use more cholesterol. Lovastatin decreases endogenous cholesterol biosynthesis (see later), and niacin (nicotinic acid) apparently decreases the production of VLDL and, consequently, LDL. It also results in an HDL increase. Antioxidants that inhibit the conversion of LDL to oxidized LDL have also been used with some success. These are high doses of vitamin E and the drug probucol. 

Brown resinous product formed. Aliphatic aldehydes (except formaldehyde) carbohydrates and soluble starch (sucrose and ordinary starch only faintly coloured). 

Sugar analysis by hplc has advanced greatly as a result of the development of columns specifically designed for carbohydrate separation. These columns fall into several categories. (/) Aminopropyl-bonded siHca used in reverse-phase mode with acetonitrile—water as the eluent. (2) Ion-moderated cation-exchange resins using water as the eluent. Efficiency of these columns is enhanced at elevated temperature, ca 80—90°C. Calcium is the usual counterion for carbohydrate analysis, but lead, silver, hydrogen, sodium, and potassium are used to confer specific selectivities for mono-, di-, and... 

Lu and Pizzi [83] showed that lignocellulosic substrates have a distinct influence on the hardening behavior of PF-resins, whereby the activation energy of the hardening process is much lower than for the resin alone [84]. The reason is a catalytic activation of the PF-condensation by carbohydrates like crystalline and amorphous cellulose and hemicellulose. Covalent bonding between the PF-resin and the wood, especially lignin, does not play any role [84]. 

Class of colloidal substances prepared from plants. Composed of complex carbohydrates and organic acids that swell in water. Also, a number of natural resins are gums. 

Choi and Won (1999) have reported a very u.seful strategy of recovering relatively nonvolatile lactic acid (e.g. from fermentation of carbohydrates) as volatile methyl lactate using a cationic ion-exchange resin as the catalyst. In another column reactor the methyl lactate is hydrolysed, using a cationic ion-exchange resin as the catalyst, to lactic acid and methanol, and the latter is recycled. 

Photolabile linkers play an important role in solid-phase organic synthesis (SPOS) due to their stability under both acidic and basic conditions. The ONb photolabile linker was modified to improve cleavage rates and yields Fmoc-Tos-OFI was released in 87% yield after 23 h (Scheme 4) [24]. Specifically, the primary alcohol was changed to a secondary benzylic alcohol and the attachment to the resin was through an alkyl chain as opposed to an amide function. Linker 20 was used for the production of carboxylic acids or carbohydrates. A second example... 

Acetal handle 78 synthesized from Merrifield resin and 4-hydroxy-benzaldehyde was applied to the solid-phase synthesis of carbohydrates and 1-oxacephams (Scheme 41) [90]. For the latter, a 1,3-diol was initially anchored to the support to form a cyclic acetal. A ring opening reaction with DIBAL generated a resin-bound alcohol which was converted to the corresponding triflate for A-alkylation with 4-vinyl-oxyazetidin-2-one. A Lewis acid catalyzed ring closure released 1-oxa-cephams from the support. 

The chemical composition of the natural resins is very diverse, and their molecular structure may be highly complex most resins of vegetable origin, however, are chemically related to the carbohydrates. Dry vegetable resins... 

First attempts to combine pyrolysis with in situ HMDS silylation of organic art materials were reported by Chiavari et al., who were successful in obtaining trimethylsilyl derivatives of fatty acids [52], amino acids [53] and carbohydrates [54]. The same authors also applied pyrolysis-silylation to the analysis of different kinds of natural resins and for each of them diagnostic silylated compounds were identified, even if many were difficult to assign precise structures [55],... 

Heterogeneous catalysts, particularly zeolites, have been found suitable for performing transformations of biomass carbohydrates for the production of fine and specialty chemicals.123 From these catalytic routes, the hydrolysis of abundant biomass saccharides, such as cellulose or sucrose, is of particular interest. The latter disaccharide constitutes one of the main renewable raw materials employed for the production of biobased products, notably food additives and pharmaceuticals.124 Hydrolysis of sucrose leads to a 1 1 mixture of glucose and fructose, termed invert sugar and, depending on the reaction conditions, the subsequent formation of 5-hydroxymethylfurfural (HMF) as a by-product resulting from dehydration of fructose. HMF is a versatile intermediate used in industry, and can be derivatized to yield a number of polymerizable furanoid monomers. In particular, HMF has been used in the manufacture of special phenolic resins.125... 

Riley and Taylor [39] have studied the uptake of about 30 organics from seawater onto the resin at pH 2 - 9. At the 2 - 5 p,g/l level none of the carbohydrates, amino acids, proteins or phenols investigated were adsorbed in any detectable amounts. Various carboxylic acids, surfactants, insecticides, dyestuffs, and especially humic acids are adsorbed. The humic acids retained on the XAD-1 resin were fractionated by elution with water at pH 7, M aqueous ammonia, and 0.2 M potassium hydroxide. 

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