Synthetic organic resins

Synthetic organic resins used in TLC are polyamide 6 (Nylon 6) and polyamide 11, which consist of polymeric caprolactam and undecanamide, respectively. Therefore, polyamide 6 is more hydrophilic than polyamide 11, owing to the shorter hydrophobic chain of its monomeric unit. 

Fig. 2. Structural distribution of exchangeable ions in a synthetic organic resin after W. C. Bauman [p. 50 of reference (Nl)).

These materials can be broadly categorized into those which are totally inorganic in nature and those that are synthetic organic resins. 

The synthetic organic resins consist of cross-linked polymer matrix which is functionalized to provide their ion exchange capacity. The matrix usually must undergo additional reactions to provide the strong acid cation, strong base anion, weak acid cation or weak base anion functionality. 

Another organic sorption material for thin-layer chromatography is polyamide. In contrast to celluloses, polyamides are synthetic organic resins. Two types of polyamides are used polyamide 6 and polyamide 11. Polyamide 6 consists of a polymeric caprolactam, while polyamide 11 is a polyundecanamide. Polyamides are synthesized as coarse granulates. To get a particle size distribution suitable for thin-layer chromatography two different techniques are applied ... 

The process of ion exchange relies on the use of synthetic organic resins, which carry ionic groups capable of exchanging cations or anions with similar species in an aqueous solution. TTie resins come in the form of small beads (2 to 3 mm) made up of a polymeric skeleton into which the ionic groups are introduced by suitable... 

Cyclic Hydrocarbons. The cyclic hydrocarbon intermediates are derived principally from petroleum and natural gas, though small amounts are derived from coal. Most cycHc intermediates are used in the manufacture of more advanced synthetic organic chemicals and finished products such as dyes, medicinal chemicals, elastomers, pesticides, and plastics and resins. Table 6 details the production and sales of cycHc intermediates in 1991. Benzene (qv) is the largest volume aromatic compound used in the chemical industry. It is extracted from catalytic reformates in refineries, and is produced by the dealkylation of toluene (qv) (see also BTX Processing). 

PhenoHc-based resins have almost disappeared. A few other resin types are available commercially but have not made a significant impact. Inorganic materials retain importance in a number of areas where synthetic organic ion-exchange resins are not normally used. Only the latter are discussed here. This article places emphasis on the styrenic and acryHc resins that are made as small beads. Other forms of synthetic ion-exchange materials such as membranes, papers, fibers (qv), foams (qv), and Hquid extractants are not included (see Extraction, liquid-liquid Membrane technology Paper.). 

New areas in adsorption technology include carbonaceous and polymeric resins (3). Based on synthetic organic polymer materials, these resins may find special uses where compound selectivity is important, low effluent concentrations are required, carbon regeneration is impractical, or the waste to be treated contains high levels of inorganic dissolved soHds. 

Tertiary bismuthines appear to have a number of uses in synthetic organic chemistry (32), eg, they promote the formation of 1,1,2-trisubstituted cyclopropanes by the iateraction of electron-deficient olefins and dialkyl dibromomalonates (100). They have also been employed for the preparation of thin films (qv) of superconducting bismuth strontium calcium copper oxide (101), as cocatalysts for the polymerization of alkynes (102), as inhibitors of the flammabihty of epoxy resins (103), and for a number of other industrial purposes. 

Decreasing the viscosity of the currently applied synthetic alkyd resins reduces the amount of organic solvent that is needed in these paints for optimal performance. This could either be accomplished by decreasing the molecular weight of the applied alkyd resin, or by using polymers having a narrower... 

Very few enzyme-catalysed reactions involving the reduction of alkenes have achieved any degree of recognition in synthetic organic chemistry. Indeed the only transformation of note involves the reduction of a, (3-unsaturated aldehydes and ketones. For example, bakers yeast reduction of (Z)-2-bromo-3-phenylprop-2-enal yields (S)-2-bromo-3-phenylpropanol in practically quantitative yield (99 % ee) when a resin is employed to control substrate concen-tration[50]. Similarly (Z)-3-bromo-4-phenylbut-3-en-2-one yields 2(5), 3(,S)-3-bromo-4-phenylbutan-2-ol (80% yield, >95% ee)[51]. Carbon-carbon double bond reductases can be isolated one such enzyme from bakers yeast catalyses the reduction of enones of the type Ar—CH = C(CH3)—COCH3 to the corresponding (S)-ketones in almost quantitative yields and very high enantiomeric excesses[52]. 

The chemistry is both wide ranging and interesting. It involves carbohydrate chemistry, the chemistry of inorganic pigments, organic resins —both natural and synthetic—and many other organic and polymeric additives. The sheet formation process also involves a considerable amount of colloid and surface chemistry. Polymer chemistry and environmental and analytical chemistry also play an important part. 

However, there also some disadvantages. Specifically, the limited radiation and thermal stability set limits to the usage of synthetic organic ion-exchange resins. Regarding temperature, 150 °C is the maximum temperature that cation-exchange resins can withstand, whereas 70 °C is the limit for anion-exchange resins. Consequently, hot streams to be treated have to be cooled below these temperatures. 

Another large use of normal butenes in the petrochemical industry is in the production of 1,3-butadiene (CH2 = CH = CH = CH2). In the process, a mixture of n-butenes, air, and steam is passed over a catalyst at a temperature of 500°C to 600°C. Butadiene is used extensively to produce synthetic rubbers (see Isoprene) in polymerization reactions. The greatest use of butadiene is for styrene-butadiene rubber, which contains about a 3 1 ratio of butadiene to styrene. Butadiene is also used as a chemical intermediate to produce other synthetic organics such as chloroprene, for adhesives, resins, and a variety of polymers. 

Another use of urea is for resins, which are used in numerous applications including plastics, adhesives, moldings, laminates, plywood, particleboard, textiles, and coatings. Resins are organic liquid substances exuded from plants that harden on exposure to air. The term now includes numerous synthetically produced resins. Urea resins are thermosetting, which means they harden when heated, often with the aid of a catalyst. The polymerization of urea and formaldehyde produces urea-formaldehyde resins, which is the second most abundant use of urea. Urea is dehydrated to melamine, which, when combined with formaldehyde, produces melamine-formaldehyde resins (Figure 96.2). Melamine resins tend to be harder and more heat-resistant than urea-formaldehyde resins. Melamine received widespread attention as the primary pet food and animal feed contaminant causing numerous cat and dog deaths in early... 

Sodium ion exchange. Sodium ion exchange on zeolites (Section 7.3) or on synthetic organic cation-exchange resins such as Dowex-50 (a sulfonated polystyrene Fig. 14.1), in most circumstances, is superior to the above softening methods.13 The exchange process favors binding of Ca2+ or Mg2+ over Na+ in the solid resin phase ... 

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