Typical Commercial Preparations

The resols are usually prepared in typical reaction kettles, using 1.5-2.0 moles of formaldehyde per mole of the phenol. The reactions are rapid and the condensations to resoles might be accomplished in 1 h. Formaldehyde is often added in the form of formalin. The quantity of the added caustic or ammonia might comprise one percent of the phenol in the reaction mixture. These reactions are carried out at water reflux for a specified time. The pH is then lowered to neutral and the water is distilled off, usually at reduced pressure. The progress of the condensation is followed by measuring the melting point, the gel time (time required for the material to become thermoset at a specified temperature), solubility, or free phenol content. 

Cresols are also often used in preparatiOTis of phenolic resins. These may be individual isomers or mixtures of all three. Cresilic acids, mixtures of all three isomers, rich in w-cresol and low in o-cresol are preferred. 

Xylenols (aU six isomers) are now also in common use to form alkali-resistant grades of phenolic resins. High 3,5-xylenol mixtures are preferred. Also, resorcinol, which forms very reactive phenolic resins, is used in preparations of cold-setting adhesives. Higher homologues of phenol, like Bisphenol A, are used to prepare special phenol-formaldehyde condensates. 

7 Step-Growth Polymerization and Step-Growth Polymers 

---

Polymorphisms in the sequences of human albumin are quite rare, but are relatively common in cattle, horses, and sheep (Tucker, 1968). To date, the positions of 43 single-site point mutations in HSA have been determined, largely due to the efforts of F. W. Putnam, and these data are presented in Table 111. The majority of the variants have been identified by anomalous electrophoretic migration (Tarnoky, 1980) or, in one case, by the unusually high affinity for thyroxin (Borst et ai, 1983). Therefore, typical commercial preparations of HSA produced from outdated, pooled blood can be considered essentially homogeneous in amino acid sequence. 

Describe typical commercial preparations of resols and novolacs. 

Although many types of catalysts have been investigated for the hydrogenation of carbon monoxide and carbon dioxide to methane, catalysts of high nickel content are most commonly used for gas purification. Typical commercial preparations contain 20 to 35% nickel and are available in the form of tablets, extruded pellets, rings, and small spheres of various sizes. The catalyst does not require regeneration, and has a typical service life on the order of ten years when operated with a poison-free feed gas. The properties of a typical methanation catalyst are given in Table 13-19. 

The most connnon commercially prepared amplifier systems are pumped by frequency-doubled Nd-YAG or Nd-YLF lasers at a 1-5 kHz repetition rate a continuously pumped amplifier that operates typically in the 250 kHz regime has been described and implemented connnercially [40]. The average power of all of the connnonly used types of Ti-sapphire amplifier systems approaches 1 W, so the energy per pulse required for an experiment effectively detennines the repetition rate. 

Hydroiodic acid, the colorless solution formed when hydrogen iodide gas dissolves in water, is prepared by reaction of iodine with hydrogen sulfide or hydrazine or by an electrolytic method. Typically commercial hydroiodic acid contains 40—55% HI. Hydroiodic acid is used in the preparation of iodides and many organic iodo compounds. 

Other. Insoluble alkaline-earth metal and heavy metal stannates are prepared by the metathetic reaction of a soluble salt of the metal with a soluble alkah—metal stannate. They are used as additives to ceramic dielectric bodies (32). The use of bismuth stannate [12777-45-6] Bi2(Sn02)3 5H20, with barium titanate produces a ceramic capacitor body of uniform dielectric constant over a substantial temperature range (33). Ceramic and dielectric properties of individual stannates are given in Reference 34. Other typical commercially available stannates are barium stannate [12009-18-6] BaSnO calcium stannate [12013 6-6] CaSnO magnesium stannate [12032-29-0], MgSnO and strontium stannate [12143-34-9], SrSnO. ... 

Addition Chlorination. Chlorination of olefins such as ethylene, by the addition of chlorine, is a commercially important process and can be carried out either as a catalytic vapor- or Hquid-phase process (16). The reaction is influenced by light, the walls of the reactor vessel, and inhibitors such as oxygen, and proceeds by a radical-chain mechanism. Ionic addition mechanisms can be maximized and accelerated by the use of a Lewis acid such as ferric chloride, aluminum chloride, antimony pentachloride, or cupric chloride. A typical commercial process for the preparation of 1,2-dichloroethane is the chlorination of ethylene at 40—50°C in the presence of ferric chloride (17). The introduction of 5% air to the chlorine feed prevents unwanted substitution chlorination of the 1,2-dichloroethane to generate by-product l,l,2-trichloroethane. The addition of chlorine to tetrachloroethylene using photochemical conditions has been investigated (18). This chlorination, which is strongly inhibited by oxygen, probably proceeds by a radical-chain mechanism as shown in equations 9—13. 

Native, multi-subunit KLH also should not be frozen. Freeze-thaw effects cause extensive denaturation and result in considerable amounts of insoluble material. Commercial preparations of native KLH are typically freeze-dried solids that no longer fully dissolve in aqueous buffers and do not display the protein s typical blue color due to loss of chelated copper. The partial denatured state of these products often makes conjugation reactions difficult. 

Endrin aldehyde and endrin ketone were never commercial products, but occurred as impurities of endrin or as degradation products (EPA 1985e IARC 1974 SRI 1987). While commercial preparations of solid endrin were typically 95-98% pure, the following chemicals (in addition to endrin aldehyde and endrin ketone) have been found as trace impurities aldrin, dieldrin, isodrin, heptachloronorbomadiene, and heptachloronorborene (HSDB 1995). The active ingredient would often be mixed with one or more organic solvents for application in a liquid form. Carriers included xylene, hexane, and cyclohexane (HSDB 1995 Zabik et al. 1971). 

A simple and rapid RP-HPLC method was developed for the determination of retinoid in galenicals. Commercial preparations were diluted, filered and used for separation. Measurements were carried out in an ODS column (150 X 4.6 mm i.d. particle size 3 /xm). Solvents A and B were methanol-10 mM ammonium acetate (75 25, v/v) and methanol-THF (84 16, v/v), respectively. The flow rate was 0.8ml/min. Gradient conditions were 0-25 min, 0 per cent B 35 min, 100 per cent B, isocratic for 10 min. Typical chromatograms are shown in Fig. 2.37. The repeatability of peak area ranged between 0.48 -3.2 per cent for UV-DAD and 0.57 - 3.1 per cent for fluorescence detection. The reproducibility varied between 0.26 - 4.6 per cent. It was found that the method is precise, selective, sensitive and linear, therefore, it can be employed for the routine quality control of this class of drags [85],... 

Recognizing the need for a more economically and environmentally friendly citric acid recovery process, an adsorptive separation process to recover citric acid from fermentation broth was developed by UOP [9-14] using resin adsorbents. No waste gypsum is generated with the adsorption technique. The citric acid product recovered from the Sorbex pilot plant either met or exceeded all specifications, including that for readily carbonizable substances. An analysis of the citric acid product generated from a commercially prepared fermentation broth is shown in Table 6.2, along with typical production specifications. The example sited here is not related to zeolite separation. It is intent to demonstrate the impact of adsorption to other separation processes. 

MSW-fed digesters are operating under less than optimal enzyme titers. Table IV shows the activity optima for selected cellulase related enzymes found in actual laboratory digesters 51) and the optima for a typical commercially available cellulase preparation. 

Olefin metathesis chemistry has had a profound impact in several areas of chemical research, including organome-tallics, polymer chemistry, and small molecule synthesis,many of which have industrial applications. For example, CM is currently utilized in the commercial preparation of several agrochemicals, polymer and fuel additives, and pharmacophores. Unlike RCM reactions, which are typically conducted under dilute... 

A concept has been presented for preparing a large macromonomer - the molecular weight can be 10,000 or 20-30,000 grams/ mole - with a single unsaturated group at the end of the polymer chain. How can it be proved that a molecule this big, if indeed it has functionality, will react and how will it react with typical commercially available low molecular weight monomeric species ... 

Compositions and functions of typical commercial products in the 2-alkyl-l-(2-hydroxyethyl)-2-imidazolines series are given in Table 29. 2-Alkyl-l-(2-hydroxyethyl)-2-imidazolines are used in hydrocarbon and aqueous systems as antistatic agents, corrosion inhibitors, detergents, emulsifiers, softeners, and viscosity builders. They are prepared by heating the salt of a carboxylic acid with (2-hydroxyethyl)ethylenediamine at 150—160°C to form a substituted amide 1 mol water is eliminated to form the substituted imidazoline with further heating at 180—200°C. Substituted imidazolines yield three series of cationic surfactants by ethoxylation to form more hydrophilic products quatemization with benzyl chloride, dimethyl sulfate, and other alkyl halides and oxidation with hydrogen peroxide to amine oxides. 

---