Condensation glycol

In recent years, however, the ester exchange reaction has been decreasingly used, with manufacturers now usually preferring to use direct acid glycol condensation with purified terephthalic acid. 

The gas from the glycol/condensate separator can be used for fuel gas. In many small field gas packaged units this gas is routed directly to fire tubes in the reboiler, and provides the heat for reconcentrating the glycol. This se[>.irator is sometimes referred to as a gas/glycol separator or pump gas separator. 

Incorporation of a carbonyl group into the alkyl side chain also proved compatible with biologic activity. The key intermediate (76) is obtainable by Michael addition of the anion from diethyl malonate to methylvinyl ketone followed by ketalization with ethylene glycol. Condensation of 76 with hydrazobenzene leads to the pyrazolodione hydrolysis of the ketal group affords ketasone (78). ... 

Glycol Condensation products. See under Ethyleneglycol Condensation Products in this vol, p E254-L... 

The melting point falls as the binding forces holding chains together decrease, and higher elastic stretch is an indication of random molecular arrangement. The ethylene glycol condensation polymers formed with... 

Abo-Shosha, M.H., Nasar, F.A., El-Sayed, Z., Hassabo, A.G., 2009. Preparation and characterization of fatty acid/polyethylene glycol condensates and utilization as textile softeners. Res. J. Text. Appar. 13, 46-60. 

Formaldehyde, glyoxal, glutaraldehyde, polyaldehyde (polyacrolein), aldehyde-amine condensation products, aldehyde-glycol condensation products, bronopol o-Phenyl phenol, o-benzyl-jn-chlorophenol,p-chloro-m-xylenol, o, p, p -trichloro-o -hydroxydiphenyl ether (Triclosan) Nonylphenoxypoly(ethyleneoxy) ethanol-iodine complex, ethoxylated nonyl phenol-iodine complex, polyvinyl pyrrolidone-iodine complex... 

Poly(ethylene terephthalate) (PET) is commonly prepared by melt-phase polycondensation reactions. Bis(hydroxyethyl) terephthalate (BHET) was converted to PET under a variable flow (2-10 mL/min) of CO2 at 20.7 MPa (207 bar) (95). Molecular weights were obtained over the range 3 x 10 to 6.3 x 10 g/mol and increased significantly with flow rate and/or reaction time. These values are low compared to normal molecular weights obtained in commercial processes (approx. 2 X 10 g/mol) and may be attributed to the decreased solubility of the ethylene glycol condensate in CO2 compared with phenol in the polycarbonate system. 

Condensation polymerization differs from addition polymerization in that the polymer is formed by reaction of monomers, each step in the process resulting in the elimination of some easily removed molecule (often water). E.g. the polyester polyethylene terephthalate (Terylene) is formed by the condensation polymerization (polycondensation) of ethylene glycol with terephthalic acid ... 

Dehydration can be performed by a number of methods cooling, absorption and adsorption. Water removal by cooling is simply a condensation process at lower temperatures the gas can hold less water vapour. This method of dehydration is often used when gas has to be cooled to recover heavy hydrocarbons. Inhibitors such as glycol may have to be injected upstream of the chillers to prevent hydrate formation. 

Trimethylene Dibromide. In a 1-litre round-bottomed flask place 500 g. (338 ml.) of 48 per cent, hydrobromic acid and add 150 g. (82 ml.) of concentrated sulphuric acid in portions, with shaking. Then add 91 g. of trimethylene glycol (b.p. 210-215°), followed by 240 g. (130-5 ml.) of concentrated sulphuric acid slowly and with shaking. Attach a reflux condenser to the flask and reflux the mixture for 3 hours. Arrange for downward distillation and distil, using a wire gauze, until no more oily drops pass over (30—40 minutes). Purify the trimethylene dibromide... 

Place 36 -0 g. of redistilled acetophenone, b.p. 201° (Section IV,136), 300 ml. of diethylene glycol, 30 ml. of 90 per cent, hydrazine hydrate and 40 g. of potassium hydroxide pellets in a 500 ml. Claisen flask provided with a reflux condenser and a thermometer dipping into the liquid (compare Fig. Ill, 31, 1). Warm the mixture on a boiling water bath until most of the potassium hydroxide has dissolved and then reflux (free flame) for one hour. Arrange the apparatus for distillation and distil until the temperature in the liquid rises to 175° (1) keep the distillate (ca. 50 ml.). Replace the reflux condenser in the flask and continue the refluxing for 3 hours. 

Diethylene glycol method. Place 0-5 g. of potassium hydroxide pellets, 3 ml. of diethylene glycol and 0 5 ml. of water in a 10 or 25 ml. distilling flask heat the mixture gently until the alkali has dissolved and cool. Add 1-2 g. of the ester and mix well. Fit the flask with a thermometer and a small water-cooled condenser in the usual way. Heat the flask over a small flame whilst shaking gently to mix the contents. When only one liquid phase, or one hquid phase and one solid phase, remains in the flask, heat the mixture more strongly so that the alcohol distils. Identify the alcohol in the distillate by the preparation of the 3 5 dinitrobenzoate (Section 111,27,2). 

Chapter III. 1 Heptene (111,10) alkyl iodides (KI H3PO4 method) (111,38) alkyl fluorides (KF-ethylene glycol method) (111,41) keten (nichrome wire method) (111,90) ion exchange resin catalyst method for esters (111,102) acetamide (urea method) (111,107) ethyl a bromopropionate (111,126) acetoacetatic ester condensation using sodium triphenylmethide (111,151). 

ETHYLENE We discussed ethylene production in an earlier boxed essay (Section 5 1) where it was pointed out that the output of the U S petrochemi cal industry exceeds 5 x 10 ° Ib/year Approximately 90% of this material is used for the preparation of four compounds (polyethylene ethylene oxide vinyl chloride and styrene) with polymerization to poly ethylene accounting for half the total Both vinyl chloride and styrene are polymerized to give poly(vinyl chloride) and polystyrene respectively (see Table 6 5) Ethylene oxide is a starting material for the preparation of ethylene glycol for use as an an tifreeze in automobile radiators and in the produc tion of polyester fibers (see the boxed essay Condensation Polymers Polyamides and Polyesters in Chapter 20)... 

Those polymers which are the condensation product of two different monomers are named by applying the preceding rules to the repeat unit. For example, the polyester formed by the condensation of ethylene glycol and terephthalic acid is called poly(oxyethylene oxyterphthaloyl) according to the lUPAC system, as well as poly (ethylene terephthalate) or polyethylene terephthalate. 

Reactions of the Methyl Groups. These reactions include oxidation, polycondensation, and ammoxidation. PX can be oxidized to both terephthahc acid and dimethyl terephthalate, which ate then condensed with ethylene glycol to form polyesters. Oxidation of OX yields phthaUc anhydride, which is used in the production of esters. These ate used as plasticizers for synthetic polymers. MX is oxidized to isophthaUc acid, which is also converted to esters and eventually used in plasticizers and resins (see Phthalic acids and otherbenzenepolycarboxylic acids). 

By-product water formed in the methanation reactions is condensed by either refrigeration or compression and cooling. The remaining product gas, principally methane, is compressed to desired pipeline pressures of 3.4—6.9 MPa (500—1000 psi). Einal traces of water are absorbed on siHca gel or molecular sieves, or removed by a drying agent such as sulfuric acid, H2SO4. Other desiccants maybe used, such as activated alumina, diethylene glycol, or concentrated solutions of calcium chloride (see Desiccants). 

Glycols may undergo intramolecular cyclization or cycHcaHy condense with other molecules to form a number of ring stmctures. Transesterification of carbonates with ethylene glycol produces ethylene carbonate [96-49-1] (eq. 4). Numerous materials catalyze carbonate transesterifications. 

An early source of glycols was from hydrogenation of sugars obtained from formaldehyde condensation (18,19). Selectivities to ethylene glycol were low with a number of other glycols and polyols produced. Biomass continues to be evaluated as a feedstock for glycol production (20). 

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