Surface Esters with Alcohols

Lundquist (1999) described a process for esterification and transesterification, particularly of, organic acids with alcohols, or of, esters with alcohols catalyzed with surface-functionalized, crosslinked vinylaromatic polymer beads. Zupan and Segatin... 

Ethyl phenylethylmalonate. In a dry 500 ml. round-bottomed flask, fitted with a reflux condenser and guard tube, prepare a solution of sodium ethoxide from 7 0 g. of clean sodium and 150 ml. of super dry ethyl alcohol in the usual manner add 1 5 ml. of pure ethyl acetate (dried over anhydrous calcium sulphate) to the solution at 60° and maintain this temperature for 30 minutes. Meanwhile equip a 1 litre threenecked flask with a dropping funnel, a mercury-sealed mechanical stirrer and a double surface reflux condenser the apparatus must be perfectly dry and guard tubes should be inserted in the funnel and condenser respectively. Place a mixture of 74 g. of ethyl phenylmalonate and 60 g. of ethyl iodide in the flask. Heat the apparatus in a bath at 80° and add the sodium ethoxide solution, with stirring, at such a rate that a drop of the reaction mixture when mixed with a drop of phenolphthalein indieator is never more than faintly pink. The addition occupies 2-2 -5 hoius continue the stirring for a fiuther 1 hour at 80°. Allow the flask to cool, equip it for distillation under reduced pressure (water pump) and distil off the alcohol. Add 100 ml. of water to the residue in the flask and extract the ester with three 100 ml. portions of benzene. Dry the combined extracts with anhydrous magnesium sulphate, distil off the benzene at atmospheric pressure and the residue under diminished pressure. C ollect the ethyl phenylethylmalonate at 159-160°/8 mm. The yield is 72 g. 

It possesses surface-active properties in its acid form as well as in the form of its salts. In the case of 1 mol alcohol reacting with 1 mol phosphoric acid, a so-called primary or monoalkyl phosphoric acid ester with two remaining acid groups arises see Eq. (6). 

Although the true waxes, such as beeswax, are esters of fatty acids with alcohols, the term is often applied to certain solid substances which melt at fairly low temperatures, e.g., paraffin wax. Paraffin waxes (crystalline and microcrystalline) are obtained from the refining of petroleum, and are used in rubber compounding as protective agents. They have the property of blooming to the surface of the product, forming a thin film which replenishes itself if removed in service. 

Esterification. Another reaction which can be used in the determination of surface silanol groups is their esterification with alcohols. This reaction has also found industrial application. The formation of surface esters by the action of alcohols on silica is covered in a patent to Her (226). The reaction products, called estersils, are hydrophobic. 

Amidon et al. [39] have correlated the aqueous solubility of 127 aliphatic hydrocarbons, alcohols, ethers, aldehydes, ketones, fatty acids, and esters with their total molecular surface area ... 

The lubrication system is extremely complex. The mechanism of lubrication is partly dictated by the nature of interactions between the lubricant and the solid surface. Additives blended into lubricating oil formulations either adsorb onto the sliding surfaces, eg., fatty alcohols, fatty amines, amides, phosphoric acid esters (friction modifiers), or react with the surface, eg., ZDDP, MoDTC, MoDDP organic phosphates (extreme pressure). Some interactions affecting the surfaces of metals include adsorption, chemisorption, and tribochemical reactions-these form new compounds on the surface and lubrication by reaction products (Bhushan and Gupta, 1991 Briscoe et al., 1973 Briscoe and Evens, 1982 Heinicke, 1984 Hsu and Klaus, 1978 and 1979 Klaus and Tewksbury, 1987 Lansdown, 1990 Liston, 1993 McFadden et al., 1998 Studt, 1989). 

In some instances the carrier of the guest plays the role of emulsifier. For example, alcohols and lower fatty acids or their esters are used in the formation of fat-starch complexes.676 In this case, conditions for preparation of complexes resemble conditions for extraction, and unexpected results can accompany both processes. For example, it has been shown that extraction of lipids with 1-propanol from their surface complex with oat starch produced a helical lipid-starch complex that was absent prior to extraction.677... 

Attempts to achieve optical induction during the reduction of aromatic ketones to the secondary alcohol with the help of a single layer of chiral catalyst covalently attached to a graphite cathode have been much less successful. Reduction of 4-acetylpyridine at a graphite surface coated with (S)-phenylalanine methyl ester afforded an enantiomeric excess of the (S)-pyridinylethanol. In other experiments, ethyl glyoxylate afforded ethyl (—)-mandelate with 9.7% enantiomeric excess [101]. Results using such modified surfaces have, however, proved highly irreproducible [102]. 

Baizer and coworkers established the most brilliant industrial electroorganic synthesis of the hydrodimerization of acrylonitrile to adiponitrile. They extended this hydrodimerization to a variety of activated olefins and in some cases [41 3] paid attention to the stereochemistry of products. However, their stereochemical data were not enough to discuss the stereochemical course of the reaction. Afterward, an attempt was made to provide a working hypothesis in the hydrodimerization of cinnamates by considering an orientated adsorption of radical anion intermediates on a cathode surface, but this was not persuasive because of a lack of experimental data on the stereochemistry of both the starting olefins and products. Recently Utley and coworkers [44-46] have reported stereochemical data of hydrodimers derived from a variety of cinnamic acid esters with chiral alcohol components. 

Properties Water-white, stable liquid odorless bitter taste. Fp -40.5C, refr index 1.5002 (25C), surface tension 37.5 dynes/cm (20C), viscosity 31.3 centistokes (OC), vap press 14 mm Hg (163C), 30 mm Hg (182C), 734 mm Hg (295C), bp 298C, flash p325F (162.7C) (OC), wt/gal approximately 9.31 lb (20C), d 1.120 (25/25C). Miscible with alcohols, ketones, esters, aromatic hydrocarbons partly miscible with aliphatic solvents insoluble in water. Combustible. 

The data points to the importance of two parameters, that of adhesive interactions between adsorbate and surface, and lateral interactions between adsorbate molecules on the surface. In general, the free energy of adsorption (at zero coverage) is of the order of 10-30 kJ mol for alcohols, carboxylic acids and esters on ferrous surfaces, consistent with hydrogen bonding between surface and adsorbate. 

Terminal carboxyl groups in monolayers can also be activated by treatment with carbodiimides such as dicyclohexylcarbodiimide (DCC) or l-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) 59). Alternatively, conversion to a mixed anhydride can be effected by reaction of a carboxyl-terminated film with ethyl chloroformate 49). Exposure of the surface to gaseous SOCI2 has been reported to produce carboxyl chloride groups 48,60). These activated acid derivatives then react smoothly with alcohols or amines to form esters or amides (Scheme 2). 

Since silica gel contains large numbers of reactive silanol groups extending from the surface, the Si-OH groups can be esterified by reaction with alcohols to yield silicate esters. 

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