PHYSICAL PROPERTIES OF ESTER

Many of the lower aliphatic esters form minimum boiling-point azeotropes with water (Table 11.2). The lower molecular weight esters have low flash points, low surface tensions and are only partially soluble in water. These acetates have mid-range Hansen polarity and hydrogen bonding solubility parameter values. The acetates offer a wide range of evaporation rates (see Table 11.9). 

The Exxate solvents (Table 11.3) have much higher flash points, very little water solubility, and surface tensions similar to the lower aliphatic acetates. The lower evaporation rates of the Exxate (see Table 11.9) make them ideal solvents for certain coating applications. 

The dibasic esters (DBE) are a series of acetate mixtures with high temperature distillation ranges, very high flash points, and low water solubility. The DBE solvents with their medium range Hansen solubility parameters are ideal solvents for certain cleaners and paint strippers. The typical compositions and physical properties of the seven DBE blends marketed by DuPont are shown in Table 11.5. 

The physical properties of the formate, propionate, and butyrate esters are given in Table 11.6. These esters have properties similar to the aliphatic acetates. Table 11.7 lists the physical properties of several lactate, oxalate, and carbonate esters. These esters have specialized uses that will be discussed in the section on solvent applications. The phthalate and phosphate esters shown in Table 11.8 are often used as plasticizers for polymeric compositions. Their Hansen solubility parameter values range from middle to high values. 

From carboxyiic acids (Sections 15.8 and 19.14) In the presence of an acid catalyst, alcohols and carboxylic acids react to form an ester and water. This is the Fischer esterification. 

From acyl chlorides (Sections 15.8 and 20.3) Alcohols react with acyl chlorides by nucleophilic acyl substitution to yield esters. These reactions are typically performed in the presence of a weak base such as pyridine. 

Acyi transfer from an acid anhydride to an aicohoi is a standard method for the preparation of esters. The reaction is subject to cataiysis by either acids (H2SO4) or bases (pyridine). 

Ketones are converted to esters on treatment with peroxy acids. The reaction proceeds by migration of the group R from carbon to oxygen. It is the more highly substituted group that migrates. Methyl ketones give acetate esters. 

CHAPTER TWENTY Carboxylic Acid Derivatives Nucleophilic Acyl Substitution 

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Table 1.13, on the next page, describes some of the physical properties of esters. As you will see, esters have different physical properties than carboxylic acids, even though esters and carboxylic acids are isomers of each other. 

Summary of physical properties of esters and phthalate esters... 

Write structures and describe the physical properties of esters. 

Table IV,183 summarises the physical properties of a few selected aromatic esters.

The physical properties of cyanoacetic acid [372-09-8] and two of its ester derivatives are Hsted ia Table 11 (82). The parent acid is a strong organic acid with a dissociation constant at 25°C of 3.36 x 10. It is prepared by the reaction of chloroacetic acid with sodium cyanide. It is hygroscopic and highly soluble ia alcohols and diethyl ether but iasoluble ia both aromatic and aUphatic hydrocarbons. It undergoes typical nitrile and acid reactions but the presence of the nitrile and the carboxyUc acid on the same carbon cause the hydrogens on C-2 to be readily replaced. The resulting malonic acid derivative decarboxylates to a substituted acrylonitrile ... 

Table 11. Some Physical Properties of Cyanoacetic Acid and Methyl and Ethyl Esters ...

Butanediol. 1,4-Butanediol [110-63-4] tetramethylene glycol, 1,4-butylene glycol, was first prepared in 1890 by acid hydrolysis of N,]S3-dinitro-l,4-butanediamine (117). Other early preparations were by reduction of succinaldehyde (118) or succinic esters (119) and by saponification of the diacetate prepared from 1,4-dihalobutanes (120). Catalytic hydrogenation of butynediol, now the principal commercial route, was first described in 1910 (121). Other processes used for commercial manufacture are described in the section on Manufacture. Physical properties of butanediol are Hsted in Table 2. 

Physical properties of acryHc acid and representative derivatives appear in Table 1. Table 2 gives selected properties of commercially important acrylate esters, and Table 3 Hsts the physical properties of many acryHc esters. 

Table 3. Physical Properties of Acrylic Esters, CH7=CHC00R ...

The physical properties of the principal commercial acryhc esters are given ia Table 4. A more comprehensive listing of physical properties, including other less common acrylates, is provided ia the article Acrylic acid and derivatives. 

The physical properties of the monomers must be discussed along with those of the cured polymers because consideration of one without the other presents an incomplete picture. The 2-cyanoacryhc ester monomers are all thin, water-clear Hquids with viscosities of 1 3 mPa-s(=cP). Although a number of the esters have been prepared and characterized, only a relative few are of any significant commercial interest, and, of those, the methyl and ethyl esters by far predominate. The physical properties of the principal monomers are included in Table 1. 

The bulk physical properties of the polymers of the 2-cyanoacryhc esters appear in Table 2. AH of these polymers are soluble in /V-methy1pyrro1idinone, /V,/V-dimethy1foTm amide, and nitromethane. The adhesive bonding properties of typical formulated adhesives are Hsted in Table 3. 

Dibasic Acid Esters. Dibasic acid esters (diesters) are prepared by the reaction of a dibasic acid with an alcohol that contains one reactive hydroxyl group (see Esters, organic). The backbone of the stmcture is formed by the acid. The alcohol radicals are joined to the ends of the acid. The physical properties of the final product can be varied by using different alcohols or acids. Compounds that are typically used are adipic, azelaic, and sebacic acids and 2-ethyIhexyl, 3,5,5-trimethyIhexyl, isodecyl, and tridecyl alcohols. 

Physical Properties. The physical properties of cyanoacetic acid [372-09-8] NM7—CH2COOH (28) ate summarized in Table 4. The industrially most important esters ate methyl cyanoacetate [105-34-0] and ethyl cyanoacetate [105-56-6]. Both esters ate miscible with alcohol and ether and immiscible with water. 

Selected physical properties of various methacrylate esters, amides, and derivatives are given in Tables 1—4. Tables 3 and 4 describe more commercially available methacrylic acid derivatives. A2eotrope data for MMA are shown in Table 5 (8). The solubiUty of MMA in water at 25°C is 1.5%. Water solubiUty of longer alkyl methacrylates ranges from slight to insoluble. Some functionalized esters such as 2-dimethylaniinoethyl methacrylate are miscible and/or hydrolyze. The solubiUty of 2-hydroxypropyl methacrylate in water at 25°C is 13%. Vapor—Hquid equiUbrium (VLE) data have been pubHshed on methanol, methyl methacrylate, and methacrylic acid pairs (9), as have solubiUty data for this ternary system (10). VLE data are also available for methyl methacrylate, methacrylic acid, methyl a-hydroxyisobutyrate, methanol, and water, which are the critical components obtained in the commercially important acetone cyanohydrin route to methyl methacrylate (11). 

The physical properties of the acids, the most important anhydrides, and the full methyl esters are summarized ia Tables 2, 3, and4. Detailed Hsts of physical properties for phthaUc acid and its anhydride, terephthaUc acid and dimethyl terephthalate, isophthaUc acid, trimeUitic acid and its anhydride, and pyromeUitic acid and its dianhydride/ are provided under the sections describiag these compounds. 

Derivatives. In general, the esters of terephthaHc acid derived from saturated alcohols undergo the same reactions as dimethyl terephthalate. Some physical properties of six of these esters are Hsted in Table 23. The di- -butyl and di-2-ethyIhexyl esters find use as plasticizers (qv). Terephthaloyl chloride, which is prepared by reaction of terephthaHc acid and thionyl chloride, is used to prepare derivatives of terephthaHc acid. 

Derivatives. The dual functionaUty of trimellitic anhydride makes it possible to react either the anhydride group, the acid group, or both. Derivatives of trimellitic anhydride include ester, acid esters, acid chloride, amides, and amide—imides (136). Trimellitate esters are the most important derivatives, and physical properties of more significant esters are Hsted in Table 34. 

Physical properties of isopropyl alcohol are characteristic of polar compounds because of the presence of the polar hydroxyl, —OH, group. Isopropyl alcohol is completely miscible ia water and readily soluble ia a number of common organic solvents such as acids, esters, and ketones. It has solubiUty properties similar to those of ethyl alcohol (qv). There is a competition between these two products for many solvent appHcations. Isopropyl alcohol has a slight, pleasant odor resembling a mixture of ethyl alcohol and acetone, but unlike ethyl alcohol, isopropyl alcohol has a bitter, unpotable taste. 

Table 3 gives the corresponding physical properties of some commercially important substituted pyridines having halogen, carboxyHc acid, ester, carboxamide, nitrile, carbiaol, aminomethyl, amino, thiol, and hydroxyl substituents. 

Rosin ester resins are used as modifiers in the formulation of chewing gum. The rosin derivative modifies the physical properties of the polymer used, providing the desired masticatory properties. The glycerol ester of hydrogenated rosin is the predominant choice, because stabilized materials have improved aging resistance, which extends the shelf life of the gum. 

Table 8. Physical Properties of Salicylic Acid Esters...

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