ESTERS OR ETHEREAL SALTS

Esters or ethereal salts are derivatives of alcohols formed by the reaction of an alcohol with an acid. As they are thus acid derivatives also and as the more important esters are those formed from the organic acids, which we shall soon study, the chief discussion of them as a group will come later. There are, however, to be considered the esters formed from inorganic acids and these will be presented now. The chemical properties of alcohol in its relation to both bases and acids are of especial interest and importance. We have spoken of the fact that alcohol as an hydroxyl compound belongs to the water type, and that the other representatives of this type are the metal hydroxides or bases, and the non-metal hydroxides or acids. 

Now we know that while water stands as it were on the dividing line between metal and non-metal hydroxides, and is a perfectly neutral compound, there are other hydroxides which may be placed on either side, i,e., they may form either bases or acids. The elements whose hydroxides are of this nature may be illustrated by the element aluminium. Toward strong bases aluminium hydroxide acts as an acid and forms salts in which the aluminium plays the part of a non-metal. 

Alcohol a Base or an Acid.—Now alcohols are similar to aluminium hydroxide in their property of reacting with both bases and acids, as follows  

With sodium hydroxide or better with sodium, alcohol forms sodium alcoholate, a salt in which the ethyl radical plays the part of a non-metal, while with hydrochloric acid it forms ethyl chloride, a salt in which the ethyl radical plays the part of a metal. Now while alcohol acts as an acid toward only the strong bases it acts as a base toward practically all acids. We may say then that the basic character of alcohol is more pronounced than the acid. In both of these cases we have reactions that are simply the neutralization of an acid or a base by a base or an acid, the products being the same as in all neutralizations, viz., a salt and water. Both sodium alcoholate and ethyl chloride are to be looked upon then as salts. 

Esters or Ethereal Salts.—The metal salts of alcohol are not of special importance, but the ethyl salts of acids are extremely important compounds. These salts in which the ethyl radical acts as a metal are called esters or ethereal salts. While the name ethereal salt is perhaps the best and most significant, as it indicates the salt character of the compound, the name ester will be used as it has been generally adopted. The reaction given is a general reaction of alcohols. The general formula for ester being R—(Acid R) or an alkyl radical joined to an acid radical. 

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The nature of esters or ethereal salts has been fully discussed already in connection with the esters of inorganic acids and alcohols (p. 102). The name salts applies because they are formed by neutralizing an alcohol, acting as a base, with an acid. It must be emphasized, however, that in so terming these compounds salts we do not mean this to apply in a physical chemical sense as describing their properties in solution in accordance with the electrolytic theory of ionic dissociation. We are dealing here with questions of composition and constitution. Ethereal salts differ from metal salts, at least as to the degree of their dissociation into ions when in solution. 

Saponification.—As we shall see later, this is the kind of reaction which takes place when soap is made from fats and on that account it is termed an action of saponifikation. In this way the acids are obtained as salts from the naturally occurring fats, oils and waxes in which they are present in the form of esters. The hydrolysis of esters or ethereal salts is then the general reaction by which, with the taking up of the elements of water, an ester is reconverted into the two compounds from which it was formed, viz., into an acid and an alcohol. Esterification and hydrolysis or saponification are, therefore, complementary names applying to the reversible reaction effecting the synthesis and decomposition of esters. The reversible character of the reactions of esterification and... 

This reaction, it will be recalled, is typical of all esters or ethereal salts. Because it is, in fact, a reaction due to the action of water, it is known as hydrolysis. It is the reverse of the reaction of esterification. 

Esters.— The simplest class of compounds present in essential oils are the esters or ethereal salts (p. 140). In our early discussion of these compounds in the aliphatic series it was stated that the odor and flavor of common fruits is probably due to ester compounds and that certain empirical mixtures of esters are used as artificial fruit essences. Artificial apple essence, for example, may be prepared by mixing certain proportions of ethyl nitrite, ethyl acetate and amyl valerate with chloroform, aldehyde and alcohol. An example of an essential oil which consists of a single ester is oil of wintergreen. vAdxh is the methyl ester of salicylic acid, ortho-hydroxy benzoic acid (p. 714). 

To synthesize new surfactants, having incorporated both structural elements, the known siloxanyl modified halogenated esters and ethers of dicyclopentadiene [5] were treated with different amines according to the reaction scheme. Triethylamine yielded quaternary ammonium salts directly. Alternatively, after reaction with diethylamine or morpholine, the isolated siloxanyl-modified tertiary amines were also converted to quaternary species. To obtain anionic surfactants, the halogenated precursors were initially reacted with n-propylamine. In subsequent reaction steps the secondary amines formed were converted with maleic anhydride into amides, and the remaining acid functions neutralized. Course and rate of each single reaction strongly depended on the structure of the initial ester or ether compound and the amine applied. The basicity of the latter played a less important role [6]. 

Solvent polymeric membranes, conventionally prepared from a polymer that is highly plasticized with lipophilic organic esters or ethers, are the scope of the present chapter. Such membranes commonly contain various constituents such as an ionophore (or ion carrier), a highly selective complexing agent, and ionic additives (ion exchangers and lipophilic salts). The variety and chemical versatility of the available membrane components allow one to tune the membrane properties, ensuring the desired analytical characteristics. 

Endo et al. investigated the reductive decomposition of various electrolytes on graphite anode materials by electron spin resonance (ESR). In all of the electrolyte compositions investigated, which included LiC104, LiBF4, and LiPFe as salts and PC, DMC, and other esters or ethers as solvents, the solvent-related radical species, which were considered to be the intermediates of reductive decomposition, were detected only after prolonged cathodic electrolysis. With the aid of molecular orbital calculation, they found that the reduction of salt anion species is very difficult, as indicated by their positive reduction enthalpy and that of free solvent (A/4 — 1 kcal mol ). However, the coordination of lithium ions with these solvents dramatically reduces the corresponding reduction enthalpy (A/ —10 kcal mol ) and renders the reaction thermodynamically favored. In other words, if no kinetic factors were to be considered, the SEI formed on carbonaceous anodes... 

The first cyanoacrylate patent describes the preparation of cyanoacrylate monomer by reacting the sodium salt of a cyanoacetate ester with a halomethyl ester or ether. This forms the polycyanoacrylate from which the monomer is recovered by thermal decomposition (Eq. 1). However,... 

P. exhibit the typical chemical properties of other reducing sugars (hexoses) oxidation to the salts of the corresponding acids or their lactones, reduction to polyalcohols (pentites), substitution of the alcoholic groups by esters or ethers, dehydration splitting (water elimination) to ftirfural, fermentation by microorganisms. 

Commercial lecithin is insoluble but infinitely dispersible in water. Treatment with water dissolves small amounts of its decomposition products and adsorbed or coacervated substances, eg, carbohydrates and salts, especially in the presence of ethanol. However, a small percentage of water dissolves or disperses in melted lecithin to form an imbibition. Lecithin forms imbibitions or absorbates with other solvents, eg, alcohols, glycols, esters, ketones, ethers, solutions of almost any organic and inorganic substance, and acetone. It is remarkable that the classic precipitant for phosphoHpids, eg, acetone, dissolves in melted lecithin readily to form a thin, uniform imbibition. Imbibition often is used to bring a reactant in intimate contact with lecithin in the preparation of lecithin derivatives. 

As shovm above, the attachment of the aromatic ring to the carbon chain bearing the basic nitrogen may be accomplished through an ester or an amide configured in either direction. A simple ether linkage fulfills this function in yet another compound that exhibits local anesthetic activity. Thus, alkylation of the mono potassium salt of hydroquinone with butyl bromide affords the ether (77) alkylation of this with w-C3-chloropropyl)morpholine affords pramoxine (78)... 

Ether carboxylates are used not only in powdered detergents but in liquid laundry detergents for their hard water stability, lime soap dispersibility, and electrolyte stability they improve the suspension stability and rheology of the electrolyte builder [130,131]. Formulations based particularly on lauryl ether carboxylate + 4.5 EO combined with fatty acid salt and other anionic surfactants are described [132], sometimes in combination with quaternary compounds as softeners [133,163]. Ether carboxylates show improved cleaning properties as suds-controlling agents in formulations with ethoxylated alkylphenol or fatty alcohol, alkyl phosphate esters or alkoxylate phosphate esters, and water-soluble builders [134]. 

Alkyl lV,lV-dinitramines (154) have been prepared from the reaction of the tetraalkylam-monium salts (155) of primary nitramines with nitryl fluoride in acetonitrile at subambient temperature. The same reaction with the primary nitramine or its alkali metal salts yields the corresponding nitrate ester. Treatment of the ammonium, potassium, or lithium salts of primary nitramines (156) with a solution of nitronium tetrafluoroborate in acetonitrile at subambient temperature yield alkyl iV,iV-dinitramines. ° The same reactions in ether or ester solvents enables the free nitramine to be used. The nitrolysis of A-alkylnitramides (157) and N,N-diacylamines with nitronium tetrafluoroborate in acetonitrile, and the nitration of aliphatic isocyanates with nitronium tetrafluoroborate and nitric acid in acetonitrile, also yield alkyl A,A-dinitramines (154). 

Countless reductions of esters to alcohols have been accomplished using lithium aluminum hydride. One half of a mol of this hydride is needed for reduction of 1 mol of the ester. Ester or its solution in ether is added to a solution of lithium aluminum hydride in ether. The heat of reaction brings the mixture to boiling. The reaction mixture is decomposed by ice-water and acidified with mineral acid to dissolve lithium and aluminum salts. Less frequently sodium hydroxide is used for this purpose. Yields of alcohols are frequently quantitative [83,1059]. Lactones afford glycols (diols) [575]. 

The simple acidic nature of chlorosulphonic acid is also manifested in the existence of corresponding ethereal salts, the ethyl ester C1.S02. OCaII8 being obtainable indirectly by the action of phosphorus penta-chloride on ethyl hydrogen sulphate (ethylsulphuric acid), C2H50. S03.0H, or by the interaction of sulphuryl chloride and ethyl alcohol 1... 

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