Salts of carboxylic acids

Lithium, sodium, potassium, or other salts of benzoic acid, phthalic acid, sulfoben-zoic acid, citric acid, and others are useful eluents for anions. These are rather large organic anions that are less mobile than most inorganic anions and therefore have lower equivalent conductances. For example. Table 4.1 shows that the benzoate anion has a limiting equivalent eonductance of 32 S cm equiv, while ehloride, nitrate, sulfate, and other typieal sample anions have higher equivalent conductances (approximately 70 S cm equiv ). If a sodium benzoate eluent is used, the equivalent conductance is the sum of sodium ion (50) and benzoate (32), or 85 S cm equiv . The equivalent conductance of an anion is the sum of equivalent eonductances of the sodium ion (50) and the anion (70), or 120 S cm equiv. On an equivalent basis, this amounts to almost a 50 % increase in conductance. 

Benzoate or p-hydroxybenzoate, which is more soluble and therefore to be preferred, are two of the most useful carboxylate ions for eluents. Phalate or hydrogen phthalate is also widely used. Benzoate salts are useful for separation of acetate, bicarbonate, fluoride, chloride, nitrite, nitrate, and other early-eluting anions. Divalent anion and other late-eluting anions such as thiocyanate and perchlorate are not eluted effectively by benzoate. The concentration of a benzoate eluent that should be used depends on the type and capacity of anion-exchange resin used, but is typically 0.5-5.0 mM. 

Alkali metal salts of benzenesulfonic acid are similar to benzoate in their eluting power although benzenesulfonate retains its 1- charge at a lower pH. 

In the presence of strong bases such as sodium hydroxide, carboxylic acids are neutralized rapidly and quantitatively  

PROBLEM 19.3 Write an ionic equation for the reaction of acetic acid with each of the following, and specify whether the equilibrium favors starting materials or products  

SAMPLE SOLUTION (a) This is an acid-base reaction ethoxide ion is the base. CH3CO2H -f CH3CH2O- ---------------------- CH3C02 + CH3CH2OH 

The position of equilibrium lies well to the right. Ethanol, with a of 10 (p/Ca16), is a much weaker acid than acetic acid. 

Sample Solution (a) This is an acid-base reaction ethoxide ion is the base. CH3CO2H + CH3CH20 CH3C02 + CH3CH2OH 

The salts formed on neutralization of carboxylic acids are named by first specifying the metal ion and then adding the name of the acid modified by replacing -ic acid 

A strong base can completely deprotonate a carboxylic acid. The products are a carboxylate ion, the cation remaining from the base, and water. The combination of a carboxylate ion and a cation is a salt of a carboxylic acid. 

For example, sodium hydroxide deprotonates acetic acid to form sodium acetate, the sodium salt of acetic acid. 

Because mineral acids are stronger than carboxylic acids, addition of a mineral acid converts a carboxylic acid salt back to the original carboxylic acid. 

In an aqueous solution, an acid will be mostly dissociated if the pH is above (more basic than) the acid s pKa, and mostly undissociated if the pH is below (more acidic than) the acid s pKa. 

Carboxylic acid salts have very different properties from the acids, including enhanced solubility in water and less odor. Because aeids and their salts are easily inter-converted, these salts serve as useful derivatives of earboxylic acids. 

What is the most acidic neutral molecule characterized by the formula C3Hj(02  

---

Sodium benzoate,—Burns with great difficulty, and after prolonged heating leaves a white infusible residue of NajCOj. Scrape this residue into a test-tube, and test for carbonate in the usual way. Typical of alkali salts of carboxylic acids. 

Metal carboxylates are ionic and when the molecular weight isn t too high the sodium and potassium salts of carboxylic acids are soluble m water Carboxylic acids therefore may be extracted from ether solutions into aqueous sodium or potassium hydroxide... 

The solubility behavior of salts of carboxylic acids having 12—18 carbons is unusual and can be illustrated by considering sodium stearate (sodium octadecanoate) As seen by the structural formula of its sodium salt... 

We ve seen how Grignard reagents add to the carbonyl group of aldehydes ketones and esters Grignard reagents react m much the same way with carbon dioxide to yield mag nesium salts of carboxylic acids Acidification converts these magnesium salts to the desired carboxylic acids... 

Aluminum salts of carboxylic acids, aluminum carboxylates, may occur as aluminum tricarboxylates (normal aluminum carboxylates), Al(OOCR)2 monohydroxy (monobasic) aluminum dicarboxylates, (RCOO)2Al(OH) and dihydroxy (dibasic) aluminum monocarboxylates, RCOOAl(OH)2. Aluminum carboxylates are used in three general areas textiles, gelling, and pharmaceuticals. Derivatives of low molecular weight carboxyUc acids have been mainly associated with textile appHcations those of fatty carboxyUc acids are associated with gelling salts and more complex carboxylates find appHcations in pharmaceuticals. 

Alkyl chlorosulfates and alkali salts of carboxylic acid D ... 

CO2 insertion into M C bonds has, of course, been known since the first papers of V. Grignard in 1901 (p. 134). Organo-Li (and other M and M") also react extremely vigorously to give salts of carboxylic acids, RCO Li, (RC02)2Be, etc. Zinc dialkyls are much less reaetive towards CO2, e.g. 

Organic or inorganic inhibitors This distinction is based on the chemical nature of the inhibitor. However, in their inhibitive action many compounds that are organic in nature as, for example, the sodium salts of carboxylic acids, often have more similarities with inorganic inhibitors. 

Evaporation gives the salt sodium acetate, which contains Na+ and CH3COO ions. Many of the salts of carboxylic acids have important uses. Sodium and calcium propionate (Na+ or Ca2+ ions, CH3CH2COO ions) are added to bread, cake, and cheese to inhibit the growth of mold. 

Metal salts of carboxylic acids obviously possess some organic character, but decompositions of these substances can be considered in the present context. Many metal carboxylates decompose at a reactant—product interface and their nucleation and growth processes are similar to the behav-... 

Trimerization to isocyanurates (Scheme 4.14) is commonly used as a method for modifying the physical properties of both raw materials and polymeric products. For example, trimerization of aliphatic isocyanates is used to increase monomer functionality and reduce volatility (Section 4.2.2). This is especially important in raw materials for coatings applications where higher functionality is needed for crosslinking and decreased volatility is essential to reduce VOCs. Another application is rigid isocyanurate foams for insulation and structural support (Section 4.1.1) where trimerization is utilized to increase thermal stability and reduce combustibility and smoke formation. Effective trimer catalysts include potassium salts of carboxylic acids and quaternary ammonium salts for aliphatic isocyanates and Mannich bases for aromatic isocyanates. 

When a carbonyl group is bonded to a substituent group that can potentially depart as a Lewis base, addition of a nucleophile to the carbonyl carbon leads to elimination and the regeneration of a carbon-oxygen double bond. Esters undergo hydrolysis with alkali hydroxides to form alkali metal salts of carboxylic acids and alcohols. Amides undergo hydrolysis with mineral acids to form carboxylic acids and amine salts. Carbamates undergo alkaline hydrolysis to form amines, carbon dioxide, and alcohols. 

Conjugated dienes give 1,4 addition. This reaction has also been performed with salts of carboxylic acids in what amounts to a method of alkylation of carboxylic acids (see also 10-96). ... 

Speakman JC (1972) Acid Salts of Carboxylic Acids, Crystals with some Very Short Hydrogen Bonds. 12 141-199 Spirlet J-C, see Muller W (1985) 59/60 57-73... 

CHROMIUM TRIOXIDE-PYRIDINE COMPLEX, preparation in situ, 55, 84 Chrysene, 58,15, 16 fzans-Cinnamaldehyde, 57, 85 Cinnamaldehyde dimethylacetal, 57, 84 Cinnamyl alcohol, 56,105 58, 9 2-Cinnamylthio-2-thiazoline, 56, 82 Citric acid, 58,43 Citronellal, 58, 107, 112 Cleavage of methyl ethers with iodotri-methylsilane, 59, 35 Cobalt(II) acetylacetonate, 57, 13 Conjugate addition of aryl aldehydes, 59, 53 Copper (I) bromide, 58, 52, 54, 56 59,123 COPPER CATALYZED ARYLATION OF /3-DlCARBONYL COMPOUNDS, 58, 52 Copper (I) chloride, 57, 34 Copper (II) chloride, 56, 10 Copper(I) iodide, 55, 105, 123, 124 Copper(I) oxide, 59, 206 Copper(ll) oxide, 56, 10 Copper salts of carboxylic acids, 59, 127 Copper(l) thiophenoxide, 55, 123 59, 210 Copper(l) trifluoromethanesulfonate, 59, 202... 

Alternatively, esterification of carboxylic acid can be carried out in aqueous media by reacting carboxylic acid salts with alkyl halides through nucleophilic substitutions (Eq. 9.10).20 The reaction rate of alkyl halides with alkali metal salts of carboxylic acids to give esters increases with the increasing concentration of catalyst, halide, and solvent polarity and is reduced by water. Various thymyl ethers and esters can be synthesized by the reactions of thymol with alkyl halides and acid chlorides, respectively, in aqueous medium under microwave irradiation (Eq. 9.11).21 Such an esterification reaction of poly(methacrylic acid) can be performed readily with alkyl halides using DBU in aqueous solutions, although the rate of the reaction decreases with increasing water content.22... 

Alkenes with monosubstituted carbon atoms are oxidatively cleaved to salts of carboxylic acids by hot basic permangnate solutions. 

Another Pd-catalyzed reaction of aryl- and alkylzinc halides used carboxylic anhydrides as starting organic compounds (Scheme 127).328 One of the advantages of this method is that anhydrides can be synthesized in situ from the corresponding sodium salts of carboxylic acids and ethyl chloroformate. The scope of the method includes aliphatic and aromatic anhydrides, phenyl-, ethyl-, isopropyl-, and n-butylzinc iodides. 

---