Ion carboxylic acid

Although phenoxlde ion has more number of resonating structures than carbojQ late Ion, carboxylic acid is a stronger acid than phenol. Why ... 

Keywords co-adsorption, cadmium ions, carboxylic acids, titania, goethite, silica... 

Stability of carboxylate ions. Carboxylic acids are more acidic than alcohols because carboxylate ions are more stable than alkoxide ions. A carboxylate ion has its negative charge delocalized over two oxygen atoms, compared with only one oxygen atom bearing the negative charge in an alkoxide ion. 

Hydroxyethyl esters can be prepared from the free acid by reaction with ethylene carbonate. During an attempt to protect the ketone group of a keto-acid by 1,3-dioxolane formation, it has been found that mixed carboxylate sulphonate esters [e.g. (121) from ethylene glycol and tosic acid] can easily be formed extensions of this reaction show it to have a general applicability. In the presence of fluoride ions, carboxylic acids become sufficiently nucleophilic to attack alkyl halides. Thus, reaction between an acid and 1,3-dibromopropane leads to diesters (122). Molecular sieves have been recommended as suitable absorbants... 

For both these reasons, the positive charge on the carbonyl carbon and delocalization of the carboxylate ion, carboxylic acids are much more acidic than alcohols. 

Low molar mass tnuisition metal ions carboxylic acids... 

Ionic conductors arise whenever there are mobile ions present. In electrolyte solutions, such ions are nonually fonued by the dissolution of an ionic solid. Provided the dissolution leads to the complete separation of the ionic components to fonu essentially independent anions and cations, the electrolyte is tenued strong. By contrast, weak electrolytes, such as organic carboxylic acids, are present mainly in the undissociated fonu in solution, with the total ionic concentration orders of magnitude lower than the fonual concentration of the solute. Ionic conductivity will be treated in some detail below, but we initially concentrate on the equilibrium stmcture of liquids and ionic solutions. 

Spanel P and Smith D 1998 SIFT studies of the reactions of FijO", NO and Ot with a series of volatile carboxylic acids and esters Int. J. Mass Spectrom. Ion Proc. 172 137-47... 

The presence of certain substituents e.g., the amino group) may markedly affect the solubibty and other properties of the sulphonic acid or carboxylic acid. Thus such sulphonic acids as the aminobenzenesul-phonic acids, pyridine- and quinoline-sulphonic acids exist in the form of inner salts or zwitter-ions that result from the interaction of the basic amino group and the acidic sulphonic acid. Sulphanilic acid, for example, is more accurately represented by formula (I) than by formula (II) ... 

Inspired by the many hydrolytically-active metallo enzymes encountered in nature, extensive studies have been performed on so-called metallo micelles. These investigations usually focus on mixed micelles of a common surfactant together with a special chelating surfactant that exhibits a high affinity for transition-metal ions. These aggregates can have remarkable catalytic effects on the hydrolysis of activated carboxylic acid esters, phosphate esters and amides. In these reactions the exact role of the metal ion is not clear and may vary from one system to another. However, there are strong indications that the major function of the metal ion is the coordination of hydroxide anion in the Stem region of the micelle where it is in the proximity of the micelle-bound substrate. The first report of catalysis of a hydrolysis reaction by me tall omi cell es stems from 1978. In the years that... 

Acetic acid and other carboxylic acids are protonated in superacids to form stable carboxonium ions at low temperatures. Cleavage to related acyl cations is observed (by NMR) upon raising the temperature of the solutions. In excess superacids a diprotonation equilibrium, indicated by theoretical calculations, can play a role in the ionization process. 

Cyclopentene derivatives with carboxylic acid side-chains can be stereoselectively hydroxy-lated by the iodolactonization procedure (E.J. Corey, 1969, 1970). To the trisubstituted cyclopentene described on p. 210 a large iodine cation is added stereoselectively to the less hindered -side of the 9,10 double bond. Lactone formation occurs on the intermediate iod-onium ion specifically at C-9ot. Later the iodine is reductively removed with tri-n-butyltin hydride. The cyclopentane ring now bears all oxygen and carbon substituents in the right stereochemistry, and the carbon chains can be built starting from the C-8 and C-12 substit""" ... 

Friedel-Crafts acylation of aromatic compounds (Section 12 7) Acyl chlorides and carboxylic acid anhydrides acylate aromatic rings in the presence of alumi num chloride The reaction is electrophil ic aromatic substitution in which acylium ions are generated and attack the ring... 

FIGURE 19 6 Space filling model of a micelle formed by association of car boxylate ions derived from a long chain carboxylic acid The hydrocarbon chains tend to be on the inside and the carboxylate ions on the surface where they are in contact with water mole cules and metal cations... 

Step 1 The carboxylic acid is protonated on its carbonyl oxygen The proton donor shown in the equation for this step is an aUtyloxonium ion formed by proton transfer from the acid catalyst to the alcohol... 

Mass Spectrometry Aside from a peak for the molecular ion which is normally easy to pick out aliphatic carboxylic acids undergo a variety of fragmentation processes The dominant fragmentation m aromatic acids corresponds to loss of OH then loss of CO... 

Once formed the tetrahedral intermediate can revert to starting materials by merely reversing the reactions that formed it or it can continue onward to products In the sec ond stage of ester hydrolysis the tetrahedral intermediate dissociates to an alcohol and a carboxylic acid In step 4 of Figure 20 4 protonation of the tetrahedral intermediate at Its alkoxy oxygen gives a new oxonium ion which loses a molecule of alcohol m step 5 Along with the alcohol the protonated form of the carboxylic acid arises by dissocia tion of the tetrahedral intermediate Its deprotonation m step 6 completes the process... 

In base the carboxylic acid is deprotonated giving a carboxylate ion... 

Step 6 Proton transfer processes yielding ammonium ion and the carboxylic acid ... 

In base the tetrahedral intermediate is formed m a manner analogous to that pro posed for ester saponification Steps 1 and 2 m Figure 20 8 show the formation of the tetrahedral intermediate m the basic hydrolysis of amides In step 3 the basic ammo group of the tetrahedral intermediate abstracts a proton from water and m step 4 the derived ammonium ion dissociates Conversion of the carboxylic acid to its corresponding carboxylate anion m step 5 completes the process and renders the overall reaction irreversible... 

Nitriles are classified as carboxylic acid derivafives because fhey are convened fo car boxylic acids on hydrolysis The condifions required are similar fo fhose for fhe hydrol ysis of amides namely healing m aqueous acid or base for several hours Like fhe hydrolysis of amides nilrile hydrolysis is irreversible m fhe presence of acids or bases Acid hydrolysis yields ammonium ion and a carboxylic acid... 

In aqueous base hydroxide ion abslracls a proton from Ihe carboxylic acid Isolalmg Ihe acid requires a subsequenl acidilicalion step... 

Mass Spectrometry A prominent peak m the mass spectra of most carboxylic acid derivatives corresponds to an acyhum ion derived by cleavage of the bond to the car bonyl group... 

Section 20 17 Like ester hydrolysis amide hydrolysis can be achieved m either aque ous acid or aqueous base The process is irreversible m both media In base the carboxylic acid is converted to the carboxylate anion m acid the amine is protonated to an ammonium ion... 

Section 21 7 The malonic ester synthesis is related to the acetoacetic ester synthesis Alkyl halides (RX) are converted to carboxylic acids of the type RCH2COOH by reaction with the enolate ion derived from diethyl mal onate followed by saponification and decarboxylation... 

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