Carboxylic acid salt formation

The interaction of Ca2+ with pectins is discussed. The role of carboxylic acid salt formation and the degree of polymerization are first considered in terms of electrostatic and/or cooperative specific interactions. Then the effect of the degree of esterification and that of the pattern of carboxylic group distribution are discussed pectin esterase forms blocks which behave as fully hydrolyzed polymers and favor aggregation. Finally, the role of the calcium addition on the degree of aggregation was established. All the data show the important role of molecular structure of the pectins on calcium interactions. 

Introduction. The object of this experiment is to illustrate a number of general reactions of carboxylic acids. Salt formation is a characteristic property of the carboxyl group. The salts of the alkali metals as a rule are soluble. The higher, sparingly soluble, fatty acids form salts which give colloidal dispersions. The soluble salts are prepared by neutralization of the acid with alkali, or by boiling with an excess of the metallic carbonate and evaporating the solution. 

The carbanionic species thus formed is protonated to give the final product 3. The use of an alkoxide as base leads to formation of a carboxylic ester as rearrangement product use of a hydroxide will lead to formation of a carboxylic acid salt ... 

Unsymmetrical as well as symmetrical anhydrides are often prepared by the treatment of an acyl halide with a carboxylic acid salt. The compound C0CI2 has been used as a catalyst. If a metallic salt is used, Na , K , or Ag are the most common cations, but more often pyridine or another tertiary amine is added to the free acid and the salt thus formed is treated with the acyl halide. Mixed formic anhydrides are prepared from sodium formate and an aryl halide, by use of a solid-phase copolymer of pyridine-l-oxide. Symmetrical anhydrides can be prepared by reaction of the acyl halide with aqueous NaOH or NaHCOa under phase-transfer conditions, or with sodium bicarbonate with ultrasound. 

The reaction of sodium salt of carboxylic acid (sodium formate) with acid chloride. 

The first step in lithium aluminum hydride reduction of carboxylic acids is formation of a complex aluminum salt of the acid and hydrogen ... 

Barnett and Sohn (12, 13, see also 14) have discovered that the iodolactoni-zation of b,r-unsaturated carboxylic acid salts 37 yield, under kinetically controlled conditions, the Y-iodo-B-lactones 39 in preference to the more stable B-iodo-Y-lactones l. Similar results were obtained in the course of the bromolactonization reaction. Thus, here again, the formation of a four-membered ring is more facile than that of a five-membered ring. This can be rationalized on the basis of Stork s analysis, i.e. the internal opening by the carboxylate anion of the three-membered ring iodonium ion (or bromonium) 38 39 is preferred over the other mode of opening 40 41 for stereoelectronic reason. 

Fig. 13.10. Formation of carboxylate enolates ("carboxylic acid dianions") by reaction of carboxylic acid salts with strong bases.

Potassium formate and a few other carboxylic acid salts are one result of the breakdown of the DEA molecule. These salts are benign at low concentrations. However, when at concentrations of 5% or more, they interfere with operations by altering the physical properties of the carbonate solution. Some amine degradation compounds are even considered to be corrosion accelerators. They may solubilize iron, keep it in solution and prevent it from forming the passivation layer on the pipe and equipment. UOP s ACT-1 activator is an amine that contains a more-stable molecule that is more resistant to degradation206. 

Nomenclature of Carboxylic Acid Salts Salts of carboxylic acids are named simply by naming the cation, then naming the carboxylate ion by replacing the -ic acid part of the acid name with -ate. The preceding example shows that sodium hydroxide reacts with acetic acid to form sodium acetate. The following examples show the formation and nomenclature of some other salts ... 

Reactions of Carboxylic Acids 3.16.2.1 Acidity Salt Formation... 

Furthermore, If carboxylic acid salts are generated in the reaction, these can react with the 5-carbonyl of an NCA to generate a carboxylic acld-carboxyllc acid chain end. As has already been shown by Mlwa and Stahman (64), such structures have acylatlng capability. The formation of hydantoln acetic acid derivatives from NCA s in DMF solution Is a rather favorable process (65) and this Is therefore also a likely source of acylatlng capability In the systems studied by Pegglon. 

As stated above, Knoevenagel condensations can occur on catalysts combining acidic and basic sites. A well-known system is the combination of an amine and its carboxylic acid salt. Such catalysts seem to activate the carbonyl substrates, usually by imine or enamine formation, and the activated substrate is subsequently activated by protonation. The base assists the deprotonation of a methylene-active compound, forming a carbanion, followed by nucleophilic attack on the proto-nated imine (Scheme 3A). 

Earlier methods of converting /3y-unsaturated carboxylic acid salts into y-lactones by treatment with iodine have now been shown to involve initial formation of /S-iodo-lactones (41), and a modified procedure has... 

The most common chemical transformations of carboxylic acids in food are reactions caused by the cleavage of the O-H bond of the carboxylic group (salt formation), esterification, decarboxylation and reactions ongoing on the hydrocarbon residue. 

The cmc of bile salts is strongly influenced by its structure the trihydroxy cholanic acids have a higher cmc than the less hydrophilic dihydroxy derivatives. As expected, the pH of solutions of these carboxylic acid salts has an influence on micelle formation. At sufficiently low pH, bile acids which are sparingly soluble will be precipitated from solution, initially being incorporated or solubilized in the existing micelles. The pH at which precipitation occurs, on saturation of the micellar system, is generally about one pH unit higher than the pK of the bile acid. 

Complexation by the amino acids prior to polymerization alters the kinetics of chain propagation, which is consistent with the presumed catalytic role of the metal in these reactions (57), but amino acid salt formation has further implications from the standpoint of chemical evolution the polymerizations may be performed at temperatures that more closely resemble those found on the Earth s surface. Amino acids form salts with carboxylic acids (e.g. formic and acetic), and these salts tend to melt at lower temperatures than the corresponding amino acid. For example, a nrixtuie of the formate salts of glutamic acid and glycine (analogous to the first Harada-Fox melt, reference 27) fuses at 150°C, and the yield of polymer after foiu hours exceeds the typical yield obtained with the corresponding melt of amino acids. This trend towards lower melting points continues as one increases the number of amino acids in the mixture as a mixture of their formate salt, the Fox-Harada mixture of 16 amino acids (cf. reference 28) is a viscous paste at room temperature. The formation of peptides and ultimately precipitation of macromolecules from a concentrated aqueous solution of amino acid salts can be effected at 50°C. 

Scheme 6.18 End-capping the living poly(2-oxazoline) chains by the addition of carboxylic acid salts (a) or by the in situ formation of the carboxylic acids salts from the acid and 2,6-dimethylpyridine (b).

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