Concentration of carboxylic acid

The concentration of carboxylic acid sites is proportional to the concentration of hydroxyl sites. Equations 9 and H may be solved, yielding... 

Cathode Cathode potential Electrolyte (V) Quantity of electricity (C) Current efficiency (%) Concentration of carboxylic acid ( x 10 3 mol/dm3) ... 

The key to a controlled molecular weight build-up, which leads to the control of product properties such as glass transition temperature and melt viscosity, is the use of a molar excess of diisopropanolamine as a chain stopper. Thus, as a first step in the synthesis process, the cyclic anhydride is dosed slowly to an excess of amine to accommodate the exothermic reaction and prevent unwanted side reactions such as double acylation of diisopropanolamine. HPLC analysis has shown that the reaction mixture after the exothermic reaction is quite complex. Although the main component is the expected acid-diol, unreacted amine and amine salts are still present and small oligomers already formed. In the absence of any catalyst, a further increase of reaction temperature to 140-180°C leads to a rapid polycondensation. The expected amount of water is distilled (under vacuum, if required) from the hot polymer melt in approximately 2-6 h depending on the anhydride used. At the end of the synthesis the concentration of carboxylic acid groups value reaches the desired low level. 

Khwaja, H. A., "Atmospheric Concentrations of Carboxylic Acids and Related Compounds at a Semiurban Site, Atmos. Environ., 29, 127-139(1995). 

Copolymer particles can also be prepared from HIPEs [159]. Thus, a HIPE dispersed phase consisting of styrene and methacrylic acid was polymerised to give copolymers. The surface concentration of carboxylic acid groups increased linearly with concentration of methacrylic acid in the feed. The small amount of water present in the concentrated emulsion, relative to conventional emulsion polymerisation, reduces the loss of methacrylic acid, which is highly water-soluble. 

Total acidities and concentrations of carboxylic acid groups were measured by what are now well-established procedures (2, 8). 

Quantification of metal ion binding and the determination of the nature of the binding sites are extremely difficult for humic acid because of its polymeric (molar masses ca. 5 x 104) and heterogeneous nature. The results of such attempts are often contradictory.15,16 Frequently a 1 1 metal humic acid ratio is assumed for the complexes, a very surprising assumption for such large molecules with high concentrations of carboxylic acids. There is evidence for other stoichiometries, including... 

Both, TFE and VDF may be copolymerized with suitable comonomers in order to obtain macromolecular materials with improved end-use properties. One fluori-nated monomer that was copolymerized under mild conditions (308 K and 9-11 MPa) was perfluoropropyl-vinylether (PPVE) (CF3CF2CF2OCF=CF2). The copolymer was obtained in the form of a free-flowing powder, with almost quantitative yields moreover, its composition could be altered by changing the molar ratio of the comonomers in the feed. Interestingly, chains were synthesized with molecular weights greater than that of the commercial product with a concentration of carboxylic acid or acid fluoride end groups similar to those detected in polymers prepared in CFCs [101],... 

In an earlier paper (22) studies on a commercial latex as a model system indicated clearly no difference in F/T results when NH3 or NaOH was used to adjust pH. It is now observed that at the minimum acid levels, the quantity of alkali and not pH is the controlling factor. Thus, Table IV shows that less NaOH than NH3 is required to obtain pH 9.5, but an equal number of equivalents is necessary to achieve F/T stability. Moreover, as might have been expected, if more than the minimum acid content is present, F/T stability can be obtained at a lower pH so long as an equivalent amount of alkali is added—i.e., as long as the same concentration of carboxylic acids are converted to carboxylate ions. 

As shown in Figure 8a and b, the concentrations of carboxylic acids are also influenced by fhe presence of Fe " " ions. For the Fe-assisted PC reaction, MeAc and FuAc concentrations slightly supersede the concentration for the unpromoted PC runs in the middle of the experiment and decrease more rapidly later. Similar trends were observed for OxAc and FoAc. 

The Kdbe dimerizatiMi is believed to be favored by the following reaction cmditions high concentration of carboxylic acid, low pH value, absence of foreign anions, high cunent density and use of a plati-num anode. 

Many research studies have been carried out to examine the possibilities for conversion of biomass feedstocks to liquid products by direct thermochemical treatment. These studies include the treatment of aqueous and nonaqueous slurries of wood particles with different reactants and catalysts at elevated temperatures and pressures, and the pyrolysis of wood under conditions that maximize liquid yields (Chapter 8). The prime objective was to develop processes for production of liquid fuels and not chemicals. The resulting products are generally acidic and contain high concentrations of carboxylic acids, phenolic compounds, and heterocyclic oxygen and alicyclic oxygenated compounds. With only a few exceptions, the products contain low concentrations of BTX. 

It is possible to extend the middle phase region by increasing the concentration of carboxylic acid, coupled with an increase in alcohol concentration. The phase behavior of a mixed microemulsion system containing 5 gm/dl TRS 10—410, 1.5 gm/dl octanoic acid and 8 gm/dl IBA at 22°C is shown in Figure 17. Between 1.5 and 4 gm/dl NaCl, if only NaOH concentration is varied then upper - middle - lower phase transitions occur, apparently due to an increase in the ionization of the surfactant. Extension of salinity and NaOH concentrations in Figure 17 is expected to show upper - middle - lower + middle, and other phase transitions as observed in the oleic acid system (4). 

Figure 1. Concentration of carboxylic acid and retention of the PVA membrane ...

Low concentrations of carboxylic acids. Acetic acid and formic acids have boiling points near (formic) or above (acetic) water. Acetic acid does not form an azeotrope and the boiling point of the formic acid-water azeotrope is 107 °C. So, LLE is a viable option to extract these acids from water. 

Problem 5.5 A nonstoichiometric mixture of a dicarboxylic acid and a glycol having 20 mol % excess of the latter and a carboxyl group concentration of 5.64 mol/kg, was polymerized to about 80% esterification of the carboxylic acid groups. The mixture was then further polymerized in the presence of a strong acid catalyst which yielded the following data of the concentration of carboxylic acid groups in the mixture versus reaction time. 

Table I. MAXIMUM REPORTED CONCENTRATIONS OF CARBOXYLIC ACID ANIONS IN PRODUCED FORMATION WATERS...

A comparison of the NEXAFS spectra of isolated humic substances and pristine soil organic molecules for a pine ultisol indicate that the undisturbed soil samples indicate much greater concentrations of carboxylic acids when compared to that of aromatic C (Fig. 13, details discussed later). Similar behavior is observed for N, P, S and Cl functional groups (discussed later). These studies suggest that chemical extraction procedures used in the isolation of humic substances preferentially concentrate the aromatic C over the carboxylic groups. 

In 1999, however, the group of Thomas reported a series of selective oxidations of alkanes in which the redox metals were retained within the framework by working under solvent-free conditions and at sufficiently low conversions (<10%) that only low concentrations of carboxylic acids were present. Under these conditions, and by judicious choice of the framework type of the aluminophosphate and the substituted metal, a family of selective... 

The concentration of carboxylic acid groups in the membrane is determined according to the Langmuir relation. 

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