Acid, organic

Organic acids can be separated by TLC under various sets of conditions. According to Braun and Geenen [11], it is convenient to prepare a 2% solution of the ammonium salts of the acids in ethanol-water (1 + 1) and to apply 2 mm (= 40 [xg). A selection is given below of the adsorbent layers and corresponding solvents which have been tried out so far  

Benzene-methanol-acetic acid (79 + 14 + 7) chamber saturation 110 min time of run [71]. 

Benzene-dioxan-acetic acid (75.6 + 21 + 3.4) separates like II [71]. 

Kieselguhr layers, impregnated with polyethylene glycol [45, 46] 

Diisopropyl ether-formic acid-water (90 + 7 -f 3), saturated with polyethylene glycol M 1000 use of the M 4000 gives rise to small deviations. 

Organic acids are toxic and corrosive. Corrosivity is a form of toxicity to the tissues that the acid contacts. However, the organic acids have other toxic effects. Formic acid is corrosive to skin and tissue. It has a TLV of 5 ppm in air and an IDLH of 30 ppm. Pure acetic acid is toxic by ingestion and inhalation. It is a strong irritant 

A wide variety of toxic liquids and solids do not fit neatly into any of the families discussed so far. Some of the most dangerous and more common ones will be listed here, but this will, by no means, be a comprehensive listing. The intent is to foster familiarity with the many different types of toxic chemicals that may be encountered in the real world, both in transportation and fixed facilities. The chemicals presented will be drawn from the DOT Hazardous Materials Tables and the NFPA Hazardous Chemicals Data listing. 

7 ppm in air, and the IDLH is 50 ppm. The target organs are the central nervous system, cardiovascular system, kidneys, and liver. The four-digit UN identification number is 1051 for anhydrous (without water) and 1614 when it is absorbed in a porous material. The NFPA 704 designation is health 4, flammability 4, and reactivity 

Methyl isocyanate (MIC), CH3NCO, is a colorless liquid. It is water-reactive, with a specific gravity of 0.96, which is lighter than water. This is the chemical that was released in Bhopal, India, that killed over 3000 people in 1984. Methyl isocyanate is toxic by skin absorption and a strong irritant. The TLV is 0.02 ppm in air. 

Organic acids frequently occur in polluted water, sometimes in considerable concentrations, e.g. in leakage water from rubbish tips, household and 

Apart from inorganic anions, a number of organic anions can also be separated with a conventional anion exchanger. Interferences are possible because real-world samples often contain both inorganic and organic anions. 

Under standard conditions (0.0028 mol/L NaHC03 + 0.0022 mol/L Na2C03) benzoate exhibits only a small retention in an IonPac AS4 separator column. Therefore, in- 

It is generally observed that the order of elution is aliphatic monocarboxylic acids, followed by aromatic monocarboxylic acids, followed by aliphatic dicarboxylic acids. Fig, 3-86, in which the retention behavior of aliphatic dicarboxylic acids is compared with that of inorganic anions, reveals that compounds such as succinic acid, malonic acid, maleic acid, and tartaric acid elute in the retention volume of nitrate and sulfate. 

A sufficient separation of all these compounds, therefore, is only achieved by using two AS4 columns in series. However, the separation of the two stereoisomers, maleic acid and fumaric acid, is much easier. It is obtained under standard conditions and is shown in Fig. 3-87. In contrast to monocarboxylic acids, the retention of aliphatic dicarboxylic acids increases with decreasing pK value. The corresponding data are summarized in Table 3-20. This finding is explained by the charge-stabilizing effect exerted by the +1-effect of the methylene groups which decreases from succinic acid to oxalic acid  

The presence of additional hydroxide groups at the dicarboxylic acid, as in malic and tartaric acid, increases the acidic character and, thus, the retention (Table 3-21). A corresponding chromatogram is shown in Fig. 3-88. However, a separation of malic acid (monohydroxysuccinic acid) and malonic acid is not possible under these conditions, while tartronic acid (hydroxymalonic acid) exhibits a significantly higher retention. 

The organic acids maleic acid and fumaric add are cis-trans or Z- isomers (see diagram below), while cinnamaldehyde—responsible for the odour of cinnamon—occurs in the trans or form only. 

Organic acids are of such widespread occurrence that they are not strictly secondary metabolites in fact many occur during the citric 

Chiral comes from the Greek word for hand—it refers to the property whereby the right hand is a mirror image of the left hand. 

Monobasic adds contain a single carboxyl group (COOH). They include the fatty acids as well as isovaleric add, a sedative principle found in Valeriana officinalis and Huntulus lupulus. One of the most important in this group is acetic add, the main constituent in vinegar. Acetic acid is the precnrsor of lipids as well as some essential oils and alkaloids. 

Polybasic acids contain two or more carboxyl gronps and generally have a slight laxative effect. They include oxalic, sucdnic and fumaric acids, the last one occurring in Fumaria officinalis. 

Citric acid makes up almost 85% of the total volume of the organic acid market, ft was first described in 1784 when isolated from lemon juice. In 1917, it was discovered that certain fungi accumulate citric acid. In 1923, the first US commercial plant was built to produce citric acid by fermentation citric acid is now used mainly in soft drinks, desserts, jams, jellies, candies, wines and frozen fruits. 

Lactic acid, initially produced in 1880, was the first organic acid made industrially by fermentation of a carbohydrate. Nowadays it is made both by fermentation and by chemical synthesis. About 85% of the use of lactic acid is in food and food-related applications, with some use in the making of emulsifying agents and poly(lactic acid). 

Jordan and Dumbaugh have also measured the heats of ionization of the series of dibasic acids from oxalic to azelaic acid (except suberic acid) and the results are shown in Table 6. Along this series 

Free energies, heats and entropies of ionization of some organic dibasic acids 

The decrease in acid strength from oxalic acid to azelaic (except for succinic acid) is thus mainly an entropy effect once more. Presumably with the lower acids oxalic and malonic there is some steric restriction, due to the closeness of the negative charges, which reduces the extent of electrorestriction of water molecules. With increasing separation of the charges, as the series is ascended, the entropy losses on ionization will be increased. 

BOND STRENGTHS IN SILICON, PHOSPHORUS AND SULPHUR C03IP0LNDS 

Two main causes hare been suggentf d to accoimt for bond strength-oiling in eovnlent molecules. The first is that electronegativity difference s between the atoms A and B, in a bond A-—B, reflect a certain amount of polar character of the bond. This means 

The solubility of aromatics in sulfuric acid can be significantly improved by using a cosolvent, preferably an organic acid since this is completely removed in the work-up procedure. Acetic acid is the best cosolvent (60JCS3301), and trifluoroacetic acid has also been used [74JCS(P2)394], 

Compounds containing the group -OH constitute the largest category of acids, especially if the organic acids (discussed separately farther on) are included. M-OH compounds also include many of the most common bases. 

Whether a compound of the general type M-O-H will act as an acid or a base depends in the final analysis on the relative strengths of the M-O and the O-H bonds. If the bond is weaker, then the -OH part will tend to retain its individuality and will act as a hydroxide ion. If the O-H bond is weaker, the MO- part of the molecule will remain intact and the substance will be acidic. 

As one moves into Group 2 of the periodic table the M-OH compounds become less soluble thus a saturated solution of Ca(OH)2 is only weakly alkaline. Hydroxides of the metallic elements of the p-block and of the transition metals are so insoluble that their solutions are not alkaline at all. Nevertheless these solids dissolve readily in acidic solutions to yield a salt plus water, so they are formally bases. 

The carboxyl group -CO(OH) is the characteristic functional group of the organic acids. The acidity of the carboxylic hydrogen atom is due almost entirely to electron-withdrawal by the non-hydroxylic oxygen atom if it were not present, we would have an alcohol -COH whose acidity is smaller even than that of H2O. 

This partial electron withdrawal from one atom can affect not only a neighboring atom, but that atom s neighbor as well. Thus the strength of a carboxylic acid will be affected by the bonding environment of the carbon atom to which it is connected. This propagation of partial electron withdrawal through several adjacent atoms is known as the inductive effect) and is extremely important in organic chemistry. A very 

8 mmol/L Na2C03 flow rate 1 mL/min detection suppressed conductivity injection 50 pL solute concentrations 3 mg/L fluoride (1), 40 mg/L acetic acid (2), 20 mg/L glycolic acid (3), 10 mg/L a-hydroxyiso-caproic acid (4), 20 mg/L each of formic acid (5), oxamic acid (6), methanesulfonic acid (7), amidosulfonic acid (8), and a-ketoisocaproic acid (9). 

The following elution order is generally observed aliphatic monocarboxylic acids, followed by aromatic monocarboxylic acids, followed by aliphatic dicarbo-xylic acids. In Fig. 3-125, the retention behavior of aliphatic dicarboxylic acids is 

This finding is expkined by the charge-stabilizing effect exerted by the -hI-effect of the methylene groups which decreases from succinic add to oxahc add  

A composition for dissolving filter-cake deposits left by drilling mud in wellbores is composed of an aqueous solution of citric acid and potassium chloride, alkali metal formate, acid tetraphosphate, alkaline earth chloride, and alkali metal thiophosphate [1012]. 

The composition is useful as an additive for clearing stuck pipe in wellbores and as a fixer spacer for cementing pipe in wellbores. Another use of the composition is as a well stimulation fluid in oil and gas production wells, in which the composition is effective to dissolve filter-cake that blocks pores in the production formation. 

Horizontal completions in unconsolidated formations are being enhanced by a hydrochloric acid (HCl) breaker system for well clean up. Typically, the use of HCl in open-hole environments is avoided because of wellbore stability concerns. However, HCl successfully removes salt fluid loss control materials in wells without noticeable hole collapse [33]. 

These are the second great field of application for aluminum alloys, with the exception of aluminum magnesium alloys. One restriction always applies 

It is possible to carry out such oxidation processes as the conversion of acetaldehyde to acetic acid, or methyl alcohol to formaldehyde in aluminum plants, thus avoiding boiling anhydrous acids. The metal is especially valuable for handling delicate chemicals, which must not acquire metallic taste or color. For these reasons, aluminum has found extensive use in the food, dairy, brewing and fishing industries. 

Neutral salts and aqueous solutions of various acids generally follow the acid action. Aluminum has no apparent action or microbiological processes (i.e., the production of antibiotics by deep-vessel fermentation). Fermentation tanks, as well as various absorbing and extracting units, can be made from aluminum. 

Since aluminum is not attacked by hydrogen sulfide (HjS) solutions, it is used widely as a material in refineries for the handling of hydrocarbons made from sour crudes. In the strongly oxidizing conditions of manufacturing hydrogen peroxide, aluminum is one of the few materials that does not undergo decomposition. 

Steam-heated aluminum castings are used for the melt spinning of nylon and polyester fibers and have been used for storage of raw materials during manufacturing, as well as for storage of acetic acid in cellulose acetate plants. 

This compound does not complex with copper at a low pH (around 2-3) due to protonation of the carboxylate group. Similar to citric acid, this compound cannot compete effectively with hydroxide at high pH either. Thus, these compounds can only be used at intermediate pH values, around 4-7, in order to achieve high metal ligand binding efficiency. In a similar 

The use of oxalic acid as a complexing agent has been investigated using polishing and potentiodynamic studies [54]. Maximum removal rates were observed at pH 3. This is consistent with the fact that oxalic acid (HX) had the maximum concentration of X at pH = 3.00, which causes complexation with the positive copper surface at the acidic pH condition. 

The impact of complexing agents on a metal system in the presence of an oxidizer under various pH conditions can be described in a quantitative format such as a Pourbaix diagram. Fig. 7.9 shows a typical shift in CU-H2O Pourbaix diagram in terms of the stability and the composition of the species due to the 

FIGURE 7.9 Potential-pH diagrams of Cu-glycine-H20 system at two different activities of Cu at the glycine concentration of 0.1 M (from Ref 55). 

The formation of lactic acid and its role as a food preservative were already discussed in connection with food fermentations, where it is produced in small concentrations. It is also possible to isolate it as a neat acid to convert the acid to the corresponding esters. Ethyl and butyl esters are good solvents for polymers and resins. Ethyl lactate, for instance, is used in the electronics industry to remove salts and fat from circuit boards it is also a component in paint strippers. Ethyl and butyl esters are approved food additives. This illustrates their low toxicity. 

Acetic acid is produced by oxidation of ethanol by Acetobacter organisms. It is either used in diluted form as vinegar or distilled to give neat (100 percent pure) acetic acid. For many centuries, acetic acid was produced only via the fermentation route. Since the advancement of the petrochemical industry, it is also produced synthetically, at least for industrial use. 

By changing the fermentation conditions to aerobic, using Aspergillus niger microorganisms, it is possible to produce citric acid from 

Adapted from Easter R A 1988 Acidification of diets for pigs. In Haresign W and Cole D J A (eds) Recent Advances in Animal Nutrition - 1988, London, Butterworth. 

Although the exact modes of action of the acids are not clear, their addition to pig diets has proved beneficial in terms of nutrient digestibility, growth and food conversion efficiency (Table 24.3). This is so particularly for newly weaned pigs, when coupled with good feeding management procedures. 

Formic and propionic acids are more effective than fumaric or citric acids at the same rate of inclusion because the former have a lower molecular weight. Suggested levels of inclusion of acid (kg/torme diet) are formic acid 6-8, propionic acid 8 10, fumaric acid 12-15 and citric acid 20-25, but recommendations vary. 

Compound Whole milk powder Skim milk powder 

Orotic acid as well as total creatinine and uric acid are suitable indicators for the determination of the proportion of milk in foods. The average values for whole-milk and skim-milk powder given in Table 10.21 can serve as reference values. 

Minerals, including trace elements, in milk are compiled in Table 10.22. 

Citric acid (1.8 g/1) is the predominant organic acid in milk. During storage it disappears rapidly as a result of the action of bacteria. Other acids (lactic, acetic) are degradation products of lactose. The occurrence of orotic acid (73 mg/1), an intermediary product in biosynthesis of pyrimidine nucleotides, is specific for milk  

Milk contains all the vitamins in variable amounts (Table 10.23). During processing, the fat-soluble vitamins are retained by the cream, while the water-soluble vitamins remain in skim milk or whey. 

Filamentous fungal fermentation is a cornerstone of bioprocess manufacturing and generates a wide array of products used in the food, enzyme and pharmaceutical industries. Some of the key products for these applications are reviewed here. 

especially Aspergilli, are recognized for their prolific ability to yield a repertoire of organic acids. Conditions that produce an almost quantitative conversion of carbon substrate into acid are exploited in the large-scale manufacture of organic acids. Moreover, many 

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An adequate prediction of multicomponent vapor-liquid equilibria requires an accurate description of the phase equilibria for the binary systems. We have reduced a large body of binary data including a variety of systems containing, for example, alcohols, ethers, ketones, organic acids, water, and hydrocarbons with the UNIQUAC equation. Experience has shown it to do as well as any of the other common models. V7hen all types of mixtures are considered, including partially miscible systems, the... 

Enthalpies are referred to the ideal vapor. The enthalpy of the real vapor is found from zero-pressure heat capacities and from the virial equation of state for non-associated species or, for vapors containing highly dimerized vapors (e.g. organic acids), from the chemical theory of vapor imperfections, as discussed in Chapter 3. For pure components, liquid-phase enthalpies (relative to the ideal vapor) are found from differentiation of the zero-pressure standard-state fugacities these, in turn, are determined from vapor-pressure data, from vapor-phase corrections and liquid-phase densities. If good experimental data are used to determine the standard-state fugacity, the derivative gives enthalpies of liquids to nearly the same precision as that obtained with calorimetric data, and provides reliable heats of vaporization. 

VPLQFT is a computer program for correlating binary vapor-liquid equilibrium (VLE) data at low to moderate pressures. For such binary mixtures, the truncated virial equation of state is used to correct for vapor-phase nonidealities, except for mixtures containing organic acids where the "chemical" theory is used. The Hayden-0 Connell (1975) correlation gives either the second virial coefficients or the dimerization equilibrium constants, as required. 

Subroutine MULLER. MULLER iteratively solves the equilibrium relations and computes the equilibrium vapor composition when organic acids are present. These compositions are used by subroutine PHIS2 to calculate fugacity coefficients by the chemical theory. 

ENERGY parameter DIVIDED BY BOLTXMAN CONSTANT. CONTROL PARAMETER NORMALLY ZERO WHICH IS SET EQUAL TO 1 WHEN ORGANIC ACIDS ARE PRESENT (ANY ETA( IJ).GE.4.S ). 

ERROR FLAG INDICATING FAILURE OF SUBROUTINE MULLER TO CONVERGE lUSED ONLY WHEN ORGANIC ACIDS PRESENT CNTRL VARIABLE... 

IF BINARY SYSTEM CONTAINS NO ORGANIC ACIDS. THE SECOND VIRTAL coefficients ARE USED IN A VOLUME EXPLICIT EQUATION OF STATE TO CALCULATE THE FUGACITY COEFFICIENTS. FOR ORGANIC ACIDS FUGACITY COEFFICIENTS ARE PREDICTED FROM THE CHEMICAL THEORY FOR NQN-IOEALITY WITH EQUILIBRIUM CONSTANTS OBTAINED from METASTABLE. BOUND. ANO CHEMICAL CONTRIBUTIONS TO THE SECOND VIRIAL COEFFICIENTS. 

If the mixture includes organic acids, the equations of Hayden and O Connell yield equilibrium constants for all possible dimerization reactions. 

Typical organic acids contain the --C(0)0H group, but many other acid groupings, e.g. the sulphonic -S(0)20H give acidic properties to organic compounds. Phenols have acidic properties and are classified with enols as pseudo-acids. 

Oxidation first produces soluble oxygenated compounds of molecular weights between 500 and 3000 that increase the viscosity of oil then they polymerize, precipitate, and form deposits. Oxidation also causes formation of low molecular weight organic acids which are very corrosive to metals. 

In the former, it gives precipitates with halides (except the fluoride), cyanides, thiocyanates, chromates(VI), phosphate(V), and most ions of organic acids. The silver salts of organic acids are obtained as white precipitates on adding silver nitrate to a neutral solution of the acid. These silver salts on ignition leave silver. When this reaction is carried out quantitatively, it provides a means of determining the basicity of the acid... 

Checking the Purification. The purity of the dry re-crystallised material must now be determined, as it is possible that repeated recrystallisation may be necessary to obtain the pure material. The purity is therefore checked by a melting-point determination, and the recrystallisation must be repeated until a sharp melting-point is obtained. Should the compound have no well-defined melting-point e.g.y the salt of an organic acid or base), it must be analysed for one suitable component element, until its analysis agrees closely with that theoretically required. 

This conversion cannot easily be carried out on a semi-micro scale by ordinary chemical means. Liberation of an acid from one of its salts by dil. H SO is feasible when the organic acid is insoluble in water (e.g. an aromatic acid) or... 

Aminoazobenzene is a very weak base, and consequently it will not form salts with weak organic acids, such as acetic acid, although it will do so with the strong mineral acids, such as hydrochloric acid. Aminoazobenzene is a yellowish-brown compound, whilst the hydrochloride is steel blue. The colour of the latter is presumably due to the addition of the proton to the phenyl-N-atom, the cation thus having benzenoid and quinonoid forms ... 

Salts of many organic acids give precipitates with mercuric chloride solution. hut these are in uallv soluble in dfl. HCl. 

In the separations (2) and (3) above, it is often advisable to dissolve the original mixture in a water-insoluble solvent. Select a solvent which will dissolve the entire mixture, and then shake the solution with either (i) dil. NaOH or (ii) dil. HCl. Separate the aqueous layer, and to it add either (i) dil. HCl or (ii) dil. NaOH to liberate the organic acid or the organic base, as the case may be. The non-aqueous layer now contains the neutral component. Reextract this layer with either (i) dil. NaOH or (ii) dil. HCl to ensure removal of traces of the non-neutral component. 

Residual solution. Make just acid with dil. HjSO, and then just alkaline to litmus-paper with Na,COs solution. Extract phenol with ether, distil off latter and identify the residue. Identify the organic acid in the aqueous layer, as in (A) (ii). 

If RCOOH is a comparatively simple organic acid and R OH a monohydric alcohol then the enzyme is called an esterase. Examples of such esters are ethyl butyrate, C3H7COOC2H5, and ethyl mandelate, CeHjCH(OH)COOC2Hj. 

Pancreatic lipase pancreas fats and other organic esters organic acid and alcohol (often gly ceroi) 7-0... 

Organic acids Anhydrous sodium, magnesium or calcium sulphate. 

Dilute sodium hydroxide solution (and also sodium carbonate solution and sodium bicarbonate solution) can be employed for the removal of an organic acid from its solution in an organic solvent, or for the removal of acidic impurities present in a water-insoluble solid or liquid. The extraction is based upon the fact that the sodium salt of the acid is soluble in water or in dilute alkali, but is insoluble in the organic solvent. Similarly, a sparingly soluble phenol, e.g., p-naphthol, CioH,.OH, may be removed from its solution in an organic solvent by treatment with sodium hydroxide solution. 

S-Benzyl-wo-thiuronium chloride (S-benzyl-iao-thiourea hydrochloride) reacts with the alkali metal salts of organic acids to produce crystalline S benzyl-MO-thiuronium salts ... 

It is frequently advisable in the routine examination of an ester, and before any derivatives are considered, to determine the saponification equivalent of the ester. In order to ensure that complete hydrolysis takes place in a comparatively short time, the quantitative saponi fication is conducted with a standardised alcoholic solution of caustic alkali—preferably potassium hydroxide since the potassium salts of organic acids are usuaUy more soluble than the sodium salts. A knowledge of the b.p. and the saponification equivalent of the unknown ester would provide the basis for a fairly accurate approximation of the size of the ester molecule. It must, however, be borne in mind that certain structures may effect the values of the equivalent thus aliphatic halo genated esters may consume alkali because of hydrolysis of part of the halogen during the determination, nitro esters may be reduced by the alkaline hydrolysis medium, etc. 

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