Esters solubility

Lippi et. al (87) and Dirstine (88) circumvented titration by converting the liberated fatty acids into copper salts, which after extraction in chloroform are reacted with diethyldithio-carbamate to form a colored complex which is measured photometrically. While the end point appears to be more sensitive than the pH end point determination, the advantages are outweighed by the additional steps of solvent extraction, centrifugation and incomplete extraction when low concentrations of copper salts are present. Other substrates used for the measurement of lipase activity have been tributyrin ( ), phenyl laurate (90), p-nit ro-pheny1-stearate and 3-naphthyl laurate (91). It has been shown that these substrates are hydrolyzed by esterases and thus lack specificity for lipase. Studies on patients with pancreatitis indicate olive oil emulsion is definitely superior to water soluble esters as substrates for measuring serum lipase activity. 

In the liquid acid-catalyzed processes, the hydrocarbon phase and the acid phase are only slightly soluble in each other in the two-phase stirred reactor, the hydrocarbon phase is dispersed as droplets in the continuous acid phase. The reaction takes place at or close to the interface between the hydrocarbon and the acid phase. The overall reaction rate depends on the area of the interface. Larger interfacial areas promote more rapid alkylation reactions and generally result in higher quality products. The alkene is transported through the hydrocarbon phase to the interface, and, upon contact with the acid, forms an acid-soluble ester, which slowly decomposes in the acid phase to give a solvated... 

In contrast to the a and AS parameters, log k was not related to lipo-philicity, despite the unreactivity of the poorly water-soluble esters. 

In nonpolar media, on the other hand, the newly formed oxonium ion will either quickly convert to the corresponding soluble ester, or it will precipitate, since monomeric or short-chain oligomeric oxonium salts have low solubility in such media. The soluble ester is structurally similar to the initiator and may add another THF molecule. The resulting oxonium ion will again revert to the ester or precipitate. In fact, precipitates are generally observed durina the eairly stages of polymerization in media of low polarity. They have been isolated and characterized as monomeric or short chain oligomeric oxonium salts (17). 

Glucocorticoids are available in a wide range of preparations, so that they can be administered parenterally, orally, topically, or by inhalation. Obviously the oral route is preferred for prolonged therapy. However, parenteral administration is required in certain circumstances. Intramuscular injection of a water-soluble ester (phosphate or succinate) formed by esterification of the C21 steroid alcohol produces peak plasma steroid levels within 1 hour. Such preparations are useful in emergencies. By contrast, acetate and tertiary butylacetate esters must be injected locally as suspensions and are slowly absorbed from the injection site, which prolongs their effectiveness to approximately 8 hours. 

Sodium methoxide in methanol, often with chloroform as cosolvent, has customarily been the basic reagent employed. Less frequently, particularly with water-soluble esters, sodium or potassium hydroxide in aqueous solution has been used. Generally, an excess of the basic reagent is taken, except where the possibility of epoxide migration arises (see p. 127). In the latter situation, only a limited excess of reagent is used, at low temperature, or, alternatively, the... 

Classically, lipases hydrolyse ester bonds in emulsified esters, i.e. at a water/oil interface, although some may have limited activity on soluble esters they are usually activated by blood serum albumin and Ca2 + which bind free fatty acids, which are inhibitory. Little lipolysis normally occurs in... 

Table 1.1 shows the proportion of the several constituents found in the dissolved, diffusible state. Actually, phosphate is present in five classes of compounds inorganic dissolved, inorganic colloidal, water-soluble esters, ester-bound in caseins, and lipid. These can be determined by making the following analyses ... 

Arsenious oxide is soluble in a number of organic liquids. Thus, 100 parts of absolute alcohol dissolve at 15° C. 0-025 part, and at boiling point 3-402 parts of the octahedral form. The solubility is increased by the addition of water. The vitreous modification dissolves to the extent of 1-060 parts per 100 at 15° C. and addition of water decreases the solubility. Esters of arsenious acid may be obtained by heating, with stirring, a mixture of the oxide and an alcohol in the presence of a hydrocarbon such as benzene, toluene or xylene.7... 

Colla, L., E. DeClercq, R. Busson, and H. Vanderhaeghe. 1983. Synthesis and antiviral activity of water-soluble esters of acyclovir [9-[(2-hydroxyehtoxy)methyl]guanirvA]Med. Chem26 602-604. 

D. R. Dodds, Process for the preparation of chiral propanoic adds via enantioselective enzymic hydrolysis of their water-soluble esters, PCT Int. Appl. WO 8909765,1989. 

Organic-soluble ester is brought to the reactor with the organic feed solution and freely permeates the immobilized organic liquid membrane to reach the catalyst enzyme. The ester is then hydrolyzed. The alcohol and acid products of hydrolysis are much more polar than the ester and, as such, are water soluble but relatively organic insoluble. These products diffuse to the aqueous permeate solution. The membrane both provides an active site for the reaction and separates the products of reaction from the feed [38]. 

Acyl chloride-functionalized SWCNTs are also susceptible to reactions with other nucleophiles, e.g. alcohols. Haddorfs group reported the preparation of soluble ester-functionalized carbon nanotubes SWCNT-COO(CH2)17CH3 (Fig. 1.6a) obtained by esterification with octadecanol [134]. The syntheses of soluble polymer-bound and dendritic ester-functionalized SWCNTs have been reported by Riggs et al. by attaching poly(vinyl acetate-co-vinyl alcohol) (Fig. 1.6b) [135] and hydrophilic and lipophilic dendron-type benzyl alcohols [119], respectively, to SWCNT-COC1 (Fig. 1.6c). These functional groups could be removed under basic and acidic hydrolysis conditions and thus additional evidence for the nature of the attachment was provided [119, 136]. 

The natural substrates for lipases are triglycerides but, because of the complexity of these and the fact that they seldom contain a chromophore or other label to enable ready detection of the products, several synthetic substrates have been developed. These enable different detection techniques such as spectrophotometry, fluorimetry, chromatography, or radiometry to be used. It is important to note that, by definition, true lipases are active only on water-insoluble esters while esterases cleave only water-soluble esters (Jaeger et al., 1994). Thus, it is important that methods used for milk and milk products use substrates, which detect true lipase but not esterases as lipases play a major role in the hydrolysis of milk fat, while the role of esterases is considered insignificant (McKay et al., 1995). 

Hydrocortisone is readily absorbed from the gastrointestinal tract, and peak blood concentrations are attained in about 1 h. The plasma half-life is about 100 min, and hydrocortisone is more than 90% bound to plasma proteins. Following intramuscular injection, absorption of the water-soluble sodium phosphate and sodium succinate ester is rapid, whilst absorption of free alcohol or lipid-soluble esters is slower. 

Subcellular localization studies have identified P-450-dependent monooxygenase activity in adult hairless mice sebaceous glands. Phase II conjugation pathways have also been identified in skin. Extracellular enzymes including esterases are present in skin, which has been utilized to formulate lipid-soluble ester prodrugs which penetrate the stratum corneum and then are cleaved to release active drug into the systemic circulation. Finally, co-administration of enzyme inducers and inhibitors modulate cutaneous biotransformation and thus alter the systemic toxicity profile. These metabolic interactions that occur in skin have attracted a great deal of research attention and clearly illustrate that skin is more than a passive barrier to toxin absorption. 

Solubility Esters, ketones, Ketones ether alcohols, glycol ethers Ketones, esters Alcohols, aromatic hydrocarbons... 

During alkylation a small quantity of reactants and impurities remain trapped in the acid phase as acid soluble esters. The term ester, as enq)loyed here, refers to any compound formed by the replacement of at least one of the acid-hydrogen by a hydrocarbon... 

Cyclopentolate was introduced into clinical practice in 1951. A stable water-soluble ester with a pKa of 8.4, cyclopentolate is primarily in an ionized state at physiologic pH. It is commercially available in 0.5%, 1%, and 2% solutions (see Table 9-2). 

Sodium, potassium, and alkylamine salts are commonly formulated as aqueous solutions, while the less water soluble esters are applied as emulsions. Low molecular weight esters are more volatile than the acids, salts, or long-chain esters. 

As previously mentioned, the triglycerides found in biomass are esters of the triol, glycerol, and fatty acids (Fig. 3.6). These water-insoluble, oil-soluble esters are common in many biomass species, especially the oilseed crops, but the concentrations are small compared to those of the polysaccharides and lignins. Many saturated fatty acids have been identified as constituents of the lipids. Surprisingly, almost all the fatty acids that have been found in natural lipids are straight-chain acids containing an even number of carbon atoms. Most lipids in biomass are esters of two or three fatty acids, the most common of which are lauric (Cn), myristic (Cu), palmitic (Cia), oleic (Cis), and linoleic (Cis) acids. Palmitic acid is of widest occurrence and is the major constituent (35 to 45%) of the fatty acids of palm oil. Lauric acid is the most abundant fatty acid of palm-kemel oil (52%), coconut oil (48%), and babassu nut oil (46%). The monounsaturated oleic acid and polyunsaturated linoleic acid comprise about 90% of sunflower oil fatty acids. Linoleic acid is the dominant fatty acid in com oil (55%), soybean oil (53%), and safflower oil (75%). Saturated fatty acids of 18 or more carbon atoms are widely distributed, but are usually present in biomass only in trace amounts, except in waxes. 

The chemical method for the measurement of interfacial area in liquid-liquid dispersions was first suggested by Nanda and Sharma (S19). They calculated the effective interfacial area a by sparingly extracting soluble esters of formic acid such as butyl formate, amyl formate, etc., into aqueous solutions of sodium hydroxide. This method has been employed by a number of workers, using esters of formic acid, chloroacetic acid, and oxalic acid, which are sparingly soluble in water (D9, DIO, FI, F2, F3, 04, P8, SI5, S20). Sankholkar and Sharma (S5) employed the extraction of diisobutylene into aqueous sulphuric acid. Sankholkar and Sharma (S6, S7) have also found that the extraction of isoamylene into aqueous solutions of sulphuric acid, and desorption of the same from the loaded acid solutions into inert hydrocarbons such as n-heptane and toluene, can be used for determining the effective interfacial area. Recently, Laddha and Sharma (L2) employed the extraction of pinenes into aqueous sulphuric acid. 

Garlon [Dow]. TMfor herbicides containing water-soluble salts or oil-soluble esters of 3,5,6-tri-chloro-2-pyridyloxyacetic acid. 

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