Solvent carboxylates

Incorporation of carboxyl groups in vinyl polymers (J) and polyolefins (1, 7) improves the adhesion of these polymers to various materials. However, many of these carboxylated polymers, particularly the carboxylated polyolefins, have limited solubility in volatile, lacquer-type solvents such as butyl acetate or methyl ethyl ketone and thus are limited in their ability to improve the adhesion of coatings applied from solvents. Carboxylated polyesters that are soluble in these solvents can be prepared. We were therefore interested in determining the effects of structure and carboxyl content on the adhesion of coatings of various classes of polymers blended with carboxylated polyesters. 

Solubilization of carboxylic acids, such as acetic acid and oleic acid, by dino-nylnaphtalenesulfonates (DNNS) in hexane was studied by infrared spectroscopy. Since DNNS salts form reverse micelles and have an aggregation number of approximately 7 in low polar solvents, carboxylic acids would be solubilized in the polar core of the RMs (Inoue and Nose, 1987 Inoue et al. 1965). 

Depending on the nature of X, the (CH3)4SbX products were found to be either covalent molecular species (OH, OR, SR, F) or saltlike materials (azide, thiocyanide, chloride, dimethylphosphinate). The state of bonding may be different in solution from the solid state, and it may vary with the nature of the solvent (carboxylates). Only the stronger acids, if employed in excess, will afford the R3SbX2 species. This is true with the halogen hydrides, halosulfuric or -phosphonic acids, etc. 

In the series of the alkali metal carbonates and -hydroxides the cesimn compounds are the strongest bases [14]. For reasons of simpler handling the less hygroscopic carbonate is often preferred to the hydroxide. In dipolar aprotic solvents, carboxylic acids [15], phenols [16], thiols [17, 18] and sulfonamides [19] are easily deprotonated by cesium carbonate, whereas with carbamates such as e.g. benzyloxycarbonyl- ( Z -)protected amino acids no reaction occurs [20]. 

Thus we see that, except for the acids of four carbons or less, which are soluble both in water and in organic solvents, carboxylic acids and their alkali metal salts show exactly opposite solubility behavior. Because of the ready interconversion of acids and their salts, this difference in solubility behavior may be used in two important ways for identification and for separation,... 

The ionization of a carboxylic acid, phenol, enol, or alcohol in a solvent (S) [AH -I- S = A -I- SH+] always results in the net production of ions (ionogenic reaction), while the ionization of an ammonium ion [AH" -I- S = A -I- SH+] is an isoelectric reaction. Because of the greater stability of ions in water than in organic solvents, ionogenic reactions are particularly sensitive to the nature of the solvent. While the pKa values of ammonium ions are similar in aqueous and nonaqueous solvents, carboxylic acids, phenols, and so on are much weaker acids in organic solvents. 

Nitrosyl fluoroborate Acids from amides at low temp, in organic solvents Carboxylic and sulfonic acids... 

Non-solvent carboxylic acids, chlorinated hydrocarbons, esters, hydrocarbons, ketones, lower alcohols, THF ... 

Dissociation of acids and bases depends very strongly on the solvent. The solvent SH ofren acts itself as an acid, and the strength of the dissolved base or acid depends on its acid-base properties. Acetonitrile is a weaker acid and base than water, its ion product being 3 10 . Therefore, in acetonitrile HBr, HCl, and H2SO4 dissociate incompletely, unlike their dissociation in water. In acetonitrile = 5.5 for HBr, 7.3 for H2SO4, and 8.9 for HCl. Thus, acetonitrile is a differentiating solvent. Carboxylic acids also dissociate in it to a lower extent than in water the difference between pAT of CH3CN and H2O is 14. 

Benzene. Pure benzene (free in particular from toluene) must be used, otherwise the freezing-point is too low, and crystallisation may not occur with ice-water cooling alone. On the other hand, this benzene should not be specially dried immediately before use, as it then becomes slightly hygroscopic and does not give a steady freezing-point until it has been exposed to the air for 2-3 hours. Many compounds (particularly the carboxylic acids) associate in benzene, and molecular weights determined in this solvent should therefore be otherwise confirmed. 

Protonated and diprotonated carbonic acid and carbon dioxide may also have implications in biological carboxylation processes. Although behavior in highly acidic solvent systems cannot be extrapolated to in vivo conditions, related multidentate interactions at enzymatic sites are possible. 

It requires a certain flexibility of mind to accept the proposal of using the same THF as extraction solvent in some cases. Ue discovered this possibility, when we tried to remove this solvent from carboxylic acids in a water-pump, vacuum it appeared difficult to remove the last traces of this solvent, even when heating at 70-80°C in a vacuum of 10-15 mmHg was applied. It seemed that there is some weak complexation. This led us to the idea of using THF for the extraction of carboxylic acids from the aqueous phase (after saturation with... 

HCl and 50 ml of water. The upper layer was separated off and the aqueous phase was extracted five times with small portions of THF. After drying the combined solutions over magnesium sulfate the solvent was removed in a water-pump vacuum. The residue was distilled through a 30-cm Vigreux column, connected to an air condenser. After a preliminary aqueous fraction of the carboxylic acid the main fraction passed over at 100°C/15 mmHg. The compound solidified in the receiver and (partly) in the condenser. The yield was almost quantitative. 

The less hindered f/ans-olefins may be obtained by reduction with lithium or sodium metal in liquid ammonia or amine solvents (Birch reduction). This reagent, however, attacks most polar functional groups (except for carboxylic acids R.E.A. Dear, 1963 J. Fried, 1968), and their protection is necessary (see section 2.6). 

To illustrate the specific operations involved, the scheme below shows the first steps and the final detachment reaction of a peptide synthesis starting from the carboxyl terminal. N-Boc-glycine is attached to chloromethylated styrene-divinylbenzene copolymer resin. This polymer swells in organic solvents but is completely insoluble. ) Treatment with HCl in acetic acid removes the fert-butoxycarbonyl (Boc) group as isobutene and carbon dioxide. The resulting amine hydrochloride is neutralized with triethylamine in DMF. 

The intramolecular reaction oF allcenes with various O and N functional groups offers useful synthetic methods for heterocycles[13,14,166]. The reaction of unsaturated carboxylic acids affords lactones by either exo- or endo-cyclization depending on the positions of the double bond. The reaction of sodium salts of the 3-alkenoic acid 143 and 4-alkenoic acid 144 with Li2PdCl4 affords mostly five-membcrcd lactones in 30-40% yields[167]. Both 5-hexe-noic acid (145) and 4-hexenoic acid (146) are converted to five- or six-mem-bered lactones depending on the solvents and bases[168]. Conjugated 2,4-pentadienoic acid (147) is cyclized with Li2PdCl4 to give 2-pyrone (148) in water[i69]. 

Carboxylic acids are produced in water. Selection of solvents is crucial and the carbonylation of the enol triflate 480 can be carried out in aqueous DMF, and that of the aryl triflate 481 in aqueous DMSO using dppf as a ligand[328,334]. The carbonylation of the enol triflate 482 to form the a, 0. unsaturated acid 483 using dppf as a ligand in aqueous DMF has been applied in the total synthesis of multifunctionalized glycinueclepin[335]. 

COi is another molecule which reacts with conjugated dienes[10,95,96], COt undergoes cyclization with butadiene to give the five- and six-membered lactones 101. 102. and 103, accompanied by the carboxylic esters 104 and 105[97.98], Alkylphosphines such as tricyclohcxyl- and triisopropylphosphine are recommended as ligands. MeCN is a good solvent[99],... 

A solution of benzyl indole-5-carboxylate(1.0g, 3.98 mmol) and methyl 4-(bro-momethyl)-3-methoxybenzoate (2.06 g, 7.97 mmol) in dry DMF (10 ml) was heated at 80°C for 24 h. The reaction solution was cooled, poured into water (100 ml) and the product extracted with EtOAc (3 x 75 ml). The extract was washed with water and brine and dried over MgSO, . The product was obtained by evaporation of the solvent and purified by chromatography on silica gel using 1 4 EtOAc/hexane for elution. The yield was 1.11 g (32%) and some of the indole (30%) was recovered unreacted. 

Solvent Effects on the Rate of Substitution by the S 2 Mechanism Polar solvents are required m typical bimolecular substitutions because ionic substances such as the sodium and potassium salts cited earlier m Table 8 1 are not sufficiently soluble m nonpolar solvents to give a high enough concentration of the nucleophile to allow the reaction to occur at a rapid rate Other than the requirement that the solvent be polar enough to dis solve ionic compounds however the effect of solvent polarity on the rate of 8 2 reactions IS small What is most important is whether or not the polar solvent is protic or aprotic Water (HOH) alcohols (ROH) and carboxylic acids (RCO2H) are classified as polar protic solvents they all have OH groups that allow them to form hydrogen bonds... 

Carboxylic acids are exceedingly difficult to reduce Acetic acid for example is often used as a solvent in catalytic hydrogenations because it is inert under the reaction con ditions A very powerful reducing agent is required to convert a carboxylic acid to a pri mary alcohol Lithium aluminum hydride is that reducing agent... 

NMR The H NMR signals for the hydroxyl protons of phenols are often broad and their chemical shift like their acidity lies between alcohols and carboxylic acids The range is 8 4-12 with the exact chemical shift depending on the concentration the solvent and the temperature The phenolic proton m the H NMR spectrum shown for p cresol for example appears at 8 5 1 (Figure 24 4)... 

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