Salts, hydrolysis salt formation

Solvents influence the hydrogenation of oximes in much the same way as they do hydrogenation of nitriles. Acidic solvents prevent the formation of secondary amines through salt formation with the initially formed primary amine. A variety of acids have been used for this purpose (66 ), but acids cannot always be used interchangeably (43). Primary amines can be trapped also as amides by use of an anhydride solvent (2,/5,57). Ammonia prevents secondary amine formation through competition of ammonia with the primary amine in reaction with the intermediate imine. Unless the ammonia is anhydrous hydrolysis reactions may also occur. 

Normally the reaction Is useful for the conversion of alkyl halides to primary amines without concomitant formation of secondary amines.29 Treatment of polymer 17 with hexamethylenetetramine in a mixture of ethanol/THF afforded an insoluble resin. Using diazabicyclooctane (DABCO), we demonstrated that the reaction could be limited to attack by a single nitrogen in a multifunctional amine, so we did not anticipate crosslinking via bis-quat salt formation. Hydrolysis of 2 with anhydrous HC1 in ethanol generated free amino groups as evidenced by a positive ninhydrin test, but quantitative hydrolysis could not be achieved and the product remained insoluble. One would have expected a simple bis-quat to hydrolyse and open the crosslinked structure. 

The hydrogen chloride is removed either by reduced pressure or by salt formation with pyridine or sodium bicarbonate the latter procedure gave high yields of the pure ester. Toy (47) also measured the hydrolysis rates and compared the toxicities of a series of tetraalkyl pyrophosphates. Of these tested, the tetraethyl ester was the most toxic to white mice. 

Bromosilanes, hydrolysis, 42 162-163 Bromouranate salts, heats of formation, 34 99 Bromyl fluoride... 

The same regiochemistry is observed when nitroimidazole (48-2, 48-3) acts as a nucleophile in unionized form. Thus, the reaction of a compound with benzoyl-aziridine (49-1) in the presence of boron trifluoride probably involves an initial salt formation with an amide attack by the imidazole results in a ring opening and the formation of the alkylated product (49-2) the free primary amine (49-3) is obtained on basic hydrolysis. Acylation of the primary amine with methyl thiochloroformate gives the corresponding thiourethane, carnidazole (49-4) [52]. 

With the (S)-PGA enamine-amide route, sitagliptin was prepared in 65% overall yield from 2,4,5-trifluorophenylacetic acid (9) in 4 chemical steps [18]. Two addi-honal crystallization steps are required for enanhomeric purity upgrade and final salt formation. The (S)-PGA enamine-amide hydrogenahon approach eliminated the ester hydrolysis and amide formation steps of the (S)-PGA enamine-ester route by incorporating the newly developed Meldrum s acid chemistry, which enabled direct amidahon with triazole 3. 

Fig. 8. Effects of added salts on the rate coefficients for the hydrolysis and formation of y-butyrol-actone. Open symbols represent points for NaCl closed symbols for NaCIO. Data from ref. 114.

The weak base HgO can be dissolved in weak acids to form mercury(II) salts. Usually an excess of the acid is necessary to prevent hydrolysis and the formation of basic salts. The complex formation between mercury(II) and carbonate has been studied.277 Three complexes were found, the simplest formulations being as shown in equations (12)-(14). 

Reaction LXV. (a) Reduction of Phenolic Acids to the corresponding Aldehydes by the action of Sodium Amalgam and Boric Acid in the presence of a Primary Aromatic Amine. (B., 41, 4147.)—This is one of the few methods of reducing an acid to the corresponding aldehyde in satisfactory yield. The presence of the primary aromatic base is essential to protect the aldehyde it condenses with it as formed, and inhibits further reduction to the alcohol. A weak acid such as boric acid is used partly because salt formation by the base would hinder condensation and partly to avoid hydrolysis of the condensation product. 

Here again, loss of Y = H would result in rearomatization and formation of 12, but in the case of Y = Me, this cannot occur. However, assistance by the amine nitrogen lone pair can aid the rearomatization process, producing the copper-bound phenol product and an imininm salt. Hydrolysis during the workup procedure could release the 2-meth-ylphenol product and result in a retro-Mannich reaction to give the observed secondary amine (PY2) and formaldehyde. A small amount (<10%) of N—Me—PY2 is often observed as a byproduct and its yield is at the expense of the PY2 and formaldehyde thus, it appears to be derived from direct reduction of the intermediate iminium salt [167],... 

Pyrethroids are commercially important insecticides that usually contain a cyclopropyl unit that is m-substituted and a cyanohydrin derivative. They are usually sold as a mixture of isomers. However, asymmetric routes have been developed, especially because these compounds are related to chrysanthemic esters (Chapter 12).251 The pyrethroids can be resolved through salt formation or by enzymatic hydrolysis.252... 

FIGURE 7.4 Of the 16 chemistry topics examined (1-16) on the final exam, overall the POGIL students had more correct responses to the same topics than their L-I counterparts. Some topics did not appear on all the POGIL exams. Asterisks indicate topics that were asked every semester and compared to the L-I group. The topics included a solution problem (1), Lewis structures (2), chiral center identification (3), salt dissociation (4), neutralization (5), acid-base equilibrium (6), radioactive half-life (7), isomerism (8), ionic compounds (9), biological condensation/hydrolysis (10), intermolecular forces (11), functional group identification (12), salt formation (13), biomolecule identification (14), LeChatelier s principle (15), and physical/chemical property (16). 

The addition of bromine to 22-(l-piperidyl)bisnor-4,20(22)-chol-adien-3-one (42) is formally analogous to salt formation. On hydrolysis of the intermediate /J-bromo-immonium salt, 3-oxo-20-bromobisnor-4-cholen-22-al (43) was obtained.204... 

The acid-catalysed hydrolysis of an ester is not as effective as basic hydrolysis because all the steps in the mechanism are reversible and there is no salt formation to pull the reaction through to products. 

The white residue is next modified by treatment with a strong base in alcohol. It is known that bases can hydrolyze the imide ring of ULTEM polyetherimide (18). Figure 9 shows that both chemical and physical changes to the residue have occurred following immersion in methanolic potassium hydroxide. XPS results are consistent with imide ring hydrolysis and formation of the potassium salt of a carboxylic acid. 

Trivalent molybdenum is found in a few simple compounds. The black hydroxide, Mo(OH)3, dissolves in acids -with salt formation, yielding reddish-purple solutions which darken in colour. Upon evaporation crystalline salts are not obtained, but when the solution is taken to dryness a greyish-black residue remains, which can be redissolved in water to a dark grey solution. This may be accounted for by the readiness with which the salts undergo hydrolysis, with formation of the black hydroxide, possibly in the eoUoidal form. The similarity of molybdenum to chromium is seen in the series of complex For indications of basic properties in the trioxide, see p. 137. 

Factors influencing the rate of chemical reaction are surface tension polarity of the organic solvent acid-base properties of the aqueous phase relative rate of hydrolysis and other side reactions (salt formation, etc.) rate of separation of polymer out of solution rate of removal of side products of the reaction. 

---