Basic solutions reactions

Fig. 8-43. Anodic and cathodic polarization curves observed for a redox electron transfer at metallic tin electrodes covered with an anodic oxide Sn02 film of various thicknesses d in a basic solution reaction is a redox electron transfer of 0.25 M Fe(CN)6 A).25 M Fe(CN)6 in 0.2 M borate buffer solution of pH 9.1 at 25°C. d = film thickness dj = 2 nm ...

Oxidation of Benzhydrol in Basic Solution. Reaction of benzhydrol with oxygen in basic solution results in the formation of benzophenone, or in DMSO solutions the benzophenone—DMSO adduct. Table VIII summarizes data on the oxidation of benzhydrol in three solvents and in the presence of various concentrations of potassium ferf-butoxide. The rates are the maximum oxidation rates, often observed after an inductive period (Figure 3). 

The base-induced reaction of the symmetrical dipropanoic anhydride (15) illustrates the mechanism of base hydrolysis with anhydrides, in a reaction that gives two equivalents of propanoic acid. Acyl addition of the nucleophilic hydroxide gives tetrahedral intermediate 16. In this case, the best leaving group is the carboxylate anion 18, which gives propanoic acid, 17. Because 17 is formed in a basic solution, reaction with hydroxide gives 18. A second step is required to convert 17 to 18, using aqueous acid (aqueous sulfuric acid or aqueous HCl). 

In the strongly basic medium, the reactant is the phenoxide ion high nucleophilic activity at the ortho and para positions is provided through the electromeric shifts indicated. The above scheme indicates theorpara substitution is similar. The intermediate o-hydroxybenzal chloride anion (I) may react either with a hydroxide ion or with water to give the anion of salicyl-aldehyde (II), or with phenoxide ion or with phenol to give the anion of the diphenylacetal of salicylaldehyde (III). Both these anions are stable in basic solution. Upon acidification (III) is hydrolysed to salicylaldehyde and phenol this probably accounts for the recovery of much unreacted phenol from the reaction. 

Alkylation of A-4-thiazoline-2-one may yield O-R or N-R derivatives according to experimental conditions. With diazomethane in ethanol O-raethylation takes place (29. 36. 214). N-Methylation is reported when a basic solution of A-4-thiazoline-2-one reacts with methyl iodide or dimethylsulfate (21, 29, 215, 216), Reaction of l-chloro-2-dimethyl-aminoethane with the sodium salt of 4 R-A-4-thiazoline-2-one (91) in alcohol, first claimed to yield the aminoalkylether (217, 218), was shown after infrared investigation to give the N-substituted derivative (92) (107), even when R Ph (Scheme 45). More probably the site of reaction in... 

Inversion of configuration is observed at the carbon that is attacked by the nucleophile irrespective of whether the reaction takes place m acidic or basic solution... 

It IS necessary to keep the acidity of phenols in mind when we discuss prepara tion and reactions Reactions that produce phenols when earned out in basic solution require an acidification step to convert the phenoxide ion to the neutral form of the phenol... 

Balance the following redox reactions, and calculate the standard-state potential and the equilibrium constant for each. Assume that the [H3O+] is 1 M for acidic solutions, and that the [OH ] is 1 M for basic solutions. 

The concentration of nitromethane, CH3NO2, can be determined from the kinetics of its decomposition in basic solution. In the presence of excess base the reaction is pseudo-first-order in nitromethane. For a standard solution of 0.0100 M nitromethane, the concentration of nitromethane after 2.00 s was found to be 4.24 X 10 M. When a sample containing an unknown amount of nitromethane was analyzed, the concentration remaining after 2.00 s was found to be 5.35 X 10 M. What is the initial concentration of nitromethane in the sample ... 

For acidic solutions, balance the hydrogen in each half-reaction by adding H3O+ and H2O to opposite sides of the reaction for basic solutions, add OH and H2O to opposite sides of the reaction. 

When the surface conditions are acidic or the ambient humidity is low enough to affect the cure significantly, a surface accelerator may be used to promote the reaction. Available from most manufacturers, these basic solutions may be dip, wipe, or spray appHed. Recentiy, new additive chemistry has been developed that accelerates the cure under adverse conditions without the need for a separate accelerator. 

The extent of the initial hydrolysis depends on temperature and how the water is added. Hydrolysis is reduced at slower addition rates and lower temperatures. The hydrolysis subsequent to the initial fast reaction is slow, presumably because part of the acid is converted to fluorosulfate ions which hydrolyze slowly even at elevated temperatures. The hydrolysis in basic solution has also been studied (17). Under controlled conditions, hydrates of HSO F containing one, two, and four molecules of water have been observed (18,19). 

W ter ndAlcohols. Silanes do not react with pure water or slightly acidified water under normal conditions. A rapid reaction occurs, however, in basic solution with quantitative evolution of hydrogen (3). Alkali leached from glass is sufficient to lead to the hydrolysis of silanes. 

Other Reactions. Poly(vinyl alcohol) forms complexes with copper in neutral or slighdy basic solutions (165). Sodium hydroxide or potassium hydroxide forms an intermolecular complex with PVA (166,167), causing gelation of the aqueous solution. 

Diazophenols, ie, o-hydroxyaryldiazonium salts, couple to 1-naphthol in weaMy basic solution primarily in the para position, but as the hydroxyl ion concentration is increased, formation of the ortho isomer is favored and is frequentiy the sole product. Pyridine and pyridine derivatives, urea, and acetate, etc, used as buffers can also catalyze azo coupling reactions (28). l-amino-2-naphthol-4-sulfonic acid [116-63-2] (1,2,4-acid) and 1-naphthol yield the important Eriochrome Black A [3564-14-5] (18a, R = H) (Cl Mordant Black 3 Cl 14640) which is reportedly (20) a mixture of ortho and para isomers. 

Amides. Because amides are less basic, they chlorinate less rapidly than amines. A/-Halamides are converted to amines in basic solution via intermediate formation of an isocyanate (Hofmann reaction) (91). 

Pyrazoles and imidazoles exist partly as anions (e.g. 108 and 109) in neutral and basic solution. Under these conditions they react with electrophilic reagents almost as readily as phenol, undergoing diazo coupling, nitrosation and Mannich reactions (note the increased reactivity of pyrrole anions over the neutral pyrrole species). 

Rate differences observed between the same bromophenylcarbene (241) when prepared by two different routes, diazirine photolysis and the reaction of benzylidene dibromide with potassium r-butoxide, vanish when a crown ether is added to the basic solution in the latter experiment. In this case the complexing potassium bromide is taken over by the crown ether, and selectivity towards alkenes reaches the values of the photolytic runs (74JA5632). 

When the addition is completed, the bath is removed and stirring is continued for 1 hour while the reaction mixture gradually cools to room temperature. Sodium carbonate (100 g.) is added in portions, followed by the cautious addition of 60 g. of sodium bicarbonate (Note 3). The water is removed from the slightly basic solution by heating the solution in a 3-1. round-bottomed flask under reduced pressure on a steam bath. To aid in removing the last traces of water, 250 ml. of ethanol is added to the residue and the mixture is heated under reduced pressure on a steam bath until it ajipcars dry (Note 4). 

The Canni2zaro reaction is a disproportionation that takes place in strongly basic solution and converts benzaldehyde to benzyl alcohol and sodium benzoate. 

The accessibility of enols and enolates, respectively, in acidic and basic solutions of carbonyl compounds makes possible a wide range of reactions that depend on the nucleophilicity of these species. The reactions will be discussed in Chapter 8 and in Chapters 1 and 2 of Part B. 

Adolph Baeyer is credited with the first recognition of the general nature of the reaction between phenols and aldehydes in 1872 ([2,5-7] [18], Table 5.1). He reported formation of colorless resins when acidic solutions of pyrogallic acid or resorcinol were mixed with oil of bitter almonds, which consists primarily benzaldehyde. Baeyer also saw resin formation with acidic and basic solutions of phenol and acetaldehyde or chloral. Michael and Comey furthered Baeyer s work with additional studies on the behavior of benzaldehyde and phenols [2,19]. They studied a variety of acidic and basic catalysts and noted that reaction vigor followed the acid or base strength of the catalyst. Michael et al. also reported rapid oxidation and darkening of phenolic resins when catalyzed by alkaline materials. 

Nucleophiles other than Grignard reagents also open epoxide rings. These reactions are carried out in two different ways. The first (Section 16.12) involves anionic nucleophiles in neutral or basic solution. 

Section 20.11 Ester hydrolysis in basic solution is called saponification and proceeds through the same tetrahedral intermediate (Figure 20.5) as in acid-catalyzed hydrolysis. Unlike acid-catalyzed hydrolysis, saponification is ineversible because the carboxylic acid is deprotonated under the reaction conditions. 

As with FCIO2 and FIO2, hydrolysis regenerates the halate ion, the reaction with FBr02 being of explosive violence. Hydrolysis in basic solution at 0° can be represented as... 

The reactions of carbenes, which are apparently unique in displaying electrophilic character in strongly basic solutions, include substitution, addition to multiple bonds, and co-ordination with lone pairs of electrons to form unstable ylides. This last reaction is of obvious relevance to a consideration of the reactions of heterocyclic compounds with carbenes and will be summarized. 

In order to obtain good yields from a Weiss reaction sequence, the H+-concentration has to be adjusted properly in the reaction mixture. The reaction is usually carried out in a buffered, weakly acidic or weakly basic solution. By the Weiss reaction simple starting materials are converted into a complex product of defined stereochemistry. There is no simpler procedure for the synthesis of the l,5-c -disubstituted bicyclo[3.3.0]octane skeleton it has for example found application in the synthesis of polyquinanes. ... 

A mixture of 1B g of 1 -acetamido-3,5-dimethvladamantane, 3B g of sodium hydroxide, and 300 ml of diethylene glycol was refluxed for a period of 6 hours. The reaction product mixture was cooled and poured onto about IfiQQ ml of crushed Ice. The basic solution thus obtained was extracted five times with 250-ml portions of benzene and the aqueous layer was discarded. The combined benzene extracts were dried over sodium hydroxide and the dried benzene solution concentrated in vacuo to give a crude oil weighing 14 g and having np =... 

Ammonia is one of the most important inorganic chemicals, exceeded only by sulfuric acid and lime. This colorless gas has an irritating odor, and is very soluble in water, forming a weakly basic solution. Ammonia could be easily liquefied under pressure (liquid ammonia), and it is an important refrigerant. Anhydrous ammonia is a fertilizer by direct application to the soil. Ammonia is obtained by the reaction of hydrogen and atmospheric nitrogen, the synthesis gas for ammonia. The 1994 U.S. ammonia production was approximately 40 billion pounds (sixth highest volume chemical). 

In acidic solution at low pH, a carboxylic acid is completely undissociated and exists entirely as RCO2H- In basic solution at high pH, a carboxylic acid is completely dissociated and exists entirely as RC02 - Inside living cells, however, the pH is neither acidic nor basic but is instead buffered to nearly neutral pH—in humans, to pH = 7.3, a value often referred to as physiological pH. In what form, then, do carboxylic acids exist inside cells The question is an important one for understanding the acid catalysts so often found in biological reactions. 

Write balanced equations for the following reactions in basic solution. 

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