Weakly basic reaction

Both types of surface oxides are found on technical products. Rubber grade carbon blacks are produced in different processes. Channel blacks are made by cooling a flame on iron plates, the so-called channels. The resulting carbon blacks are acidic in character because an excess of air is present (25). In the production of furnace blacks, the fuel, mostly oil or natural gas, is burned with a limited supply of air. Thermal blacks are obtained by thermal cracking of the gas, which sometimes is diluted with hydrogen. In consequence, both types show weakly basic reaction in aqueous suspension. 

Hydroxylamines and alkylhydroxylamines possess high nucleophilicity and can react with a variety of primary and secondary alkylating agents. The reactivity of hydroxylamines in the majority of these reactions resembles that of primary and secondary amines. While hydroxylamine and Af-alkylhydroxylamines 1 are ambident nucleophiles, under neutral or weakly basic reaction conditions alkylation proceeds exclusively on nitrogen atom to give products of type 2 (equation 1). Deprotonation of the OH group of hydroxylamines results in O-alkylation products. 

Figure 7.12 outlines how hydantoin is produced during the synthesis of methionine depicted in Figure 7.11. Initially, the aminonitrile B is formed. With its amino group it adds to carbon dioxide, which—under the weakly basic reaction conditions—is followed by the formation of the carbamate ion D. In a fully analogous fashion, ammonia reacts with carbon dioxide to give ammonium carbamate (cf. Section 8.2). The intermediate D in Figure 7.12 permits the intramolecular and thus kinetically favored—i.e., fast—addition of the oxyanion to the C=N triple bond. The addition product is the negatively charged heterocycle F, which in...

Chlorination of the acylated enamines 14 with AT-chlorosuccinimide gives conjugated chloroenamines 16 via intermediate unconjugated chloroenamines 15. Finally, nucleophile Nu attacks the intermediate imminium ion 17 from the exo face to give en /o-morpholino products 18. However, the tosylcarbamoyl moiety in 17b is deprotonated in the weakly basic reaction medium. This anionic center in the exo position repels nucleophiles attacking from the exo face, and endo-cyano product 19 is obtained exclusively. ... 

SchifT s bases A -Arylimides, Ar-N = CR2, prepared by reaction of aromatic amines with aliphatic or aromatic aldehydes and ketones. They are crystalline, weakly basic compounds which give hydrochlorides in non-aqueous solvents. With dilute aqueous acids the parent amine and carbonyl compounds are regenerated. Reduction with sodium and alcohol gives... 

Because of these difficulties, special mechanisms were proposed for the 4-nitrations of 2,6-lutidine i-oxide and quinoline i-oxide, and for the nitration of the weakly basic anilines.However, recent remeasurements of the temperature coefficient of Hq, and use of the new values in the above calculations reconciles experimental and calculated activation parameters and so removes difficulties in the way of accepting the mechanisms of nitration as involving the very small equilibrium concentrations of the free bases. Despite this resolution of the difficulty some problems about these reactions do remain, especially when the very short life times of the molecules of unprotonated amines in nitration solutions are considered... 

Torgov introduced an important variation of the Michael addition allylic alcohols are used as vinylogous a -synthons and 1,3-dioxo compounds as d -reagents (S.N. Ananchenko, 1962, 1963 H. Smith, 1964 C. Rufer) 1967). Mild reaction conditions have been successful in the addition of ],3-dioxo compounds to vinyl ketones. Potassium fluoride can act as weakly basic, non-nudeophilic catalyst in such Michael additions under essentially non-acidic and non-basic conditions (Y. Kitabara, 1964). 

Glycosidic thiol groups can be introduced into glycosyl bromides by successive reactions with thiourea and aqueous sodium disulfite (D. Horton, 1963 M. Cemy, 1961, 1963). Such thiols are excellent nucleophiles in weakly basic media and add to electrophilic double bonds, e.g., of maleic esters, to give Michael adducts in high yields. Several chiral amphiphiles have thus been prepared without any need for chromatography (J.-H. Fuhrhop, 1986 A). 

Acylation of pyridazinones and related compounds in the presence of weakly basic catalysts such as pyridine or sodium acetate produces IV-acylated products, while O-acylated products are obtained under strongly basic conditions. However, the reaction between 6-chloropyridazin-3(2//)-one with chlorocarbonates and that of maleic hydrazide with unsaturated acid chlorides or chloromethylsulfonyl chloride gives preferentially N-substituted products. 

Primary and secondary aliphatic and aromatic amines react readily with thiiranes to give 2-mercaptoethylamine derivatives (Scheme 76) (76RCR25, 66CRV297). The reaction fails or gives poor yields with amines which are sterically hindered e.g. N,iV-dicyclohexylamine) or whose nitrogen atom is weakly basic e.g. N,A/ -diphenylamine). Aromatic amines are less reactive and higher reaction temperatures are usually required for them. The reaction mechanism is Sn2 and substituted thiiranes are attacked preferentially at the least hindered... 

Neutralization Acidic or basic wastewaters must be neutrahzed prior to discharge. If an industry produces both acidic and basic wastes, these wastes may be mixed together at the proper rates to obtain neutral pH levels. Equahzation basins can be used as neutralization basins. When separate chemical neutralization is required, sodium hydroxide is the easiest base material to handle in a hquid form and can be used at various concentrations for in-line neutralization with a minimum of equipment. Yet, lime remains the most widely used base for acid neutr zation. Limestone is used when reaction rates are slow and considerable time is available for reaction. Siilfuric acid is the primary acid used to neutralize high-pH wastewaters unless calcium smfate might be precipitated as a resmt of the neutralization reaction. Hydrochloric acid can be used for neutrahzation of basic wastes if sulfuric acid is not acceptable. For very weak basic waste-waters carbon dioxide can be adequate for neutralization. 

Weakly basic anion resins derive their functionality from primary (R-NH), secondary (R-NHR ), tertiary (R-N-R 2), and sometimes quaternary amine groups. The weakly basic resin readily absorbs such free mineral acids as hydrochloric and sulfuric, and the reactions may be represented according to the following ... 

Because the preceding reactions are also reversible, the weakly basic resins can be regenerated by applying caustic soda, soda ash, or ammonia. The weak-base... 

It has already been mentioned that monobromination of 5a-3-ketones gives 2a-bromo compounds (18). Further bromination occurs under acidic or distinctly basic conditions (the reaction is not satisfactory in weakly basic... 

Compounds of Tl have many similarities to those of the alkali metals TIOH is very soluble and is a strong base TI2CO3 is also soluble and resembles the corresponding Na and K compounds Tl forms colourless, well-crystallized salts of many oxoacids, and these tend to be anhydrous like those of the similarly sized Rb and Cs Tl salts of weak acids have a basic reaction in aqueous solution as a result of hydrolysis Tl forms polysulfldes (e.g. TI2S3) and polyiodides, etc. In other respects Tl resembles the more highly polarizing ion Ag+, e.g. in the colour and insolubility of its chromate, sulfide, arsenate and halides (except F), though it does not form ammine complexes in aqueous solution and its azide is not explosive. 

All the evidence suggests that such groups always exist in the amino form, and the reactions and behavior of these compounds resemble those of aniline and the naphthylamines. For example, the amino form of 7-aminophenazin-2-ones (246) would be expected to be more stable than the imino form (247), and their weak basicity supports this expectation. ... 

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. ... 

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). 

Solution (a) This is likely to be an SnjI reaction because the substrate is secondary and ben-zyiic, the nucieophiie is weakly basic, and the solvent is protic. 

Secondary alkyl halides Sjvj2 substitution occurs if a weakly basic nucleophile is used in a polar aprotic solvent, E2 elimination predominates if a strong base is used, and ElcB elimination takes place if the leaving group is two carbons away from a carbonyl group. Secondary allylic and benzyiic alkyl halides can also undergo S l and El reactions if a weakly basic nucleophile is used in a pro tic solvent. 

As the amines become more weakly basic, the normal method of diazotization becomes progressively more difficult. The equilibrium between amine and ammonium salt increasingly favors the former which, usually because of its poor solubility in water, is prevented from taking part in the reaction. Research into the mechanism of diazotization has demonstrated that the important step is the addition of the nitrosating agent to the base of the amine. Thus, the acidity for each diazotization should be so chosen that the equilibrium concentration of base corresponds to that of its saturated solution. This rule leads to the use of higer concentrations of aqueous mineral acid for weakly basic amines. 

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