Amide, sodium bases

Water can also be a Brpnsted acid donating a proton to a base Sodium amide (NaNH2) for example is a source of the strongly basic amide ion which reacts with water to give ammonia... 

However, attempts to make an aqueous solution of the base sodium amide would result in the formation of sodium hydroxide and ammonia. The amide ion is a strong base and abstracts a proton from water, a weak acid. The reverse reaction is not favoured, in that hydroxide is a weaker base than the amide ion, and ammonia is a weaker acid than water. Take care with the terminology amide the amide... 

Acetylides are formed by treating terminal acetylenes with a strong base, sodium amide in liquid ammonia being the one most commonly employed. Acetylenes with a hydrogen atom attached to the triple bond are weakly acidic (pATa about 25) due to the stability of the acetylide anion (see Section 4.3.4),... 

Acetylides are formed by treating terminal acetylenes with a strong base, sodium amide in liquid ammonia being that most commonly employed. 

The production of phenothiazines involves heating the appropriate meta-substituted diphenylamine with sulfur and an iodine catalyst to close the ring. Treatment with the strong base sodium amide gives the anion on the ring nitrogen, which then displaces the chlorine of the appropriate second reactant. 

Alkynes can be prepared from dihaloalkanes by elimination of two molecules of HX. This reaction requires very strongly basic conditions so potassium hydroxide at elevated temperatures or the stronger base sodium amide (NaNH2) is commonly employed. Examples are provided by the following equations ... 

We have already encountered one type of organometallic compound with a negative charge on carbon sodium acetylides, covered in Section 9-7. Terminal alkynes are weakly acidic, and they are converted to sodium acetylides by treatment with an unusually strong base, sodium amide. These sodium acetylides are useful nucleophiles, reacting with alkyl halides and carbonyl compounds to form new carbon-carbon bonds. 

Horner-Wittig modification Alternatively, phosphine oxide reacts with aldehydes in the presence of a base (sodium amide, sodium hydride or potassium t-butoxide) to give an alkene. The phosphine oxide can be prepared by the thermal decomposition of alkyl-triphenylphosphonium hydroxide. Deprotonation of phosphine oxide with a base followed by addition to aldehyde yields salt of (3-hydroxy phosphineoxide, which undergoes further syn-elimination of the anion Ph2P02. The lithium salt of (3-hydroxy phosphineoxide can be isolated, but Na and K salt of (3-hydroxy phosphine oxide undergoes in situ elimination to give alkene (Scheme 4.26). 

French chemists report that treatment of rrorw-l,2-dibromocyclohexane (1) with the "complex base sodium amide-sodium r-butoxide produces cyclohexene (2, 36% yield) and l-bromocyclohexene (3. 60% yield). Use of either base (separately) leads... 

The first account of the preparation of an arsonium ylide (1) (see Section I) involved what is known as the salt method , namely the reaction of a halogeno compound with triphenylarsine to form an arsonium salt, which is then treated with a suitable base to provide the ylide (see Scheme 1). Stable ylides are frequently made and isolated by using aqueous alkali. Reactive ylides need anhydrous conditions and the use of a suitable strong base, and are used in situ. Thus triphenylarsonium methylide (25) has been prepared in solution " " it was isolated by using as base sodium amide in tetrahydrofuran under an atmosphere of nitrogenTrimethylarsonium methylide (26) has been made indirectly, by desilylation of the trimethylsilyl methylide (27) with trimethylsilanoP. Ylide... 

The Birch reduction comprises a means for adding two hydrogen atoms to an aromatic ring by means of a metal, most often lithium, and an alcohol in liquid ammonia as solvent. A co-solvent, often tetrahydrofuran (THF), is often added due to the very poor solubility of steroids in ammonia. The use of the more expensive sodium was at one time precluded because traces of iron in that metal catalyzed the conversion of the metal to the strong base sodium amide. Very pure sodium, free of iron impurities, is now used for commercial-scale reductions. 

Due to the low critical temperature and pressure (Tc = 31°C, jPc = 24 bar), SCCO2 is certainly the most investigated supercritical medium, as also witnessed by the examples reported here. However, alternative supercritical fluids must be explored in cases where the intrinsic reactivity of CO2 cannot be neglected. As recently reported, the PT-catalyzed alkylation of phenyl-acetonitrile with ethyl bromide can be conveniently carried out in supercritical ethane in the presence of tetrabutylammonium bromide (TBAB) and solid potassium carbonate as a base (Fig. 13). Under classical liquid-liquid PTC conditions, this reaction typically requires the use of strong aqueous bases (sodium amide,... 

A hydrogen atom on a triply bonded carbon is weakly acidic and can be removed by a very strong base. Sodium amide, for example, converts acetylenes to acetylides. 

Draw the acid-base reaction of ethanol with the base sodium amide, NaNHg. 

In the next chapter, we will learn a method for preparing alkynes (compounds containing C C triple bonds). In the following reaction, a dihalide (a compound with two halogen atoms) is treated with an excess of strong base (sodium amide), resulting in two successive E2 reactions. Draw the mechanism for this transformation. 

Reaction The alkylation of carbanions plays a very important role in organic synthesis because products used as key blocks for numerous medicine and organic syntheses are obtained. Phase transfer catalysis has been proven to be the most efficient way of carrying out this type of reaction. Compared to traditional synthetic routes, it has a number of advantages it requires neither expensive bases (sodium amide, metal hydrides, etc.) nor hazardous solvents (ether, benzene, dimethyl sulfoxide, etc.), ensuring at the same time high selectivity and yields. 

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