Sodium alkynides

Sodium alkynides can be prepared by treating terminal alkynes with NaNH2 in liquid ammonia. 

Sodium alkynides are useful intermediates for the synthesis of other alkynes. 

Sodium alkynides react with aldehydes and ketones to yield alcohols. 

Grignard reagents, organolithium compounds, and sodium alkynides react with formaldehyde to produce primary alcohols, all other aldehydes to produce secondary alcohols, and ketones to produce tertiary alcohols. 

Initial dehydrohalogenation of the w r-dihalide produces a mixture of two bromoalkenes that are not isolated but that undergo a second dehydrohalogenation. The terminal alkyne that results from this step is deprotonated (because of its acidity) by the third mole of sodium amide (see Section 7.9). To complete the process, addition of ammonium chloride converts the sodium alkynide to the desired product, 1-butyne. 

These syntheses can be accomplished by treating the sodium alkynide with a primary alkyl halide ... 

The products of the elimination are an alkene and the alkyne from which the sodium alkynide was originally formed ... 

Sodium alkynides also react with aldehydes and ketones to yield alcohols. An example is the following ... 

An alkyne Sodium amide An alkynide anion R must be methyl or 1° and... 

The silver acetylides appear to have substantially covalent carbon-metal bonds and are less ionic than sodium and potassium alkynides. Silver-ammonia solution may be used to precipitate 1-alkynes from mixtures with other hydrocarbons. The 1-alkynes are regenerated easily from the silver precipitates by treatment with strong inorganic acids. It should be noted, however, that silver alkynides may be shock sensitive and can decompose explosively, especially when dry. 

With those RX derivatives that undergo nucleophilic displacement readily, this is a general method of forming a C—C bond, thereby leading to substituted alkynes. The alkynide salts generally used are those of lithium, sodium, potassium, or magnesium. 

A terminal alkyne is an alkyne that has a hydrogen substituents (Fig. H). This hydrogen substituent is acidic and can be removed with strong base (e.g. sodium amide NaNH2) to produce an alkynide (Fig. I). This is an acid-base reaction. 

Very strong bases (such as sodium amide, NaNH2) deprotonate terminal acetylenes to form carbanions called acetylide ions (or alkynide ions). Hydroxide ion and alkoxide ions are not strong enough bases to deprotonate alkynes. Internal alkynes do not have acetylenic protons, so they do not react. 

Alkyne Sodium amide Sodium Ammonia alkynide... 

The acetylenic proton of ethyne or any terminal alkyne (pA 25) can be removed with a strong base such as sodium amide (NaNH2). The result is an alkynide anion. 

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