Sodium Hydrogen Acetylide

Sodium Acetylide. See in Vol 1, A82-L under Monosodium Acetylide or Sodium Hydrogen Acetylide ... 

Monosodi.um Acetylide or Sodium Hydrogen Acetylide (Ethynylsodium) NaHC, mw 48.02 wh to yel friable solid, d 1.33i mp expl ca 150° with evoln of gases that catch fire in the air leaving a blk residue which is still very reactive decomp explosively on contact with w or ale and burns with flame in atm of Cl or Br at RT it is sol in liq NH, and insol in eth benz. Was first prepd by Berthelot (Ref 2) by heating Na with CjHj and then by Moissan (Ref 3) from Na and C.H, at RT but under pressure. Many other methods of prepn are given in the literature. Its prepn from Na CjH, in liq NH3 and from sodamide and CjHj in liq NHj are described in Refs 4-7 Re/s DBeil 1,238,( 104),L217] 19091... 

Terminal alkynes are only reduced in the presence of proton donors, e.g. ammonium sulfate, because the acetylide anion does not take up further electrons. If, however, an internal C—C triple bond is to be hydrogenated without any reduction of terminal, it is advisable to add sodium amide to the alkyne solution Hrst. On catalytic hydrogenation the less hindered triple bonds are reduced first (N.A. Dobson, 1955, 1961). 

Chlorine Ammonia, acetylene, alcohols, alkanes, benzene, butadiene, carbon disulflde, dibutyl phthalate, ethers, fluorine, glycerol, hydrocarbons, hydrogen, sodium carbide, flnely divided metals, metal acetylides and carbides, nitrogen compounds, nonmetals, nonmetal hydrides, phosphorus compounds, polychlorobi-phenyl, silicones, steel, sulfldes, synthetic rubber, turpentine... 

Hydrogen chloride Acetic anhydride, aluminum, 2-aminoethanol, ammonia, chlorosulfonic acid, ethylenediamine, fluorine, metal acetylides and carbides, oleum, perchloric acid, potassium permanganate, sodium, sulfuric acid... 

The most striking difference between alkenes and alkynes is that terminal alkynes are weakly acidic. When a terminal alkyne is treated with a strong base, such as sodium amide, Na+ -NH2, the terminal hydrogen is removed and an acetylide anion is formed. 

The present method developed by the submitters is the only practical process for preparation of l-cyano-6-methoxy-3,4-dihydronaphthalene. Birch and Robinson have reported that 6-methoxy-l-tetralone did not react with hydrogen cyanide or sodium acetylide. 

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),... 

A stereospecific synthesis for cw-3-hexen-l-ol starts with the ethylation of sodium acetylide to 1 -butyne, which is reacted with ethylene oxide to give 3-hexyn-l-ol. Selective hydrogenation of the triple bond in the presence of palladium catalysts yields cw-3-hexen-l-ol. Biotechnological processes have been developed for its synthesis as a natural flavor compound, e.g., [12]. 

One of the important processes for manufacturing linalool is from the (3 - me thylhep ten o ne intermediate produced by the methods from petrochemical sources discussed earlier. For example, addition of sodium acetylide to (3-methylheptenone gives dehydrolinalool (4), which can be selectively hydrogenated, using a Lindlar catalyst, to produce linalool. 

Triple bonds are linear and the carbons are sp-hybridized (Figure 3.16). Alkynes, like alkenes, undergo addition reactions. A hydrogen connected to a triply bonded carbon is weakly acidic and can be removed by a very strong base such as sodium amide, NaNH2, to give acetylides. 

Carbon nucleophiles are very useful species because their reactions with carbon electrophiles result in the formation of carbon—carbon bonds. Section 10.8 introduced acetylide anions as nucleophiles that could be used in Sm2 reactions. These nucleophiles are prepared by reacting 1-alkynes with a strong base such as sodium amide. The relatively acidic hydrogen on the. vp-hybridized carbon is removed in this acid-base reaction ... 

O Sodium amide, a strong base, was used to remove the acidic hydrogen of ethyne. The resulting acetylide ion was used as a nucleophile in an SN2 substitution (see Section 10.8). 

Sodium amide (Na+ NH2) is frequently used as the base in forming acetylide salts. The amide ion ( NH2) is the conjugate base of ammonia, a compound that is itself a base. Ammonia is also a very weak acid, however, with Ka = 10 35 (pA = 35). One of its hydrogens can be reduced by sodium metal to give the sodium salt of the amide ion, a very strong conjugate base. 

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