Potassium, in liquid

The reaction can be performed under a variety of conditions. Origin-aiiyi2o,i26,234 acetylene and potassium in liquid ammonia were used. Subsequently, this was simplified by the use of potassium r-amylate in r-amyl alcohol and later this system was found to react selectively at C-17 in the presence of an A-ring a,j5-unsaturated ketone. A closer investigation of these reaction conditions revealed the formation of a small amount (2-3 %) of the disubstituted acetylene this can be avoided by reacting the 17-keto steroid with acetylenedimagnesium bromide in ether-tetrahydrofuran (see chapter 10.)... 

Acetylene and Potassium in Liquid Ammonia Potassium (40 g) is dissolved in 1 liter of dry liquid ammonia. Dry acetylene is then bubbled into the solution until the blue color is discharged. A solution of 15 g of estrone in 300 ml of dioxane is prepared and diluted with 300 ml of ether, cooled, and added to the potassium acetylide solution over a period of 10 min. The liquid ammonia is allowed to evaporate, an additional 500 ml of ether is added, and the mixture is allowed to stand overnight. About 3 liters of 5 % sulfuric acid is added and the organic layer separated. The water layer is re-extracted with fresh ether, and the combined ether extracts are washed twice with 5 % sodium carbonate solution, th6n several times with water, and finally evaporated under reduced pressure. The residue is dissolved in 150 ml of methanol, then an equal quantity of hot water is added and the mixture cooled. The precipitated solid is collected, washed with cold 60 % methanol and crystallized once from methanol-water to give 14.8 g (85%) of 17a-ethynylestradiol mp 143-144°. 

A useful alternative to catalytic partial hydrogenation for converting alkynes to alkenes is reduction by a Group I metal (lithium, sodium, or potassium) in liquid ammonia. The unique feature of metal-ammonia reduction is that it converts alkynes to bans alkenes, whereas catalytic hydrogenation yields cis alkenes. Thus, from the same alkyne one can prepare either a cis or a bans alkene by choosing the appropriate reaction conditions. 

The versatility of cyanide and bipyridyl ligands has been used to stabilize low oxidation states. By using potassium in liquid ammonia, K3Ti (CN)6 is reduced to K2Ti (CN)4 and TiBt3 - - KCN to K4Ti°(CN)4. With ZrBt3 and M CN (M = K, Rb) in liquid ammonia, ammonolysis occurs and zerovalent Zr is produced ... 

Besides [Ni(CO)4] and organometallic compounds discussed in the next section, nickel is found in the formally zero oxidation state with ligands such as CN and phosphines. Reduction of K2[Ni (CN)4] with potassium in liquid ammonia precipitates yellow K4[Ni (CN)4], which is sensitive to aerial oxidation. Being... 

When 2,7-dimethyloxepin is treated with potassium in liquid ammonia at — 70 C, a mixture of oct-4-en-2-one (1) and octa-4,6-dien-2-one (2) in a ratio of 75 20 is obtained.203 The major product can be separated by preparative gas chromatography in 23% yield. The analogous reaction of 3-benzoxepin gives, in 30% yield, a mixture of (2-cthylphenyl)acetaldehyde (3) and (2-ethynylphenyl)acetaldehyde (4) that resists separation.203 The Latter product can be formed exclusively in 17% yield when 3-benzoxepin is treated with sodium amide in tetra-hydrofuran at 33 C for 210 minutes.203... 

Treatment of low-rank coal (or of a vitrinite fraction from such coal) with variously concentrated solutions of potassium in liquid ammonia did not cause an increased -OH content in the reacted material. Nor was the hydroxyl content affected by such treatment after prior exhaustive methylation of the coal with dimethyl sulphate and CO acetone (13). On the other hand,... 

Produced by action of carbon monoxide on potassium in liquid ammonia at —50°C, the yellow powder bums explosively in contact with air, halocarbons, halogens, alcohols, water and any material with acidic hydrogen. Analogous metal derivatives are reviewed. 

During the reductive cleavage of cyclopolyenes with potassium in liquid ammonia, the intermediate anionic species are quenched with iodine-pentane mixtures. The possibility of formation of explosive nitrogen triiodide and the need for precautions are stressed. 

Amination of 4-methyl-, 4-A -methylamino-, and 4-anilino-5-bromopyrim-idine with potassium in liquid ammonia yields the corresponding 6-... 

Sulphur, Selenium, and Tellurium Compounds.—The crystal structure of the metal-rich zirconium sulphide Zr Sj has been determined and each sulphur atom shown to be at the centre of a square antiprism of zirconium atoms. The reaction of ZrS2 with potassium in liquid ammonia has been shown to give four K ZrS2 phases (.x = 1, 0.86, 0.71, or 0.71—0.22) which differ in the nature of the co-ordination sites occupied by the potassium atoms between the ZrS2 layers. ZrCl reacts with NaS2P(OEt)2 in toluene to form [Zr S2P-(OEt)2 4], which appears to involve a trigonal-dodecahedral arrangement of sulphur atoms about the metal. ... 

Vinyl ethers were reductively cleaved by lithium, sodium or potassium in liquid ammonia especially in the absence of alcohols (except terf-butyl alcohol) A mixture of l-methoxy-1,3- and l-methoxy-l,4-cyclohexadiene gave in this way first methoxycyclohexene and, on further reduction, cyclohexene Reductive cleavage of a-alkoxytetrahydrofurans and pyrans will be discussed in the chapter on acetals (p. 104). 

The parent azocine (91) was isolated at —190 °C from flash vacuum pyrolysis of diazabas-ketene (90) (71JA3817). The compound, which must be handled in KOH-coated glassware, decomposes at -50 °C to colored tarry material. Characterization was by mass spectrum (m/e 107), NMR spectrum (see 91) and conversion with potassium in liquid ammonia to a dianion, which on quenching and hydrogenation gave azocane in low yield. 

Isoelectronic with nickel carbonyl are the anions, Ni(CN)44- and Pd(CN)44-, which are obtained as their potassium salts by reduction of the corresponding cyanides of oxidation state +2 with potassium in liquid ammonia (32, 65, 186). The infrared spectrum of the nickel complex has been reported (67) to show only one band at 1985 cm-1, in the triple-bond... 

This ion now can be reduced to one with an 18-electron configuration. When treated with a solution of potassium in liquid ammonia it forms the compounds K3Ni(CN)4 (with seventeen electrons) and eventually K4Ni(CN)4, in which the ions have apparent valencies of 1 and 0, respectively. The latter compound... 

Triazine and some of its 3-methoxy, 3-methylthio or 3-amino derivatives (103) with the 5-position unsubstituted react with potassium cyanide to afford two products, the i-triazinyls (105) and the l,2,4-triazine-5-carboxamides (104). These are proposed to be formed via a cyanide adduct (73JHC343, 74JHC43). The bi-l,2,4-triazinyls (105) were also isolated when the triazines (103) were treated with sodium methoxide or potassium in liquid ammonia. It is suggested that the methoxide-catalyzed dimerization proceeds via an anionic intermediate (106), while the reaction with potassium in liquid ammonia occurs via a free radical process. 

Compare this value with that of solvated electron from potassium in liquid ammonia, <7k-nh, = 2.0012 0.0002 (C. A. Hutchinson and... 

Approximately 25 years after Mond and co-workers had prepared the first carbonyl of cobalt, Co2(CO)8 (78), Hieber obtained HCo(CO)4 by the acidification of salts containing [Co(CO)4] (79), one of the first established carbonylmetallates (80). In 1941, Behrens, a student of Hieber, initiated his important and extensive investigations on the reduction of metal carbonyls and their derivatives by alkali and alkaline earth metals in liquid ammonia (81). At this time he established that various salts of [Co(CO)4]-, including Na[Co(CO)4] and K[Co(CO)4], could be obtained from the neutralization of HCo(CO)4 or the reduction of Cd[Co(CO)4]2 by sodium or potassium in liquid ammonia (4). On the basis of Behrens pioneering studies, we were... 

Of the homoleptic carbonylmetallates(l -) we have attempted to reduce, [Co(CO)4] appears to be the most difficult. Although the sodium salts of [M(CO)6] (M = V, Nb, and Ta) were quickly reduced in liquid ammonia by sodium metal to provide the corresponding trianions, [M(CO)5]3 (vide supra), it seems unlikely that we have ever effected complete reduction of Na[Co(CO)4] to Na3[Co(CO)3]. Even after 2 days of refluxing (at — 33°C) anhydrous ammonia solutions of Na[Co(CO)4] with excess Na, considerable amounts of the tetracarbonylcobaltate(l —) remained. Low yields of a heterogeneous-appearing brown to olive-brown insoluble solid were isolated this solid has been shown to contain Na3[Co(CO)3] (vide infra). As in the case of [Re(CO)s], we found that solutions of potassium in liquid ammonia were far more effective at reducing [Co(CO)4]-. However, unlike [Re(CO)s], [Rh(CO)4], or [Ir(CO)4] (vide infra), there was no evidence that [Co(CO)4] was reduced by sodium or potassium metal in hexa-methylphosphoric triamide. We observed that excess sodium naphthalenide slowly (over a period of 40-50 hr at room temperature) converted Na[Co(CO)4] in THF to an impure and insoluble brown powder that contained Na3[Co(CO)3], but this synthesis appeared to be of little or no utility. 

Reduction of [Co(CO)4] by sodium or potassium in liquid ammonia proceeded according to the Eq. (26) (shown for the potassium reaction). 

The role played by the micro Wien effect in dissociating the disodium spinide with increasing concentration beyond the conductance minimum is strongly indicated by the temperature coefficient of the conductance of solutions of sodium and potassium in liquid ammonia. Here we have data for the temperature coefficient of sodium and potassium from relatively dilute solutions up to saturation. 

Figure 5. A comparison of the temperature effect of potassium in liquid...

A fairly comprehensive review of the information on the volume expansion exhibited by metal solutions may be found in the paper of R. Catterall (4). Our purpose here is to emphasize our most recent work on these solutions, namely, to discuss the expansion studies of potassium in liquid ammonia at —34° C. and to compare these results with the earlier investigations obtained at —45° C. 

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