Boiling point alkali metals

TABLE 2.1 ALKALI METALS BOILING POINTS AND MELTING POINTS ... 

Liquid ammonia. This can be prepared by compressing ammonia gas. It has a boiling point of 240 K and is an excellent solvent for many inorganic and organic substances as well as for the alkali metals. Liquid ammonia is slightly ionised. ... 

The esterification reaction may be carried out with a number of different anhydrides but the literature indicates that acetic anhydride is preferred. The reaction is catalysed by amines and the soluble salts of the alkali metals. The presence of free acid has an adverse effect on the esterification reaction, the presence of hydrogen ions causing depolymerisation by an unzipping mechanism. Reaction temperatures may be in the range of 130-200°C. Sodium acetate is a particularly effective catalyst. Esterification at 139°C, the boiling point of acetic anhydride, in the presence of 0.01% sodium acetate (based on the anhydride) is substantially complete within 5 minutes. In the absence of such a catalyst the percentage esterification is of the order of only 35% after 15 minutes. 

Figure 4.3 Melting point and boiling point of alkali metal halides.

Schimmel Co. attempted to acetylise the alcohol by means of acetic anhydride, but the reaction product only showed 5 per cent, of ester, which was not submitted to further examination. The bulk of the alcohol had been converted into a hydrocarbon, with loss of water. Ninety per cent, formic acid is most suitable for splitting off water. Gne hundred grams of the sesquiterpene alcohol were heated to boiling-point with three times the quantity of formic acid, well shaken, and, after cooling, mixed with water. The layer of oil removed from the liquid was freed fi-om resinous impurities by steam-distillation, and then fractionated at atmo.spheric pressure. It was then found to consist of a mixture of dextro-rotatory and laevo-rotatory hydrocarbons. By repeated fractional distillation, partly in vacuo, partly at ordinary pressure, it was possible to separate two isomeric sesquiterpenes, which, after treatment with aqueous alkali, and distillation over metallic sodium, showed the following physical constants —... 

The alkali metal hydroxides, instead of the alkali metals per se, can be employed to produce the alkali metal 2,2,2-trifluoroethanolate. However, this introduces water in the reaction mixture which requires removal prior to vinylation with acetylene. The crude products, on further distillation, yielded 2,2,2-trifluoroethyl vinyl ether having a boiling point of 43.1°C at 759 mm. 

Zinc phthalocyanine (PcZn) is prepared from phthalonitrile in solvents with a boiling point higher than 200 C, e.g. quinoline277,278 or 1-bromonaphthalene,137 or without solvent in a melt of phthalonitrile.83,116 The zinc compound normally used is zinc(ll) acetate or zinc powder. The reaction of zinc(II) acetate with phthalic acid anhydride, urea and ammonium mo-lybdate(VI) is also successful.262 The metal insertion into a metal-free phthalocyanine is carried out in an alcohol (e.g.. butan-l-ol).127,141,290 This reaction can be catalyzed by an alkali metal alkoxide.112,129... 

Alkali-metal phthalocyanines 1 are commonly prepared in situ by the reaction of the appropriate phthalocyanine with lithium in an alcohol like pentan-l-ol. If higher temperatures are required during the synthesis, octan-1-ol with its substantially higher boiling point is used. The reaction mixture is then refluxed with a compound containing the desired metal atom to yield the appropriate metal phthalocyanine 2. 

Primary aromatic amides are crystalline solids with definite melting points. Upon boiling with 10-20 per cent, sodium or potassium hydroxide solution, they are hydrolysed with the evolution of ammonia (vapour turns red litmus paper blue and mercurous nitrate paper black) and the formation of the alkali metal salt of the acid ... 

Although our initial entry into this area of study was by accident when we happened to mix MgC with potassium biphenylide(61), our early work concentrated on reductions without the use of electron carriers. In this basic approach, reductions are conveniently carried out using an alkali metal and a solvent whose boiling point exceeds the melting point of the alkali metal. The metal salt to be reduced must also be partially... 

The blue color is attributed to the solvated electron. The blue solutions react with ketones to form highly colored substances resembling the metal ketyls formed by reaction with the alkali metals. The blue solutions decompose into trialkylamine and hydrocarbon on standing at the boiling point of liquid ammonia. 

A summary of all the metal pairs showing partial or complete immiscibility in the liquid state is presented in the map of Fig. 2.17. In the same figure metal pairs giving solid-gas equilibria are also shown. The solid-gas equilibria are especially observed in systems in which there is a large difference in the boiling points of the components (see for instance the systems formed by the alkali metals with refractory metals such as Cr, Mo, V etc.). Several groups of systems forming miscibility... 

Protection of the molten metals from air and moisture The protection of the molten metals has always been an essential point. Fusion under vacuum or an inert atmosphere (pure He or Ar, possibly gettered) is systematically used. In the past, also for small scale laboratory preparations, fusion under a protective layer of molten non-reactive salts was often used. Low density salt mixtures having low-melting point and high-boiling point were generally employed (for instance eutectic mixtures of anhydrous stable alkali halides). 

In the metallic state, lithium is a very soft metal with a density of 0.534 g/cm. When a small piece is placed on water, it will float as it reacts with the water, releasing hydrogen gas. Lithium s melting point is 179°C, and it has about the same heat capacity as water, with a boiling point of 1,342°C. It is electropositive with an oxidation state of + 1, and it is an excellent conductor of heat and electricity. Its atom is the smallest of the alkali earth metals and thus is the least reactive because its valence electron is in the K shell, which is held closest to its nuclei. 

Not a great deal is known about francium s properties, but some measurements of its most stable isotope have been made. Its melting point is 27°C and its boiling point is 677°C, but its density is unknown. It is assumed to have a +1 oxidation state (similar to all the other alkali metals)... 

As the first element in group 2 (IIA), beryllium has the smallest, lightest, and most stable atoms of the alkali earth metals. Its melting point is 1278° C, its boiling point is 2970°C, and its density is 1.8477 g/cm. Its color is whitish-gray. 

Radium is the last element in group 2 and is very similar to the other alkali earth metals, which makes it the largest and heaviest element in the group. It particularly resembles barium, which is just above it in group 2 of the periodic table. Radium is a bright white radioactive luminescent alkali earth metal that turns black when exposed to air. Its melting point is 700°C, its boiling point is 1,140°C, and its density is approximately 5.0 g/cm. ... 

Neodymium, along with lanthanum, cerium and praseodymium, has low melting points and high boiling points. The fluorides of these and other rare earth metals are placed under highly purified helium or argon atmosphere in a platinum, tantalum or tungsten crucible in a furnace. They are heated under this inert atmosphere or under vacuum at 1000 to 1500°C with an alkali or alkaline earth metal. The halides are reduced to their metals ... 

As one moves down the halogen column, one notices that the boiling point increases. However, when examining the alkali metal family, one discovers that the melting point decreases as one moves down the column. 

TABLE 6.4 Properties of Alkali Metals Melting Boiling Point (°C) Point (°C) Density (g/cm3) First Ionization Energy (kj/mol) Abundance on Earth (%) Atomic Radius (pm) Ionic (M+) Radius (pm)... 

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