US2577289A - Method of activating alkali metals - Google Patents

Description

Patented Dec. 4, 1951 METHOD-OF ACTIVATIN METALS Leonhard Tiganik, Skoghall, Sweden No Drawing. Application June 5, 195.0,

' Serial No. 166,297

8 Claims.

It is well known that alkali metals, particularly sodium, are used in organic chemistry, .e. g. in the Wurtz-Fittig reactions, for substituting hydrogen in certain amines, etc. However, it has been found that certain reactions cannot be carried out with sodium and therefore the more expensive potassium has to be used. In some instances a theoretically possible reaction .cannot be carried outwith sodium or with an alloy of sodium and potassium or even with pure potassium. A possible explanation of the passivity of the alkali metals is that as currently available they are too nearly or quite pure.

I have found that this state of passivity of the alkali metals, particularly sodium, may be avoided or in other Words'that the alkalimetals may be activated for certain reaction purposes by suitably incorporating'therein small quantities of copper. I have also found that silver, lead and tin have a similar but not equally strong effect in this respect as copper. Other metals having the same or similar properties, however, have hitherto not been found.

I have further found that when one of the activatingmetals is'incorporatedinto one of the alkali metals even in very small amounts by a process involving the use of mercury as a mutual solvent a strong activation of the alkali metal for organic chemical reactions is produced.

Mymethod consists in dissolving the-activating metal in mercury, i. e. producing an amalgam or a mercury alloy of the activating metal and then mutually dissolving the alkali metal and the said amalgam of the activating metal in each other. Thus if sodium is to be activated by an addition of copper the copper is first dissolved in mercury and the resulting mercury solution of copper is alloyed with or dissolved in the molten sodium by stirring them together while protecting them against oxidation by contact with .the atmosphere.

The quantities of the activating metals required, when incorporated as-described, are very small. Copper as already stated is the :most effective of theactivating metals and is effective when only a mere trace, e. g. .00002% calculated onthe weight .of the sodium is present. Copper is effective as an activator for the alkali metals in quantities ranging from .00002% up to about 0.5%. No substantial increase in activity results from increasing the copper content of the alloy above about 0.5%. In the case of the other activating metals Ag, Pb and Sn about twice as much is required for optimum activation of the alkali metal.

Other factors involved in the preparationof the alloys are the following:

In the case of copper which due to contact with the atmosphere, usually has a protective copper oxide skin which prevents it from alloying with .the mercury it generally is necessary to carry out the combination of the copper "and the mercury in the presence of an acid .to remoye .the oxide skin. The result n me cur copper alloy readily combines with sod um 59 give the desired alloys. .If, ,on the other hand, it is :attempted .to .form the alloy vby .diSSOl AE copper in -asodium amalgam, i. e. by first combining mercury with the sodium and :then dissolving the copper in the sodium mercu iyzalloy it will be found that copper does notidissolve in the sodium amalgam even at temperatures considerably above the melting point of sodium and the product obtained shows no increase in reactivity when used in organic chemical reactions asis the case with -a product made'by dissolvingthe copper inthe mercury and then-dissolving the copper-mercury in the sodium. The situation is the same if one attempts to melt sodium, mercury and copper together. As -a result of attempts to combine copper, mercury and sodium iirother ways, I have found th-at the other methods are difilcult or impossible to carry out and the products lessuseful than-those made by my method.

In the case of tin, lead and.silven-these metals alloy-with mercury by heatingemore readily than copperand the use of acid-to removeoxide skin, as in the case of copper, 'isnotnecessary. The resulting mercury-tin, mercury-lead iand inercury-silveralloys are readily alloyedwvith sodium at its melting point to give alloys within :the scope of my invention. IL-on the' other hand, mercury, an alkali metal, and .tin .or :lead are molten togetherlin one-.operationa certain-activating efiect is obtained which, :however, is inferior to that obtained by first alloying the activating metal with mercury and thereafter alloying such amalgam :with :the alkali :metal. presumably'due to less uniform distribution-of the activating metal obtainable in the .one .step operation. Whennsing silveras activating metal it is practically impossible to produce the: alloy by heating a mixture ot silver. mercury v:and..so-- dium even at temperatures considerably above the melting pointpf .sodiumrand equally, difliclllt or impossible :is iitifirst .to :alloy the :alkaltmetal. e. g. sodium, with .mercury ::and. then to dissolve silver in .said alloy, just :asis the;casewhenalsinig copper as activating element.

Another important consideration in parrying out my methodiiszthe'quantity of::mercu1iymres ent in the alloy of :mercuryendactivatingmetal which is to -be dissolved in thesodium. Infthe case of; copper, two parts ofmercury'andonemart 0'1 copperiorm ahard copper amalgam which after ageing is verydiiiicultly soluble in csodium. However, if the copper amalgam is made to-eontain at least ,3 parts .and preferably atleast ,5 parts of mercury to one part of copperit dissolves readily in sodium ,evenaitena eingor-storagelior a long time. ,ltfollows that with .too littlemercury present itis practically impossible .tm-ldisperse the desired. amount of copperin the sodium,

It is preferred to use a copper amalgam containinglnot more than 15% of copper although an amalgam containing up to 30% of copper can be used when freshly produced. The specified quantity of mercury serves, as stated above, to safeguard the amalgam against ageing which renders the more concentrated amalgams practically useless and also serves to incorporate the activating metal into the alkali metal in such a dissolved or highly dispersed form that it is effective for activating the alkali metal for organic chemical reactions.

In addition to the limitations noted above that the activating metal must be present in the alkali metal in quantity within the range from more traces up to 0.5% for copper and up to 1% for silver, tin and lead, the mercury must be present in quantity equal to at least three times and preferably at least five times that of the activating metal but not greater than the quantity of alkali metal.

The invention is illustrated by the following specific examples:

Example I .-Copper-activated. sodium metal Copper amalgam is first produced according to known methods, e.g. by rubbing mercury with a small quantity of precipitated copper in the presence of moderately diluted sulphuric acid. After the amalgamation has taken place, the mixture is washed with water and dried by means of e. g. filter-paper. According to the relations between the quantities of copper and mercury a more or less paste-like substance is obtained, which can in some cases be separated into one free-flowing liquid part and one kneadable semisolid part. The liquid part contains about 002% Cu. at room temperature while the well squeezed-out semi-solid part consisting of about A; of Cu and of Hg. The liquid part as well as the semi-solid can be used for activating metallic sodium. The procedure may be as follows.

1000 grams of sodium are melted under petroleum in a suitable vessel. While stirring, -20 grams. of the liquid amalgam are added in small parts. The reaction between the sodium and the amalgamis very violent; therefore precaution should be taken. The mixture is well stirred, so that the copper will really be homogenously divided, and is then allowed to cool. The activated sodium thus obtained difiers externally in no way from ordinary sodium but when cutting the activated sodium is harder than non activated sodium. Although this sodium contains only .00002 to .00004% of copper it behaves very actively relatively to organic halides, particularly aliphatic chlorides and makes it possible to carry out reactions, which otherwise cannot be carried out at all, or only with the utmost difficulty.

Sodium thus activated proves to be particularly apt-for so-called Wurtz-Fitting reactions, for silane-syntheses, etc. For other purposes a more strongly activated sodium is needed. In such cases more and higher concentrated, e. g. copper amalgam is used in a quantity of about 23% counted on the weight of sodium.

Example II .-Tin-activated sodium Tin amalgam is produced by a slight heating of 'mercury and tin. The said amalgam is melted together with sodium in the desired proportion and under such conditions that oxidation is prevented. Very small quantities of tin, e. g. .01% Sn, gives the alkali metal a considerably increased reaction capacity.

Erample III.Sz'laer-activated potassium By heating mercury and silver filings a silver amalgam is produced which in the manner described before is melted together with metallic potassium.

This application is a continuation-in-part of my application Serial No. 45,787 filed August 23, 1948, now abandoned.

I claim:

1. A method of producing activated alkali metals for use in organic chemical reactions which comprises dissolving an activating metal of the group consisting of copper, silver, tin, and lead in at least three times its weight of mercury and dissolving the resulting solution in an alkali metal in quantity sufficient to give a composition containing a quantity of the activating metal amounting to from mere traces to 1% of the alkali metal.

2. Method as defined in claim 1 in which the activating metal is copper and the alkali metal is sodium and in which the ratio of mercury to copper is at least five to one.

3. Method as defined in claim 1 in which the activating metal is silver.

4. Method as defined in claim 1 in which the activating metal is tin.

5. Method as defined in claim 1 in which the activating metal is lead.

6. Method of activating sodium for use in organic chemical reactions which comprises dissolving copper in mercury in the presence of an acid, the quantity of dissolved copper amounting to about .002% of the mercury and dissolving from 1 to 2 parts of the resulting copper-mercury solution in about parts of sodium.

7. An alloy suitable for promoting organic chemical reactions consisting essentially of an alkali metal, mercury and a metal of the group consisting of Cu, Ag, Sn and Pb, the latter in quantity within the range from .0002 to 1 percent calculated on the weight of the alkali metal and the mercury in quantity within the range from three times the weight of the metal of said group to a quantity equal to the weight of the alkali metal.

8. An alloy suitable for promoting organic chemical reactions consisting essentially of sodium, mercury and copper, the latter in quantity within the range from .0002 to 0.5 percent of the sodium and the mercury in quantity within the range from three times the weight of the copper to a quantity equal to the weight of the sodium.

LEONI-IARD TIGANIK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 71,307 Johnston Nov. 26, 1867 1,360,346 Worrall Nov. 30, 1920 2,109,005 Bake Feb. 22, 1938 FOREIGN PATENTS Number Country Date 2,229 Great Britain Aug. 30, 1865 692,990 Germany June 29, 1940

Claims (1)

1. A METHOD OF PRODUCING ACTIVATED ALKALI METALS FOR USE IN ORGANIC CHEMICAL REACTIONS WHICH COMPRISES DISSOLVING AN ACTIVATING METAL OF THE GROUP CONSISTING OF COPPER, SILVER, TIN, AND LEAD IN AT LEAST THREE TIMES ITS WEIGHT OF MERCURY AND DISSOLVING THE RESULTING SOLUTION IN AN ALKALI METAL IN QUANTITY SUFFICIENT TO GIVE A COMPOSITION CONTAINING A QUANTITY OF THE ACTIVATING METAL AMOUNTING TO FROM MERE TRACES TO 1% OF THE ALKALI METAL.