The Chemistry of Beryllium. V. Organic Compounds of Beryllium

T H E CHEMISTRY OF BERYLLIUM. V

ORGANICCOMPOUNDS OF BERYLLIUM~ HAROLD SIMMONS BOOTH

AND

DOROTHY GORDON PIERCE

Morley Chemical Laboratory, Western Reserve University, Cleveland, Ohio Received August 5, i9@ INTRODUCTION

The organic compounds of beryllium have been very little studied. There have been many attempts to produce beryllium salts of organic acids, such as succinic, malonic, salicylic, and the fatty acids (l),but with the exception of beryllium trichloroacetate the products (2) have been mixtures of beryllium hydroxide with the respective acids, owing to the fact that they were prepared by neutralizing the acid with beryllium hydroxide or carbonate. Since solutions of beryllium salts (3) dissolve large amounts of beryllium hydroxide the products were contaminated by this excess. Some (4) have tried to overcome this difficulty by using an excess of the organic acid, but it is evident that this procedure must yield impure products except when the solubilities of the acid and salt differ enough to permit separation by recrystallization. Even this is often impossible because many beryllium salts hydrolyze as soon as the acid is removed. The trichloroacetate furnishes an example of this. This difficulty might be obviated by crystallization from organic solvents. These mixtures were long thought to be true compounds because: (1) when washed with alcohol the products were finely granular although they showed no true crystals under the microscope; (2) the determination of their composition was based solely on the beryllium oxide content which we now know varies with temperature, concentration of acid, and amount of beryllium hydroxide or carbonate used; (3) the methods generally used for determining their molecular weights were inaccurate, because beryllium hydroxide dissolves in solutions of its normal salts, causing the freezing points to be abnormal (5). A simple and satisfactory solution of the problem of their preparation in a pure state, a t least in the case of the sulfonates, is described in this paper by a method which does not seem to have been used before. The beryllium salts were prepared by double decomposition of barium salts '

1 For former articles on beryllium, Bee This Journal 36, 2465, 2492, 3111 (1931); 36,2641 (1932).

59

60

HAROLD SIMMONS BOOTH AND DOROTHY GORDON PIERCE

of the respective acids with beryllium sulfate. This method is not applicable to the preparation of easily hydrolyzed compounds, but the fact that the sulfonates are gummy when prepared by neutralization would seem to indicate that previous failure might not be due entirely to hydrolysis but partly to the excess of hydroxide dissolved by the beryllium salt solution. The extreme solubility of beryllium sulfonates made recrystallization from water impracticable and therefore mixtures of organic solvents were used. To establish the definite chemical nature of the compounds (1) they were examined with the polarizing microscope; (2) the compounds were not analyzed in the usual way by ignition to oxide but after thorough drying were completely decomposed by fuming nitric acid in Carius tubes, and analyzed not only for the beryllium content, determined by the ignition of the precipitated hydroxide, but also for sulfate; (3) as a further proof a molecular weight determination was made by the boiling point rise method with acetone as solvent. PREPARATION AND PURIFICATION OF MATERIALS

The ethyl acetoacetate, the ethyl benzoate, the benzene, chloroform, dichloromethane, carbon disulfide, sulfonic acid, and carbon tetrachloride used were pure chemicals as obtained. Acetophenone was redistilled. . The acetone was dried over anhydrous sodium sulfate and redistilled. Toluene was stood over barium oxide for five hours, then distilled, and the fraction boiling a t 108.5"C.was used.

Barium hydroxide The crude barium oxide2was placed in a large evaporating dish and distilled water was added slowly, but rapidly enough to keep up a vigorous evolution of steam. When the addition of water caused no further reaction, the boiling hot mixture was poured quickly into another large evaporating dish full of distilled water to yield white crystals of barium hydroxide octahydrate. This mixture was brought to a boil, a few grams of barium peroxide were added to oxidize iron compounds, the mixture was boiled for 5 minutes and then allowed to cool, yielding colorless crystals of barium hydroxide octahydrate, iron free. Beryllium sulfate tetrahydrate was made by evaporating pure beryllium nitrate tetrahydrate crystals, made from purified beryllium hydroxide, with concentrated sulfuric acid until no fumes were noticeable (6). The product was twice recrystallized. Melting points were determined by the usual capillary method using a 360" thermometer calibrated a t the highest point, at the transition point

* Kindly furnished by Mr. M. J . Rentschler, J. H. R. Products Company, Willoughby, Ohio.

CHEMISTRY OF BERYLLIUM

61

of sodium sulfate decahydrate, at the steam point, and at the melting point of pure tin. For the determination of decomposition points the samples were heated in capillary tubes in a fused mixture of sodium and potassium nitrates. The molecular weights were determined by the boiling point method, using the electrically heated Beckman apparatus. ANALYSES

All the compounds except beryllium dibenzoylmethane were decomposed by fuming nitric acid in Carius tubes and the beryllium was determined by precipitation with ammonium hydroxide as beryllium hydroxide and ignition to beryllium oxide. I n the case of the sulfonates the filtrates from the beryllium hydroxide precipitate were used for the determination of the sulfates by precipitation as barium sulfate. PARTI SULFONATES OF BERYLLIUM

As stated before, the sulfonates of beryllium cannot be made pure by neutralizing solutions of the sulfonic acids with beryllium hydroxide or beryllium carbonate, because solutions of beryllium salts dissolve beryllium hydroxide, the solutions remaining acid to litmus although they contain a large excess of beryllium hydroxide. Crystals sometimes separate from these solutions after several months, but they are gummy and coated with beryllium hydroxide. Too little attention to this has been the cause of serious error in the past (7). An exception to this is the recent work of Sidgwick and Lewis (4) who prepared beryllium benzenesulfonate and beryllium p-toluenesulfonate by evaporating a mixture of the hydroxide with a slight excess of the acid. The salt crystallized out on cooling a concentrated solution. They stated that both sulfonates separated with four molecules of water, but they did not obtain the anhydrous salts, because they decompose on heating. They based the composition simply on the weight of beryllium oxide obtained by ignition. They did not make a detailed study because the salts were not suitable for their purpose. If the salts are made by neutralization, they may be separated from concentrated solutions containing beryllium hydroxide by precipitating the hydroxide with absolute alcohol, in which the beryllium salts are soluble, followed by filtering, and allowing the filtrate to evaporate. Even then, the crystals are gummy. If these crystals are allowed to stand for several months, the beryllium hydroxide becomes inactive and finally dehydrated, and will no longer dissolve in absolute alcohol, so that if the mixture is now dissolved in alcohol and filtered, good crystals may be obtained from the filtrate. This method is too slow and uncertain to be practicable. In this laboratory a quick and easy way to prepare the pure salts was

62


found to be by double decomposition of the barium salts with beryllium sulfate. The acid was neutralized with pure barium hydroxide, filtered, and evaporated to incipient crystallization. Most of the barium salts are beautifully crystalline and not very soluble. They were recrystallized from water when necessary. A solution of the pure salt was then mixed with one of beryllium sulfate, until further addition of either causedno precipitation. This point was determined by filtering a small portion of the mixture till clear, dividing into two portions, and testing one with a few drops of the solution of the barium salt and the other with the solution of beryllium sulfate. The mixtures were allowed to stand ten minutes. When exactly the right amount of beryllium sulfate had been added, the solution was digested to enlarge the barium sulfate particles, filtered, and evaporated nearly to dryness. If heated too strongly, or if evaporated to dryness, some of the salts hydrolyze or char, so the evaporation was completed in a vacuum desiccator. In some cases, crystals containing water of crystallization formed after the water had almost entirely evaporated. In other cases, only a crystalline mass remained. The products had to be dried in an over before they could be crystallized from organic solvents, because too much water prevents the formation of good crystals, and even if a precipitate does form, it partially redissolves. However, some water was evidently left in the salts, because the solvents used were free from water, and yet the products contained water of ~rystallization.~ The salt was dissolved in as small a quantity of acetone as possible, and the toluene, carbon tetrachloride, or chloroform was added until considerable precipitate had been formed. The mixtures were then filtered as quickly as possible. Fine crystals separated at once. These were redissolved by heating the mixture. It was then allowed to cool slowly. Mixtures of toluene and acetone, carbon tetrachloride and acetone, or chloroform and acetone were found to be the best solvents from which to recrystallize them. All these salts show polarization colors when examined under the microscope by polarized light. I n dry acetone solution, the dried salts are not acid to litmus, but after a few moments exposure to the air, enough moisture is condensed on the surface of the solution to cause hydrolysis, and the litmus turns pink, All the sulfonates dissolve a t once in liquid ammonia, and beryllium hydroxide is precipitated if the ammonia is not dry. The analyses and the fact that the microscope showed only one kind of crystal in each case, indicate that the products are pure. The molecular The exact amount was not determined in all cases because we were interested in obtaining anhydrous salts, but the melting points showed that several hydrates exist for each salt.


63

weight determination shows that, when dry, they are not associated or combined with the solvent. Beryllium p-toluenesulfonate [CEHI(CH~SO~I~~~

Beryllium p-toluenesulfonate crystallizes from a mixture of acetone and chloroform in colorless, monoclinic needles containing water of crystallieation. This may be driven off by drying in an oven, if the temperature is raised slowly enough. After being dried several hours a t 19O"C., the salt does not melt until it decomposes a t 318.5"C. (cor.). The analysis also shows that all the water has been driven off.

FIG. 1. BERYLLIUM p-TOLUENESULFONATE

Beryllium p-toluenesulfonate is very soluble in water, absolute alcohol, and acetone, and insoluble in ether, benzene, and dichloromethane. It is insoluble in cold glacial acetic acid, but very soluble in hot. It may be crystallized from water, but its extreme solubility makes this impracticable. When crystallized from a mixture of acetone and chloroform, it melts in its water of crystallization a t 133.8"C. (cor.), and again a t 143.5-145.5"C. (cor.). It appears to lose water from 120°C. up, even if the capillary tubes are sealed. It decomposes a t 318.5-319.5"C. (cor.). Analysis. (1) 0.2078 gram sample gave 0.0154 gram Be0 and 0.2760 gram BaSOd. Calculated: BeO, 7.14; S, 18.25. Found: BeO, 7.41; S,

64


18.24. (2) 0.1902 gram sample gave 0.0142 gram Be0 and 0.2558 gram BaS04. Calculated: BeO, 7.14; S, 18.25. Found: BeO, 7.47; S. 18.47. Beryllium p-XylenesuEfonate [CeHa(CHs),SOsIlBe.5HzO

Beryllium p-xylenesulfonate, unlike the other sulfonates, crystallizes readily from water solution. It may be boiled to dryness without decomposition, although solutions are acid to litmus. Since it is not hydroscopic, like the other sulfonates, the water of crystallization was easily determined, by drying in an oven at 140°C. It was found to contain five molecules of water of crystallization. Large, perfect crystals may be readily obtained on slowly cooling a hot water solution, if the concentration is correct. They are apparently

FIG.2. BERYLLIUM p-XYLENESULFONATE

monoclinic, having an extinction angle of 9" in one position, and showing parallel extinction in the other two. When thin, the crystals exhibit brilliant polarization colors. Beryllium p-xylenesulfonate is very soluble in water, absolute alcohol, hot glacial acetic acid, and acetone, and insoluble in ether, benzene, carbon tetrachloride, toluene, chloroform, dichloromethane, and carbon disulfide. When crystallized from water, it melts in its water of crystallization a t 143.2-144.2OC. (cor.), solidifies, and melts again at 177.8-178.8" (cor.). When dried a t 19O"C., it does not melt, but decomposes a t 326.9332.2' (cor.). Analysis. 0.1428 gram sample gave 0.0096 gram BeO; 0.2474 gram sample gave 0.3042 gram BaS04; 0.2078 gram sample lost 0.0400 gram water. Calculated: BeO, 6.62; S, 16.90; HzO, 19.20. Found: BeO, 6.72; S, 16.89; HzO, 19.25.


65

Beryllium 2-chlorotoluene-5-suEfonate [CsH,(CHd (C1)S0812Be

Beryllium 2-chlorotoluene-5-sulfonate is the only one of the sulfonates which does not melt, and yet a few crystals were once obtained which did melt in their water of crystallization. A detailed study was not made, but it would appear that crystallization under different conditions might produce different hydrates, The crystals do not melt even if the melting point tube is sealed and suddenly immersed in the sulfuric acid bath every ten degrees, and yet they lose weight when heated in an oven a t 190-200'C.

FIQ.3. BERYLLIUM 2-CHLOROTOLUENE-5-SULFONATE

The salt may be boiled t o dryness without much hydrolysis. It crystallizes from a mixture of dry acetone and carbon tetrachloride in long, colorless needles which are apparently monoclinic, since they have an extinction angle of 4' in one position, and show parallel extinction in the other two. Beryllium 2-chlorotoluene-5-sulfonate is very soluble in water, absolute alcohol, hot glacial acetic acid, and acetone, and insoluble in carbon disulfide, ether, benzene, carbon tetrachloride, toluene, chloroform, and dichloromethane. It decomposes a t 384.7-399.7'C. (cor.). Analysis. (1) 0.2964 gram gave 0.0178 gram Be0 and 0.3378 gram BaS04. Calculated: BeO, 5.97; S, 15.26. Found: BeO, 6.01; S, 15.65.

66


(2) 0.2514 gram gave 0.0158 gram Be0 and 0.2814 gram BaS04. Calculated: BeO, 5.97; S, 15.26. Found: BeO, 6.29; S, 15.37. Molecular weight: calculated, 420.24; found 440.3,418.0.

Beryllium benzenesulfonate (C6Hd303hBe

The barium salt used in the preparation of beryllium benzenesulfonate was not made from the acid because it was not available. Instead, a mixture of benzene sulfochloride and water was boiled, barium hydroxide being added slowly, until, after boiling a few minutes, the solution no longer became acid. The solution was then filtered by suction, the barium benzenesulfonate immediately crystallizing out in colorless plates, apparently triclinic, showing brilliant polarization colors under the microscope.

FIQ.4. BERYLLIUM BENZENESULFONATE Beryllium benzenesulfonate was made by double decomposition in the usual way. If the solution is evaporated on a water-bath, a hard solid results, which contains water of crystallization. This cannot be entirely removed by drying in an oven because the salt decomposes. After drying at about 120"C., the salt was cooled in a desiccator, pulverized, and recrystallized from a mixture of acetone and chloroform. The product gave no test for chlorides, even though there was a large amount mixed with the crude salt. Beryllium benzenesulfonate crystallizes from water in monoclinic plates having an extinction angle of 6" in one position and showing parallel extinction in the other two. These crystals appear to contain more water of crystallization than those recrystallized from a mixture of acetone and chloroform. The latter seem to be deliquescent. Beryllium benzenesulfonate is very soluble in water, glacial acetic acid,


67

alcohol, and acetone. It is insoluble in carbon disulfide, ether, benzene, carbon tetrachloride, toluene, and dichloromethane. It seems to be very slightly soluble in hot chloroform. When crystallized from a mixture of acetone and chloroform, the salt melts in its water of crystallization a t 72.9-74.9"C. (cor.), and again a t 94.4OC. (cor.), but if dried in the oven a t 90-100°C., it melts only a t 94.4"C. If it is carefully dried in the oven in a capillary tube, the temperature being slowly raised to 19O"C., it does not melt, It begins to decompose a t 358.7"C. (cor.). For analysis, the samples were placed in small tubes and carefully dried to constant weight at 120-130°C. Some samples seemed to lose all their

/ FIQ.6. BERYLLIUM 2-NITROTOLUENE-4-SULFONATE water at this temperature, but others decomposed, or else still contained water. Analysis. Calculated: BeO, 7.71. Found: BeO, 7.76.

Beryllium 2-nitrotoluene-4-su~onate tCsH3(CHd(N0dS0312Be

The barium salt used in the preparation of beryllium 2-nitrotoluene-4sulfonate was also made by hydrolysis of the sulfochloride, instead of by neutralizing the free acid. It crystallizes from water solution in large yellow plates, which seem to be triclinic and show brilliant polarization colors. The beryllium salt was made in the usual way, and recrystallized from a mixture of acetone and toluene. The salt crystallizes from this solution

68


in monoclinic needles having an extinction angle of 6 ' in one position and showing parallel extinction in the other two. They exhibit polarization colors. Beryllium 2-nitrotoluene-2-sulfonate is very soluble in water, absolute alcohol, acetone, and glacial acetic acid, and insoluble in carbon disulfide, ether, benzene, carbon tetrachloride, toluene, chloroform, and dichloromethane. It appears to be slightly hygroscopic. When crystallized from a mixture of acetone and toluene, it melts in its water of crystallization a t 140.6 -141.6"C. (cor.), then solidifies, and melts again a t 181.3-182.3"C.(cor.). If carefully dried in an oven a t 160"C.,it does not melt, but decomposition is noticeable a t 273.6"C.(cor.). Analysis. Calculated: BeO, 5.69; S, 14.53. Found: BeO, 6.05; S,

14.85.

FIG. 6.

BERYLLIUM m-NITROBENZENESULFONATE

Beryllium m-nitrobenxenesuEfonate [CeHdNOz)SOslnBe

Beryllium m-nitrobenzenesulfonate was made in the usual way. The water solution cannot be evaporated to dryness over a flame without decomposition. After evaporation in a vacuum desiccator, it was carefully dried in an oven and recrystallized from a mixture of acetone and carbon tetrachloride. It is hygroscopic. The crystal system of the salt when crystallized from a mixture of acetone and carbon tetrachloride was not determined, but the crystals forming on a slide as the solvent evaporated were monoclinic, having an extinction angle of 7" in one position and showing parallel extinction in the other two. Beryllium m-nitrobenzenesulfonate is very soluble in water, absolute alcohol, acetone, and hot glacial acetic acid, It is insoluble in carbon


69

disulfide, ether, benzene, carbon tetrachloride, toluene, chloroform, and dichloromethane. When crystallized from a mixture of acetone and carbon tetrachloride, it melts in its water of crystallization a t 146.8"C. (cor). If dried at 18OoC., it melts at 203.7-204.7"C. (cor.). It does uot solidify on further heating, but begins to decompose a t 231.8OC. (cor.). Analysis: Calculated: BeO, 6.07. Found: BeO, 5.95.

PARTI1 CHELATE BERYLLIUM COMPOUNDS

I n striking contrast to the beryllium salts of organic acids, beryllium acetylacetonate is a well-defined chemical compound 18). It is the product formed by replacing one hydrogen atom of each of two molecules of acetylacetone by one atom of beryllium, and is one of a series of metallic salts of tautomeric enol-keto compounds, the so-calle'd chelate compounds. The replaceable hydrogen atoms in the keto-form (9) are attached to a carbon atom which is between two carbonyl groups, OEC-CH2-C=O

I

I

The enol form, which forms salts, is H-O-C=CH-C=O

Or, as Sidgwick states, in beryllium acetylacetonate there are "rings with one definite coordinate link, in which the metallic (or hydrogen) atom is joined to the ring on one side by a normal link, and on the other by a coordinate link,

CHs -C-0

II

CH

I

CHs-C=O

0-C-CHs

II I

\ /

CH

Be

7

f

Y

O=C-CHa

Chelate rings of this type are very stable. Such compounds have very different properties from the ordinary salts of organic acids; for instance, they are soluble in most organic solvents and practically insoluble in water. The possibility of their being of use as solutes for the electrodeposition of beryllium and in other ways led to the second part of this work-the preparation of a few beryllium salts of such compounds. The copper salts of these compounds have been the most investigated. They are usually made by shaking an alcoholic solution of the ketone or ester or its sodium salt with copper acetate or sulfate, often with the THE JOURNAL OF PEYlICAL CHEMISTRY, VOL. XXXVII, NO.

1

.

70

HAROLD SIMMONS BOOTH AND DOROTHY GORDON P I E R C E

addition of ammonia. If chlorides are used an addition product, consisting of the copper salt and the metallic chloride or hydrogen chloride, is formed. The copper salts, as well as those of most metals, are crystalline and insoluble in water and ether, but are easily recrystallized from hot alcohol, benzene, or chloroform. Although it is possible to make the beryllium salts in this way, it is not desirable, because the product is generally very impure, owing to the insolubility of beryllium hydroxide or carbonate in the ketone or ester used. Therefore a different procedure was followed in each case, according to the solubilities of the raw materials and products. Two ketones, benzoylacetone, CJ%COCH2COCHs, and dibenzoylmethane, CBH6COCH2COCBHs and one ester, ethyl acetoacetate, CHsCOCH2COOC2Hr,were chosen as typical enol-keto compounds from which to make beryllium salts, in order to find out whether their properties resemble those of beryllium acetylacetonate. Each contains the grouping -COCHCO-

I

Be

-COdHCO-

Beryllium benzoylacetonate CHs

I C-0-Be-0-C /I tl'

C&

I /I C-H 1 1 H-C I e o -O=c H-c I I Enol form

We first tried to prepare beryllium benzoylacetonate by a method similar to that used by Combes (11). An alcoholic solution of benzoylacetone4 was added to moist freshly precipitated beryllium hydroxide, to which a little absolute alcohol had been added. Since the benzoylacetone is very insoluble in water, it immediately precipitates, along with the beryllium benzoylacetonate. The latter may be separated from the excess beryllium hydroxide by extraction with chloroform, but, since this also dissolves the benzoylacetone, the product is very impure. However, the two may be separated by alcohol in which the salt is not very soluble, whereas the ketone is very soluble. The yield is very poor. The benzoylacetone was made according to Vanino, Priiparative Chemie, Band 2, p. 537.

CHEMISTRY O F BERYLLIUM

71

We found that the salt also may be made by allowing beryllium sulfate to stand in an alcohol solution of benzoylacetone, but this too is a poor method, yielding a mixture. The best method we found was to add a weighed amount of beryllium nitrate dissolved in as little absolute alcohol as possible, drop by drop, to an equivalent weight of benzoylacetone also dissolved in as small a quantity of alcohol as possible, because the salt is soluble enough not to precipitate if the solutions are too d i l ~ t e . ~ The crystals were washed with absolute alcohol to remove the mother liquor and any excess benzoylacetone, which is very soluble in alcohol. They were then stirred with water to remove any beryllium nitrate or nitric acid, again washed with alcohol, and then ether, and recrystallized from pure toluene or benzene. Large

FIG.7. BERYLLIUM BENXOYLACETONATE

crystals may be obtained after a little practice. The temperature must be allowed to drop very slowly or else small crystals separate out even a t 70°C. A small beaker containing the boiling toluene solution was placed in a boiling water-bath and the temperature of the latter was allowed t o fall 20" every three hours. The solution was seeded a t 75°C. A t 55°C. the temperature was kept constant for two hours and then allowed to drop slowly to room temperature. Even then small crystals separated on filtering. The crystals were filtered immediately and washed with absolute alcohol and dry, fat-free ether. Large, perfect crystals may be obtained by allowing a benzene solution to evaporate, but on exposure to the air, these apparently lose benzene, becoming a white powder. Those crystallized In the latter case, crystals will sometimes form on standing, but usually the salt decomposes, yielding a brown oil. The crystals formed on standing are yellow, but if immediately precipitated, the product is nearly white. Considerably more of the salt may be recovered from the filtrate by evaporation under reduced pressure at 5G60"C.

72


from toluene do not change. They have the same melting point as the white powder left after the benzene evaporates from the other crystals. This would seem to indicate that they contain no toluene. The crystals are highly refractive and show brilliant polarization colors. They show neither pleochroism nor absorption. They are monoclinic, having an extinction angle of 15" in one position and showing parallel extinction in the other two. Beryllium benzoylacetonate is insoluble in water, almost insoluble in ether, fairly soluble in alcohol, benzene, carbon tetrachloride, toluene, and hot carbon disulfide, and very soluble in chloroform, acetone, and dichloromethane. It is insoluble in cold, but very soluble in hot glacial acetic acid. It is very slightly soluble in liquid ammonia. Ammonium hydroxide will not precipitate beryllium hydroxide, because the salt is insoluble in water, even if boiled seven hours, but if it is first boiled with nitric acid, and then made slightly alkaline with ammonium hydroxide, a heavy gelatinous precipitate results. It is very soluble in cold, concentrated sulfuric and nitric acids, and it dissolves in cold, concentrated hydrochloric acid on standing twenty-four hours. It is hydrolyzed by refluxing with dilute (1 :4) nitric acid in half an hour, and dissolves in dilute hydrochloric and sulfuric acids after boiling four hours. The crystals melt sharply a t 210.2-211.2"C. (cor.), and begin to decompose noticeably a t 22423°C. (cor.). They may be sublimed if heated quickly, before they have time to melt. Analysis. Calculated: BeO, 7.58. Found: BeO, 7.69, 7.65. Molecular weight: calculated, 331.24; found, 327.45, 343.6.

Beryllium dibenzoylmethane Ce"

I

C-0-Be-0-C

I

CeHs

CfiHs

I

I

CeHs

Dibenzoylmethane was made by condensing ethyl benzoate with acetophenone by means of sodium and extracting the resulting sodium salt with a mixture of ice cold water and ligroin. The dibenzoylmethane was separated by adding acetic acid to the solution of the sodium salt, filtering, and recrystallizing from methyl alcohol. This method is exceedingly tedious, and gives a very small yield, because the sodium salt hydrolyzes easily, producing a brown oil (probably acetophenone or a derivative), which clogs the filter paper and cannot be separated from the product


73

even by recrystallization. We found that a much quicker, easier way is to allow the ethyl benzoate, acetophenone, and sodium mixture to stand four or five days for the reaction to become complete, because a red-brown substance coats the sodium, making the reaction very slow. The resulting sodium salt was then washed with ether alone until it became nearly white, and dried in the air. The product was dissolved in water, and filtered quickly because it hydrolyzes easily. For the same reason it cannot be heated to get it into solution. The ketone was precipitated from this solution with acetic acid, a t once. The crystals were collected on a filter, washed with water until a flame test showed only a trace of sodium, and allowed t o dry in the air. The yield was fairly good, and the product almost white, although the melting point indicated that it was not pure. The beryllium salt6 was made by mixing equivalent amounts of the ketone and beryllium nitrate in absolute alcohol. The solutions must be made with as little alcohol as possible, because otherwise the crystallization is very slow, and the crystals impure. A warm solution of beryllium nitrate was added drop by drop to a warm solution of dibenzoylmethane. As soon as all the beryllium nitrate was added, and not before, needles of the beryllium salt began to separate' until the solution became almost solid. The crystals were filtered, washed with alcohol and ether and recrystallized from absolute alcohol. Since the salt is not very soluble, this is a slow process. It crystallizes in long, pale yellow needles, which are pure. The crystals are light and mat easily. They do not stick together, but adhere to everything else, so that it is practically impossible to make pellets of them for a molecular weight determination. They cannot be introduced into the tube by a paper funnel because they stick to the paper. If the salt is put into small glass tubes and then slid into a larger tube, it does not dissolve completely out of the tubes even if allowed to boil all day. Therefore a molecular weight determination was not made. The needles show brilliant polarization colors and are apparently monoclinic, having an extinction angle of 5" in one position and showing parallel extinction in the other two. The ends are always jagged, as no pinacoid or prism faces form. (See figure 8, page 75.) Beryllium dibenzoylmethane is insoluble in water, slightly soluble in It cannot be made by mixing the ketone with beryllium hydroxide because the ketone, being insoluble in water, precipitates immediately, along with what little of the salt is formed. If the materials are not in equivalent amounts, or if the dibenzoylmethane is not almost white, no crystals separate. If it stands long enough, or is distilled under reduced pressure, a brown paste results which cannot be easily purified. A very small amount may be recovered by leaching out the impurity with alcohol, in which beryllium dibeneoylmethane is not very soluble. If the dibeneoylmethane is pure, a good deal of the product may be recovered from the filtrate by evaporation under reduced pressure.

74


ether, fairly soluble in carbon tetrachloride, toluene, and hot alcohol, and very soluble in benzene, chloroform, acetone, carbon disulfide, and dichloromethane. It is insoluble in cold glacial acetic acid, but very soluble when heated. It is insoluble in liquid ammonia. Beryllium hydroxide is not precipitated on addition of ammonium hydroxide to a mixture of the salt and water, owing to the insolubility of the salt, but after it is boiled a few minutes with nitric acid, ammonia causes a heavy gelatinous precipitate. It is neither dissolved nor hydrolyzed by water, even after seven hours boiling. It is very soluble in cold concentrated sulfuric acid and nitric acid. It does not dissolve in cold, concentrated hydrochloric acid, but dissolves when heated. It is insoluble in dilute sulfuric acid and hydrochloric acid, even when boiled seven hours. After two hours boiling, it dissolves in dilute nitric acid, with the separation of a white, powdery precipitate. The crystals melt sharply at 214-215°C. (cor.), and do not decompose easily. A noticeable change in color occurred a t 262" (cor.). The compound may be sublimed if heated quickly, before it melts. Analusis. Calculated: BeO, 5.51. Found: BeO, 5.60. I

Beryllium ethyl acetoacetate CHa

I

CHs

'11

I

C-0-Be-0-C

ii

C-H

1 c=oI

OCA

H-C

/I

I 1-o==c1

I

OCzH6

Beryllium ethyl acetoacetate was prepared by stirring ethyl acetoacetate into moist beryllium hydroxide t o which a little absolute alcohol had been added. As soon as the acetate was added, a salmon-pink oil began to separate. The reaction must be watched, because if allowed to stand too long, the mixture becomes a mass of crystals which cannot be separated from the excess beryllium hydroxide. The reaction may be complete in one hour or may take several days. The beryllium ethyl acetoacetate cannot be separated by extraction with ether, because some ethyl acetoacetate is dissolved also, contaminating the product. Therefore small portions of the oil were removed by a pipet about every five minutes and dropped into ice-cold distilled water. When a sample formed crystals immediately, the oil was quickly separated from the beryllium hydroxide by a pipet. The oil was separated by a suction filter from any beryllium oxide which might have been included and poured into about twenty times


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its own volume of ice-cold distilled water. The beaker was packed in ice and left until the oil had entirely solidified. If left in the water too long, the salt hydrolyzes. Since the crystals are light, they leave the oil and rise to the surface. As soon as this happened, the mass was separated from the liquid on a suction filter. The crystals were removed from the funnel and stirred with 400-600 cc. of distilled water at room temperature, and again filtered. The washing was repeated until the product was pure white. It must be done quickly in order to prevent hydrolysis. Dried in a vacuum desiccator, the salt becomes a pure white, fluffy, crystalline product which melts sharply a t 60.6"C., giving a clear melt. It is too soluble in most organic solvents to be easily recrystallized. The product

FIQ.8. BERYLLIUM DIBENZOYLMETHANE may be separated from any beryllium oxide by dissolving in fat-free ether and filtering. Since crystals do not form until the ether has evaporated, a photograph of the separate crystals is difficult to obtain. As the ether evaporates, crystals build up on the edges of the filter paper, and these were scraped off and photographed. Owing to the fact that the crystals could not be separated from the mother liquor, it was difficult to determine the crystal system to which they belong. They seem to be monoclinic, having an extinction angle of 7" in one position and showing parallel extinction in the other two. Beryllium ethyl acetoazetate is insoluble in water and very soluble in alcohol, ether, benzene, carbon tetrachloride, dichloromethane, and glacial acetic acid. It is only slightly soluble in liquid ammonia contained in a n open beaker. It begins to decompose into beryllium hydroxide and ethyl

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acetoacetate if allowed to stand in water a few moments, and hydrolysis is complete on boiling. It dissolves instantly in cold concentrated hydrochloric acid, in nitric acid, and in dilute sulfuric acid. In the latter case, an oil separates. Beryllium ethyl acetoacetate is very soluble in cold, concentrated sulfuric acid, in dilute hydrochloric acid, and in dilute nitric acid. It melts sharply a t 60.6-61.1"C. (cor.), giving a clear melt. If heated slowly, i t begins to decompose a t 228.5"C. (cor.), turning yellow. Since the most carefully made salt still contained about 7 per cent of beryllium oxide, which was the only impurity provided the washing was thorough, this had to be removed before analysis. A pure product was obtained by dissolving the impure salt in dry, fat-free ether, filtering, and driving off the ether on a water-bath. The melted salt was then poured

FIG.9. BERYLLIUM ETHYL ACETOACETATE into a weighed glass tube, such as is used in Carius analyses, and cooled in a desiccator and analyzed. Analysis. Calculated: BeO, 9.39. Found: BeO, 9.52, 9.46. Molecular weight: calculated, 267.24; found, 266.8, 261.2. After this work was finished, an article (13) appeared describing the preparation of beryllium ethyl acetoacetate by a slightly different method from that by which it was prepared in this laboratory. "Beryllium acetoacetic ester was prepared according to the method described by Konrad (Ann. 188, 273) for the preparation of the aluminum compound. A berylate solution was prepared by adding strong potassium hydroxide to 10.1 grams of beryllium sulfate until the alkali was slightly in excess, and then adding 17 grams of freshly distilled acetoacetic ester. From the originally clear solution, there soon separated colorless leaflets, which could be recrystallized from petroleum ether, and which melted a t 63°C. The yield was 3 grams, 20 per cent of the theoretical. The crystals may be


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easily distilled in a vacuum a t 166°C. under a pressure of 13 mm. They are readily soluble in alcohol, benzene, etc." SUMMARY O F PART I1

Beryllium benzoylacetonate and beryllium dibenzoylmethane were found to be very similar to beryllium acetylacetonate. They are both crystalline, well-defined compounds, soluble in alcohol, acetone, chloroform, benzene, carbon tetrachloride, toluene, carbon disulfide, and dichloromethane, and insoluble in water. They melt sharply, but a t much higher temperatures than the acetylacetonate, 210.2"C. and 214"C., respectively, and they do not sublime readily, although they may be sublimed if heated quickly, before they have time to melt; beryllium acetylacetonate melts a t 108°C. and begins to sublime even before 100°C. They are soluble in concentrated acids, but are not hydrolyzed by water even after boiling seven hours. Beryllium ethyl acetoacetate, however, although it dissolves in the same solvents, is much too soluble to be crystallized from any of them. It is very easily hydrolyzed to beryllium hydroxide and ethyl acetoacetate, even in cold water. Hydrolysis also takes place when toluene, benzene, or ether solutions are allowed to evaporate slowly and is probably due to water absorbed by solvent. Beryllium ethyl acetoacetate melts a t a much lower temperature than the other two compounds, namely, 60.6"C. It may be sublimed if heated quickly under reduced pressure, but under atmospheric pressure it melts, and, if carefully heated, may be distilled a t about 150°C., although some decomposition always takes place. A comparison of the solubilities of the salts in ether is interesting. Beryllium ethyl acetoacetate is exceedingly soluble ; beryllium acetylacetonate is soluble; beryllium dibenxoylmethane is slightly soluble; while beryllium benzoylacetonate is almost insoluble. SUMMARY

The following compounds have been made and analyzed, and their properties studied: beryllium p-toluenesulfonate, beryllium p-xylenesulfonate, beryllium 2-chlorotoluene-5-sulfonate, beryllium benzenesulfonate, beryllium 2-nitrotoluenesulfonate, beryllium m-nitrobenzenesulfonate, beryllium beneoylacetonate, beryllium dibenzoylmethane, and beryllium ethyl acetoacetate. REFERENCES (1) PARSONS: The Chemistry and Literature of Beryllium, p. 71. The Chemical Publishing Co., Easton, Pa. (1909). (2) PARSONS: J. Am.Chem. SOC.31, 1205 (1909). (3) PARSONS: J. Phys. Chem. 11,659 (1907). (4) SIDQWICK AND LEWIS: J. Chem. SOC.129, 1287 (1926).

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( 5 ) Reference 1, p. 17.

(6) (7) (8) (9) (10)

(11) (12) (13)

BOOTHAND TORREY: J. Phys. Chem. 36. 2468 (1931). Reference 1, p. 69. PARSONS: J. Am. Chem. SOC.26, 732 (1904). SIDGWICK: The Electronic, Theory of Valency, p. 240. Oxford University Press, London (1929). MORGAN: J. Chem. SOC.T106, 189 (1914); T117, 1457 (1920) for a discussion of the structure of these compounds. COMBES:Compt. rend. 119, 1221 (1894). VANINO:Praparative Chemie, Zweit,e Auflage, Band 2, Organische Teil, p. 538. A N D FOREEL: Ber. 69, 2246-7 (1926). WEYGAND

The Chemistry of Beryllium. V. Organic Compounds of Beryllium

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