THE ACTION OF BASES ON NON-METALS A. LAURENCE CURL.THE OHIOSTATEUNIVERSITY, COLUMBUS, OHIO
Most of the non-metallic elements, with the exceptions of nitrogen and the rare gases, react with the alkali hydroxides. I n general the reactions take place i n accordance with the type Cb
+ 2NaOH +NaCl + NaOCl + H1O.
Compounds i n which the non-metallic element i s respectierely negatine and positiue, or the decomposition products of the same, are formed. The exact mechanism of this type of reaction is not k n m and i s not discussed. The rea~tionwith carbon i s anomalous. Further evidence is obtained by the reactions with the alkali amides, which are analogous to the hydroxides in the ammonia system of compounds. In ammonia, the polysulfides, polyphosphides, etc., are more stable than in water, but the ammono salts are less stable than the corresponding aquo salts.
. . . . . .
Reactions are known to take place between bases and many of the elements. These elements may be divided into two classesthe metals a t the left of the periodic table, and the non-metals. Most of the intermediate elements are not very readily attacked. The purpose of this paper is to discuss the action of bases upon the nonmetallic elements, most of which react with bases, with the exceptions chiefly of the Group 0 gases and nitrogen. Some of these reactions are used commercially, as for example the production of bleaching powder and of lime-sulfur spray by the action of chlorine and sulfur, respectively, on calcium hydroxide. At 6rst sight, it seems as though these various reactions have no close relation to each other. However, i t has been shown that these reactions can generally be referred to a certain type ( I ) , namely, C12
+ 2NaOH -+NaCI + NaOCl + H.0,
in which one atom of chlorine ~ a i n an s electron and is converted into the negative chloride ion CI-, and the other loses an electron and goes into the hypocblorite ion C10-, in which the chlorine has a positive valence of one. The hypochlorite ion may be pictured as analogous to the hydroxide ion OH-, in which positive hydrogen is replaced by positive chlorine. There are two general conditions under which these reactions may take place, the first being the use of solutions of the bases, and the second the use of the fused bases. In the case of a given element, these two conditions may give quite different reaction products, but closer study reveals the fact that these variations are probably due chiefly to the difference in temperature and concentration. Reactions in aqueous solutions of bases take place a t temperatures up to a few degrees above 100°C., whereas sodium hydroxide melts a t 318OC. and potassium hydroxide a t 3 6 0 ° C and the reactions of the fused substances usually take place in the vicinity 490
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ACTION OF BASES ON NON-METALS
4$1
of, or above, the melting point. The difference in the two types of reactions may be explained, in part a t least, as being due to the instability of some of the initially formed products a t the higher temperature of the fusion process. The mechanism of this type of reaction is not well known. It will suffice here to point out that the course of the reaction usually results in the formation of one compound in which the non-metal is negative, and another in which it is positive (as in NaCl and NaOCl in the first equation), or the decomposition products of the same. The usual reaction of chlorine and sodium hydroxide is given in the first equation. When chlorine is passed into a hot solution of sodium hydroxide, some sodium chlorate is formed by a reaction of auto-oxidation and reduction 3NaCIO d NaC103
+ 2NaCI
and similarly, when a solution of sodium chlorate is heated, auto-oxidation and reduction again occurs. 4NaCI03 -+3NaCIOh
+ NaCl
Bromine and iodine react with alkalies in a similar manner to chlorine. Fluorine, however, has a differentreaction.
This apparent anomaly can be brought into line by assuming the formation of the hypofluorite, which breaks down immediately into the fluoride and oxygen. 2NaOF --+- 2NaF
+ O2
Indeed, hypochlorous acid is known to break down on heating with the evolution of oxygen. 2HOC1+
2HC1+ On
Further evidence for the intermediate formation of the hypofluorite is the discovery of oxygen difluoride ( 2 ) .OF%,which has been separated from the gases evolved from the action of fluorine upon a two per cent solution of sodium hydroxide. This oxide may be considered as the anhydride of the hypothetical hypofluorons acid. In group six we find that sulfur, selenium, and tellurium react with sodium hydroxide in a similar manner. In the case of sulfur the reaction may be summarized in this equation,
The reaction takes place with the primary formation of the sulfide and sulfite, which then add on sulfur to form, respectively, the polysnlfide and thiosulfate.
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The reaction differs in the case of selenium and tellurium in the nonformation of the thioselenate and thiotellurate from the selenite and tellurite. (22
+ 1)Se + fiNaOH +2Na2Se, + NarSeO. + 3H10
The equation representing the reaction of phosphorus and sodium hydroxide is usually written: 4P
+ 3NaOH + 3H.O
4 PH.
+ 3NaHaP01
The reaction is more complicated than represented by this equation (3). The following equations probably express the reaction better, although not accounting for all of the products formed.
+
+
+
4P lONaOH -+2NarP 2Na.HPO. 4Hn0 2NaaP 7H204 PHs NaHsPO* NaOH 2Ha
+
+
Combining these equations: 4P
+ lONaOH + 3H.O
4 pH8
+
+
+ ZNalHPOs + NaHzP02
The presence of the higher oxidation'product has been shown, as well as the presence of higher hydrides of phosphorus. The first equation postulates the initial formation of the phosphide, in which phosphorus is negative, and the phosphite in which it is positive, the phosphide then hydrolyzing in a more complex manner than would be supposed from the simple equation Na3P
+ 3Hs0 -+3NaOH + PHI
When arsenic is boiled with a solution of sodium hydroxide, arsine and an alkali arsenite are formed. As
+ 3NaOH
4ASH.
+ NasAsO.
The arsiue probably results from the sodium arsenide which might be expected to form first. When arsenic is fused with sodium hydroxide, sodium arsenide, sodium arsenite, and hydrogen are formed. The following equations express the reactions.
Some sodium arsenide would be expected to remain as the water would be driven out immediately. These two reactions of arsenic differ chiefly in the temperature a t which they take place, the arsine being decomposed a t the higher temperature. The reaction with carbon, although much studied, is not very well defined. Sodium has been prepared by reduction of the hydroxide with
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ACTION OF BASES ON NON-METALS
493
carbon. Sodium carbonate, carbon monoxide, hydrogen, hydrocarbons, and various complex compounds have been reported in reactions of various forms of carbon with the hydroxides. It seems as though the reaction is not definite enough to attempt to bring i t in line with the others. Silicon, germanium, and tin all react similarly with the bases. M
+ 4KOH --+ K4MO4+ 2H2
M represents the various elements. The ortho compounds are not stable and consequently the meta salts of the type K8M03are obtained. In Group 111, boron reacts with sodium hydroxide to form sodium orthoborate and hydrogen. 2B + 6NaOH --+ 3Na8BOa + 3Hs The evolution of hydrogen is probably similar to the cases of silicon, germanium, and tin. Further evidence that the non-metals in general react with bases in accordance with the equation C12
+ 2NaOH -+NaCl + NaOCl + H1O
is advanced by a study of the reactions of the non-metals on the alkali amides, which are the strong bases of the ammonia system of compounds. The alkali amides are thus the analogs of the alkali hydroxides (4). Ammonia resembles water closely in many of its abnormal properties, i. e., boiling point, heat of vaporization, surface tension, the property of dissolving salts to form conducting solutions, etc. Sodium hydroxide may be considered as derived from water by replacing a hydrogen by a sodium atom. In fact, this is one method of preparing sodium hydroxide. In an analogous manner, sodium amide may be derived from ammonia by replacing a hydrogen by a sodium atom. This reaction also takes place, but the velocity is much less than the previous one. 2Na + 2HOH --+ NaOH + HZ 2Na
+ 2HNHz +NaNH* + H2
The following reactions show the similarity between these two types of compounds. Ba(N0.). Ba(NO&
+ 2KOH --+ Ba(0H). + 2KNOa + 2KNHs +Ba(NH& + 2KN01 (5)
In water, barium hydroxide is precipitated if the solutions are not too dilute. In ammonia, barium amide, the analogous compound, is precipitated.
+ 2KOH + 4HzO +KOAI(OH)n+ 3H9 + 2KNHg + 4NHa +KNHAI(NH& + 3H2 (6)
2A1 2A1
Aluminum dissolves in potassium hydroxide solution to form potassium aluminate. In potassium amide solution, potassium ammonoaluminate is formed.
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JOURNAL OF CHEMICAL EDUCATION 2CaHaCHO ZCsHsCH=NH
MARCH, 1931
+ KOH --+ CsHsCH20H + CeH6COOK
+ KNHa+C6H6CH3NH1 + CsHaC(NH)NHK (7)
Benzal imine, the ammono analog of benzaldehyde, undergoes the Cannizzaro reaction with potassium amide, benzylamine, an ammono alcohol, and potassium benzamidine, the salt of an ammono acid, being formed.
+ +
+ NazSOp + NalSOi ( 8 )
C6HsSOaONa NaOH --+ CsHrOH CaHsS020Na NaNHz +CaH.NH2
The sodium salt of benzene sulfonic acid when fused with sodium hydroxide forms phenol; when i t is fused with sodium amide, aniline, the ammono analog, is formed. These reactions serve to show the similarity in the reactions of the alkali hydroxides and amides. The reactions of the non-metals with potassium amide are in general similar to those of potassium hydroxide. There are two chief differences in the reactions. One is the increased stability of homo-atomic anions, i. e., polyphosphides, polysulfides, polystannides, etc., in liquid ammonia (9), since ammonolysis does not take place to the extent that hydrolysis goes on in water. The other is that salts of ammono acids, such as the ammonohypochlorites, are not as stable as the corresponding aquo salts, the hypochlorites. This instability is characteristic of many compounds of nitrogen, such as the nitrides, a number of which are quite explosive. The reaction between the halogens and potassium arnide in liquid ammonia or boilimg toluene is as follows, where Xt represents the halogen.
+ 6NaNHn --+ 6NaX + N Z+ 4NHa (10)
3x1
This reaction is quite similar to the reaction of fluorine on sodium hydroxide since the ammonohypohalites are unstable. In each case, the halide, the solvent, and the negative element of the solvent are formed. Hydrogen reacts with sodium amide a t 300' as follows: HZ
+ N a N H l S NaH + NH8 (11)
Pure sodium hydride has not been prepared by this method. This reaction takes place in the preparation of sodium amide from sodium and ammonia when the reaction is stopped before all of the sodium has reacted. It is probably fundamentally different from the other reactions, but is similar in that sodium hydride and ammonia are formed, in which compounds hydrogen is respectively negative and positive. Sulfur, selenium, and tellurium react with sodium amide in liquid ammonia (12) to form respectively polysulfides, polyselenides, and polytellurides, and what are believed to be ammonosulfites,selenites, and tellurites, such as S(NK)%. These compounds are the analogs of the sulfite, OS(OK)a. In the case of sulfur, the ammono salts are complex in nature, and those of selenium and tellurium are very explosive. In the reactions of the fused amides (13) the ammono salts are unstable, and decompose,
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495
evolving nitrogen in a similar manner as the halogens. The formation of complex ions such as S,--, Te,--, etc. (S.S--, SzS--, SaS--, SaS--, etc.), does not change the theory of these reactions because it has been shown by Kraus (14) that such compounds are salts and that the excess of electronegative element (S, etc.) present in the homo-atomic anion appears to alter in no way the valence of the one electronegative element originally in the anion. Ruff and Geisel (15), Franklin and Kraus (16), and Bergstrom (17) have found that sulfur slowly dissolves in liquid ammonia a t ordinary temperatures without evolution of gas. I t has been shown that sulfur reacts with ammonia in accordance with the equation 10s
+ 4NH3+6 H 8 + N9,.
Ammonia forms ammonium sulfide with hydrogen sulfide and with nitrogen sulfide a mixture of two acids, S(NH)%and S2(NH)2,which may be regarded, respectively, as a sulfurous and a thiosulfuric acid of the ammonia system. The reaction is thus similar to the reaction of chlorine on water. C1,
+ H,O +HCI + HOCl
Phosphorus reacts with sodium amide to form a polyphosphide and what is believed to he a sodium ammonophosphite, P(NNa)NHNa (IS), analogous to sodium phosphite. The reaction with arsenic and antimony in solution (18) is similar, whereas when antimony and bismuth are fused with the amides (13), polyantimonides and polybismutbides are formed. and nitrogen is evolved, the ammonoantimonate and hismuthate heing unstable a t this temperature. Carbon reacts with sodium amide around 500-600°C. to form disodium cyanamide and hydrogen. 2NaNH2
+ C +NaNCN + 2Ha (19)
Near 800°C. the cyanamide reacts with the excess of carbon to form the cyanide. NaNCN
+ C -+2NaCN (20)
These reactions seem to depend somewhat upon concentration because hydrogen and cyanamide are formed when sodium cyanide is dissolved in fused sodium amide at 400°C. NaCN
+ NaNHl +NasNCN + H2 (21)
Germanium also evolves hydrogen when treated with potassium amide, a mixture of ammonogermanite and germanate probably heing formed (13). Tin (22) and lead (23) react similarly, except that the polystannides and polyplumhides are stable and no hydrogen is evolved. lOSn
+ 6KNH1+
2SnNK.2NH8
+ K'Sn.
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JOURNAL OF CHEMICAL EDUCATION
MARCH.1931
By analogy, in the reaction with KOH, the stannide would be formed, which would decompose with the evolution of hydrogen.
In the case of lead, potassium polyplumbide, K4Pbs, and presumably potassium ammonoplumbite are formed. Thus i t can be shown that there are certain similarities in the reactions of non-metallic elements and bases. The reactions are generally analogous for sodium hydroxide and sodium amide, but varying as to the stability of the various products formed. The polystannides and similar compounds are much more stable in ammonia than in water, but the ammono salts are less stable than the corresponding aquo salts. The majority of these reactions are all of the same type, i . e., C4
+ 2 N a O H j NaCl + NaOCl + HIO
The mechanism of these reactions is not very clear, but it is possible to classify most of these reactions under a single type and thus clarify what might otherwise be a rather confusing and apparently diverse series of reactions. The writer wishes to express his appreciation to Dr. W . C. Fernelius for his helpful suggestions and criticisms. Literature Cited (I)
BERGSTROM, "Reactions of the Type CI.
+ ZKOH +KC1 + KC10 + H.0,"
J. Phys. Chem., 30, 12 (Jan.. 1926). and DAMIENS, "Sur un nouveau mode de pr6paratian du fluorure d'oxy(2) LEBEAU g&ne," Compt. rend., 188, 1253 (May, 1929); Rum and MENZEL,Z. anorg. Chem., 190, 257 (1930). ( 31 WINTER."An Investieation of Sodamide and of Certain of Its Reaction Prod~, ucts," J. Am. Chem. Sac., 26, 1509 (Nov., 1904). and JOHNSON, "Liquid Ammonia as a Solvent and the Ammoniz (4) FERNELIUS System of Compounds. 11. Inorganic Ammonia Compounds," J. CHEM. Eouc., 5, 828 (July, 1928). (5) FR-IN, "Potassium Ammonobarate, Ammonostrontiate and Ammonocalciate," J. Am. Chem. Soc., 37, 2298 (Oct., 1915). (6) BE~osTRonn,"Displacement of Metals from Solutions of Their Salts by Less Electropositive Elements. I. The Replacement of Sodium and Potassium by Magnesium and Aluminum," ibid., 45, 2278 (Dee.. 1923). (7) STRAIN,"Hydrobenzamide and Benzylidene Imine as Ammono Aldehydes," ibid., 49, 1563 fJune, 1927). "Eine neue Darstellungsweise fiir aromatische Amine," Bn., 39, 3006 (8) SACKS, (Sept.. 1906). "Liquid Ammonia as a Solvent and the Ammonia ( 9 ) JOHNSON and FERNELIUS, System of Compounds. V. The Properties of Solutions of Metallic Compounds in Liquid Ammonia," J. CHEM. Eouc., 7, 981 (May, 1930).
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EPRRAIU, "Zur K a n t n i s des Natriumamids," 2. anorg. Ckem., 44, 189 (Mar., 1905); (b)see ref. (I). M m s , "The Reaction between Sodamide and Hydrogen," Pmc. Roy. Soc. Edinburgh, 35, 134 (April, 1915); GUNTZand BENOIT,"Sur l'amidure de sodium industriel," Bull. soc. chim. [4]41,434 (1927). See ref. (I),p. 14. FERNELIUS and BERcsTRoM, forthcoming publication. W u s , "The Constitution of Metallic Substances," J. Am. Chem. Soc., 44, 1216 Oune. 1922). RUFF and GEISEL, "Das Sulfammonium und seine Beziehungen zum Schwefelsti&stoff," Ber.. 38, 2659 (1905). FRANKLINand RRAUs, "Liquid Ammonia as a Solvent," Am. Chem. J., 20, 830 (Dec.. 1898). B E n c s ~ n o ~"Solutions , of the Electronegative Elements in Liquid Ammonia. I. The Action of Selenium, Tellurium, Arsenic and a Solution of Sulfur in Liquid Ammonia upon Cyanides," J. Am. Chen. Soc., 48,2319 (Sept., 1926). (a) See ref. (I),p. 15; (b) see ref. (13). SVARVASY, "Electrolysis of the Nitrogen Hydrides and of Hydroxylamine," J. Chem. Soc., 77, 606 (1900); DENNISand B R ~ W N "Hydronitric E, Acid and the Inorganic Trinitrides." J. Am. Chem. Soc., 26, 588 (June. 1904). MARTIN,"Industrial Chemistry," Part 11, Vol. I , D. Appleton and Ca., New York City, 1915, p. 486. "Verfahren zur Darstellung von Alkalicyanamid," D. R. P. 124.977,October 22. 1901 (see C h m . Cent?., 1901, 11, 1100). See ref. (18) (a). See ref. (I),p. 18. (a)
