SILVER PERCHLORATE AND NITRATE COMPLEXES WITH ALKYNES
Aug. 20, 1937
refractive index corresponds with that of a mixture containing 51.1% a-pinene. The mixture, 2.05 g., was treated with silver perchlorate, 0.75 e., and left t o stand at 25' for 7 hr., when the products were-separated by the method described abo;e. The liquid, 1.00 g. (49%), distilled from the mixture had a Z 5 D +30.7", ~ Z ~ L 1.4662. D These figures correspond with those of a mixture of a-pinene with @-pinenecontaining 78.3 and 78.2y0 a-pinene, respectively. The liquid, 0.60 g. (297c), obtained by treating the solid phase with water, 2 ml., had a Z 5-14.7', ~ n 2 5 1.4756. ~ These figures correspond with those of a mixture cmtaining 92.2 and %.lyO 8-pinene, respectively. The agreement between the two methods of analysis for both fractions confirms that no chemical change had occurred and that the recovered liquids consisted of only the mixed pinenes. Behavior of @-Pinene and B-Pinene toward Aqueous Silver Perchlorate.-A solution of silver perchlorate, 6 g., in water, 5 ml., was shaken with 8-pinene, 0.5 ml., for several minutes a t 2 5 " . The 8-pinene was thereby completely converted t o a white solid, which was not analyzed but was probably the same complex as that formed in the absence of water. An identical experiment in which a-pinene was substituted for the 8-pinene did not produce any solid, the apinene remaining instead as a separate liquid phase. A further experiment, in which a mixture, 0.5 ml., of equal volumes of the two pinenes was taken, gave a mixture of solid and two liquid phases. This might be a promising
[CONTRIBUTION No. 2191
FROM THE
434 I
method for the separation of a-pinene and &pinene from each other. Preparation of Silver Nitrate-Cyclohexene Complex.l5Silver nitrate, 3.6 g., was dissolved in a warm mixture of cyclohexene, 15 ml., and ethanol, 2 ml. At room temperature a system of two colorless phases was formed, and a t 0" the lower phase gave a mass of needle-shaped crystals. Filtration a t ca. 4' gave 4.6 g. of product, m.p. 24-32'. Anal. Calcd. for AgNOs.2CsHio: Ag, 32.3. Found: Ag, 33.2, 33.3. Pinenes and Silver Nitrate.-Attempts t o obtain a solid complex were unsuccessful with pinene (practical) or pinene diluted with a solvent, for example, acetone, methanol or ethanol. Miscellaneous Observations.-Silver perchlorate dissolves readily in 2-pentene, in I-hexene and in 4-methyl-2pentene t o form systems consisting of two colorless liquid phases.lB Crystals form when the 2-pentene system is cooled below room temperature. Silver nitrate dissolves t o some extent in 2-pentene and in 4-methyl-2-pentene, but no second liquid phase results. (15) The complex, but not its preparation, has previously been described by Salomon.6 (16) Francis7 found t h a t silver nitrate gave two liquid phases with propene and 1-butene but not with mixed pentenes
PASADETA, CALIF.
GATESAND CRELLINLABORATORIES OF CHEXISTRY, CALIFORNIA INSTITUTE OF TECHSOLOGY]
Coordination of Silver Ion with Unsaturated Compounds. X. Complexes of Silver Perchlorate and Silver Nitrate with Alkynes1 BY
ALANE. COMYNS~ AND HOWARD J. LUCAS3 RECEIVED MARCH6, 1957
Systems of silver nitrate and silver perchlorate with 2-butyne, 2-pentyne and 3-hexyne have been studied. plexes are formed, and their solubilities in the alkynes have been measured a t 25'.
Previous investigations in this ~ e r i e sof~ ,the ~ coordination6of alkynes with silver ion were devoted to measuring equilibrium constants in aqueous solution. We now report studies on systems formed in the absence of added solvent. As before, only dialkylacetylenes have been studied in order to obviate complications from the presence of acidic hydrogen atoms on 1-alkynes. Silver perchlorate and silver nitrate differ markedly in their solubilities in the three alkynes, as shown in Table I. Except in the case of the TABLE I SOLUBILITIES OF AgClO,
AND
AgN03 COMPLEXES IN AL25'
KYSES AT
2-Butyne
2-Pentyne
3-Hexyne
AgC104" 0.10 68 65 .10 211 185 AgC1Odb 0.22 0.24 AgN03n .28 Grams of AgClOa or AgN03 per 100 g. of solution. Grams of Age104 per 100 g. of solvent. (1) This research has been made possible by support extended the California Institute of Technology by the O5ce of Naval Research under Contract Nonr-270(00). (2) Arthur Amos Noyes Fellow, 1952-1953. (3) To whom requests for reprints should be sent. ( 4 ) W.S. Dorrey and H. J. Lucas, THISJOURNAL, 18, 1665 (1956). ( 5 ) G. K. Helmkamp, F. L. Carter and H. J. Lucas, ibid., 19, 1306 (1957). (6) The reaction is considered t o be complexing; J. G. Traynham and M. F. Sehnert, ibdd., 18, 4024 (1956).
Solid coni
silver perchlorate-2-butyne system, where a solid complex is rapidly and quantitatively formed, the solids in contact with the "saturated" solutions were mixtures of unreacted silver salt with solid complexes. This was due to the slowness with which solid complexes were formed, and in consequence the solubilities given in Table I are not true equilibrium values. Silver Perchlorate Complexes.-The solubility of silver perchlorate in 2-pentyne and 3-hexyne is about two thousand times that in 2-butyne. This is probably a consequence of the symmetry of the 2-butyne molecule, which favors packing into a crystal lattice, rather than the formation of concentrated solutions. Similar behavior is found in related systems: thus silver perchlorate is insoluble in dioxane' but very soluble in tetrahydropyran8 and is sparingly soluble in cyclohexene but very soluble in l - h e ~ e n e . ~In each of these systems the solvents of more symmetrical structure readily form solid complexes with silver perchlorate but are poor solvents for these complexes. The compositions of the "saturated" solutions of silver perchlorate in 2-pentyne and 3-hexyne a t 25' correspond with molal ratios of alkyne to silver perchlorate of 1.4:l. Partial evaporation of the (7) A. E. Comyns and H. J. Lucas, ibid., 76, 1019 (1964). ( 8 ) A. E. Comyns and H. J. Lucas, unpublished results. (9) A. E. Comyns and H. J. Lucas, T H I SJOURNAL, 79, 4339 (1957).
4342
ALAN
E.
c O > I Y X S AND
HOWARD J. LUCAS
VOl. 79
alkyne gives in each case a solid in which this ratio When 2-butyne and 2-pentyne were shaken with is approximately 1: 3 silver nitrate at 25" for five days, some silver niSolutions of 7.2 to 41y0 silver perchlorate in 2- trate remained unchanged. 2-Butyne became pentyne (molal ratios of alkyne to silver perchlorate yellow and a silver mirror was deposited on the between 39:l and 4.3:l) exist a t 25' as two con- walls of the vessel. When a mixture of 2-butyne jugate liquid phases of these compositions. Solu- and silver nitrate was warmed gently to 65', the tions containing less than 7.2% and between 41 and crystals of silver nitrate dissolved and a second, (j8% of silver perchlorate in 2-pentyne consist of denser, initially yellow liquid phase appeared. one liquid phase. The more concentrated solutions This rapidly became dark brown and a silver mirare viscous and become pale brown after standing ror was deposited. Because of this side reaction, for several days. no satisfactory complex was isolated. Solutions of silver perchlorate in alkynes silverPowdered silver nitrate reacted quantitatively plate metallic copper, as do solutions of silver salts with 3-hexyne in 8 weeks to give the colorless crysof fluoro acids in aromatic hydrocarbons.1° Con- talline complex, AgNOaC,Hlo. l 2 rentrated solutions in 2-pentyne and 3-hexyne esExperimental plode on contact with mercury. Materials.-Silver perchlorate and silver nitrate were of X-apor pressure data obtained on the system reagent grade, the former from the G. F. Smith Co. The silver perchlorate-2-butyne, are plotted in Fig. 1. alkynes were all purchased from the Farchan Research Systems containing 2-butyne in excess of the for- Laboratories and purified by standing over sodium for 24
200 240
e8
i
160
40
1 1
1
2.4 2.6
1
1
1
2.8 3.0
1
1
3.2
L
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3.4
1
1
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3.6 3.8
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