417s
COMMUNICATIONS TO
THE
EDITOR
1701.
7s
and is, in fact, identical with the observed intermediate having an absorption maximum a t 356 mp. However, these results do not exclude other compounds, such as the hypothetical formiminotetrahydrofolic acid,12 as intermediates which could give rise to 10-formyl-THF directly or by way of 5,lO-f ormyl !-THF.
terpretation of the results. The probable error with the applied technique is within 2-70. The values for silicon tetrafluoride were obtained from measurements a t various concentrations in carbon tetrachloride and in n-hexane, and extrapolation of the value for the pure compound. For this particular measurement we believe that the (12) R . D. Sagers, J. V. Beck, W.Gruber a n d I. C. Gunsalus, THIS maximum probable error does not exceed *30 JOURNAL, 78,694 (1956). cycles per second. The fluorine resonance of our reference substance SATIONAL INSTITUTE OF ARTHRITIS AND METABOLIC DISEASES JESSEC. RABINOWITZis shifted 2,665 cycles per second toward higher SATIONAL INSTITUTES O F HEALTH W. E. PRICER,JR. fields from that of trifluoroacetic acid, and thus the UNITEDSTATESPUBLICHEALTH SERVICE F19resonance of silicon tetrafluoride is 3,479 cycles BETHESDA,MARYLAND per second higher than that of trifluoroacetic acid. RECEIVED JUNE 25, 1956 (This would correspond to 0.554 gams a t 25.4G mc., which is the frequency used by Gutowsky and THE NUCLEAR MAGNETIC RESONANCE SPECTRA Hoffman’ when they found 0.611.) OF F” I N METHYL- AND ETHYLFLUOROSILANES The shielding of the fluorine atoms in the fluoroSir : silanes may well be controlled by a number of It has been suggested that the chemical shift effects the most important of which are probably of F19 atoms in binary fluorides has a direct rela- an inductive effect, and a s-bonding effect. Subtionship with the electronegativity of the’ atom stitution of electron-releasing alkyl groups on bound to fluorine.‘ The extent of magnetic silicon should result in an increase in shielding of shielding of fluorine in the fluorosilanes is reported the fluorine atoms. An opposing effect leading to here. As would be expected the chemical shift a reduction in the fluoride shielding would be the differs from one compound to another. occurrence of Si-F d s - p s - b ~ n d i n g . ~ From our Figure 1 shows the relative shifts of the methyl- present knowledge of chemical bonding it is not and ethylfluorosilanes and silicon tetrafluoride in possible to quantitatively predict the extent of these cycles per second in a magnetic field of approxi- two opposing effects. Certainly the electronmately 9,989 gauss. We used diethyldifluorosilane releasing effect would be increased by substituting as reference substance. All the values given corre- ethyl groups for methyL4 spond to the pure liquids a t room temperature. Extensive study of the proton resonance in Extrapolation of values for an infinitely dilute solu- methyl derivatives of silicon and the other group tion in carbon tetrachloride from data obtained a t I V elements is now being conducted by hlr. A. L. various concentrations does not change the sequence Xllred of this laboratory, and i t is hoped that this of the shifts, nor does i t affect the qualitative in- will shed further light on the shifts of fluorine resonance noted above.
t
I
(3) F. G. A. Stone a n d D. Seyferth, J. Iiaorg. and Nuclear C h e m . , 1, 112 (1956). ( 4 ) J. W. Baker, “Hyperconjugation,”. Oxford a t t h e Clarendon Press, p. 6.
I
I
\\
MALLINCKRODT CHEMICAL LABORATORY HARVARD UNIVERSITY ERHARD SCHNELL CAMBRIDGE, MASS. EUGENE G. ROCHOW RECEIVED JULY11, 1956
CYCLOHEXADECA-I,J,9,11-TETRAYNE,A
CYCLIC
TETRA-ACETYLENE
Sir.
Number of A l k y l
Groups
P
Fig. 1. (1) H. S. Gutowsky a n d C. J. Hoffman, P h y s . Rev., 80, 110 (1950); J. Chem. P h y s . , 19, 1295 (19511, a n d 20,200 (1952), who have measured a large number of fluorine compounds including silicon tetra0uoride. ( 2 ) Measurements were m a d e o n a Varian N-M-R Spectrometer a t 40 megacycles using a 5-mm. spinning sample t u b e containing a 1-mm. sealed capillary of reference substance a s described b y Aksel A. BothnerBy a n d Richard E. Glick, THISJOURNAL, 78, 1071 (1956).
We have prepared the cyclic tetra-acetylene, cyclohexadeca-1,3,9,ll-tetrayne(11), in one step from octa-1,7-diyne (Ia) by a novel cyclization reaction. In the course of a general investigation into the oxidative coupling of terminal diacetylenes, t h e aerial oxidation of octa-1,7-diyne (Ia) in the presence of cuprous chloride and ammonium chloride was studied. When the reaction mixture in water was shaken in air a t 20°, the ordinary dimer,’ hexadeca- 1,7,9,15-tetra yne (Ib) (m.p. 2 1-22 O, b.p . 119-120’ (0.1 mm.), n Z 31.5205, ~ Amax 226, 238 and 253 mp, log e, 700, 620 and 430 respectively, VmaX 3300 and 2235 cm.-’, found: C, 91.32; H, 8.80) (1) T h e terms “dimer” a n d “ t e t r a m e r ” are used t o denote products derived respectively from t w o and four molecules of monomer, although their empirical formulas are of course not exact multiples of t h e monomer.
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r\ug. 20, 1956
4 179
was essentially the only product formed. How- heavy water mixtures has been investigated. Irever when the reaction was carried out in aqueous radiations were carried out in six cylindrical sample ethanol a t E",air being bubbled through the mix- holders rotating about their own axes and around ture, three substances were formed. The first two central 2-Curie CoB0sources. Ferric ion con(ca. 40% yield) was the dimer Ib, which on hydro- centrations were determined colorimetrically USgenation gave hexadecane. The second (ca. 20y0 ing the ferric thiocyanate complex. We found extinction curves to be dependent on the concenyield) was the tetramer, dotriaconta-1,7,9,15,17,23,25,31-octayne (IC)(m.p. 92-93', Amax. 226, 240 tration of heavy water and have determined these and 254 mp, log E 1190, 1140 and 720, respectively, curves experimentally for all water compositions used. The solutions irradiated were 0.8 T in Yma,, 3310 and 2235 crn.-l, found: C, 92.11: H, 7.93), the structure of which was confirmed by H2SO4and 1 mM. in ferrous ammonium sulfate and hydrogenation to dotriacontane. The third (ca. contained oxygen. Radiation doses varied from 10% yield) was the cyclic dimer I1 [m.p. 158- 1 to 20 X lozo ev./liter. Results of our experi160' (dec.), Amax. 227, 239 and 2,54 mp, log E , 380, ments are shown in Table I : 600 and 360, respectively, vmax. 2235 cm.-l (-C= C-) but not a t ca. 3330 ern.-' (no =C-H), found: TABLE I C, 92.48; H, 7.621. The structure was conFERRIC IONYIELDSFOR HsO-DpO MIXTURES firmed by the infrared spectrum, the absence of a Atom YOD in solvent precipitate with alcoholic silver nitrate and by full hydrogen G F ~ +, hydrogenation to cyclohexadecane, identified by 1 5 . 5(assumed) 0 direct comparison with an authentic sample. 16.1 0 . 2 55 ,-C=C--C=C
H[-C=C-(CH?)~-C=EC-]
,,H(CH?)I
*
1
(CH?)r
LC=C-.C=C-~
8.5 98
17.0 =t0 . 5 18 A + 0 . 8
1
I t is reported by Hart' that the primary yield for molecular hydrogen is higher in light than in heavy water. Probably this means that the radical DO? is formed with a higher yield than HO? and The cyclic dimer I1 must have been formed di- this difference may play an important role in the rectly from two molecules of the monomer by cou- differences we have observed. He also indicates pling a t both ends, rather thag via the dimer I b that the difference between the yield of free radiwhich' cyclizes internally, for separate oxidative cals in heavy water and in light water is more coupling of the dimer Ib yielded only the tetramer than equivalent to the first difference. If this ICand none of the cyclic dimer 11. excess is real i t is reasonable to ascribe it t o a The cyclic tetra-acetylene 11, the first carbo- higher recombination rate of hydroxyl radicals cyclic compound incorporating more than two with free atoms of light hydrogen than of deuteacetylenic linkages,? contains two parallel straight rium. For both these reasons it is of interest to a-diacetylene chains bound together on both sides consider our G-values as a function of the ratio of by a tetramethylene bridge. As in the compounds light hydrogen t o deuterium in the free hydrogen studied by Cram, et al., in which two parallel groups radicals in the solution. If we calculate the light or -C=C-) are joined by two tetra- hydrogen to deuterium ratio in the free atoms from the figures given by Topley and E y i n g , ? methylene bridges,?Z3the chromophoric systems in we find that our G-values depend on the isotope IT are too far apart for appreciable interaction to ratio in the free atoms in a way which is not far occur, as judged by the normal ultraviolet spec- from linear. I t should be kept in mind, however, trum. that representations of similar simplicity of the The scope of the new cyclization reaction and the value of G can be obtained as a function of other properties and transformations of I1 are now being quantities such as the mole fraction of DOD moleinvestigated. We are indebted to Prof. V. Prelog cules in the liquid. These considerations seem t o for a sample of cyclohexadecane. make i t important to compare by direct measure(2) D. J. C r a m a n d N. I-. hllinger (THIS J O U R N A L , 7 8 , 2518 (1926)) ment the G-values of molecular HS, H D and Dz in have recently described t h e preparation of cyclododeca-l,7-diyne via solutions of ferrous sulfate in various concentraa n acyloin t y p e cyclization. Moreover G Eglinton and A . R. Galtions of light and heavy water. hraith have privately communicated t o us t h a t they have prepared Thanks are due to the Foundation for Fundacyclic polyacetylenes by t h e coupling o f terminal diacetylenes. ( 3 ) D . J. Cram, e l nl , ibin'.. 76, 6132 ( 1 9 5 4 ) : 7 7 , 4090 (1953). mental Research of Matter (F.O.M.) and the DANIELSIEFFRESEARCH INSTITUTE Organization for Pure Research (2.W.O.) who supWEIZMAXN INSTITUTE OF SCIEYCE FRANZ SONDHEIMER ported this work. C.N.T. is indebted to the REHOVOTH, ISRAEL YAACOV AMIEL U.S.E.F. Neth. for a Fulbright Grant. la, n = 1 b,n = 2 c,n = 4
(111
(-a-
RECEIVED JCSE 28, 1956
ACTION OF GAMMA RAYS ON FERROUS ION SOLUTIONS IN HEAVY WATER Sir :
The action of cobalt 60 gamma radiation on solutions of ferrous ammonium sulfate in light and
INSTITUCT VOOR KERNPHYSISCH OXDERZOEK CONRAD N. TRUMBORE A. H. W.ATEN, J R . .4MSTERDAM, HOLLAND RECEIVED JULY 5, 1956 (1) E. J. H a r t , W. R. McDonell, and S . Gordon Proceedings of t h e Geneva Conference o n Peaceful Uses of Atomic Energy (1;nitt.d Nations, New York, 1956) Volume 7, p. 593 (1955). (2) B . Topley and H . Eyring, J . Chem. P h y s . , 2, 217 (1934).
