R. P. GUPTA
1128
=
[C&1
(consumed)
+
[fl +0 1+ v
[CHd
+ 2[C2Hd + 3[C&I + 4lbutenesl + 5 6
The amount of cyclohexene originally placed in the pyrolysis flask was determined from the pressure, temperature and volume of the pyrolysis flask. Since the volume of the flasks was not quite constant, the volume of each vessel was determined after its contents had been analyzed. The firstorder decomposition constants are shown in Table IV. As may be noted, experiments with different initial pressures of
The relation between the amount of cyclohexene present a t time t and the original amount of cyclohexene
(0).
is given by equation 19
(19)
show the reaction to be
first order. The effect of added surface is very small. Experiments run for different times of reaction showed that the products had no profound effects on the rate constant. The Arrhenius plot of the rate constants for the rate of disappearance of cyclohexene is shown in Fig. 1. The probable error and the number of observations are also indicated. The and intercept are from the least squares fit of the data, and give ko = 7.7 X l O I 6 exp(-67600/RT set.-'>* The calculation of the rate constants for the two unimolecular intramolecular reaction paths were calculated from the rate Of appearance Of and the sum Of
6 c]and
Vol. 65
The Path Producing ethylene, for
example, earl be formulated. d( CzHJ - d r = k1
(0)
(18)
Substituting equation 19 in equation 18 and integrating ki =
ko(CzH4)
(20)
(1 - (exp(-kot))
kl may be calculated readily from equation 20 since all the quantities on the right-hand side are determined. The first-order constants for formation of ethylene and of cyclohexadiene are shown in Table IV, and the ~ ~ plots of~ the rate1 constants in Fig. 1. The specific first-order rate constants calculated from the least squares best fit of the dataarek, = 1.4 x 101'exp (-72700/RT) set.-', and lc2 = 1.9 X 10l6 exp (-71200/RT) sec. -I. Acknowledgments.-We wish to thank Rilrs. Helen R. Young and Mr. Joseph H. Johnson for the mass spectrometer analyses and computations.
NUCLEAR MAGNETIC RESONAKCE STUDY OF SOME LIQUID-CONTAIKING POLY-(HEXAPllETHYLENE ADIPAMIDES) BY R. P. GUPTA] Department of Physics, The Pennsylvania Slate University, Universily Park, Pa. Reeeiz3ed December I , 1960
Nuclear magnetic resonance studv of poly-(hexamethylene adipamide) containing ethylene glycol, ethyl alcohol, methyl alcohol and acetic acid, has been done with the object to observe the effect of liquid contents on the molecular motion in the polymer. Two main transitions have been observed for the soaked samples: one about a t 16OoItransition has shifted for only about 5' / 0.08 toward lower temperature side, with respect to ethylene glycol and for methyl alcohol it has shifted further by about 10'. A further shift oi. about 10°K. is observed for acetic acid soaked ? 0.06 specimen. The content of the liquids in nyloii 66 ' Z varies a little bit but this niay not be the only f 0.04 reason to cause this shift in transition temperature amongst themselves. The shift in transition temperature is clue to two reasons: one is that the per cent. content of the liquids varies from sample to sample, though this variation is not much. The other reason is that acetic acid is more chemi100 I50 200 250 300 350 400 cally active compared with ethylene glycol or Temp., "K. ethyl alcohol on a nylon sample; therefore it muses Fig. 3.-xylon 66 containing ethylene glycol. a greater lowering or" the transition temperature. Dynamic mechanical observations show a simi. lar shift in transition temperature for the soaked samples as shown in Fig. 3-5 (the plots lor damping versus temperature for ethylene glycol soaked sample, ethyl alcohol soaked sample and acetic acid soaked sample). The frequency used for the above measurements has been varied in a range oi 2500 to 500 c.p.5;. between liquid nitrogen and room temperatures, for these samples. Dyiiamic mechanical results tally, reasonably, v i t h n.m.r. remilts. I n case 0; ethyl alcohol soaked sample we get a peak at about 280'K. n-hich is probably due to motion in crystallites and corresponds to the second peak in n.1n.r. The corresponding peak lor dry material appears a t 365'IZ. For methyl alcohol soaked sample clnly one peak has been reported by Woodward. Acetic acid soaked nylon sample shows thrw pealis. The first and second peaks corI ' 100 150 200 250 300 350 400 respond to the peaks detected by n.m.r. The third peak may be due to incomplete saturation of Temp., "IC. nylon with acetic acid. This could cause the Fig. 4.--Nylon 66 containing ethyl alcohol. motion in crystallites in two phases and a t two different temperatures. The peaks detected by the dynamic mechanical method in the case of the 0.10 dry sample correspond to 1i.m.r. peaks. There has been a good agreement betv-een dynamic mechanical and n.1n.r. results, but there are some differences which arise mainly because the frequencies used in the two methods are quite different. To explain the process one may say that the liquids afiect the amorphous regions principally, in a partially carystalline polymer and lower the amorphous region transition due to disruption of interchain bonding forces and lead to greater chain rigidity below this transition temperature. The liquid molecule; may more between amide and methylene groups and break the hydrogen bonds in the amorphous regions. This teiids to keep the hydrocarboii portion ol" adjacent chains sepa100 150 200 250 300 350 400 rated and leads to a better packing oi these porTemp., "K. tions. This ma,y be the reason !or the higher second Fig. 5,--Nylon 66 containing acetic :ic~1-1. moment for soaked specimens than :or dry ones, before the first transition temperature. The tran- about 350'K. Transition at about 170'IZ. is due to sition a t rtbout 260'Ii. could be attributed to the segmental motion of a small number of CH, groups segmental motion of methylene groupi: arid adja- in betu-een amide groups, in the amorphous region. cent non-bonded amide groups. This 14 due t o -1ddition or^ liquid acts to decrease this CH, group glass transition but not lor the dry material. motion. It could be due to interference of liquid For dry material thr same transition appears a t moleculrs with moving hydrocarboii segments. 0
h
z
v h
d
r-
0
1132
RALPHA. ZISGAROAND RICHARD M. HEDGES
Acetic acid being more active for this disruption in nylon, compa,red with ethylene glycol, therefore, it causes a greater shift in the transition temperature. Acknowledgment.--I am very much thankful to Dr. Woodward for suggesting this problem and
Vol. 65
taking interest in it. I am grateful, also, to DI. Sauer for arranging a financial grant from the Atomic Energy Commission to support this work. My thanks are due to Miss K. Fielenbach for her encouragement during the coiirse of this work.
PHOSPHINE OXIDE-HALOGEN COMPLEXES: EFFECT ON P-0 AND P-S STRETCHING FREQUESCIES' BYRALPH A. ZINGAROAND RICHARD h4. HEDGES Department of Chemistry of the Agricultural and Mechanical College of Texas, College Station, Texas Received December 18, 1060
The P-0 or F-S stretching frequency of a free phosphine oxide or sulfide molecule shifts to a lower frequenc on halogen complexing. This shift indicates that such interaction occurs through the oxygen atom. The factors which aJect the P-0 band are discussed and an empirical correlation relating the steric and polar substituent constants to the location of this band is presented. phme oxide was furnished by the Oak Ridge National LabIntroduction oratory. Its purification paralleled that for TOP?. As part of an over-all study involving molecular The material used had a refractive index of 1.4643 a t 20 . complex formation between phosphine oxides, All of the other phosphine oxides and phosphine sulfides sulfides or selenides and halogens or interhalogens, were prepared in this Laboratory. Every sample was recrystallized to a constant melting point and checked by we have exainined the effect of such interaction analysis. The preparative techniques employed and the upon the P-0 and P-S stretching frequencies. physical constants of the compounds used are described elseIn these donor molecules, interaction must occur where .e Halogens and Interhalogens.-The preparation and/or through the oxygen, sulfur or selenium atom, alpurification of all of the halogens and halogenoids is dethough the possibility of interaction involving scribed elsewhere.' Solutions of these compounds were aromatic substituents must also be considered in prepared by dissolving weighed amounts in appropriate the arylsubstituted compounds. Reported and volumes of solvent. The solvents were of spectral grade discussed are the results observed for a series of and were dried and redistilled before use. Attempts to prepare fairly concentrated (-1 M ) soluseven phosphine oxides and four phosphine sul- tions of either iodine monochloride or iodine monobromide in fides. The P--Se stretching frequency is beyond the carbon disulfide led to unexpected resultfi. The solution range of rock salt and the effect of halogen complex- warmed rapidly and after a few seconds reacted most vigoring on this vibration is not presently reported. ously, in fact, almost violently, the contents of the flask being very widely scattered. The formation of either sulPlans are being made for such investigation. furyl chloride or sulfuryl bromide, as reaction products, Although molecular complex formation involving was noted. Inasmuch as iodine monochloride is described the halogens .has been the subject of considerable in standard reference books as being soluble in carbon distudy during the past decade, to the best of our sulfide,*it appears that this is true only within certain limits of concentration. Due to the force of the reaction and the knowledge, these represent the initial observations toxicity of the reaction products, this observation seemed involving phosphine oxides as donor molecules. worthy of note. Consequently it was necessary to prepare Tsubomura and Kliegman2 have carried out an solutions of these interhalogens in carhon tetrachloride. ultraviolet study of the iodine-tri-n-butyl phos- While this was undesirable, due to infrared absorption of this it was nevertheless unavoidable. phate system and have speculated on the donor solvent, Measurement of Spectra.-All measurements were made properties of the P-0 groups as compared with the on a Beckman IR-4 instrument. The instrument was caliR-0 groups in alkyl phosphates. The absence of brated by means of standard polystyrene sample before each R-0 groups in the phosphine oxides eliminates run. Single beam scanning of all Eolutions was carried out, possible, ueing comparable slit widths for a given this difficulty. Sheldon and Tyree3 and Cotton whenever series so that relative intensities coiild be compared. and co-workers4 have investigated the effects of A number of experimental difficulties were encountered metal ion coordination on the P-0 stretching which made observations impossible in some cases or which frequencies of the trimethyl- and triphenyl- deriv- reduced the value of some observations. The strong absorption of carbon tetrachloride and chloroform at about 1220 atives in the solid state. em.-' overlaps the P-0 band in the raw of triphenylphosphine oxide and the intense absorption of these solvents in Experimental Phosphine Oxides and Sulfides.-Tri-n-octylphosphine oxide (TOPO) of high purity was used and its purification is described e l s e ~ l i e r e . ~A sample of tri-2-ethylhexylphos___-
(1) Presented a t the Southwest Regional Meeting of the American Chemical Society, Oklahoma City, Oklahoma, December 1, 1960. (2) H. Tsubomura and J. Kliegman, J . A m . Chem. Soc., 8 2 , 1314 (1960). (3) J. C. Sheldon and 9. Y . Tyree, ibid., 80, 4775 (1958). (4) F. A. Cotton, R. D. Barnes and E. Bannister, J . Chem. Soc., 2199 (1960). (5) R. A. Zingaro and J. C. White, J . Inorg. Nucl. Chem., 12, 315 (1960).
the 720-800 em.-' region interfered in thv case of measurements of the phosphine sulfides Eince this is the region or the P-S stretching vibration. In a few cases, the phosphine oxide or sulfide was insoluble in carbon disulfide and similar difficulties were preeented due to solvent interference. These
(6) C. G. Screttas, Master's Thesis. Agricultural and Mechanical College of Texas, 1960, to be published. (7) R. A. Zingaro and W. B. Witmer, J . Phus. Chem., 64, 1705 (1960). (8) E.&, "Handbook of Chemistry and Physics," Chemical Rubber Publishing Co., Cleveland, Ohio, 1957-1958 edition, p . 537, and other standard reference works.
