March, 1961
NUCLEsR 31AGNETIC
RESONANCE O F Sy?Z-anti ISOMERISM
of P(O), however, as it is reasonable to expect much of Ihe effects of correlation to cancel. In any case the entire polymer chain would collapse to within A’ of the surface as P(0,t’) for the polymer given by Fig. 2 approaches unity. A significant point with regard to equation 15 and the curves of Fig. 2 is that P(0) may bevery sensitive to 8 over a certain range of 8. In considering the thermodynamics of chain adsorption*J the number of anchoring segments v = P(O)t is an important factor. It is seen that for e going from 0 to 0.9, v may vary over a wide range (-a factor of ten) if, say K-10 a t 0 = 0 (or K-1 a t 8 = 0.9 if KO remains constant). Any isotherm equation should take this variation of v into account if agreement with experiments is to he expected. Comparison of Calculations with Data Recently Fontana and Thomas13 have carried out some very interesting experiments bearing on the problem of the configuration of adsorbed polymers. They were able to directly determine P(0) for poly-(alkyl methacrylate), PLMA, adsorbed onto silica by infrared spectrometry. Their investigation showed that, for this system, P(0) is relatively independent of 8 over a wide range of e. Since it is clear from their work that the mechanism of adsorption involves hydrogen bonding between the surface hydroxyl groups on (13)
E. J. I’ontana and J. R. Thomas, J . Phys. Chem., 66, 480
(1961).
IN
KETOXIMES
49 1
the silica and the carbonyl groups on the polymer, e is very likely relatively large (>5kT) for this case. Thus, their data is consistent with the idea that this system is operating a t the upper regions of the curves in Fig. 2 where P(0) is relatively insensitive to 8. These investigators found, however, that the relatively constant value for P(0) was not unity but instead about 0.4. This, as the authors point out, most probably is a result of the combination of polymer backbone inflexibility and availability of properly spaced adsorption sites. It is to be expected that as P(0) approaches a value as high as 0.4 the chain becomes relatively rigid (as compared to the solution configuration) and surface site spacing and surface uniformity requirements become more critical. Furthermore, under these conditions both intermolecular and intramolecular overlapping of portions of the chains will lead to smaller P(0) because of steric effects. Alternatively it may be stated that at P ( 0 ) = 0.4 the entire PLMA chain is collapsed t o the surface to the extent that equation 18 might be more appropriate. Acknowledgments.-The author wishes to acknowledge the very helpful suggestions and discussions concerning the problem with Drs. 0. L. Harle, J. R. Thomas and B. J. Fontana. He also gives thanks to Professor R. L. Scott for his critical examination of the methods employed in this article.
A NUCLE9R MAGNETIC RESONANCE STUDY OF syn-anti ISOMERISM I N KETOXIMES BY ERNEST LUSTIG Division of Physical Chemistry, h’ational Bureau of Standards, Washington $5, D.C. Received September $1, 1060
Isomerism of the syn-anti kind has been detected for the first time in several aliphatic ketoxinies and ketoxime ethers and is indicated by the presence of two resonance lines for the protons on carbon atoms next to the >C=KOH or >C=SOR group. The separation of these two lines depends on (a) the presence of aromatic compounds, acids or bases in the oxime solution, and (b) on the concentration. A differential ring-current effect and the presence of oxime ions are assumed to be responsible for these separations. Steric effects and internal hydrogen-bonding seem to account for the apparent absence of a second isomer in some cases.
Introduction The separation of geometrical isomers and the behavior of oximes has been a subject for controversy. 1 Although the chemical behavior of these substances gives valuable clues to their isomerism, only direct methods for determining molecular structure can reliably establish the non-linearity of the C=NO- group which gives rise to this isomerism. Several X-ray diffraction studies have shown that the CNO angle is 113 f 2”. The only oxime for which the structure of both isomers has been determined is p-chlorobenzaldoxime.2 In the anti form, the oxygen atom was found to lie closer to the (1) J . Meisenheimer and W . Theilacker, “Stereochemie des Stickstaffs,”in “Stereochemie” (K.Freudenberg, ed.), F. Deuticke, Leipzig and Vienna, 1933. (2) B. Jerslev, Nature, 166, 741 (1950); 180, 1410 (1958).
ring than in the syn form. This result confirms earlier assumptions about the structure of these two aldoxime isomers. Nuclear magnetic resonance is a valuable technique complementary to the preceding, since hydrogen atoms (or fluorine atoms) in the neighborhood of the oxime group can be probes for detecting asymmetry in oxime molecules of the R&=XOH type, as well as in alternative isomeric structures of the R’R”C=XOH type. Phillips3 has recently reported work on aliphatic aldoximes (RHC=KOH). The fact that the spectra show txyo multiplets, separated by about 0.6 p.p.m., for the aldehydic hydrogen atoms, was ascribed to the simultaneous exirtence of syn and anti isomers; he also assigned (3) W. D. Phillips, Ann. N. Y. Acad. S e t , 70, 817 (1958).
ERNEST LUSTIG
492
Vol. G5
TABLE I PROTON
RESONANCE SEPARATIONS FOR SYMMETIEICAL IC=XOH group, differewes resulting from the non-linearity of this group, might be sufficient to give rise to an obstrvablc chemical shift, e.g., for one methyl group in acetoxirne wil h respect t o the other. As has now been observed, however, the frequency of the resonance l i i m of these protons differs only when certain solvents are iwd, and the separation of the lines depends on concentration. Measurable separations rrere found in “aromatic” solvents, such as benzene, thiophene, furan, and their derivatives, and in solutions of naphthalene in carbon tetrachloride and carbon disulfide. In pyridine solutions separatioiis n ere alqo observed, but because of the basic nature of pyridine, there may have been an additional eff‘cct due to OH- (see below). The magnitiitlcs of thew splittings were found to depend on the iicld z.t~cngt11,so that spin-spin coupling is cxcludcd.
Experimental All data weri: taken with a Varian 60 mc./sec. n.m.r. fipectrometer, etcept for a few measurements made a t 24.3 mc./sec. to check the field dependence. The scale of the
spectra mas established directly on the recorder trace by the side-band technique. All measurements were made a t room temperature and on undegassed material. Some spectra are shown in Fig. 1. The oximes were obtained from the following sources: (a) gift: 2,4-dirnethyl-3-pentanone oxime (diisopropyl ketoxime) 111,4from Prof. D. E. Pearson, Vanderbilt Univer(4) Roman numerals designate the compounds listed in Tables
111.
Separation, c./sec.
Compound
I-
15 1.5 1.5
SolVc.llt
Concn. g./100 ml. of s o h .
Benzene Benzene Benzene Carbon tetrachloride
10 10 20
Benzene
10
Acetone Benzene Benzene
10 10 10
sity; (b) commercial sourres: acetoxime I, from Eastman; butanone oxime VIII, from Matheson, Coleman, and Bell; acetophenone oxime, from Eastman; (c) prepared in this Laboratory: all other oximes (see Tables I and I11 for references). The compound CF3-C(=iYOH)-CsH5, 2,2,2trifluoroacetophenone oxime, which is not described in the literature, was prepared by refluxing 12.3 ml. of the ketone with 100 ml. of a 1:1 methanol-water mixture containing 10 g. of NHzOH.HC1 and 14 g. of NaOAc.3Hz0, for two hours; 50 ml. of liquid were then distilled off. The residue (which had separated into two layers) was poured into cold water, whereupon the oxime was precipitated. After recrystallization from ligroin, i t melted a t 75”.
TABLE I1 METHYLSEPARATIONS FOR ACETONE OXIME Solvent
Benzene
Concn. 41. Peparaof soln. tion. C./SPI,
g./100
20 10 5 1 5 5 5
4.1 4.9 5.5 6.2 4 4 1 3 1.5
Toluene Nitrobenzene Naphthalene (about 30% Foln. in CS,) 5 3.2 Furan Thiophene 5 4.3 Benzene-carbon tetrachloride mixtures” n=7 10 4.8 5 10 3.8 3 10 2 4 1 10 0.8 Prepared by placing I 8 . of acetone oxime in a 10-ml. volumetric flask, adding TZ ml. of benzene, and diluting to volume with CC14.
Results and Discussion In symmetrical ketoximes (see Table J), it was observed that the resonances of protons on carbon atoms adjacent to the >C=NOH group appeared in the spectrum twice, with equal intensity. This may be expected, since the two radicals bound to this group are not equivalent because of the nonlinearity of the >C=XOH group. With the exception of 111, such a “splitting” occurred in the (5) E. W. Bousquet, “Organic Syntheses,” Coll. Vol. 2. MoGrawHill Book Co., New York. N. Y.,1943, p. 313. (6) D. C. Iffland, G. X. Criner, M. Coral, F. J. Lotspeich, 2. B. Papanastassiou and S. M. White, Jr.. J. Am. Chem. Sac., 76, 4044 (1953); private communication from Prof. Iffland. (7) E. Beckmann Ber., 19, 988 (1886). ( 8 ) A. I. Vogel T \ . T . Cresswell, G. H. Jeffrey and J. Leicester, J . Chem. SOC.,514 (1952).
XUCLEAR MAGNETIC RESONANCE OF syn-anti ISOMERISM IN KETOXINES
March, 1961
493
TABLE I11 SEPARATIONS~ FOR UNSYMMETRICAL METHYLKETOXIMES, C HS-C( =N OH)-R Corn-
pound
R
Ref.
(VIII)b CHz-CRz (IX)b GHs-CHz 22 ( X) CH,-CH~-CH, 5 (XI) (CH3)z-CH-CHz 9 (XII) CHzCI 10 (XIII) (CH8)zCH 5 (XIV) CH3-C112-CH(CHa) 5 (XV) (CHJzCkCH 11 (XVI) (CeH;)z--CH 12 13 (XVII) (CHa)& (XVIII) C0OR'i:R' = H, CH3, 14,15,16 or C2:KJ In 10% behzene solution. * See Fig. c Obscured by spin-spin splittings. (I
CHa
CH2
separation
aeparation
6.2 6.1 6.3 4.9 .0 0
17.0 19.2 ?= ?" 0
..
2.5
.. ..
0 0
..
0
..
0 .. 1 for spectrum.
presence of aromatic compounds only (see Table 11), or when the oxime molecule itself had an aromatic substituent. Thus t,he presence of the phenyl group in 1-phenyl-2-propanone oxime (phenylacetone oxime, IX) was sufficient to cause separation of resonance lines. XO splittings were found in any of a large number of non-aromatic solvents t,ested. All parent, ketones in the present study exhibit a single resonance for the corresponding protons, regardless of' solvent and concentration. Other factors which affect the separation are (see Table 11): the type of aromatic ring present, the nature of the substituent, and the ratio of aromatic compound to oxime. Measurements at 24.3 mc./ sec. show that the separation of the CHs peaks in acetoxime (I) is diminished in all cases by a factor 24.3/60. It is difficult to understand why for -CH = XOH protons the shifts are at :east thirty times larger t,han for, say, -C(CH,)=XOH protons (if one disregards the solvent effects described). The fact that t,he corresponding 0. .H distances are smaller for aldoximes than for ketoximes, suggests only that the neighboring effect of oxygen is expected to be larger in aldoximes. A more quantitative interpretat'ioii seems not possiblc a t preseat. At any rate, all these observations are similar to those for proton shifts of chloroform in aromatic solvents.17 The origin of the proton shift with respect to pure chloroform has been explained as follows: a complex (e.g., CHC13-C6Hs) is formed, having the CH bond of CHCll lying approximately along the C&axis of the ring. The proton of CHC13 experiences the effect of the magnetic field of the ring, which results from t,he circulation of a-electrons. Thus a shift of the CH_C13resonance signal is
.
(9) P. Karrer and P. Dinkel, N e h . Chim. Acta, 36, 122 (1953). (IO) R. Soholl and CI. hlatthiaopoulos, Ber., 29, 1.550 (1896). (11) C. Harries and R. Gley, Ber., sa, 1330 (1899); C. Harries, Ann., 330, 185 (1903); L. Kahovec a n d IC. W. F. Kohlrausch. Monateh., 83, 615 (1952!). (12) R. Stoeriner, i b i d . , 39,2288 (1906). (13) 0. Piloty and A. Stock. ibid., 35. 3093 (1902). (14) V. hleyer and A.. Janny, ibid., 15, 1.525 (1882). (15) L. Piaux. Bull. IIOC. rhim. bid., 6, 412 (19'24). (16) G . Ponzio and G. Ruggieri. Gnzo. rhim.ital., 65, 463 (1925). (17) L. W. Reeves rind W. 0. Sehneider. Can. J. Chem., 35, 251 (1957); M. Charton-Koechlin and .If. A. Leroy, J . chim. phys.. 56, 850 (1959): 2. Pajak and F. Pellau, Compt. rend., 251, 79 (1960).
I -
Fig. 1.-Spectra of some oximes in p yobenzene solution: p is 10 for I1 and IV, 15 for VIII, and 7.5 for IX. In the spectrum of IV, the left quadruplet appears to be it superposition of two triplets; in the spectrum of cyclobutanone (not shown), the resonance of the a-protons is a triplet.
observed. In the more general case, the shift increases with the mole fraction of aromatic con!pound present and decreases for compounds, such as nitrobenzene, having electron-withdrawing substituents. The effect is of the order of 40 c./'sec. at 40 mc. 'set. ; theoretical calculatioiis17~1s indicate that it should be field dependent. In the present study, the oxime molecule is prcsumed to experience the magnetic field of a ring compound. Such a fieldlgis cylindrically synimetrical and, since the molecule is asymmetrical (the >C = S O - group is not linear) in any complex, the various parts of the oxime molecule would lie i n regions of differelit field strength. It is this difference of local field n hich is assumed to cause tho observed separations. The decrcase in separation for the ethers VI and TI1 (see Table I) indicates that the hydroxyl hydrogen atom may he involved in complex-formation. Further studies on the nature of the complex will h a w to be conceriicd with the details of the benzene fieldlg and the selfassociation of oximesz0by hydrogen bonds. Oxime ethers are not hydrogen-bonded, and their study may be simpler. A rough estimate based on the iio-shielding line? diagram given in Johnson and BOWV'Spaprr1g yields a shift of the order of 0.1 p.p.ni, for acacto!ic oxime, compatible with the shifts observed. An analysis of the experimental data based on an estension of Johnson and Rovey's tahlelYaiid t nking (18) J. Pogle, J . Chem. Phy,. 24, 1111 (19%). (19) J. S. Waugh and R. W.Fewenden, J. Am. Chem. So( 70. 646 (1957); J . 9. Waueh, abid., 80, 6697 (1958); C. E. Johnson and F. A. Bovey, J . Chem. Phys., 29, 1012 (1958). (20) See e.&, S. Califano and W. Luttke, Z. phyrrik. Chem. (Pronk(urt) [ N . F . ] ,5, 240 (1955). 6, 83 (19561, and references glven therem
ERNEST LUSTIG
494
Vol. 65
into account self-association of acetone oxime, is the spectrum of benzyl methyl nitrosamines. An under way. analogously reversed sequence of lines would also The case of diisopropyl ketoxime (111, see Table occur for p , < qg. Incidentally, in all spectra of I) is enceptional, iiot only because two septets the unsymmetrical ketoximes examined which indiappear in CCI, solutioii also, but because two (CH3)Z cate the presence of both isomers, the intensity CH-doublets. 2.5 c./sec. apart, are observed. ratio is approximately 3 : 1. Any intensity ratio in Steric hindrance of some kind may be invoked to a spectrum reflects, of course, the isomeric ratio in explain the lion-equivalence of isopropyl groups or the presence of the solvent used, which may not positions; the spectrum of diisopropyl ketone ex- necessarily be the same as that of the oxime in the hibits a single septet and a single doublet. pure state. Another group of observations concerns spectra of The case of phenylacetone oxime (IX) is of some oximes 111 the presence of acid or base. Some of the interest. The material used a t first was not crystalpreliminary rcsults are : 10% acetoxime solutions in line, although the viscous oil obtained contained 10 hTHCl, 10 N XaOH and pyridine have spectra the stoichiometric proportions of C and H for the with methyl doublets of 2.1, 5.3 and 4.7 c./sec., re- oxime. The melting point reportedz1for this comspectivtly. I’rtsumably, the chemical shifts in the pound is 70”. The spectrum (see Fig. 1) shows that ayueou> solutiolis are caused by the non-equivalence it consists of a mixture of two isomers. As in the of methyl groups in the corresponding ions (CH3)z- case of 1,3-dipheiiyl-Z-propanone oxime (V), no C=SOH2+ of (CH&C=KHOH+, and (CH& external aromatic agent is required to produce the C=KO-. In pyridine solutions, both the ring and separation of peaks which belong to non-equivalent the presciice of the anion may be responsible for the groups. The sequence of intensities is the same as shift. In the iyueous solutions, the peak separation for butanone oxime, that is 1:3 for CHz (singlets) decreases with decreasing. concentration of acid or and 3 :1 for CH3 (singlets). Further experiments base. 4dditjonal work is plaiined on oximes in with oily and crystalline material revealed that the aqueous solutioiis of different pH and in non-aque- oil is a non-equilibrium mixture of the form which ous solutions of acids and bases such as acetic acid melts at 70” and gives rise to the stronger comand triethylamine. ponents of the doublets, and the other form not In unsymmetrical ketoximes, similar separations stable a t room temperature. The isomerization were observed (see Table 111) under the conditions behavior of phenylacetone oxime is still under indescribcd for the symmetrical ketoximes. It is vestigation. assumed that the CH3-C(=NOH)- resonance of aii 4-Methyl-3-penten-2-one oxime (XV) is reported” isomer consists of just one peak, due to the absence to exist in two separate forms (solid and liquid) a t of any resolved spin-spin coupling across the C= room temperature. As suggested by the presence S O H group. Hence, oximes of the CH,-C(=SOH) - R type are believed to represent a class of com- of two methyl peaks in the ratio of about 6:1, the pounds favorable for the study of syn-anti isom- spectrum of the liquid used indicates the presence in erism. In fact, no such coupling was observed21 the liquid of 15% of the solid form as solute. In in oximes or ketones of this type, except for CH3- this connection, it should be pointed out that those GO-CF,. I n this case, the proton resonance con- ketoximes which have been known to exist in two sists of a well-resolved quadruplet (with J = 1.0 isomeric formsjl may be valuable compounds for c./sec.) caused by H-F coupling across the car- further study; not many, however, appear to be suited for n.m.r. spectroscopy. bonyl carbon atom. The spectra of some oximes listed in Table I11 The relevant part of the butanone oxime (VIII) spectrum consists of two overlapping quartets for indicate only one isomer, presumably the syn -CH,- having; an intensity ratio of about 1:3, and (methyl). Internal hydrogen-bonding may be the a pair of singlets for CH3- having an intensity ratio cause for the preferential formation of only one of about 3 : l . It is reasonable to assume that the isomer in the case of oximes (XII) and (XVIII), components with relative intensity of 1 are dis- and crowding about the R-C(=NOH) bond may played hy one of the possible geometrical isomers account for the others. (syn or anti mith respect to methyl), and that with These findings may be compared with results on relative intensity 3 by the other. The reversed the Beckman rearrangement of oximes, which so far sequence of iiiteiisities in the spectrum may be has been the method most widely used for the inrationalized as follom. Let pg and q, be the shifts vestigation of syn-anti isomerism. These results of a group in syn and anfi positions, respectively, are tabulated and discussed in a forthcoming volume and let FLIhe the resonance frequency characteris- of “Organic reaction^."^^ Compounds VI11 and tic for thc “unshifted” group. Then for syn- X seem to be a mixture of the two isomers, whereas (methyl)-butmione oxime, the spectrum will be compounds IX, XI11 and XVII apparently exist in (FcH~ -t- p c ~ - i ~ !and ~ ~ ,(FCH~ ~ P C H J and ~ ~ ~for, a single form. anti(methyl)-l?utaiioiie oxime (FcH, P C H ~ ) ~ ~ ~ ~ Single peaks were also found for the resonance of and ( F c H , Q C H J ~ ~ , ~If. one assumes that pg > the corresponding nuclei in the spectra of CHsqF[,the line.; of a mixture of s y n and anti forms ap- C(=NOH)-CsH,, CF,-C(=NOH)-CsHs, and CzH5pear i i ~thiq order: ( F c H ? (FcH?4- C(=XOH)-CeH6.24 The Beckmanii rearrangepc1x2)ant , (FcH? YCEIJ~~L,~, (FcH? P C H J ~ ~ ~ . Such a sequeiice was also observed by Phillips3 in (22) D. H. Hey, J. Chen. Soc., 18 (1930): R. hI. Jaeger and J. A.
+
+
+
+
+
+
(21) Cf. also L M. Jackman, “Applications of Nuclear Magnetic Resonance Spectroscopy in Organic Chemistry.” Pergamon Press. New York N. Y., 1059, p. 83.
van Dijk, Konznkl. Ned. A k a d . Wetensehap. Pioc., 44, 26 (1941). (23) L. G. Donaruma a n d W. Z. Heldt in “Organic Reactions” Vol. 11, John Wiley and Sons, Ino., New York, N Y.
March, 1SGl
Low TEMPERATURE THERMODYNAMIC PROPERTIES OF SIXHEPTANES
ment of CHrC(=NOH)-CsH6 yields products whose properties suggest the presence of the two isomers, whereas only one isomer mas found in the case of CzH5-C(=iYOH)-C6Hs. Since, as has been pointed out,22 the experimental conditions of the Beckmann rearrangement can be conducive to isomerization, and not all the rearrangement products are always accounted for in the literature, the conclusions drawn from reports on Beckmann rearrangement studies as to the isomeric composition of the original oxime may not always be valid. Appendix To check Phillips' assignment3 of the two -CH=NOH (24) For the preparation of CzHr-C(=NOH)-CsHs, see K. N* Campbell, B. K. Campbell and E. P. Chaput, J . Org. Chem., 8 , 99 (1943).
495
multiplets arising from syn-anti isomerism, the spectra of the two p-chlorobenzaldoxirnesz6 in dimethyl sulfoxide solution were examined. The significant portions of the spectra consisted of the following lines (c./eec.), with the center of the benzene ring multiplet taken as the origin. (With (CH&SO as reference, the origin of this multiplet in tlic antz oxime lies a t higher field by about 6 c/s than of the syn oxime.) Compound
-Ring 1
2
synoxime antioxime
-12
- 3 -13
-21
proton pealis-3
+
3 +I3
i
-12 +21
--Cg=NO!i peak
-27 +17
Thus, the -C_H=KOH resonance of the anti oxime indeed appears a t higher field, and Phillips' assignment3 seems to be correct. The syn-anti shift is, in the present case, of the order of 0.7 p.p.m., as compared to 0.6 p.p.m. for propionaldoximes. (25) H. Erdniann and E. Schwechten, Ann., 260, 53 (1890).
TEMPERATURE THERMODYNAMIC PROPERTIES OF SIX ISOMERIC HEPTAXES
~ 0 1 4 7
E:Y H. M. HUFFMAN,' M. E. GROSS,D. W. SCOTTAND J. 1.' MCCULLOUGH Contribution No. %$from the Thermodynamics Laboratory, Petroleum Research Center, Bureau of Mines, U. S. Department of the Interior, Bartlesville, Oklahoma Recewed September 21, 1960
I n a continuing program of studies of thermodynamic properties of aliphatic hydrocarbons, low-temperature thermal measurements were made on the nine isomeric heptanes, but definitive results could be obtained for the folloning six compounds only: n-heptane, 2-methylhexane, %ethylpentane, 2,2-dimethylpentane, 2,sdimethylpentane and 2,2,3-trimethylbutane. Values of heat capacity in the solid and liquid states and of the latent heats and temperatures of isothermal phase changes were determined for each of these six isomers. Also, the vapor pressure of 2-methylhexane was measured in the ranges, 0-45", 17-159 mm. From the observed data were calculated values of the free energy function, heat content function, heat conteni, entropy and heat capacity of the condensed phases at selected temperatures between 10 and 300'K. These results and literature values of heat of formation, heat of vaporization and vapor pressure mere used to compute values of the chemical thermodl namic properties for the liquid and ideal gas states a t 298.15"K.
The preparalcion of comprehensive tables of phase changes were determined for each of these thermodynamic property values for important six compounds. Also, the vapor pressure of 2homologous series of hydrocarbons requires knowl- methylhexane was measured in the ranges, 045", edge of the variation of such properties with both 17-159 mm. From the observed data were calmolecular size and structure. The Bureau of culated values of the free energy fuiiction, heat Mines has a continuing program to determine part content function, heat content, entropy and heat of the needed fundamental information by low capacity of the condensed phases at selected temtemperature calorimetric studies of selected groups peratures between 10 and 300°K. These results of hydrocarbons. For acyclic hydrocarbons, pre- and literature values of heat of formation, heat of vious publications have reported low temperature vaporization and vapor pressure were used to thermal data for nine five isomeric compute values of the chemical thermodynamic hexanes, seren 1-olefins, six isomeric ~ e n t e n e s , ~properties for the liquid and ideal gas states at and several olhers. This paper describes an 298.15"K. Detailed results of these studies are investigation of the isomeric heptanes. Studies in the Experimental section. of all nine isomers were attempted, but for reasons Discussion of Results discussed in a following section, definitive results could be obtained for only six isomers: %-Heptane, Chemical Thermodynamic Properties at 298.15' 2-methylhexane, 3-ethylpentane1 2,2-dimethyl- K.-Table I lists the chemical thermodynamic pentane, 2,4-dimethylpentane and 2,2.3-triniethyl- properties of the six heptanes a t 298.15"Ii. The butane. Talues of heat capacity in the solid and tabulated values are based only on experimental liquid states in the range 12-300°K. and of the data from this investigation and earlier studies of latent heats and temperatures of isothermal heats of formation and vaporization and vapor pressure cited in text and in the footnotes t u (1) Decease% (2) H. L. Finke, M. E. Gross, Guy Waddington and H. RI. IIuffman, Table I. Current tabulations of -4merican PeJ . Am. Chsm. Sac., 76 333 (1954). troleum Institute Research Project 14G also gii-c ( 3 ) I). R. Douslin and H. 31. Huffman, zbzd., 68, 1704 (1946). (4) J. P. McCullough, H. L. Finke. M. E. Gross. J. F. Messerly and Guy Waddington, J . I'hys. Chem., 61, 289 (1957). (5) S. 9. Todd, G. D. Oliver and H. M. Huffman, J . Am. Chem. S o c . , 69, 1519 (1947).
(6) American Petroleum Institute Research Project 44, "Selected Values of Physical and Thermodynamic Properties of Hydrocarbons and Related Compounds," Carnegie Press, Carnegie Institute of Technology, Pittsburgh, Pennsylvania, 1953.
