512
ANALYTICAL CHEMISTRY
recovered in the estimation, and the aniinonia recovered in a blank containing no fructose, respectively, then z = 21
- z(w
- z)/w,or z = w(y
- z)/(w
-
Table I.
Z)
These equations expressed the fact that only the unused poition of the cyanide contributed to the blank in the actual estiniation. I n the experiment quoted, w, y, and z were 0.982, 0.591 and 0.056 millimole, respectively, leading to a value of 0.568 millimole, or 101% of theory for the fructose, z. Duplicate estimations gave recoveries of 1007, and lOl$&. The fraction of cyanide directly hydrolyzed to ammonia in the estimation was not greatly affected by moderate changes in the concentration or by changes in pH between 7.5 and 11.5, but was markedly influenced by change in the rate of the distillation. When the temperature or the time of the c anohydrin condensation was increased, the data altered in sue{ a way as to leave the result almost unchanged, provided, of course, that the conditions were adequate for complete reaction. The condensation of 10 mg. of glucose (0.056 millimole) with 0.098 millimole of sodium cyanide ( i 5 q excess) in 25 ml. of water a t pH 8 and 45“ C., for example, nas only 32% complete after 24 hours, and 60% complete after 70 hours The method was therefore not adapted to the microscale. JVhen 25 ml. of 0.3 N potassium cyanide was distilled a t p H 11.5 after having been kept a t p H 8 for i o hours, the blank was 0.082 millimole of ammonia, but was only 0.069 millimole when 0.3 gram of purified cotton cellulose was present; after about 43 hours at pH 10, the figures were 0.09 and 0.056 millimole, respectively. These and similar results showed that the presence of cellulose tended to diminish the hydrolysis of the cyanide. The unsuitability of the method on the microscale and uncertainty about the blank probably explained why attempts to estimate the number-average degree of polymerization of hydrocelluloses gave very high results. Method A perhaps suffered from the same defect, because the viscosity averages quoted in Figure 4 of reference ( 1 ) were less than, instead of being greater than, thc cyanohydrin number averages. Method B differed from Method A in that the esccss cyanide was not removed prior to the distillation, but this difference was immaterial when 0.3 ;L’ potassium cyanide was used a t pH 8, 10, or 11.2 with fructose (Table I). Both methods gave an excessive recovery of ammonia at pH 8, and, to a lesser extent, a t p H 10, but Method A was correct a t pH 11.2. When more dilute, 0.03 M , potassium cyanide was used, Method B gave recoveries within 5 3 % of theory, both a t pH 8 and pH 11, and presumably Method A would behave in a similar way. Yundt (3’))who employed 0.11 N potassium cyanide a t pH 8.3 for the estimation of fructose by noting the amount of cyanide consumed
Estimation of Fructose by Condensation with Potassium Cyanide
(Condensation a t 29OC.) Fructose, JIetliod Millimole Hours pH With 0.30 M KCNb A 1.019 70 8 0.601 70 8 B 0.979 70 8
h-Hs Recorercd Millimolesa % theory 1.449 0,823
142 137
0.688
70
8
1.301 0.903
133 131
B
1.065 0.679
06 96
8 8
1.431 0,905
134 133
A
0.926 0.853
42 42
10 10
1.011 0.915
107 109
B
0.934 0.712
44 44
10 10
0.998 0.751
107 106
A
1.023 0.677
75
11.2 11.2
1.018 0.694
99 103
With 0.03 ,M K C N
B
0.561 0.474
7.5
8 0.573 102 8 0.488 103 B 0.592 96 10 0.571 100 0.431 96 10 0.429 97 Alethod A, corrected by simplc subtraction of blank; Method B, blank prouortioned t o unused cyanide b y formula in text. b The times a t this concentration, excessive for fructose, happened to be similar t o those used in parallel estimations with oxycelluloses. Other experiments employed 48 hours at 45‘ C. 96 96
rathcr than the ammonia produced, also obtained results high by 25%. Militzer’s ( 2 ) similar estimation was a t pH 9, and fructose rcacted rapidly and completely. The above ohservations suggested that Yundt’s conditions were unsuited to fructose, although well chosen for the estimation of aldoses. KO explanation of the curious behavior of the keto sugar appears to be available a t the present time. LITERATURE CITED
(1) F i a m y t o n , V.
I,.,Foley, L. P., S m i t h , L. L., and Malotic, J. G.,
AXIL. CHEM.,23, 1244 ( 1 9 5 1 ) . ( 2 ) Rlilitaer, W., Arch. B i o c h e ? ? ~9, , 91 ( 1 9 4 6 ) ; 21, 143 (1949). (3) Yundt, 9. P., T a p p i , 34, 95 (1951). RECEIVED for review September 29, 1952. Accepted November 12, 1952. Method B was abstracted from a B.S. thesis submitted b y R. D. Coombs I11 in M a y 1941. t o the Massachusetts Institute of Technology-. T h e comparison rvith Method A was cairied out in Montreal.
Correlations of Infrared Spectra with Structure
‘
JOSEPII BOMSTEIN, Sinclair Research Laboratories, Inc., Harcey, I l l .
and extended corre1:ttioiis for infrared spectra. are presented, based on spectrograms of the .4merican Petroleum Institute; the Xational Advisory Committee for Aeronautics: “Infrared Spectroscopy,” by Barnes, Gore. Liddel, and Williams; and unpublished work of this laboratory. Among relationships developed are spectra-structure patterns for methylene chains, para-disubstituted aromatics, and disubstituted :ironlatics generally. Many v orkers in recwit years have denionstr:ttcd the usefulness of the infrared instrument as an aid in identification. The practical application of the method depends on the fact that many chemical structures have absorption maxima a t approximately the same wave length, regardless of the molecule with which they are associated. In order to extend the range of applicability, empirical studies wcre made of existing data in fields of interest to this laboratory, and the data given herein are the first results of such studies. Since the data were collected from a variet) of sources, instrumentation is of several types. Rather than enumerate all types employed, it suffices to bear in mind that data from several sources must be used judiciously since different instrument@and operating conditions can produce n idely varying results. For this reason, EW
all nunierical values given in this paper should be considcrcd as rough approximations, not as correct absolute values. Data from this laboratory \%ereobtained either with a Model 12-B or Model 12-C Perkin-Elmer recording infrared spectrometer, equipped xvith rock salt prism and cells. SPECTROGR4JI SOURCES
Data for the compounds listed in Table I were obtained from spectra published by the S.rl.C.A. (8). In Table I1 the data for the sulfonates, phenols, p-di-tert-butylbenzene, p-tertbutyltoluene, and p-xylene n-ere obtained in the Sinclair Research Laboratories, and all others N ere taken from the catalog issued by the American Petroleum Institute ( 1 ) . I n Table I11 data for xylene and cresol were obtained in the Sinclair Research Laboratories; data for other hydrocarbons were taken from ( 1 ) ; all other data were obtained from ( 2 ) . I n each case mentioned in Table 111, data for the three isomers of one molecule were dran n from a single source. ABSORPTION POSITIONS FOR METHYLENE CHAI\S
Recent work of McPIIurry and Thornton (6) has shown thnt a definite correlation exists betn een position of absorption and the
V O L U M E 2 5 , NO. 3, M A R C H 1 9 5 3 value of r1 in paraffinic (CHz), groups, when a t least one end of the chain is attached to a methyl group. Study of available spectra shows that a similar pattern exists for molecules in which neither end of the chain is bound to the methyl group but to cycloparaffinic groups instead. HOT% ever, the absorption positions in these cases are not identical n ith those of JIcJIurry and Thornton for a given n, nor need the absolhances be the same. In Table I data are given for the n versus position relationships, and the letter J4 under Remarks indicates that the niolrcule shonn is of the type described bv Mc;\lurry and ThorntonLe., it has a terminal methyl group Examination of Table I shows that the absorption positions of the naphthenic-terminated chains fall roughly into the classification set up by JIcMurry and Thornton for the next lower value of n, down to n = 2. Absorbance differences are somewhat more pronounced as n decreases. As an example, 1,6-dicyclohexylhexane has n = 6, and has au absorbance of 0.521 a t 13.83 microns; 1,l-dicyclohexylheptanc has n = 5 and has a terminal methyl group. It has an absorliance of 0.518 a t 13.83 microns. J\-heii the cycloparaffin rings are replaced entirely or in part by phen) I groups, it is possible that another regular shift occurs as a function of n. Because of overlapping aromatic substitution bands, the shift, if present, is not observed with sufficient certaintv to \Tarrant inclusion of data in this paper. I t is iriteresting to note, that TT hile sec-butylcyclopentaiie, n-but: IC\ clopentane, and n-propylcyclopentane show the expected peaks, isobutylcyclope~itanedoes not show a long wave length peak at all. Neopentylcyclohexane also falls into the latter cluss. Apparently. chain termination by only one ring is not a sufficient condition for the correlation. I t should be borne in mind that this correlation is based on relatively few data, and mav be a special case of a more general type, in which the chain is terminated by any alkyl group. Howewr, available spectra are limited in number, and thesc apparently do not all fit the correlation, so that no generalization is made here. ABSORPTION POSITIONS FOR PARA-DISUBSTITUTED BENZEh-ES
-4s1i:rs been known for some time, para-disubstituted aromatics have a strong absorption band in the 12.0 to 12.5 micron region ( 3 , 6). If the available spectra of molecules of this type are plotted, the absorption maxima in this region fall in a very irregular pattern. If these spectra are replotted, after isolation into more narrowly defined classes, a separate narrow absorption range exists for each class. I n Table I1 are shown thoqe compounds in which one substituent is a hydroxyl group, compounds in 15 hich both substituents are alike, and compounds in a hich one substituent is a methyl group. -4s has been noted in many other correlations, both physical and chemical, the lowest member of the series is irregular in behavior ( 4 ) . I n these cases, p-xylene and p-cresol are the first members and are seen to be irregular. Excluding these two molecules, examination shows that p-hydroxy aromatics absorb in the 12.05 to 12.11 micron region, aromatics in which both substituents are alike absorb between 12.00 and 12.07 microns, p-methyl aromatics absorb betn een 12.23 and 12.32 microns, and the effect of molecular weight is relatively insignificant. Further data should be obtained to make the generalizations vaI1tl. ABSORBANCE IN 6 MICRON REGION FOR DISUBSTITUTED AROMATICS
I t is well known that aromatics in general absorb near G microns ( 5 ) , but no empirical correlations between intensity of absorption and type of substituent have been published. Obviousl?-, increasing molecular weight within a homologous wries
513 would tend to louer the intensity of absorption, since the ring would then represent a decreasing proportion of the total molerule. I n addition to this factor, the types and positions of substituents in the ling must be considered. Available spectra have been examined for the intensity of the 6 micron band in the case of disubstituted aromatics, and the data are shown in Table 111. The absorbance figures shon n are approximate and should be used only for comparison. Study of these figures reveals that a t least two factors, besides molecular weight, are important. These are orientation in the ring, and directing influence of the substituents. If those molecules having subEtituents nhich are ortho, para directors are considered first, it is apparent that intensity of absorption decreases in the order of meta, ortho, para. I n addition, those molecules in ~ h i c hone substituent is known to have a strong directive influence e.g.. hydroqd and amino, have the greatest absorbances. The first ten compounds in Table I11 are of the ortho-, para-director class (4). Unfortunately only dinitrobenzene could be found for examples of the type in which all substituents are meta-directing. Decreasing intensities T! ere in the order of ortho, meta, para. In the third category are those molecules having substituents vhich are of opposite directive influence, and of varying degrees. According to modern theory, ortho, para directors affect substitution by an activating influence on these positions, b u t meta directors operate by a deactivation of ortho and para positions (4). Theoretically, then, if thesr influences are a t work in detcrmining absorbances a t 6.2 microns, the relative intensities of
Table 1.
ibwrption IIaxinia and Absorbanres for Iletli>lene Chains Wave Length, 71
1,6-DicycloIiexylhexane 6 n-Octylcyclohexane 1,5-Dicyclohexylpentane 1 , I-Dicyclohexylheptane r) 1 4-Dicyclohexylbutane 4 4 1’1-Dicyclohexylhexane 1’3-Dicyclohexylpropane 3 l:l-Dicyclohexylpentane 3 1-Cyalohexyl-3-cyclopentylpropane 3 1,7-Dicyclopentyl-4-(3-cyclopentylpropy1)heptane 3 1 2-Dicyclohexylethane 2 l:l-Dicyclohexylbutane 2 I ,5-Dicyclohexyl-3-(2-cyclopentylethy1)-pentane 2 Dic yclohexylmethane 1 1,I-Dicyclohexylpropane I 1,2-Dicyclohexylbutane 1 1.3-Dicyclohexylbutane 1 2,Z-Dicyclohexylbutane 1 Cyclohexyl~yclopentylinethane 1
3
~
~
p
.Ibsorbanre for 0.1 l l n i . Cell
13.88 13.86 1 3 , 7:i 13.i3 13 ,o 13 78 13, ti8 13.72
0 521 0 825 0 456 0 518 0 438 0 444 0.352 0.420
13 G3
0.343
13 i G 13 33 13 ti0
0.413 0.188 0 468
13.61
0 153
13:0 2 13.20 13.38 13 00
0:3& 0.264 0,200 0 560
~
Remarks
31
~~
no peak
RI &I(not listed) .\I no peak
.~
Tahle 11. Absorption Positions for Para-disubstituted Benzenes i n the 12.0 to 12.5 Micron Region .4bsorption Maximum in I ? p Region p-reri-Octylpheno: p-tert-.\tr8ylphenul p-ten-Uutylphenol
;,--Xylene
12.06 12.10 12.11 12 23 12 03 12 0 ; 12 00 12 07 12 59
~-Hutyl-p-toluenesulibuate ,,-I’ropyI-p-toluene sulfonate Lthpl-p-toluene sulfonate 3IethyI-p-toiuene sulfonate y-/err-Butyltoluene p - Isopropyl to1 uene 1,-Fliiorotoluene y-Ethyltoluene p-Cyanotoluene p-Cresol ].-Xylene
12.32 12,32 12.23 12.27 12.26 12.23 12.24 12.28 12.27 12.23 12.59
y-cle%ol p - Di-rer:-l,ury:beneeI.t.
p-Diisopi cyylbenzene
p - I)i?uorubenzene p - Diethylhenzece
ANALYTICAL CHEMISTRY
514
Table 111. Comparative Absorbance Values for Position Isomers of Disubstituted Aromatics in the 6 I" Region Absarbhnoe far 0.1 M m . Cell Ortho&
Met&" 2.9 1.9 2.8 1.8 14.4 6.5
Xylene Diethylbenzene Ethyltoluene Diisopropylbenrene Cresol Toluidine Chiomtoluene Ethylphenol Cresyl methyl ether Cresyl ethyl ether Dinitrobenzene
0.94
0.43 0.83
0.33 7.9
5.7
0.61 14.4 5.8
1.2
>25.0 28.0 17.0
Tolunitrile
2.3
3.6
2.0
1.7
6.3 2.6 0.39
11.7
6.9
2.4
Toluic acid Nitrophenolb Nitrohnilineb Hydrorybennoio acid Aminobenrenesulfonio soid
Para.? 0.54 0.18 0.35 0.30
2.0
5.5 4.9 0.36 4.0 3.3 0.48 0.52 2.1 0.88
0.14 0.55 0.43 0.58 3.6 ... 0.80 0.71 vi0 In d l eases, rnehsurement was made of the double-band stretching brhtioll. b These were of undetermined thickness,SO that absorbance slues do not compare a i t h others shown.
the mets, ortho, pars. species should be predictable. Using this line of reasoning, if one substituent is weakly ortho-, para-directing, and the other is oomparatively strongly meta-directing, the order of decreasing intensities should be different from the first clam of molecules listed. This is the case with tolunitrile and toluic acid, and here the order of decreasing intensity is para, meta, ortho. Nitrophenol, aminobenacnesulfonic acid, and nitromiline, on the other hand, each have th-o comparatively strongly directing groups of opposite influence, so that results obtained should be
more random in nature. Absorbances shown are in fair agreement with the predictions. Hydroxybenzoic acid, from data. shown, apparently has a strong ortho-, para-directing group, and a less strong metrtdireetine emm. Both substituents are known to bo fairlv strong directors (4). The data of this scction and Table I11 have recently been substantiated by a general mitthematical treatment, in which the intensity trends have been derived on a semiquantitative basis (7). I
_
.
ACKNOWLEDGMENT
The author is grateful t o the Sinclair Research Laboratories, h e . , far permission to publish this paper. LITERATURE CITED
(1) American Petroleum Institute. Research Project 44, "Catalog of Infared Spectral Data." (2) Barnes, R. B., Goore, R. C., Liddol, V., and Williams. Y. Z.. "Infrared Spectroscopy." New York. Reinhold Publishing Corp., 1944. (3) Colthup, N. B.. J . Oplicril Soe. Am., 40, 397 (1950). (4) Fieser L. F.. and Fieser. Mary, "Organic Chemistry," Boston, D. C. Heath & Co., 1944. (5) Hersberg, G.. "Infrared and Raman Spectra," New York. D. Van Nostrand Co.. 1945. (0) MoMurry, H. L.. and Thornton, Vernon, ANAL.CHEX.,24, 318 (1952). (i) Matossi, F., private communication, to be published in 2. A'dwforsch. (8) Serijm, K. T.. Goodman, I. A, and Yankauskas, W. J., \'all. Advisoru Comm. Aeronm~t..Tech. Note 2557 (1951). REOE~VED for review September 11, 1952. Aooepted December 15, 1052.
66. o-Dibemzyl Phthala Contrihuted by JOHN KR C, JR., AND WILL4 - . . _.. . . Arrnour Research kbundation, Illinois Institute of Technology, Chicago 16, Ill.
0
0 H
Formula Weights per Cell. 4 (3.99 calculated from x-ray data). Formula Weight. 346.36. Density. 1.248 (flotation in aqueous zinc chloride); 1.250 (x-ray),
W Structural Formula for o-Dihenzyl Phthalate phthalate can be obtained from ethyl C aloahol ofando-dibeneyl ether solutions. Excellent c r y ~ t dcan ~ also RYSTALS
he obtained by seeding a melt of this compound a t 40' C. and 81lowing recrystallization to proceed with slight agitation. Figure 1 is a photomicrograph of crystals from ethyl alcohol. Figure 2 is au orthographic projection of R typical tablet of o-dibenayl phthalate.
CRYSTALMORPHOLOGY
Crystal System. Orthorhombic. Farm and Habit, Rods, tablets, and plates lying on hrachydome (021 1 showing macrodames [ 101 1 and { 102 I, and o c c a sionally basal pinacoid (0011, brachypinaeoid ( O l O ) , and brachydome (0111. Axial Ratio. a:b:c = 0.692:1:0.677._ Interfacial Angles (Polar). 0.21 A 021 = 7 3 0 ; 011 a o i i = 112"; 021A011 = 19.5": 011AOO1 = 34'; 1021,4001 = 5.115"; 011A010 = 55'; 021AOlO = 36.5'; 101,4101 := 91"; 102A102 = n? h nm 128'; 101A102 = 18.5"; 101A001 = 44.5"; 1ua2LuuL - 1c-. X-RAYDIFFRACTION DATA Cell Dimensions. a = 10.92 A ; h = 15.78 A,; e = 10.68A.
Figure 1. Crystals of o-Dihenzyl Phthalate fmm Ethyl Alcohol
