INDUSTRIAL AND ENGINEERING CHEMISTRY
310
either the specific or the mechanical theory but is dependent on the combination of the two. ACKNOWLEDGMENT
The authors wish to express their appreciation to W. G. MacElhinney and to F. A. DeMarco of the university staff for their assistance during the eourse of this work. LITERATURE CITED
(1) B i o w i e , F. L., and T r u a x , T: R . , Colloid Symposium Monograph, 4 , 258-69 (1926).
Vol. 18, No. 5
(2) Hamly, D. H., Compt. rend. Q S S O C . intern. essais semences, p p . 34553 (1938). (3) AMcBain,J. W., a n d Hopkins, D. G.. "British Adhesives Researrli Committee", Second Report, London, H . SI. Stationery Office. 1926. (4) McBain, J. IT.,a n d Lee, W.B., I b i d . , Third Report, 1932. (5) Maxwell, J. IT., Trans. A m . SOC.S l e c h . Engrs., 67, No. 2, 10410 (1945). (6) Rinker, R. C . , and Kline. G. S I . , M o d e r n PZastics. 23, N o . 3. 164 (1945). (7) Williams, E. T.. and S I a c U h i n n e y , W.G., "1Practical Method for Estimating Bonding Schedules for Hot Press Plywood". Confidential Report, S a t i o n a l Research Council. Ottawa, 1943.
X-Ray Identification and Crystallography of Aldehydes and Ketones as the 2,4=Dinitrophenylhydrazones GEORGE L. CLARK, WILBUR 1. KAYE', AND THOMAS D. PARKSz Noyes Chemical Laboratory, University of Illinois, Urbana, Ill.
I
N T H E past few years a considerable amount of research has been undertaken to work out systematic and practical methods of organic analysis for carbonyl compounds using a solution of 2,4-dinitrophenylhydrazine(2,8, IS). The reagent is usually prepared by dissolving 2,4-dinitrophenylhydrazine in ethyl alcohol acidified with either hydrochloric or sulfuric acid. The addition of an aldehyde or ketone to such a solution usually results in the rapid formation of crystals of the corresponding 2,4-dinitrophenylhydrazone. If the aldehyde or ketone initially does not contain any great amount of impurities and if the derivative is carefully purified by recrystallization, the aldehyde or ketone undergoing analysis is identified from the color, optical properties, and melting point of the derivative. When the unknown substance contains a mixture of aldehydes or ketones, the problem of identification becomes difficult since the melting point, which is the most widely used test, is so easily lowered by the presence of impurities. Furthermore, Brandstatter (4) has shown recently by thermal analysis the marked tendency of these hydrazones to form solid solutions with one another. Recourse is then usually taken to separation of the aldehyde or kctone by fractional distillation or crystallization before identification with the 2,4-dinitrophenylhydrazine reagent. Such a procedure is time-consuming and any improvement may be considered valuable. Two instrumental methods have been suggested foi identifying the derivatives of aldehydes and ketones which are affected to a lesser extent by the presence of impurities than is the usual method of melting point determinations. These are dependent upon optical crystallographic properties (refractive indices) of the derivative (6) and the x-ray powder patterns ( 3 ) . The major field of contention in the use of 2,4-dinitrophenylhydrazine as a reagent for the identification of aldehydes and ketones lies in the rather large number of modifications which have been reported from time t o time. The exact nature of these modifications has caused much speculation. Two modifications of acetaldehyde-2,4-dinitrophenylhydrazone have been clearly shown to exist (6) as well as two modifications of derivatives of the furan series (5). Still other modifications of these and other compounds seem likely in view of the varied reports of crystalline properties and melting points (1,7, 12). Present address, Tennessee Esstman 1 Obtained results on aldehydes. Corp., Kingsport, Tenn. Present address, Shell Development Co., 2 Obtained results on ketones. Emeryville, Calif.
The present x-ray diffraction investigation was undertaken, therefore, with the intention of clarifying uncertainties concerning these derivatives which are involved in this important method of identifying aldehydes and ketones, and of demonstrating the value of x-ray methods in many fields of organic analysis, both qualitative and quantitative, especially in series of related compounds of some complexity. In this paper are presented data on the unit cell dimensions and space groups of a number of aldehyde and ketone 2,4-dinitrophenylhydrazones, several of which are polymorphic; powder pattern data for rapid and certain identification by the organic analyst of aldehydes and ketones, together with techniques of handling micro or semimicro quantities of specimens; and a logical extension t o quantitative analysis of pure and mixed aldehydes. SINGLE CRYSTAL ANALYSES OF UNIT CELLS AND SPACE GROUPS
With single crystals which are ordinarily easily obtained, rotation, oscillation, and Weissenberg patterns have been made, the last type being especially valuable in this study; powder patterns were made in cameras specially designed and constructed for penicillin studies, in which the samples in cellulose acetate capillary tubes are rotated during exposure. Reciprocal lattice projections were made in all cases, but indexing of spots on the equiinclination Weissenberg patterns was easily possible by inspection of zones. All pertinent data including probable space groups on the derivatives of formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, crotonaldehyde, furfuraldehyde, and dimethyl ketone are assembled in Table I. Typical procedures are illustrated wlth the case of the formaldehyde compound. FORMALDEHYDE-2,4-DINITROPHENYLHYDRAZONE PREPARATION. The formaldehyde-2,4-dinitrophenylhydrazone was pre-
pared by adding 40% formaldehyde solution to a hot concentrated solution of 2,4dinitrophenylhydrazine dissolved in methyl alcohol approximately 2 N in hydrogen chloride. When cooled the crystals were filtered and air-dried, then recrystallized once from hot 90% ethyl alcohol and three times from hot isobutanol. The last recrystallization was slow and resulted in the growth of yellow needles and platelets about 2 to 5 mm. in length. PROPERTIES OF THE CRYSTALS.The formaldehyde-2,4-diniitrophenylhydrazone crystals melted a t 166' C. (uncorrected) agreeing with the literature (6). The density of the crystals as measured by flbating in a mixture of methyl iodide and ethyl bromide was 1.592 + 0.010 grams per ml., the density of the liquid being determined with a 25-ml. boot specific gravity bottle a t 25' C. The needle-shaped crystals are similar to the platelets in being elongated along the c axis, the difference being in the
. ANALYTICAL EDITION
May, 1946
X-ray diffraction data are used to characterize 1 2 different crystalline aldehyde-2,4-dinitrophenylhydrazones from 6 different aldehydes and 16 ketone derivatives from 1 5 ketones using Weissenberg, rotation, oscillation, and powder patterns. This series ,was selected because of its importance in organic analysis of aldehydes and ketones; because there is no previous record of investigation outside of fragmentary optical data; and because i t afforded excellent experience in extending the most modern techniques, particularly in distinction between polymorphic forms and in use of micro quantities of specimens. This study has involved the practical reciprocal lattice interpretation of the powder pattern of a triclinic crystal. Polymorphism is very generally observed in the series of hydrazones. Each i s uniquely distinguished b y its x-ray powder diffraction pattern far better than b y color, habit, or melting point. A micromethod of qualitative analysis for pure and mixed carbonyl compounds is described. Aside from the necessary x-ray equipment the apparatus required is readily available. Ordinarily 0.1 mg. is the minimum amount necessary; however, single crystals smaller than 1 microgram may b e identified. Tables listing the three most intense powder diffraction lines and the innermost line make possible the identification of 2 8 hydrazones. This method has the advantage OF analyzing mixtures of carbonyl compounds which would be difficult b y existing methods. The qualitative micromethod is converted to a quantitative method b y accurate measurement of the line densities of known mixtures of the aldehyde derivative with sodium fluoride as an internal standard. Standard intensity ratios are given for a number of the aldehyde derivatives.
growth of the (100) form of the platelets. The angles between the faces parallel to the c axis were measured as the angles through which the needle-shaped crystal had to be rotated to bring successive faces into position to reflect a beam of light into a telescope placed on the Weissenberg camera. A cleavage plane making an angle of 52" with the c axis in the ac plane was observed. EXPERIMENTAL X-RAY DATA. Rotation and Weissenberg patterns for zero, first, and second layer lines were made around the b and c axes from which bo and c g unit-cell dimensions are directly measured, while a0 is calculated from appropriate interferences on the zero layer line pattern from rotation around the b and c axes. K O systematic extinctions are observed for zero, first, or second layer lines. Since greater precision could be obtained with the powder camera of 7.0-cm. radius, patterns were made both on Agfa nonscreen film and Eastman Type A fine grain film; the latter pattern was then microphotometered with the Leeds & Northrup recording instrument. The construction of the reciprocal lattice projection of a triclinic unit cell cannot be made with a simple drawing as can be done with orthogonal unit cells. From the projection of the X Y plane the lines may be indexed as arising from hkO planes; the X Z plane projection indexes the lines h0l and the Y Z projection
Table Color Yellow
Habit Solvent Tabular (010) Isobutanol
Acetaldehyde I Acetaldehyde I1 Propionaldehyde I Propionaldehyde I1 n-Butyraldehyde I n-Butyraldehyde I1 n-Butvraldehvde I11
Yellow Orange Red Orange Yellow Orange Amber
Tabular (00 Aciculara Aciculara Acicular Aciculara Acicular" Tabular Acicular" Prisms Pyramids Aciculara Tabular Acicular
indexes the lines as from Okl planes. These reciprocal lattice projections have been constructed from data obtained from the Weissenberg patterns as follows: Consider first the lines from the planes hkO. The interferences from the zero layer line photograph about the c axis were tabulated in order of decreasing "d" values. The lines on the powder pattern will occur in this same order and may be rapidly indexed until the planes begin to overlap with the planes having indexes Okl, h01, or hkl. The intensity measurements serve as a check. The Weissenberg pattern of the zero layer line about the b axis was used in a similar manner to construct the h01 lattice layer. This procedure cannot be followed in indexing the YZ plane (Okl),since no Keissenbeig pattern was obtained with the crystal rotated about the a axis. However, it was observed that the 021 spot on the first layer line Weissenberg pattern of the crystal rotated about the c axis was very intense. Calculation of the 'Id" v$ue of this spot on the Weissenberg film leads to a vnlue of 3.08 A. This calculation \\as made using the equation COS
28
= COS
+ COS
+
where 0 is the Bragg angle, is equal to (z 'r)360/2n (where 1: is the measured distance of the spot from the center of the film, and T is the radius of the camera), and p = tan-' q / r (where q is the distance from the zero t o the firstjayer line). Knowing that line 13 on the powder pattern is the 021 line, it is possible to draw the reciprocal lattice projection of the Okl plane. From the reciprocal lattice projections of the powder pattern together with single crystal data from Laue, rotation, oscillation and Weissenberg patterns it is possible to describe the unit cell with fair accuracy. We may then say that the unit cell of formaldehyde-2,4-dinitrophenylhydrazone is triclinic: ao = 10.00+ 0.03A. bo = 10.41 * 0 . 0 5 co = 4 . 2 3 + 0 . 0 3
(2
= 940
p = 950 y = 870
Since there were no syaematic extinctions observed, the space group must be PI or P1. From the measured density of the crystal, the number of molecules per unit cell is 2.08 according t o the fo'rmula 77, = p V/1.65 M where p is the density, V the volume of the unit cell in cubic Angstroms, and AI is the molecular weight. This indicates two molecules per unit cell. The space group E1 has one equivalent position per unit cell, while space group PI has two. Since the formaldehyde-2,4dinitrophenylhydrazone molecule Eust be asymm'etric we may ascribe the probable space group P1 to this crystal. POLYMORPHISM OF 9,4-DINITROPHENYLHYDRAZONES
Proceeding in similar fashion 11 other aldehyde and 2 ketone derivatives have been analyzed as summarized in Table I. Only the formaldehyde and crotonaldehyde compounds have only one form; all others are di- or trimorphic. Analyses have indicated that these variations are not the result of impurities. I n all cases the original aldehydes and ketones were purified so that any sample had a 6oiling point range of less than 1'. The powder diffraction spacings which are listed in Tables I1 and I11 are highly characteristic and reproducible for each compound. Both
I. Crystallographic Data of 2,4-Dinitrophenylhydrazones
Conipound Formaldehyde
Dimethyl ketone 11 Yellow a Elongation parallel to a axis.
31 1
n-Propanol 166 n-Propanol 165 Xylene 150 Ethanol 148 Methanol 123 Methanol 122 Methanol 122 Benzene .~~..~~. 190 Acetone 223 Acetone 218 Ethylene dichloride 199 Ethanol 126 ~
Ethyl ether
Tetragonal Orthorhombic Orthorhombic
7.15 7.15 5.06 10.6 5 . 3 4 11.44
Axial Angle 4 . 2 3 OL = 940 B = 950 y = 87' 18.69 17.3 17.35 .....
Orthorhombic Orthorhombjc Orthorhombic Orthorhombic Monoclinic Monoclinic Monoclinic Triclinic
4.90 17.9 7 . 0 25.0 7.55 4 . 6 3 13:05 7 . 6 3 13.23 1 3:63 1 1 . 7 7.12 8.04
25.8 25.3 18.30 13,07 p 28.3 7.7 9.91
XP.* ' C. System 166 Triclinic
114
........
Orthorhombic
bo 1 0 . 0 0 10.41 aa
...
5.22
...
11.0
co
... 54.0
..... ..... ..... ..... ..... ..... .....
-. . . . .
990
E :g:
-,..
B = 86'
22.6
y
1020
Density 1.592
n 2
S.G. Pi
1.541 1.51
4 4 4
P4dn
...
...
1.3 1.3
...
1.43
... ... ...
.. ..
.. ..
P21212 C22r2
.... .... .... ....
4 4
P21212 P2/m
..
1.42
2
1
Piim
1.4
4
P21212
Pi
. 312
INDUSTRIAL AND ENGINEERING CHEMISTRY
temperature and solvent are factors in crystallization of a Dar-
Vol. 18, No. 5
end for collecting the precipitate into a compact small space;
a6alysis of very smali amounts, the celldose acetate h b e s prePared On No. 24 Chromel wire have been found more suitable than those on copper wire, since in small sizes Chromel wires are more easily handled than copper wires. After stretching the wire coated with the cellulose acetate, the tubes have an internal diameter of approximately 0.35 mm. The powder camera was designed for recording diffraction patThe radius from to’fi1m h terns Of Organio 7.00 * 0.01 cm. Minimum exposure time is gained by placing the back-defining pinhole of 0.254- or 0.635-mm. (0.010- or 0.02j-inch) diameter on the circumference of the camera and a guarded pinhole of 0.635 or 1.02 mm. (0.025 or 0.40 inch) in place 1.25 cm. (0.5 inch) from the sample. With these relatively large front QUANTITIES pinholes, exposure times could be shortened without appreciably DIFFRACTION PATTERNS losing definition through line broadening from angles greater than 20” from the central beam. A conically machined collimatTable 11, ,+,hi& gives interplanar spacing “d” values and ining tube holding the camera to the Machlett-type diffraction tube tensities of the three or four most intense lines from the powder assures positive alignment of the x-ray beam. A small beam x-ray diffraction Patterm of the aldehYde-2,4-dinitroPhenYltrap and central mounting of the specimen rotated or oscillated by a reversing motor permit the registration of spacings of less hydrazones whose unit cell dimensions and space groups have than 40 A. and measurement on both sides of the central beam. been determined and listed in Table I, and Table 111, of those TECHxlQUE OF QUALITATIVE AN.4LYS1S. The for values for ketone derivatives, provide a system of qualitative an exposure as that of formaldehyde-2,4-dinitrophenylhydrazone analysis for aldehydes and ketones. The amount of 2,Pdifiwas prepared by adding approximately 1 drop of a 40% formaltrophenylhydraxine derivative necessary for an x-ray powder dehyde solution with an eye dropper to a 0.3 ml. of a methyl alcohol-hydrochloric acid solution of 2,4-dinitrophenylhydrazine pattern is about 0.1 t o 0.5 mg.; however, satisfactory single in One Of the centrifuge tubes. This “lution Of 2,4 crystal patterns have been taken of crystals smaller than 10-8 cc. dinitrophenylhydrazine was prepared by dissolving 1 gram of (1 microgram). Fortunately, the required degree of Purity is 2,4-dinitrophenylhydrazinein 25 mi. of methyl alcohol containing not nearly so great as that required for melting point determinaapproximately 2 equivalents of hydrochloric acid gas per liter of alcoGol. Such a solution has been found relatively more stable tions and the impurities themselves may be determined if present for high concentrations of 2,4-dinitrophenylhydrazine than in quantities greater than 5%. ethyl alcohol-sulfuric acid solutions. After allowing the solution of the formaldehyde derivative to stand 0.5 hour the tube waa APPARATUS. The apparatus necessary for preparing the decentrifuged, the liquid decanted, and the precipitate washed rivative in micro quantities may be easily assembled from’ glass twice with 95% ethyl alcohol, then centrifuged and decanted tubing and commercial semimicro equipment. The essential again. A bit of filter Paper was used to remove most of the wash equipment consists of eye droppers with the ends drawn into liquid, then the remainder was removed by attaching the centrishort capillary tubes; small centrifuge tubes with constricted fuge tube to a vacuum pump for 15 minutes, A portion of the dry sample in the constricted end of the centrifuge tube was transferred t o a cellulose acetate tube by forcing some of the samTable II. “d” Values of M o s t Intense Lines of 2,4-Dinitr;ophenylhydrazine ple into the open end of the cellulose acetate tube, and Its A l d e h y d e Derivatives in Order of Decreasing Intensity then tamping the sample solidly into tube with (Relative intensity 1/10in parentheses) another Chromel wire. Compound I I1 I11 IV@
crystals were all elongated parallel t o the shortest unit cell dimension, and the tabular crystal had planes of flattening which were normal to the lonpest unit cell dimension. Several of these modifications have not been reported in the literature as such-namely, acetaldchl.de 11, propionaldehyde 11, butyraldehyde I1 and 111, furfuraldehyde I, and dimethyl ketone 11. On the other hand the reported acetaldehyde derivation with stable form from sublimation (6) could not be reproduccd with as careful repetition of conditions as possible.
2 4-D P H ZV4-D’P’H:-HC1 2:?-D:P:H.-HCl decomposed in vacuum Formaldehyde, yellow Acetaldehyde I. yellow Acetaldehyde 11, orange Propionaldehyde I, red Propionaldehyde 11. orange n-Butyraldehyde1,yellow n-Butyraldehyde 11, orange n-Butyraldehyde 111, amber Crotonaldehyde, Furfuraldehyde I,red red-black Furfuraldehyde 11, red Furfuraldehyde 111, yellow a Innermost line.
3 . 5 0 (1.0) 3 . 1 8 (1.0) 3.11 3 . 0 8 (1 .O) 3.21 (1.0) 9 . 2 1 0) 9.6 {l:O) .11.0 ( 1 . 0 ) 1 4 . 0 1 0) 11.7 [l:O) 1 2 . 6 (1 .O) 1 0) 33 .. 12 72 [l:O) 3 . 2 4 (1.0) 3 . 2 6 (1.0)
3 15 (0 6 3154 (0:8] 3.91 3 . 6 2 (0.97) 9 . 3 5 (0.70) 3 . 2 0 (0.92) 3 . 2 4 (0.70) 3 . 3 0 (0.8) 3 . 7 7 (0.32) 3 . 5 0 (0.38) 3 . 2 8 (0.83) (1.0) 33 .. 22 06 (0.76) 5 . 6 8 (0.3) 6.17 (0.5)
5 . 8 1 (0.6) 2 . 6 8 (0.5) 4.51 3 . 4 7 (0.88) 4 . 6 5 (0.37) 6 . 8 (0.38) 4 . 3 0 (0.39) 4 . 7 5 (0.3) 3 . 2 1 0.31) 3 . 4 8 10.29) 4.33 0.26) 140..290(1.0) 0 58) 5.36 !0:19) 7 . 7 (0.34)
8 . 9 0 5) 8 . 0 (012) 7.0 1 0 . 3 (0.86) 9 . 3 5 (0.70) 9 . 2 (1.0) 9 . 6 (1.0) 1 1 . 0 (1.0) 1 4 . 0 (1.0) 13.7 (0.16) 12.6 1 0) 11 30 .. 79 )1:0) (0.4) 1 1 . 7 0 03) 11.7 i0:29)
“d” Values of M o s t Intense Lines of Kotone-Pj4-Dinitrophenylhydraroner in Order of Decreasing Intensity Compound of Ketone I I1 111 IVO 3,27 (l.o) 5 , 7 0 (o,62) 9 , 3 0 (o,54) 9 , 3 0 (o,54) Dimethyl I, yellow Table
111.
Dimethyl 11, yellow needles Ethyl methyl, orange n-Propyl methyl, yelloworangemethyl, orange n-Butyl n-Amyl methyl, yelloworange Isobutyl methyl, red-orange Diethyl, red-orange Di-?&-propyl, yellow Diisopropyl, red-orange Diisobutyl, orange Pinaoalone, yellow Cyclopentanone, orange Benzyl methyl, beet red C1-acetophenone, scarlet Emeneophenonqred-orange a Innermost line.
9 . 4 5 (1.0) 12.45 (1.0) 3 . 6 1 (1.0) 12.80 ( 1 . 0 13.20 (1.0{ 13.70 (1.0) 12.60 (1.0) 14.9 (1.O) 111.20 3 . 7 (1.0) (1.0) 14.0 (1.0) 1 1 . 1 (1 .O) 3 . 3 1 (1 .O) 3.30 (1.0) 1 8 . 2 (1.0)
11.15 (0.44) 3 . 2 5 (0.71) 1 2 . 5 0 (0.78) 7 . 7 5 (0.72) 3 . 4 7 (0.70) 7 . 6 0 (0.78) 7 . 1 0 (0.76) 3 . 4 4 (0.56) 63 .. 79 20 (0.63) (0.78) 3 . 1 6 (0.52) 3 . 2 3 (0.58) 10.5 (0.82) 6 . 1 0 (0.60) 4 . 3 7 (0.80)
3 . 0 3 (0.20) 7 . 1 0 (0.54) 10.64 (0.66) 3 . 4 7 (0.56) 7 . 4 8 (0.48) 3 . 4 8 (0.42) 3 . 5 4 (0.37) 7 . 8 0 (0.30) 4 0 (0.62) 43 . 45 0 42) 7:42 !0:50) 5 . 8 0 (0.32) 6 . 1 5 (0.78) 5 . 3 5 (0.42) 8 . 8 0 (0.75)
11.15 (0.54) 12.45 (1.0) 12.50 (1.0) 12.80 (1.O) 13.20 (1.0) 1 3 . 7 0 (1.0) 1 2 . 6 ( 1 .O) 1 4 . 9 (1 .O) 113.7 1 . 2 (1.0) (1.0) 1 4 . 0 (1.0) 11.1 (1.O) 1 0 . 5 (0.82) 1 2 . 3 (0.32) 18.2 f l . 0 )
EVALUATION OF P O W D E R PATTERNS. Since there is a possibility of contaminating the samwith unchanged 2,4-dinitrophenylhydrazine and its hydrochloride, these powder p a t t e r n were taken; also a powder pattern of the hydrochloride after “decomposition” in a vacuum for 2 hours. This decomposition is accompanied by a change in color from yellow to orange red. These together with the derivatives of formaldehyde, acetaldehyde (2 forms), propionaldehyde (2 forms), butyraldehyde (3 forms), crotonaldehyde, and furfuraldehyde (3 forms) are listed in Table I1 with the three most intense lines in order of their relative intensities in a manner similar to that proposed by Hanawalt, Rinn, and Frevel (11). Since the innermost line in all cases is usually the most characteristic, it is also tabulated. Table I11 similarly lists these data for 16 ketone-2,4-dinitrophenylhydrazones. The use of the tables facilitates the identification of the unknown derivative. Further confirmation of the other weaker lines in the powder pattern of the unknown may be made by reference t o the tables of ‘[d” values listed for each standard pattern which in the interest of brevity are not tabulated in this paper.
ANALYTICAL EDITION
May, 1946
313
6. Preparation of another sample containing an unknown amount of the constituent in quesTable IV. Quantitative Data on Aldehyde-4,4-Dinitrophonylhydrazonestion with a known percentage of the internal Sodium Fluoride Patterns standard. Weight 7 . Determination of the relative line densities Intensity Ratios Ratio, from the powder pattern. D.P.H. D.P.H. D.P.H. Intensities ~8. Correction of density to give intensity of Compound NaF N a F (200) N a F ( 2 2 0 ) D.P.H. N a F (200) NaF ( 2 2 0 ) the lines. Formaldehyde 2.54 0.566 9. Calculation of the ratio of line intensities 0.607 1.23 0,950 of unknown to internal standard. Xultiplication 0.968 of this factor by the ratio determined in step 8.915 5 will give the ratio weight of unknown to internal standard. Knowing the amount of internal 1.00 (av.) ... ... ... 0.165 0.338 standard in the sample (step 6) subjected to the Acetaldehyde I x-ray examination, it is possible to calculate the (yellow) 17.70 0.876 0,440 0.549 0.63 1.2s 0.855 0,428 0.506 0.59 1.18 amount of constituent in question present in the 3.19 0.590 0.281 0.685 1.16 a.44 original sample. B.579 0,551 0,274 1,635 2.11 2.66
Butyraldehyde I (yellow)
0.992
...
1.00 (av.)
...
...
...
1.95
0,400 0.370
1.63
0.845
0.239 0.203 0.417 0.398
0.51 4.45 8.790 0.770
0.505
0.458
0.534 8.715 0.630
0.447 0.370 0.367
1 .OO (av.) 1.90
1.00 (av.) 2.08 1.00 (av.) 2,4-D.P.H. (uncombined)
...
1 . 0 0 (av.)
...
0.910
1.15 Furfuraldehyde I (red)
0.807
0.521
0.727
Crotonaldehyde
0.500
1.11
1.57 1.60
1.00(av.)
...
1.05 1.06 1.32 1.25
...
...
...
...
...
1.81 1.82 0.345
1.61
1.74 Q.695
1.127 1.22 0.935 1.06 0.597 0.436 0.420 0.280 0.293 0.235
2.13 2.21 1.89 1.93 1.14 8.907 8.84 0.519
0.580
0.465
1.20 1.19 , .
8.610 0.622
0.540 0.470
0.45 0.393 0.202
0.89 Q.755 0.395
0.885 0.970 0.955 0.810
1.75 1.87 2.07 1.60
0.570 0.638 8.635
0.325 0.340 0.317 0.350 0.209
8.645
.
...
...
...
...
0.560
...
QUANTITATIVE X-RAY ANALYSIS
The quantitative analysis of pure aldehydes by precipitation with 2,4-dinitrophenylhydrazine has been studied carefully by Iddles and Jackson ( l a ) ,who reported yields greater than 95% for simple aliphatic aldehydes. Their method, using standard quantitative procedures, is accurate when the aldehyde may be obtained relatively free of other carbonyl compounds. The use of accurate density measurements of x-ray powder patterns of samples containing some internal standard makes possible quantitative analysis of samples of mixed aldehydes and ketones. Quantitative analysis by the x-ray powder diffraction method has been reported for the analysis of mineral and metallurgical samples (IO)using sodium chloride as an internal standard. These articles have dealt rather carefully with the theory of line intensities but lack in the presentation of satisfactory laboratory procedures. These articles report a n accuracy of 5% in the determination. This is probably a good estimate for most crystalline compounds, but under favorable circumstances the accuracy may be greater. The necessary steps for obtaining a good quantitative estimation of a mixture of two known compounds are then: 1. Calibration of the film used. 2. Preparation of a known mixture of the compounds in question with some definite amount of an internal standard such as sodium fluoride. The sample must be prepared in a finely divided state and thoroughly mixed, either by rapid evaporation or fine grinding, using some inert liquid as a dispersing agent. 3. Measurement of the relative line densities of the internal standard lines and the lines of the sample under consideration. 4. Correction of the relative line densities to give line intensities by using the film calibration curve. 5 . Calculation of the ratio of line intensities of the internal standard and sample in question for a 1 t o 1 mixture.
8.657 8.665 0.615
0.408
When a film is used with a linear response t o the x-rays, steps 4 and 7 may be omitted. QUANTITATIVE X-RAYANALYSISOF ALDEHYDES. The quantitative analysis of aldehydes was accomplished in this manner. Sodium fluoride was chosen as the internal standard, since it could be obtained in large quantities having a particle size small enough to give smooth sharp diffraction lines as well as produce a relatively simple powder pattern with a minimum of absorption of the x-ray beam, The samples were prepared by mixing weighed uantities of the aldehyde-2,4-dinitrophenylhyrazone with sodium fluoride. These were ground together carefully in an agate mortar, filled in a 0.35-mm. diameter cellulose acetate tube, and exposed to the x-ray beam in the 7.00-cm. powder camera for 2.5 to 3 hours using Eastman KOScreen film. The motor on the camera was set t o rotate through 360' to smooth out any spots on the diffraction lines. The patterns were microphotometered with the Leeds dt Northrup recording microphotometer.
3
Table I V lists the intensity data from the series of aldehyde 2,4-dinitrophenylhydazone-sodium fluoride patterns. Two different standard lines (200) and (220) are chosen for sodium fluoride and the $ongest line, usually corresponding t o a "d" spacing near 3.20 A., for the hydrazones. The two sets of readings for each pattern were obtained from the two sides of the film upon which the powder pattern was registered. The 1 to 1 ratios of line intensities in the table were calculated by dividing the ratio of intensities of the aldehyde 2,4dinitrophenylhydrazone t o sodium fluoride lines (columns VI and VII) by the weight of the constituents of the sample (column IT). These 1 to 1 ratios may now be used t o calculate'the weight ratio of unknown to sodium fluoride in any given sample, after qualitative identification of the aldehyde. LITERATURE CITED
(1) Allen, C. P. H., and Richmond, J. H., J. Org. C h m . , 2, 222 (1937). (2) Allen, G. F. H., J . Am. Chem. Soc., 52, 2955 (1930). J' ''' Biochem. J . 3 359294 (lg41)' (3) (4) Brandstatter, M., Mikrochemie p e r . Mikrochim. Acta, 32, 33 (1944). ( 5 ) Bredereck, H., Ber., 65, 1833 (1932). (6) Bryant, W. 11. A . , J . Am. Chem. Soc., 54, 3758 (1932); 55, 3201 (1933) : 58, 2335 (1936) ; 60, 2815 (1938). (7) Campbell, X . , Analyst, 61,391 (1936). (8) Curtius and Dedicher, J . prakt. Chem., (2) 50, 266 (1894). (9) Fricke, R., Lohrmann, O., and Schroeder, W., 2. Elektrochm., 47,374 (1939).
(10) Gross, S. T., and Martin, D. E., IND.ENG.CHmM,, ANAL.ED., 16, 95 (1944). (11) Hanawalt, J. D., Rinn, H. W., and Frevel, L. K., Ibid., 10, 457 (1938). (12) Iddles, H. A . , and Jackson, C. E., Zbid., 6, 454 (1934). (13) Purgotti, Gam. chim. ital., 24, I, 55 (1894).
