Infrared Spectra for Analysis of Aldehyde and Ketone 2, 4

Infrared Spectra for Analysis of Aldehyde and Ketone 2,4=Dinitrophenylhydrazones J. H. ROSS Carbide and Carbon Chemicals Co., Division of Union Carbide and Carbon Corp., South Charleston, . 'K Va. these derivatives may be close, the infrared spectra permit ready identification. The method has been used for the quantitative determination of small amounts of a mixture of acetaldehyde and propionaldehyde in water by measurement of the spectra of the 2,4-dinitrophenylhydrazones in solution and for a large number of identifications of aldehydes and ketones present as impurities in compounds inert to 2,4-dinitrophenylhydrazine. Conclusive identities are obtainable with as little as 10 mg. of derivative in less than 30 minutes.

The identification of aldehydes and ketones is often required in laboratory experiments. Standard methods sometimes produce questionable results. A study of the infrared spectra of derivatives of carbonyl compounds as a means of identification of aldehydes and ketones was therefore undertaken. The infrared spectra of the 2,4-dinitrophenylhydrazones of aldehydes and ketones are unique. Even closely related aldehydes or ketones which differ only by one CH2 group exhibit markedly different infrared spectra. While the melting points of

T

occurs if @-alkoxyaldehydes ai e reacted a t conditions other than a t room temperature and in the absence of acids. Melting points of the tw-enty-five 2,&dinitrophenylhydrazones are listed in Table I along with melting points reported in the literature. The chemical analysis of acetaldol2,4-dinitrophenylhydrazone also is shown in Table I. Table I1 shows the wave lengths of all the important bands in the spectra of the derivatives. The wave lengths are accurate t o about 3~0.03micron. Measurement of Spectra. The spectra of the derivatives were obtained n-ith a Perkin-Elmer Model 21 recording infrared spectrophotometer. The range 6 to 15 microns was covered with a sodium chloride prism. Each derivative was prepared for scanning by grinding the crystals to a fine powder and mulling with a pure mineral oil to a thick, smooth paste. The thickness of the paste between two rock salt platea was adjusted until it was translucent when a strong light was observed through it Each spectrum contains absorption bands a t 6.85 microns (1460 cm.-1) and 7.26 microns (1377 ern.-') caused by mineral oil.

HE 2,4-dinitrophenylhydrazones of carbonyl compounds are n o a widely used for characterization purposes and severa1 practical methods of organic analysis are employed, such as melting point (1, S ) , ultraviolet spectra (7, 14), x-ray diffraction pattern ( 8 , 6 , IO), and optical examination of the cryetals ( 2 2 ) The melting point, the method most frequently employed, is a satisfactory means for determining identity if the 2,4-dinitrophenylhydrazone is pure, but the presence of small amounts of impurities lowers the melting point. Ultraviolet spectra provide a method for identifying the 2,4dinitrophenylhydrazones of aromatic carbonyl compounds, but the spectra of the 2,4-dinitrophenylhydrazones of aliphatic carbonyl compounds are not easily distinguishable. Characterization of the derivatives by means of the x-ray diffraction pattern involves considerable time. Thew laboratories are constantly encountering the problem of identifying aldehydes and ketones rapidly. The use of the infrared spectra of the finely ground crystals, or mulls, of the 2,4dinitropheiiylhydrazones furnishes an excellent means for identification. The derivatives exhibit unique spectra which are readily identifird by comparison of wave lengths and band shape with calibration spectra, Also, the absorption of the derivatives is fairly intense and the bands are sharp, which permits precise location of absorption wave length. Derivatives which coiitaiii as much as 5 to 10% of an impurity as another derivative may br readily characterized by means of the infrared spectrum. In a few cases the spectrum of a solution is unique with respect to others and quantitative analysis is possible. 2,4-Dinitrophenylhydrazine reacts with most aldehydes and ketones to give yields of 90% or greater of the 2,4-dinitrophrnylhydrazonrs Thus, it is possible to identify a few parts per million of these compounds in the presence of materials which are inert to 2,4-dinitrophenylhydrazine by adding the reagent to a sufficiently large quantity, heating, and subsequently removing the inci t material. The remaining 2,4-dinitrophenylhydrazone often may be identified aithout further purification by means of a simple comparison of its infrared spectrum with that of known derivatives.

Table I.

Melting Points of 2,4-Dinitrophenylhydrazones Used for Infrared Spectra Prepared from

Reported M.P., 166 (16) 168 (16) 147 f6) 154 16) 165 IS) 122 f6) 19: 1 6 )

c.

i

Preparation of Derivatives. All the derivatives w eie prepared by a standard method outlined by Brady and Elsmie (S), with the exception of acetaldol 2,4-dinitrophenylhydrazone which was prepared without hydrochloric acid at room temperature. Crotonaldehyde 2,4-dinitrophenylhydrazone is always produced when the reaction is carried out in acidic media and when the solution is heated. Similarly, hydrolysis of the alkoxy group

XI.P.>

c.

167 Formaldehyde 168 2. Acetaldehyde, form I 148 3. Acetgldehyde, form I1 154 4. Propionaldehyde 165 5. Acrolein 122 6. Butyraldehyde 192 7. Crotonaldehyde 105 8. Acetaldol 104 (16) 107 9. n-Hexaldehyde 131 134 (26) 10. 2-Ethylbutyraldehyde 11. Pyruvic aldehyde (di-2,4-dinitrophenylhy301 300 (11) drasone) 317 328 (16) 12. Glyoxal (di-2,4-dinitrophenylhydrazone) 240 237 (16) 13. Benzaldehyde 197 197 14. 2.4-Dinitrophenylhgdrazine 126 126 (16) 15. Acetone 156 156 16) 16. Diethyl ketone 75 75 116) 17. Di-n-propyl ketone 95 95 f6) 18. hIethyl isobutyl ketone 314 315 (16) 19. Biacetyl (di-2,4-dinitrophenylhydratsone) 202 203 (16) 20. Mesityl oxide 142 142 (16) 21. Cyclopentanone 250 250 (16) 22. Acetophenone 89 23. Diisobutyl ketone 116 24. Rfethyl ethyl ketone 119 25. Methyl isopropyl ketone 93 89 (1) 26. Methyl amyl ketone 205 decomp. 27. 2,4-Dinitrophenylhydrazine hydrochloride a bndysis. Calculated for CiaHnN4Oa. C, 44.77%; H, 4.51%; N, 20.89%; 0, 29.83%. Found. C,44.7%: H, 5.2%; N,20.8%; 0,29.0%. 1.

EXPERIMENTAL

Determined

1288

....

V O L U M E 25, NO. 9, S E P T E M B E R 1 9 5 3 The band a t 13.87 microns (720 cm.-1) in the spectrum of mineral oil does not appear in the spectra because the quantity of oil is small. In the case of the spectra of chloroform solutions of the derivatires shown, the absorption of the chloroform has been compensated with an appropriate amount of chloroform in the reference limn of the instrument. In those regions of intense solvent ab~ option i the spectra are not shown. Discussion of Results. The fact that the infrared spectrum at most materials in the region 8 t o 14 microns (1250 to 7142 cni.-l) is sensitive to change in structure has been pointed out in the litrrature many times (8). The spectra of a series of 2,4-dinit1 ophenylhydrazones in the crystalline phase exhibit this sensitiviti to an unusual degree. Figures 1 to 8 show the infrared y w c t i n from 6 to 15 microns (1666 to 666 cm.-‘) of 24 of these. Figurr 0 shows the spectra of the reagent and 2,4-dinitrophenylhvdrazine hydrochloride. All these spectra are obviously uniquc- and have been found to be very valuable for the purpose of itirntification. The spectra of the reagent and 2.4-dinitrophen-

1289 ylhydrazine hydrochloride are exhibited to show that thew may be readily distinguished from the spectra of the derivatives. Figure 10 shows the spectra of solutions of some 2,4-dinitrophenylhydrazones. All the solutions examined in this laboratory exhibit a doublet a t 6.20 and 6.25 microns (1613 and 1600 cm.-I) due to the phenyl group and a band attributed to the 1,2,4trisubstituted phenyl gmup a t 12.0 microns (833 cm.-I). The spectra of the solutions ordinarily do not lend themselves for use as “fingerprints” for identification. A general comparison of the spectra of the solutions with those of the crystal mulls shows that the effect of crystallization on the spectra is usually to cause a splitting of the band at 12.0 microns (833 cm.-1) into a doublet. The absorbances and spectral positions of these two bands differ considerably from one spectrum to another. The band a t about 10.8 microns (926 cm.-I) usually exhibits similar alterations. Yearly all the bands in the 9-micron (llll-cni.-l) region are characteristic in each of the spectra of the crystal mulls. Un-

(Continued on page 1698)

Table 11. Wave Lengths of Absorption Bands of 2,4-Dinitrophenylhydrazones, 2,4-Dinitrophenylhydrazine,and 2,4-Dinitrophenylhydrazine Hydrochloride (Includes mineral oil bands a t 6.85 and 7.26 microns) 2,4Dinitro?,4phenylDinitro- hydrazine phenylHydrohydrazine chloride 6.11 6.16 6.20 6.26 6 27 6.57 6.34 6.66 6.59 6.84 6.68 7.08 6.84 7.26 7.07 7.46 7.28 7.59 7 . ~ 8 7.81 7.77 8.04 8.17 8.24 8.72 8.69 8.83 8.82 9 00 9.45 9.42 10.80 10.18 10.96 10.74 11.93 10.83 12.12 12 05 13.10 13.07 13.50 13.43 14.13 14.15 14.66 14.4;

CYClOpenianone 2,4-DNPH 6.17 6.30 6.38 6.66 6 86 7.05 7.27 7.35 7.50 7.67 7.92 8.21 8.31 8.75 8.85 9.43 9.62 10.22 10.46 10.88 11.54 11.96 12.06 13.14 13.47 13.95 14.68

-4cet%EthylFormal- aldehyde Propion- Butyrn-Hexbutyrdehyde I aldehyde aldehyde aldehyde aldehyde Acetone 2,42,42,42,42,42.42.4D x m DNPH DXPH n x P n D w n DNPH DNPH 6.17 6.15 6.20 6.17 6.17 6.17 6.18 6.27 6.26 6.28 6.27 6.26 6.27 6.29 6.58 6.50 6.50 6.60 6.50 6.62 6.60 6.85 6.62 6.70 6.84 6.86 6.58 6.59 7.02 6.86 6.73 6.85 7.03 6.85 7.02 7.26 7.06 6.85 7.08 7.25 7.02 z.26 7.50 7.28 7.05 7.26 7.37 7.26 ,,57 7.54 7.38 7.61 7.29 7.53 7.48 7.77 8.18 7.70 7.51 8.18 7.35 7.68 7.62 7.94 7.94 7.69 8.81 8.81 7.52 7.85 8.27 8.22 8.15 9.29 9.24 7.80 7.68 8.80 7.94 8.77 8.38 9.50 8.00 10.28 8.89 8.26 9.07 8.75 8.22 10.60 10.27 8.97 8.77 9.33 8.90 8.82 10.53 10.80 9.40 8.91 9 49 9.36 9.09 10.80 11.38 9.42 12.07 9.57 9.35 9.84 10.90 10.80 13.11 9.70 9.52 9.73 12.00 10.12 10.94 12.08 13.43 11,73 10.82 10.78 10.20 0.18 13.11 13.80 12.04 10.41 0.79 11.83 10.87 13.45 14.62 13.08 10.81 0.85 12.03 11.30 13.78 13.44 11.91 13.15 1.62 11.93 14.62 12.09 1.91 13.87 13.43 12.04 12.79 2.02 14.58 13.83 13.10 13.14 3.11 14.57 13.44 13.50 13.83 3.44 13.98 3 . 86 14.67 4.66 14.66

Diethyl Ketone 2,4-

nwn

6.15 6.27 6.61 6.85 7.07 7.26 7.49 7.64 7.94 8.18 8.84 9.19 9.39 9.58 10.02 10.83 10.93 11.85 12.04 12.35 12.70 13.05 13.44 13.88 14.58

Di-nprops1 Ketone 2,4DNPH 6.18 6.28 6.62 6.85 7.08 7.26 7.51 7.65 7.93 8.19 8.82 9.37 9.58 10.88 11.86 12.03 13.10 13.45 13.82 14.58

Methyl Ethyl Ketone 2,4DNPH 6.16 6.27 6.66 6.86 7.08 7.33 7.50 7.65 7.93 8.20 8.83 9.40 9.58 10.25 10.84 10.92 11.80 12.03 13.11 13.45 13.88 14.63

Methyl Isopropyl Ketone 2.4-

DNP”

6.15 6.27 6.58 6.65 6.84 7.05 7.25 7.31 7.46 7.63 7.86 8.18 8.82 9.37 9.55 10.05 10.86 11.90 12.02 13.10 13.42 13.94 14.65

bIethyl Isobutyl Ketone 2,4DXPH 6.16 6.27 6.65 6.85 7 . OB 7.37 z.50 .64

,

7.74 7.93 8.20 8.80 9.30 9.50 10.84 10.92 11,84 12.05 13.10 13.44 13.80 14.60

Pyrii\ ic Methyl Glyoval Aldehyde BiacetJI CrotonBenaDiisobutyl Amyl Ace t oAcetaldol aldehyde Ketone Ketone phenone (di) aldehyde Acrolein (di) (di) 2,4-DNPH 2.4-DNPH 2,4-D?iPH 2 4-DSPH 2,4-Dh-PH 2 , 4 - D S P H 2,4-DNPH 2,4-DNPH 2,4-D?jPH 2,4-DNPH 6.20 6.19 6.07 6.15 6.15 6.18 6.18 6.17 6.18 6.26 6.26 6.19 6.27 6.29 6.28 6.30 6.28 6.28 6.32 6.67 6.68 6.61 6.50 6.50 6.60 6.53 6.66 6.67 6.85 6.62 6.63 6.84 6.85 6.61 6.70 6.85 6.84 7.08 7.02 6.83 7.03 6.72 6.84 7.07 6.85 6.99 i.45 7.05 7.25 7.25 7.07 6.84 7.06 7.27 7.31 7.53 7.27 7.52 7.36 7.28 6.90 7.27 7.61 7.55 7.65 7.47 7.82 7.51 7.39 7.05 7.32 7.85 7.92 7.60 8.18 8.20 7.65 7.65 7.54 7.25 7.52 8.24 7.80 8.77 7.85 7.85 7.65 7.50 7.63 8.80 8.45 8.89 8.22 7.94 7.69 7.60 7.70 9.30 7.92 8.25 9.20 8.37 8.80 7.93 7.90 7.95 10.24 8.03 9.09 9.45 8.80 8.19 8.20 8.22 10.50 8 74 8.18 9.34 9.20 10 25 9.23 8.58 8.42 10.79 8.54 8.84 9.55 9.48 10.49 9.43 8.73 11.38 8.64 8.86 9.25 11.60 0.83 10.66 10.20 8.80 9.95 8.87 9.45 9.28 12.06 10.70 10.22 10.70 10.85 9.00 9.41 9.16 10.85 13.10 10.89 11.98 9.31 10.45 10.82 9.35 9.55 10.91 9.50 13.45 11.80 13.10 9.44 10.55 10.93 11.83 10.88 13 80 12.03 13.44 11.98 10.81 9.78 12.03 11.90 10.00 13.11 13.60 13.12 14.62 10.50 13.12 12.06 11.97 10.13 13,46 14.13 13.46 12.04 10.75 13.46 12.49 10.32 14.65 13.60 13.77 13.86 13.48 13.08 10.83 10.84 14.55 13.45 11.17 14 60 14.60 13.82 10.97 13.81 11.60 11.75 14.65 11.96 11.90 12.00 12.03 13.06 13.01 13.16 13.45 13.84 13.45 13.92 14.41 14.52

Mesityl Oxide 2,4DNPH 6.18 6.28 6.50 6.61 6.85 7.06 7.25 7.37 7.52 7.64 7.87 8.02 8.20 8.87 9.13 9.46 9.80 10.81 10.93 11.17 11.68 11.86 12.00 12.21 13.13 13.50 13.94 14.60

Acetaldehyde 11 2,4-DNPH 6.18 6.27 6.62 6.70 6.85 7.00 7.08 7.28 7.35 7.54 7.70 7.95 8.24 8.82 8.96 9,37 10.86 10.95 11.29 11.76 12.05 13.11 13.47 13.86 14.58

ANALYTICAL CHEMISTRY

1290

W A V E N U M B E R , CM.-J 1000 900

1600l500 1400 1300 1200

1100

1600 1500 1400 1300 1200

700

800

W A V E N U M B E R , CM.-l 1100 1000 900

700

800

Figure 1. Spectra of 2,a-Dinitrophenylhydrazone Derivatives 6

7

9

IO

II

W A V E LENGTH, MICRONS

I2

13

14

15

V O L U M E 25, NO. 9, S E P T E M B E R 1 9 5 3

1600 1500 1400 IWO

1200

1291

W A V E N U M B E R , CM.-l 1000 900

1100

700

W A V E N U M B E R , CM.-I 1600 15.00 I F I300 1200

1100

1000

900

700

800

Figure 2. Spectra of 2,4-Dinitrophenylhydrazone Derivatives

6

7

8

9

10

II


12

13

14

15

1292

6


7

0

9

IO

12

I1

13

14

15

WAVE LENGTH, MICRONS

1600 1500 1400 1300 1200


WAVE NUMBER, CM.-l 1100 I000 900

to0

V O L U M E 2 5 , NO. 9, S E P T E M B E R 1 9 5 3

1293

7

6

8

10

9

12

/I

13

14


6

7

8

9

10

I1

12

13

14

I5




1294

6

7

8

9

I3

IO I1 I2 WAVE LENGTH, MICRONS

15

14

WAVE NUMBER, CM,-I 1000 900

1600 I500 1400 1300 1200

1100

8 00

700

c

2.I tE


1600 1500 1400 1300


1200

JWIUWl. 6

I

7

WAVE NUMBER, CM.-1 1000 900

1100

'/Vi"( I 8

I 9

jlw, LENI I I 10

I 11


700

800

I 12

I I

13

j

1 I 1

14

15

V O L U M E 2 5 , NO. 9, S E P T E M B E R 1 9 5 3

1295

Figure 6. Spectra of 2,4-Dinitrc1phenylhydrazone Derivatives 6

r

8

9

IO

II


12

13

14

15


1296

6

i

9 IO II 12 WAVE LENGTH, MICRONS

8

1600 15001400 1300 1200

13

14

WAVE NUMBER, CM.-' 1100 1000 900

i5

700

e00

s w

!=

pa

e Figure 7. Spectra of 2,4-Dinitrophenylhydrazone Derivatives

6

7

8

9

10 II 12 WAVE LENGTH, MICRONS

13

14

15


160015001400 1330 1200

1297

WAVE NUMBER, CM.'I 1000 900

700

1100

P

2

3 2 Figure 8. Spectra of Di-2,4-dinitrophenylhydazone Derivatives

6

7

9 10 II 12 WAVE LENGTH, MICRONS

13

14

15

A N A L Y T I C A L CHEMISTRY

1298

doubtedly hydrogen bonding and other causes described previously are responsible for these effects (IS). The spectra cannot be used to show whether an unknown is an aldehyde or a ketone, identification being possible only by comparison with calibration spectra. The spectra of crystalline derivatives of aromatic aldehydes and ketones exhibit four distinguishing bands of nearly the same intensity in the region from 13 to 15 microns (769 to 666 cm.-l). The 2,4-dinitrophenylosazones of pyruvic aldehyde, glyoxal, and compounds containing adjacent ketone groups do not exhibit a band a t 13.8microns (724 cm.-1) as do the mono-derivatives of aliphatic compounds. They usually exhibit two closely spaced bands a t about 13.45 and 13.60 microns (743 and 735 em. -1). This region is useful, therefore, to determine quickly whether an unknown is a derivative of an aromatic carbonyl compound or a derivative of a compound containing adjacent carbonyl groups. I n the 13- to 14-micron (769- to 714-em. - l ) region the spectra of isophorone (not shown) and mesityl oxide derivatives appear similar to the 2,4-dinitrophenylosazones mentioned above. Acetaldol 2,4-dinitrophenylhydrazone

exhibits a weak hydroxyl band a t about 2.90 microns 13448 cm.-1). This band is not shown in the spectrum iu Figure 6. One of the chief advantages of the use of infrared spectra for the identification of aldehyde and ketone 2,4dinitrophenylh~-drazones is the ability to distinguish and readily identify impure derivatives which cannot be characterized by melting point or are not positively identified by other methods. Figure 11 illustrates the relative ease with which impure derivatives may be identified. The center spectrum is that of a 10% mixture of the derivative of butyraldehyde with that of the derivative of hexaldehyde. The mixture was obtained by evaporation of a chloroform solution of these 2,4-dinitrophenylhydrazone-. The melting point of this mixture is about 99" C., whereas the melting point of the pure major component is 107 O C. This mixture cannot be characterized by means of the melting point, of course, but it is readily rpcognized as predominantly hexaldehyde 2,4dinitrophenylh~-diazone by comparison with the spectrum of pure hexaldehyde 2,4dinitrophenylhydrazone in the 10- to 11-micron (1000- to 909region. In general, 5 to 10% of an impurity (a. nnnthei

WAVE LENGTH. MICRONS

Figure 9.

Spectra of Crystalline Mulls of 2,4-Dinitrophenylhydrazine and 2,4-Dinitrophenylhydrazine Hydrochloride

V O L U M E 25, NO. 9, S E P T E M B E R 1 9 5 3 The hand a t 13.87 microns (720 cm.-1) in the spectrum of mineral oil does not appear in the spectra because the quantity of oil is small. In the case of the spectra of chloroform solutions of the derivativcs shown, the absorption of the chloroform has been compensated with an appropriate amount of chloroform in the reference 1 x S : i m of the instrument, In those regions of intense solvent abso1 ption the spectra are not shown. Discussion of Results. The fact that the infrared spectrum ot most materials in the region 8 t o 14 microns (1250 t o 7142 cni.-l) is sensitive to change in structure has been pointed out in the litrrature many times (8). The spectra of a series of 2,4-dinitrophenylhydrazones in the crystalline phase exhibit this sensitivitv to an unusual degree. Figures 1 to 8 show the infrared y ) t v t r n from 6 to 15 microns (1666 to 666 cm.-1) of 24 of these. Figurp 9 shows the spectra of the reagent and 2,4-dinitrophenylhvdrnzine hydrochloride. All these spectra are obviously uniquo and have been found to be very valuable for the purpose of iti(wtification. The spectra of the reagent and 2.1-dinitrophen-

1289 ylhydrazine hydrochloride are exhibited to show that these may be readily distinguished from the spectra of the derivative.. Figure 10 shows the spectra of solutions of some 2,4-dinitrophenylhydrazones. All the solutions examined in this laboratory exhibit a doublet a t 6.20 and 6.25 microns (1613 and 1600 em. -I) due to the phenyl group and a band attributed to the 1,2,4trisubstituted phenyl grbup a t 12.0 microns (833 cm.-l). The spectra of the solutions ordinarily do not lend themselves for use as “fingerprints” for identification. A general comparison of the spectra of the solutions with those of the crystal mulls shows that the effect of crystallization on the spectra is usually to cause a splitting of the band a t 12.0 microns (833 cm.-l) into a doublet. The absorbances and spectral positions of these two bands differ considerably from one spectrum to another. The band a t about 10 8 microns (926 em.-]) usually exhibits similar alterations. Senrly all the bands in the 9-micron ( l l l l - c m , - l ) region are characteristic in each of the spwtra of the crystal mulls Un-

(Confinuerlon page 1,998)

Table 11. Wave Lengths of Absorption Bands of 2,4-Dinitrophenylhydrazones,2,4-Dinitrophenylhydrazine,and 2,4-DinitrophenylhydrazineHydrochloride (Includes mineral oil bands a t 6.85 and 7.26 microns) 2,4Dinitro2,4phenylDinitro- hydrazine Hydrophenylhrdrazine ohloride 6.11 6.16 6.26 6 20 6. -27. 6.57 6.66 6.34 6.84 6.59 7.08 6.68 7.26 $84 7.46 l . 07 7.59 7. ‘“8 7.81 7 . a8 7.77 8.04 8 17 8.24 .~ 8.69 8 72 8.82 8.83 9.45 9.00 9.42 10.80 10.96 10.18 11.93 10.74 12.12 1 0 83 13.10 12 05 13.50 13.07 14.13 13.43 1 4 . 15 14.66 14.47

Cyclopentanone 2,4-DNPH 6 17 6.30 6.58 6.66 6 86 7.05 7.27 7.35 7.50 7.67 7.92 8. 21 8.31 8.75 8.85 9.43 9.62 10.22 10.46 10.88 11.54 11.96 12.06 13.14 13.47 13. 95 14.68

-4cet2-EthylFormal- aldehyde Propion- Butgrn-Hexbutyraldehyde aldehyde aldehyde aldehyde Acetone I dehgde 2,42,42 42 42 42,42,4D k P H DdPH D ~ P H DNPH DTPH DNPH DNPH 6.17 6.20 6.15 6.18 6.17 6.17 6.17 6.27 6.28 6.26 6.27 6.29 6.27 6.26 6.50 6 . 5 0 6.58 6.60 6.50 6.62 6.60 6.58 6.62 6.85 6.86 6.70 6.59 6.84 6 .85 6 . 8 6 7 . 0 2 7.02 6.85 6.73 7.03 7.02 7.06 7.26 26 7.08 6.85 7.25 7 .26 7 . 2 8 7 . 5 0 I . 57 7.26 7.05 7.37 7.38 7.54 7.61 7.77 7.53 7.29 7.48 7.51 7 . 7 0 8 . 1 8 8 . 1 8 7.68 7.35 7.62 7.69 7.94 8.81 8.81 7.94 7.52 7.85 7.80 8.27 9.24 9.29 8.22 7.68 8.15 8.00 8.80 9.50 10.28 8.77 7.94 8.38 8.22 8 . 8 9 10.27 10.60 9,07 8.26 8.75 8.82 8.97 10.53 10.80 9.33 8.77 8.90 9.09 9 . 4 0 10.80 1 1 . 3 8 9.49 8.91 9.36 9.42 9.57 10.90 12.07 10.80 9.35 9.84 9.73 9 . 7 0 1 2 . 0 0 13.11 10.94 9.52 10.12 10.18 12.08 10.20 13.45 11,73 10.78 10.82 1 0.79 1 3 . 1 1 10.41 13.80 12.04 10.87 11.83 10.85 10.81 13.45 14.62 13.08 11.30 12.03 1 1.62 11.91 1 3 . 7 8 13.44 11.93 13.15 11.91 12.09 14.62 13.87 12,04 13.43 12.02 1 2 . 7 9 14.58 13.10 13.83 13.11 13.14 13.44 14.57 13.44 13.50 13.83 13.98 13.86 14.67 14.66 14 66

z.

Diethyl Ketone 2.4DNPH 6.1; 6.27 6.61 6.85 7.07 7.26 7.49 7.64 7.94 8.18 8.84 9.19 9.39 9.58 10.02 10.83 10.93 11.85 12.04 12.35 12 7 0 13.05 13.44 13.88 14.58

Di-npropyl Ketone 2,4DNPH 6.18 6.28 6.62 6.85 7.08 7.26 7.51 7.65 7.93 8.19 8.82 9.37 9.58 10.88 11.86 12.03 13.10 13.45 13.82 14.58

Methyl Ethyl Ketone 2,4DNPH 6.16 6.27 6.66 6.86 7.08 7.33 7.50 7.65 7.93 8.20 8.83 9.40 9.58 10.25 10.84 10.92 11.80 12.03 13.11 13.45 13.88 14.63

Methyl Isopropyl Ketone 2,4DXPH 6.15 6.27 6.58 6.65 6.84 7.05 7.25 7.31 7.46 7.63 7.86 8.18 8.82 9.37 9.55 10.05 10.86 11.90 12.02 13.10 13.42 13.94 14.65

Methyl Isobutyl Ketone 2,4DSPH 6 16 6.27 6.65 6.85 7

ns

7 37 7 50 7 64 7.74 7 93 8.20 8.80 9 30 6.50 10.84 10.92 11.84 12.05 13.10 13.44 13.80 14.60

Pyruvic Methyl Glyoxal Aldehyde Biacetyl CrotonBenzDiisobutyl Amyl AcetoAcrolein (di) (di) (di) aldehyde doetaldol aldehyde Ketone Ketone phenone 2,4-DNPH 2,4-DNPH 2,4-DXPH 2 . 4 - D S P H 2 , 4 - D K P H 2 , 4 - D S P H 2,4-DNPH 2,4-DNPH 2 , 4 - D N P H 2,4-DNPH 6.18 6.18 6.17 6.15 6.15 6.19 6.07 6.20 6.20 6.18 6.30 6.28 6.28 6.28 6.27 6.19 6.26 6.26 6.34 6.29 6.61 6 . 5 3 6 . 6 6 6 . 5 0 6 . 6 0 6 . 6 8 6 . 6 7 6.32 6.66 6.50 6.70 6.62 6.85 6.61 6.85 6.85 6.84 6.67 6.86 6.63 6 .84 6 . 8 5 7 . 0 7 6 . 7 2 7 . 0 2 7 . 0 8 7 . 0 3 6 . 8 4 7 . 0 4 6.83 7.06 7.07 7.27 6,84 7.25 7.25 7.45 7.28 6 99 7.05 7 .27 7 . 3 6 7 . 2 8 6 . 9 0 7.52 7 . 5 3 7 . 6 1 7 sn 7 . 2 7 7.31 7.32 7.51 7.39 7.05 7.82 7.65 7.85 7.47 7.60 7.55 7.52 7.65 7.54 7.25 8.18 8.20 7.92 7.60 7.75 7.65 7.63 7.85 7.65 7.50 8.80 8.24 8.77 7.80 7 86 7.85 7.70 7.69 7.92 7.60 9.30 8.45 8.89 7.94 8 19 8.22 7.95 7 93 8.03 7.90 10.24 8.80 9.20 8.25 8.73 8.37 8.20 8 . 2 2 8 . 1 8 8 19 10.50 9 . 0 9 9 . 4 5 8 74 8 . 8 5 8.80 8.42 8.84 8.58 8.54 10.79 9.34 9.20 10 2: 9 24 9.23 8.73 9.25 8.64 8 86 11.38 9.55 9.48 10 49 9.43 9.51 8.87 9.45 8.80 9 28 11,60 10.66 10.20 9.83 9.95 10.84 9.00 10.85 9.16 9.41 12.06 10.70 10.85 10.70 11.92 10.22 9.35 9.55 10.91 9.31 13.10 10.89 11.98 10.82 12.02 10.45 9.50 11.83 10 88 9.44 13.45 11.80 13.10 10.93 13.17 10.55 12.03 10.00 11.90 9.78 13.80 12.03 13.44 11.98 13.48 10.81 10.13 13.12 12.06 10.50 14.62 13.11 13.60 13.12 13.70 11.97 13.46 10.32 12.49 10.75 13.46 14.13 13.46 12.04 13.86 10.84 13.48 10.83 13.77 14.65 13.60 13.08 10.97 14.60 13.82 11.17 14.55 14.60 13.45 11.60 11.75 13.81 11.90 11.96 14.65 12.00 12.03 13.01 13.06 13.16 13.45 13.45 13.84 13.92 14.41 14.52

AIesityl Oxide 2,4DNPH 6.18 6.28 6.50 6.61 6.85 7 nti

7.25 7.37 7.52 7.64 7.87 8.02 8.20 8.87 9.13 9.46 9.80 10.81 10.93 11.17 11.68 11.86 12.00 12.21 13.13 13.50 13.94 14.60

Acetaldehyde 11 2,4-DNPH 6.18 6.27 6.62 6.70 6.85 7.00 7.08 7.28 7.35 7.54 7.70 7.95 8.24 8.82 8.96 9.37 10.86 10.95 11.29 11.76 12.05 13.11 13,47 13.86 14.58

1300


WAVE NUMBER. CM-I

WAVE LENGTH. MICRONS

Figure 11. Spectra of Butyraldehyde 2,4-Dinitrophenylhydrazone, Hexaldehyde 2,4-Dinitrophenylhydrazone,and a Mixture of These 2,g-Dinitrophenyl hydrazones


1301

2.~-tlinitrophenylhydrazone) does not appear in the spectrum when ordinary sample thicknesses (described in measurement of the spect'ra)are employed. Crystalline modifications of the 2,4-dinitrophenylhydrazones yield different infrared spectra. This observation has been reported previously for other compounds in the crystalline phase (9.16). While the spectra of the polymorphic forms are different, no particular difficulty has arisen with regard to the UPP of the spectra for identification. A different polymorphic form was obtained only once during the identification of 75 unknowns. These were all crystallized from the same solvent as that, used in the preparation and recrystallization of the derivatives used for calibration-Le., ethyl alcohol. Obviously. a catalog of referelice spectra should include the spectra of :is many modificatioiis as it is possible t o prepare. Figure 12 shows the spectra of tivo polymorphic forms of acetaldfshyde 2,4-dinitrophen!-lh\-drazone. Form I was obtained b y r r ~ ~ t a l l i z a t i ofrom n ethyl alcohol, whereas form I1 as prepared

6

7

8

9

by fusion of form I according to the method of Bryant ( 4 ) . No cvidence for crotonaldehyde 2,4-dinitrophenylhydrazone. suggested bv Campbell (6) as a probable impurity obtained by Bryant (4), was detected by means of the infiared spectrum. X-ray diffraction data obtained on both forms I and I1 compared closely xyith the data reported by Clark et al. (6). .4fter the spectrum of form I1 was made the crystals were dissolved in ethyl alcohol and the solution was permitted t o evaporate. The crystals n.hich \\-ere obtained gave a spectrum identical with that of form I. These crystals melted at 152' C. Syn and anti isomers of the 2,4-dinitrophenj lhydrazones might be elpected to yield dissimilar spectra and attempts xere made to determine the influence of geometric isomerism on the infrared qpectrum in the case of methyl ethyl ketone 2,4-dinitrophenylhydraLone. hccording to Gordon et al. (10) two hands are obqerved in the chromatographic adsorption and elution of the derivative of this ketone. They suggest that a possible explanation is that the two bands result from the separation of the syn and

10 I/ WAVELENGTH, MICRONS

12

13

14

Figure 12. Infrared Spectra of Crystal Modifications of Acetaldehyde 2,4-Dinitrophenylhydrazone

IS


1302 anti isomers of the 2,4-dinitrophenylhydrazone.However, following the procedure outlined ( 1 0 ) only one band was observed when pure methyl ethyl ketone 2,4dinitrophenylhydrazone (melting point 116' C.) was chromatographed. In a few cases the spectrum of a solution of the 2,Pdinitrophenylhydrazone is unique with respect to others. Such is the case with the spectrum of the derivative of acetaldehyde shown in Figure 13. The band a t 11.39 microns (878 crn.-l) in the spectrum of acetaldehyde 2,4-dinitrophenylhydrazone was used for the quantitative analysis of this derivative in the presence of Chloroform propionaldehyde 2,4-dinitrophenylhydrazone. serves as an excellent solvent for the derivatives from the standpoints of solubility and infrared transparency. Figure 14 shows the analytical curve based on the absorbance of this band. In addition to providing a fast, positive means for the isolation and characterization of carbonyl compounds, the method often gives some information about the structure of an unknown, even though reference spectra are not available. For example, derivatives of bifunctional aldehydes or ketones which also contain an ester, carboxyl, or hydroxyl group eshibit absorption in that region of the spectrum which is characteristic of these groups. The sample size required may be as small as 10 mg. for conventional infrared equipment and the time required for scanning is less than 30 minutes. The punched card system in use by the

Figure 14. Analysis of Acetaldehyde 2,4-Dinitrophenylhydrazone Slit = 1 6 0 ~

WAVE NUMBER ,CY-I

0 Y

B

-

; a

I

6

T

f

B

4

B

I

IN CHLOROFORM (COMPENSATED . 1 I ! 1 I

li

15

Ib

I k

I

' 15

.WAVE LENGTH, MICRONS

Figure 13. Spectra of Acetaldehyde 2,4-Dinitrophenylhydrazoneand Propionaldehyde 2,4-Dinitrophenylhydrazonein Chloroform Solution


1303 ( 5 ) Campbell, K.R., Analyst, 61, 391 (1936). (6) Clark, G. L., Kaye, W. I., and Parks, T. D., IND.ENG.CHEM., ASAL.ED.,18,310 (1946). (7) Djerassi, C., and Ryan, E., J . Am. Chem. Soc., 71,1000 (1949). (8) Dobriner, K., et al., J . Biol. Chem., 172, 241 (1949). (9) Ebert, A. d.,Jr., and Gottlieb, H. B., J . A m . Chem. Soc.. 74, 2806 (1952). (10) Gordon, B. E., Wopat, F.. Jr.. Burnham. H. D.. and Jones, L. C.. Jr.. ANAL.CHE;., 23, 1754 (1951). (11) Heilbron, I. M., “Dictionary of Organic Compounds,” Vol. 111, p. 365, New York, Oxford University Press, 1946. (12) Mitchell, John, Jr., ASAL. CHEM.,21, 448 (1949). (13) Price, W.C., and Tetlow, K. S., J . Chem. Phys., 16, 1157 (1948). (14) Roberts, J. D., and Green, C., J . Am. Chem. SOC.,68, 214 (1946). (1.5) Shriner, R. L., and Fuson, R. C., “Systematic Identification of Organic Compounds,” p. 148, iYew York, John Wiley 8: Sons, 1935. (16) Wagner, E. L., and Hornig, D. F., J . Chem. Phys., 18, 296, 305 (1950).

National Research Council does not possess the necessary resolution for sorting the spectra of the 2,4-dinitrophenylhydrazones. -4 system in which the cards are punched every 0.1 micron, however, is satisfactory. ACKNOWLEDGMENT

The author wishes to thank the Carbide and Carbon Chemicals Co. for permission to publish this article. Credit is also due to H. L. Thornburg for the analysis of acetaldol 2,4-dinitrophenylhydrazone, to Alexander Brown and E. R. Walters for the x-ray data, and to W.J. Tapp, D. G. Leis, and others for the preparation of some of the derivatives. LITERATURE CITED

(1) (2) (3) (4)

Allen, G. F. €I., J . Am. Chem. SOC.,52,2955 (1930). Bell, J. V., Biochem. J., 35,294 (1941). Brady, 0. L., and Elsmie, G. V., Analyst, 51,77 (1926) Bryant, W. 11.D., J . Am. Chem. SOC., 55,3201 (1933).

RECEIVED for review September 29, 1951. Accepted July 11, 1953. Presented in part a t the Symposium on Molecular Structure and Spectroscopy, Columbus, Ohio, June 1952.

Preparation and Properties of Some Methylated lndans JACOB ENTEL, CLARENCE H. RUOF, AND H. C. HOWARD Coal Research Laboratory, Carnegie Institute of Technology, Pittsburgh, Pa.

Analysis of mixtures of methylated indans with polymethylbenzenes requires a knowledge of the methylated indans which heretofore has not been well established. In this work a group of authentic methylated indans have been synthesized and purified; the physical properties, including infrared and ultraviolet spectra, have been measured. The determination of these properties permits definite characterization of methylated indans.

I

X RECENT studies on the nuclear structure of the watersoluble polycarboxylic acids from the oxidation of bituminous coals, the esters of the coal acids have been subjected to hydrogenolysis to convert the carbalkoxy groups to methyl groups (18). The resulting methylated compounds have been fractionally distilled in precision columns and the expected di-, tri-, and tetramethylbenzenes have been isolated and definitely characterized. In addition to these polymethylbenzenes, however, other aromatic and saturated hydrocarbons and oxygenated compounds are also present. -4number of the properties of the methylated bicyclic aromatics overlap those of the methylated benzenes. TOaid in the charactcrization of such bicyclic aromatics in mixtures with polymethylbenzenefi,information on the properties of the simpler methylated bicyclics is desirable. -4s infrared spectra have proved to be of great value in the identification of hydrocarbons in mixtures, the primary aim of the work was to obtain such spectra. The present

Table I. Sample Indene Indan cis-Hexahydroindan I-hfethylindan 5-Methylindan 4-Methylindan 5-Methylindan 1,2-Dimethylindan 1,3-Dimethylindan 1,6-Dimethylindan ~

~~~~~

Physical

Boiling Point, C. 1 8 1 . 8 at 7 3 9 . 5 mm. 1 7 6 . 7 at 7 3 9 . 2 mm. 167.1 at 7 3 9 . 2 mm. 1 8 9 . 5 at 7 3 9 . 2 mm. 1 9 0 . 3 at 7 3 9 . 2 rnm. 2 0 5 . 3 at 7 4 0 . 5 mm. 2 0 1 . 1 at 7 4 0 . 5 mm. 2 1 0 . 9 at 7 4 0 . 0 mm. ~~~~~

paper deals with the preparation and properties of a group of methylated indans. The indans were synthesized by conventional methods, purified by fractional distillation in columns of 50 theoretical plates, and subjected to physical measurements. Physical properties are shown in Table I, ultraviolet spectra in Figure 1, and infrared spectra in Figures 2 to 11. The infrared spectra appear to be a very effective means of identifying methylated indans in mixtures of close-boiling polymethylbenxenes. PREPARATION OF SAMPLES

Indene, indan, and &s-hexahydroindan were samples previouEly described (6). 1-Methylindan. Seventy-three grams of %methyl-1-indanone, Prepared as described by et az. ( l o ) ,was reduced by the Clemmensen method (12,IS). The yield of 1-methylindan was 34.6 grams or 52.4%. 2-Methylindm. As outlined by Dox and Yoder ( b ) , 568 grams (3.46 moles) of a-methylhydrocinnamic acid was prepared as follows: Benzyl chloride (632 grams, 5 moles) was added to 847 grams (4.87 moles) of the diethyl ester of methylmalonic acid ( 1 4 )and 115 grams of sodium Properties of Samples in ethanol solution, and the resulting dihlolar ethyl benzylmethylmalonate (4) was specific Refraction saponified to the dibasic acid, which was n2G di5 Refraction Obsd. Calcd. then decarboxylated by refluxing a t 1.5739 0.9949 0 . 3 3 16 38.52 37.49 loo mm. The monobasic acid was con1.5355 0.9604 0.3244 38.33 37.96 V e h d to 596 grams (3.27 moles) of a1.4698 0.8808 0.3166 39.33 39.36 m e t h y ~ h ~ d r o c i n n a m&loride o y ~ by treat1.5241 0.9384 0.3261 43.11 42.58 1.5193 0.9411 0.3227 42.66 42.58 ing it with 420 ml. Of thionyl 1.5322 0.9662 0.3208 42.41 42.58 In the presence of 600 grams of anhy1 . 5 3 11

0.9442

0.3277

43.32

42.58

1.5209

0.9289

0.3278

47.93

47.20

~~_________

433 grams (2.97 moles) of 2-methyl-l(Continued a page 1S10)

Infrared Spectra for Analysis of Aldehyde and Ketone 2, 4

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