ELECTRIC MOMENTS OF A C E T Y L E N l C ALDEHYDES 4 N D KETONES
Nov., 193T
[CONTRIBUTION FROM
THE
2301
DEPARTMENT O F CHEMISTRY, UNIVERSITY OF NOTREDAME]
The Dielectric Properties of Acetylenic Compounds. E.'Acetylenic Aldehydes and Ketones BY H. L. GOEBELAND H. H. WENZKE The high moments of aldehydes and ketones are due primarily to the C=O group in the molecule. The high moments of these compounds have led certain authors2 to the conclusion that the structure Rg=C +-0- contributes appreciably to the molecule. This resonance requires that the more polar contributing form have six electrons in the valence shell of the carbon atom attached to the oxygen atom. When unsaturated groups are attached to the ketonic carbon atom this is no longer true and resonance takes place to a greater extent. Preparation of Compounds.-The acetylenic aldehydes were obtained by treating the Grignard compound of the acetylenic hydrocarbon with ethyl orthoformate and subsequent hydrolysis of the diacetal according to a method devised by Moureu and Delange.3 The acetylenic ketones were prepared from the corresponding Grignard reagents of the acetylenic hydrocarbon and acetic anhydride by a method used by Kroeger and N i e ~ w l a n d . ~Acetophenone and TABLE I PHYSICAL CONSTANTS OF ALDEHYDESAND KETONES -B. Compound
OC.
Benzaldehyde Butylpropiolaldehyde Amylpropiolaldehyde Phenylpropiolaldehyde Acetophenone Butylacetylacetylenc Amylacetylacetylene Phenylacetylacetylene
64.5 61.8 77.5 112.5 94 76 89 101
p.,--
Mm.
1.5428 1.4499 1.4516 1.5669 1.5322 1 4440 1.4463 1.5735
0.00000 .01273 ,01413 ,02445 .04327
e
Benzaldehyde 2.2760 2.4144 2.4318 2.5445 2,7533
Butylpropiolaldehyde 2.2760 2.4705 2.5092 2.6571 2.7081
0.87360 .87365 ,87366 ,87370 ,87374
Am ylpropiolaldehyde
,03808
2.2760 2.4527 2.6404 2.8104
0.87358 ,87350 ,87345 ,87332
0.00UU0 ,01704 ,02086 ,02705
I'henylpropiolaldeh yde 2.2760 2.5538 2.6166 2.7160
0.87358 ,87798 .87888 ,88069
0 00000 ,01704 ,01940 ,01982
Acetophenone 2.2760 2.4606 2.4882 2.4901
0.00000 ,01554 02445 ,02520 ,04178
Butylacetylacetylene 2.3760 2.4975 2.6078 2.6177 2.8237
0.00000 .01916 .02306 .03257 .05229
Amylacetylacet ylene 2.2760 2,5426 2.5910 2.7165 2.9650
0.87282 .87220 ,87214 .87172 ,87120
Phenylacetylacetylene 2.2760 2,4980 2.6913 2.7393
0,87358 ,87721 ,88055 ,88129
0.00000 .01203
.OB87
0.87382 .87758
.87774 .87810
0,87350 .87310 ,87288 87285 ,87244
I
TABLEI1 DIELECTRICCONSTANTS AND DENSITITESOF SOLUTIONS OF ALDEHYDES AND KETONES Solvent, benzene; temp. 25' Ct
.01667 .02719 ,03152
n%
dzs
65 12 1.0434 62.5 18 0.8770 78 17 ,8712 113 15 1.0556 94.5 20 1.0236 76.5 15 0.8631 89 5 15 ,8616 102 3 1 0239
0.00000 .01417
d
0.8738 .H757 8769 879 1 3833
(1) Article VI11 of this series, Koehl and Wenzke, Tms JOURNAL, 59, 1418 (1937). (2) Pauling and Sherman, J. Chcm. Phys., 1, 606 (1933). (3) Moureu and Delange, Comfit. rend., 138, 1339 (1904). (4) Kroeger and Nieuwland, TEIIS JOURNAL, 68, 1861 (1936).
O.OUUO(J
,01522 .02924 ,03236
TABLE 111 POLARIZATIONS AND MOMENTS OF ALDEHYDESA N D KETONES Compound P MRD P A + M p x 101s Benzaldehyde 190.:3 32.03 158.3 2.77 ::, 17 Butylpropiolaldehyde 241.4 33. 73 207 7 Amylpropiolaldehyde 248.4 38.40 2 l U . l l : 1 . l X 3.3; Phenylpropiolaldehyde 275.4 42.27 233 1 2.7; Acetophenone 193.7 36.36 157.4 3.20 Butylacetylacetylene 250.2 38.23 212.0 3.20 254.9 42.73 212.2 Amylacetylacetylene Phenylacetylacetylene 262.4 46.40 216.0 3.23
H. L. GOEBELAND H. H. WENZKE
2302
TABLE IV MOMENTS OF SOME ALDEHYDES AND KETONES (Other investigators) Butyraldehyde6 2.46 X 10-'* Hep taldehydee 2.56 X Benzaldehyde' 2.75 X 10-ls Acetones 2.72 X 10-18 Diethyl ketoneg 2.72 X 10-" Acetophenones 2.94 X lo-'*
benzaldehyde were purchased from the Eastman Kodak Co. All compounds were purified by fractional distillation. Discussion As shown in the tables the moment of benzaldehyde is greater than that of either butyraldehyde or heptaldehyde. The higher moment of benzaldehyde is due to the greater contribution of the polar forms
