Nms
3766 Table 11: Variation in J with C-H Bond Length IO-".
1.10
Coupling
&.
1.08 Calculated coupling
f1.95
JC.7
f2.19 +1.98 -0.47 +O.h8
JL.8
-0.62
-0.58
J1.S
JX.6
J,,,
1.m
constant
f1.80 -0.44 f0.54
+1.74 f1.63
-0.40 f0.499 -0.54
Aclnowledgment. This work was completed while the author was a National Research Council Resident Research Associate at Picatinny Arsenal. The author thanks the MUCOM DPSO for use of computer facilities. He also thanks Dr. Lee Pedersen of the University of North Carolina and Dr. Ted Vladimiroff of Picatinny Arsenal for encouragement and assistance.
~ . ~ .,,~ ...... . :. . . . ...
.II.,.
b
C
Carbon-13 Nuclear Magnetic Resonance Spectrosopy.
IV. Bromo-Substituted
Ethanes and Ethylenes' by Goh Miyajima* Naka W w b , Hitachi. Ltd.. Ichise 886,Kotsuta-shi, Iharaki, Japan
and Kensuke Takahashi Department of Synthetic Chemistry, Nogoya Institute o/ Technology, (Rcceiued Jonuwy 11, 1871) Gokiso-cho. Showa-ku. N a ~ o y aJapan ,
Figure 1. Typical carhon-13 nmr spectra: (a) a full spectrum of a mixture of cis- and transdibromoethylenes, with the signal mersged for 20 scans; (b) an expanded spectrum of CBn in CHeBrCBs with 130 scans; (c) an expanded spectrum of half of CHBrlCHBrawith 2.5 scans. Applied frequency increases from right to left at a constant magnetic field. The sweep rate for one scan was 50 ppm/64 see, 51 Hz/128 sec, and 34 Hs/128 sec for (a), (b), and ( e ) , respectively.
Publication m 8 t 8 assisted by S d a h u . Hitochi. Ltd.,
Carbon-13 nuclear magnetic resonance spectra have been investigated by many authors, but the data are not fully accumulated. In a previous report, chloro-substituted ethanes and ethylenes were studied.* As a comparison, other halogeno-substituted compounds with rather simple skeletons such as the above are interesting in many respects. This note presents the nmr data of bromo-substituted ethanes and ethylenes. Most experimental procedures were similar to those described in the previous reports.*,3 Chemical shifts of the samples were compared with a sample of 55% 13CC-enrichedmethyl iodide diluted with one-third volume of benzene, and then the values were recalculated to refer to CS,. The signal of the methyl iodide was at 214.5 ppm from CS,. Most compounds were measured in neat liquid. Ethyl bromide and dibromoand tetrabromoethanes were obtained from commercial sources. Other samples were prepared by the usual methods of successive dehydrobromination, bromination, and debromination of dibromo- and tetrabromoethanes. CHaCBr3could not be obtained in spite of The J o u m l of Phypienl Chemislry, Vol. 76. No. 64,1871
much effort. Some of the compounds seem to be nnstable under the measuring conditions, as the 13C nmr signals sometimes changed with time. This feature was especially apparent in the ethylene derivatives; the reason is not clear at the present time. Some typical spectra are shown in Figure 1. The spectra with 800-Hz widths can be shown in full on an nmr chart, but further details of the signals must be observed on the expanded spectra taken with a sweep rate of 1-2.5 He/ sec, as shown in Figures l b and c. 13C nmr data for 14 bromo-substituted ethanes and ethylenes except CHaCBr3are given in Table I. The data for vinyl bromide (no. 11) are only approximately given in Table I. It seems that the exact data for this compound must be obtained from the exact analysis. The case is the same for the corresponding data of vinyl
(1) Presented in brief at the 7th Symposium on Nuclear Magnetic Resonance Speetmscopy, Meijo University, Nagoya, Japan. Nov 1968, Abstract p 31. (2) G. Miyaiiriia and K. Takahashi, J . Phys. Chem.. 15, 331 (1971). (3) G. Miyajima. Y. Utsurni, and K . Takahashi. ibid., 73, 1378 (1969).
Table I : Carbon-13 Nmr Data of Bromo-Substituted Ethanes and Ethylenes
No.
Compound
1
CHaCHa
2
CHsCH2Br
Functional group
---Shift, This studya
CH3CHBrz
4 5
CHZBrCHzBr CHzBrCHBrz
6
CHZB~CB~B
7 8
CHBr&HBrz CHBrzCBrai
9 10 11
CBrd3Br3k CzHa C&Br
Others
This study'
CH,
CH3 CHBrz
157.5 152.4
CHzBr CHBrz CHzBr CBr3
152.4 150.8 139.1 155.2 143.4 135.1 149.0 140.3
173.4' 173. 5d 173. 8h 165.40 165. 5d 165.gh 158. Oh 161.3.
CHBrz CBra CHz
71.3
CHBr
79.0
trans-CzHzBrz cis-CzHzBrz gem-CzHzBrz
15
CzHBra
16
CzBaq
CHz CBrz CHBr CBrz
84.8 79.1 66.5 96.7 81.3 98.7 100.0
This study'
Others
-4.5'
129
2.1'
152
4.00
