Characteristic absorption bands of some heteroaromatic nuclei
Infrared spectroscopic analysis in organic chemistry. IV
1958 Volume 7 Issue 4 Pages 210-214
Details
1958 Volume 7 Issue 4 Pages 210-214
Characteristic absorption bands of three kinds of five-membered heteroaromatic compounds, namely furans, pyrroles, and thiophenes, have been investigated with the following results.
νC=H of the furan and the thiophene nuclei appeared in shorter wave ranges (3. 163.21μ in furans and 3. 203.24μ in thiophenes) than νC=H of the benzene ring, and their intensities were fairly strong. νC=C of the furans and the pyrroles showed two absorption bands at almost the same position (6.346.42μ and 6.626.65μ in furans, 6.336.41μ and 6.516.71μ in pyrroles) as in the benzene ring, and considerably longer wave ranges of 6.546.58μ and 7.047.12μ in thiophenes. Their intensities were fairly strong the case of conjugated types, while in nonconjugated types, they showed irregularities, the two bands in the pyrroles being of medium intensity, and those of the furans being considerably weaker in a shorter wave range, while the thiophenes showed two obscure bands in many cases. By selecting a certain wave range for the furans an absonption band (11.311.45μ) could be singled out which was extremely useful in the identification of this nucleus.
