Microwave spectroscopical investigations of some halogenated butadienes

• This thesis deals with microwave spectroscopical investigations of four mono-halogenated 1,3-butadienes. Two of the investigations are mainly concerned with the elucidation of complete molecular structures using the isotopical substitution method, whereas the other two deal chiefly with the determination of molecular charge distributions.The complete molecular structure of trans-l-chloro-1,3- butadiene was determined using the complete set of mono-isotopic species. For 2-chloro-l,3-butadiene all but one mono-isotopic species were used for the same purpose. In both cases it was an obvious advantage to use a least-squares method in order to obtain the complete molecular structure from spectroscopically determined rotational constants. Evidence for non-bonded attraction between chlorine and hydrogen was found for trans-l-chloro- 1.3- butadiene, whereas for 2-chloro-l,3-butadiene this was not the case. The two C=C distances were found to differ significantly from each other in the former molecule, but in the latter these two distances were of the same size. The structural result for trans-l-chloro-1,3-butadiene conforms with the result previously obtained for the cis-isomer of this molecule.In a third investigation a five-step preparation of 1-fluoro- 1.3- butadiene was performed. The microwave spectrum of the transisomer was analysed and among the results obtained was the value of the dipole moment. In a fourth investigation the much more difficult spectrum of the cis-isomer of the molecule was analysed. The dipole moment was determined and was compared with that of the trans-isomer. Subsequent ab initio quantum chemical calculations of the two dipole moments reproduced reasonably well the relative difference between the observed values.

Ämnesord

NATURVETENSKAP  -- Kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences (hsv//eng)

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Spektralanalys

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