STUDIES ON FLUORINATED ORGANONITROGEN COMPOUNDS

Ziad O. EL- KOUSSA

This thesis concerns attempts to synthesise conjugated per-or poly-fluoronitrosoalkenes. The Griffin-Haszeldine (1960) method for making the nitrosoalkene CF₂=CFNO, yielded only FCN and COF₂ (and decomposition products arising from the latter). This result agrees with that reported in 1966 by Heicklen.

Turning to a different strategy, base-initiated l,4-dehydrochlorination of the oxime CF₃ (C:F₂C1)C NOH was studied. Pyrolysis at 510 °C: of the oxime over hot KF gave CF₃CN and COF₂ (see above). Interestingly, treatment of chloropentafluoroacetone oxime with CsF in MeCN gave hexafluoroacetone oxime. The mechanism of this halogen exchange reaction is discussed and related to dehydrochlorination mechanisms. Water was found to decompose chloropentafluoroacetone oxime with the liberation of C1" and F, and a mechanism for this is proposed. The pKa of the chloropentafluoroacetone oxime was determined and comparison was made with hexafluoroacetone oxime.

The work was extended through an investigation of nitroso precursors to other chlorofluoroketoximes, e.g. (CF₂Cl)₂C=NOH. These were prepared by analogy with the preparative method for 1-chloropentafluororitrosopropane.

Two organometallic routes devised for the preparation of conjugated perfluoronitroso- alkenes were investigated.

A short study made of the synthesis and reactions of the known perhalogenated nitros- oalkene  CC1₂=CCINO. Bis(trifluoromethyl) nitroxide was shown to react cleanly with chloral (a  precursor  of  CCI₂=CCINO) to yield [N,N-bis (trifluoromethyl) nitroxy]  trichloromethane, [N,N-bis (trifluoromethyl)nitroxycarbonyl] trichloromethane, N,N-bis (trifluoromethyl)hydroh- ydroxylamine and traces of carbon monoxide. A mechanism is proposed.

Some comments on the shelf life of trifluoronitrosomethane [used in the synthesis of bis(trifluoromethryl) nitroxide] are made. Storage in stainless steel was found to cause the formation of the known compounds CF₃NO₂ and CF₃N=N(Ō)CF₃.