acetylene in the Gas Phase and in Solution in the Range 1100 to 4000Summary. The electronic spectra of the title compounds I(n), n = 1 to 5, were recorded under standard conditions for quantitative comparison. Spectra of 1(1) to 1(4) in the gas phase and of I(2) to 1(5) in nonpolar solutions are presented in a computer plotted form, and wave length maxima and intensities are listed. Tcntative assignments of the medium-intensity, first transition (A band) and the ultrahigh-intensity, second transition (B band) are given. Finally, spectra of I(2) to 1(5) rccorded at -150" are presented and discussed (A band). The syntheses of 1(3) to 1(5) are given in detail. treatment will appear in a separate paper [12].

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1073kcinem Fall widersprechen sich die Vorzeichen. Die Chiralitaten der asyminetrischen Zentren bestimmen sich somit zu (3S:llaS:5aR:lObR).Eine Berechnung aller intermolekularen htomabstande ergab keine ungewohnlich starken Kontakte. Der kurzeste intermolekulare Abstand, abgesehen von der ohen beschriebenen interinolekularen Wasserstoffbrucke (Fig. 4), betragt 2,2 zwischen zwei Wasserstoffatomcn. LITERATURVERZEICHNIS S.Summary. The photoelectron spectra of the four monohaloacetylenes X-CEC-H with X = F, C1, Br, I have been recorded. The first four bands of these spectra are assigned (in order of increasing ionization potentials) to the following states: band 1: 211,/2(1), 2111/2(1) ; band 2 : 211,,2(2), 21Zl/2(2); band 3: 2Z+(3); band 4 : 2Z+(4). A correlation diagram based on a simple ZDO-MO model shows that the observed band positions and the size of the splits duc to spin-orbit coupling can be satisfactorily explained in terms of such a model. I t is found that the orbital energies A x of the postulated halogen npA(X)-basis orbitals are a linear function of the ionization potentials I ( X ) of the free atoms X. The validity of the ZDO-MO-model is confirmed by the excellent qualitative agreement between the observed and predicted spacings of the vibrational fine structure of the n-bands. I) 12. Mitteilung iiber Anwendungen der Photoelektron-Spektroskopie. 11. Mitteilung : [l] Dans les publications antCrieures de cette sdrie, il a Ctd montrk que la benzoylation du methyl-1-fluorbne selon Friedel-Crafts en milieu de sulfure de carbone se fait en position 2 [2]; celle du mCthyl-2-fluor6ne, en position 7 [3]; et celle du mdthyl-3-

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