. Can. J. Chem. 55,318 (1977). The state assignments corresponding to the second and third ionization potentials of oxirane have been the subject of some uncertainty due to the great sensitivity of Koopmans' theorem predictions to the type of calculation performed for this molecule. In this study, the assignments made by Basch et a/. for oxirane are confirmed through measurement of the photoelectron spectra of methyl-, 1,l-dimethyl-, 1,2-dimethyl, ethyl-, vinyl-, phenyl-, chloromethyl-, and fluoromethyloxirane. The second and third ionizations of thiirane are confirmed to be of the opposite order from those in oxirane by correlations of these values with those reported here for methyl-, vinyl, and methoxymethylthiirane.In these compounds, mono-substitution by alkyl groups causes a decrease in ionization potential not obviously related in a simple way to the type of orbital involved. Thus, assignments cannot be made straightforwardly by observing ionization potential changes caused by hyperconjugating or ind~~ctive substituents. Alkyl group substitution in both oxirane and thiirane lowers 1P's in the same order: a , > 0, > a , > b,. The effects of alkyl and heteroalkyl groups on the four lowest IP's of oxirane are linearly related to the electronegativities of the groups, and to the influence of alkyl and heteroalkyl substituents on the z IP of ethylene.Con~parisons of the IP's of ethylheteranes and dimethylheteranes are quite useful in deternlining the site of localization of orbital density in the various orbitals.Conjugating substituents, which for symmetry reasons, selectively interact with only a few orbitals make definite assignments possible. Comparisons of experimental ionization potential changes and those predicted by Koopmans' theorem using ab inifio STO-3G calculations are in good agreement. E. J. MCALDUFF et K . N. HOUK. Can. J. Chem. 55.318 (1977). Les attributions d'etat correspondant aux potentiels d'ionisation second et tierce de l'oxiranne ont fait I'objet de beaucoup d'incertitudes dues a la grande sensibilite des predictions clu theoreme de Koopman au type de calcul effectut sur cette molecule. Dans cette etude, les attributions faites par Basch et coll. pour l'oxiranne sont confirmkes par des mesures de spectres photoelectroniques du methyles, du dimethyl-l,l, du dimethyl-1,2, de 1'Cthyl-, du vinyl-, du phtnyl-, du chloromethyl-et du fluoromCthyloxiranne. On confirme que les ionisations seconde et tierce du thiirane sont d'un ordre oppose a celles de l'oxiranne par correlation de ces valeurs avec celles rapportkes ici pour le methyl-, le vinyl et le methoxymCthylthiirane.Dans ces con~poses, la mono-substitution par des groupes alkyles cause une diminution du potentiel d'ionisation qui n'est pas reliee d'une fayon apparente ou directe avec le type d'orbitales impliqukes. Donc les attributions ne peuvent pas etre faites d'une fayon directe par les changements des potentiels d'ionisation observes et causes par des substituants qui provoquent de l'hyperconjugaison ou de l'induction. La substituti...

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The photoelectron spectra of the following substituted benzamides have been determined: p-CH3O, p-CH3, p-Cl, H, p-F, p-CN, p-NO2, m-CH3O, m-CH3, m-Cl, and m-NO2. The first six ionization potentials have been assigned with reference to the phenyl and amide moieties. As an aid to the assignment CNDO/S calculations have been performed on the methoxy, methyl, and nitro benzamides. Linear relationships have been shown to exist between the first phenyl IP of disubstituted and monosubstituted benzenes. The slopes of these relationships have been shown to be related to the electron releasing ability of the substituent.By comparison of the pes data with nmr chemical shifts, the first phenyl IP has been shown to be related to the electron density at the position of substitution of the amide group. Likewise, the amide IP centered on the nitrogen has been shown to be related to the electron density on nitrogen.

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