Compound V's bond angles and distances are highly distorted, These ideas can be described by the resonance forms Partial double bond character, consistent with delocalization of These data suggest that the CN bonds in V and IV have some IV ("in between" N) is somewhere "in between":ġ40 pm. Compound III, with its normal bond angles, alsoĬontains a normal CN single bond: 146 pm. More information can be obtained by looking at CNīond distances. The N in compound V is trigonal (angles = 121.8, 119.2, 119.0 o)Īnd the N in compound IV is somewhere "in between" (anglesīond angles like these indicate that IV and V may be resonance hybrids Molecular models show that only one N (compound III) If the lone pair electrons are localized on N. Have 4 electron pairs, one of which is a lone pair. Only one a delocalized lone pair with partial pi bonding propertiesįalls somewhere in between.) Therefore, a resonance hybrid withĪ delocalized lone pair may display distorted bond angles.Ĭonsider the N atoms in compounds III-V. (VSEPR rules treat "lone pair + sigma bond pair" as twoĮlectron pairs, and "sigma bond pair + pi bond pair" as Of bond angles, becomes uncertain when a lone pair is delocalized. The counting of electron pairs, and the prediction Imply a trigonal atom with bond angles of 120 o, VSEPR rules link bond angles to the number of electron Predictions would be made for partial single bonds and partial If the hybrid contains a partial doubleīond, the bond distance should be somewhat longer than a completeĭouble bond, and somewhat shorter than a single bond. We always expect a hybrid's bond distances to reflect the This kind of analysis is applied to all resonance The left, and ozone's geometry reflects its partial double bonds. Resonance forms I and II as shown in the dashed-line formula on Might expect to find one short OO bond of ~122 pm (this distanceĪnd one long bond of ~147 pm (this distance is observed inĪs it happens, the OO distances in ozone are identical,Īnd at 128 pm, they tends toward "short", but we couldĬall them "in between." To explain these observations,Ĭhemists say ozone's electron pattern is a "hybrid" of That is, if it was adequately described by Lewis structure I, we If ozone was a normal molecule with localized bonds, Possibly many other molecules) symmetric.Įxcellent example of a symmetrical resonance hybrid with distortedīond distances. Research on the "real" factors that make benzene (and The first two sections in this essay examine distortions Situation is a symmetric set of bond distances in a molecule thatĭoes not have a symmetric Lewis structure, but delocalization canĪlso create other kinds of geometrical distortions. Electron delocalization frequently reveals itself
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