Lone pair systems, hydrogen bonds

Sulphinyl carbanions are generally observed to show greater stability when the carbanion lone pair bisects the S-lone pair/S—O bond angle, behaviour consistent with MO predictions. However, rates of base-catalysed H-D exchange in the system (9 X = SO, R = Me, R = H) now indicate a significant solvent dependence such that a change from t-butan[ H]ol to [ H4]methanoI results in a substantial reversal of the relative rates at which the two a-hydrogen atoms are abstracted. ... 

That way, the Distributed Electrostatic Moments based on the ELF Partition (DE-MEP) allows computing of local moments located at non-atomic centres such as lone pairs, a bonds and n systems. Local dipole contributions have been shown to be useful to rationalize inductive polarization effects and typical hydrogen bond interactions. Moreover, bond quadrupole polarization moments being related to a n character enable to discuss bond multiplicities, and to sort families of molecules according to their bond order. 

For Rh and Ir diphosphine-based catalysts there exist some indications on reactive species and also on hydrogen activation. James and coworkers [43, 85] investigated the Rh-catalyzed DMA-imine hydrogenation and concluded that the imine is -coordinated to the Rh center via the nitrogen lone pair, and not via the 7i-system of the C = N bond. They also suggested that the hydrogen activation occurs after the imine is coordinated. 

Experimental results shown in Table 10 suggest that a hydrogen bond, Le., a strong nonbonded attractive interaction, is instrumental in dictating gauche preference in CH3CH2CH2X and XCH2CH2OH systems where X carries at least one lone pair. 

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