Polarizability correlates reasonably well with nucleophilicity, but really only when the nucleophile is uncharged. So H2S is a better nucleophile than H2O. But in the case of negatively charged halides, the nucleophilicity is driven more by the charge density, which correlates inversely with the size of the anion (that is, iodide has a lower charge density than fluoride, so fluoride is a better nucleophile).Half Infinity said:In halides, I- is the most polarisable and F- is the least. So shouldn't I- be most nucleophilic ( in aprotic solvent) as its cloud should most easily be distorted and transition state with electrophile should be achieved most easily? Or is polarisability very different from nucleophilicity?
Polarisability refers to the ability of a molecule or atom to undergo distortion of its electron cloud in the presence of an external electric field. Nucleophilicity, on the other hand, refers to the tendency of a species to donate a pair of electrons to form a new covalent bond.
Polarisability and nucleophilicity are related in that a higher polarisability of a molecule or atom generally indicates a higher nucleophilicity. This is because a more polarisable species is able to donate its electron pair more easily due to the increased flexibility of its electron cloud.
The polarisability and nucleophilicity of a species can be affected by several factors, including the size of the atom or molecule, the presence of polarisable functional groups, and the electronic configuration of the species.
Polarisability and nucleophilicity play important roles in chemical reactions. A higher nucleophilicity can lead to faster reaction rates and stronger chemical bonds, while a higher polarisability can affect the selectivity and stability of reaction products.
Yes, polarisability and nucleophilicity can be measured experimentally using various techniques such as nuclear magnetic resonance (NMR) spectroscopy, X-ray crystallography, and kinetic studies. These measurements can provide valuable insights into the reactivity and properties of different chemical species.