Molecules containing polar multiple bonds can act as lewis acid as they accept the pair of electron and form a new bond as depicted in below fig.

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Molecules containing polar multiple bond act as lewis acid as they accept the pair of electron to form a new bond as depicted below

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When two bonded atoms have a difference of between 0.4 and 2.0 electronegativity units (see Table 2), the electrons are shared unequally, and the bond is a polar covalent bond— there is an unsymmetrical distribution of electrons between the bonded atoms, because one atom in the bond is “pulling” on the shared electrons harder than the other, but not hard enough to take the electrons completely away. The more electronegative atom in the bond has a partial negative charge (?-), because the electrons are pulled slightly towards that atom, and the less electronegative atom has a partial positive charge (?+), because the electrons are partly (but not completely) pulled away from that atom. For example, in the HCl molecule, chlorine is more electronegative than hydrogen by 0.96 electronegativity units. The shared electrons are pulled slightly closer to the chlorine atom, making the chlorine end of the molecule very slightly negative (indicated in the figure below by the larger electron cloud around the Cl atom), while the hydrogen end of the molecule is very slightly positive (indicated by the smaller electron cloud around the H atom), and the resulting molecule is polar: