0

    The inductive effect is the effect on electron density in one portion of a molecule caused by electron-withdrawing or electron-donating groups elsewhere in the molecule.
    In a covalent bond between two atoms of unequal electronegativity the more electronegative atom draws electron density towards itself. This causes the and charges of the bond dipole.
    ##H^(+)-Cl^(-)##
    If the electronegative atom is joined to a chain of atoms the positive charge is passed along the other atoms in the chain. This is the electron-withdrawing inductive effect.
    The induced change in polarity is less than the original polarity so the inductive effect rapidly dies out. It is significant only over a short distance.
    In NMR spectroscopy the inductive effect is a factor affecting proton chemical shifts.
    If the electron density about a proton is low the induced field due to electron motions will be weaker than if the electron density is high.
    The shielding effect in will be smaller and a lower external field will be needed for the rf energy to excite the nuclear spin.
    The proton is deshielded and its signal is shifted downfield.
    For example the CH group in propane appears at 1.4.
    An OH group attached to the CH shifts the signal downfield to 3.6.
    The effect decreases with distance from the OH group. For example in butan-1-ol the CH signals are
    CHCHCHCHOH
    C-3 = 1.4; C-2 = 1.5; C-1 = 3.6

                                                                                                                                      Order Now