User talk:Alfaifis

For an SN2 reaction, the effect of solvent polarity is usually much less, but the ability (or really lack there of) of the solvent to solvate the nucleophile is the important criteria, as shown by the relative rate data for the SN2 reaction of nBuBr with N3-.

Solvent Dipole moment, m Dielectric constant, e Relative Rate Type CH3OH 2.87 33 1 protic H2O 1.84 78 7 protic DMSO 3.96 49 1,300 aprotic DMF 3.82 37 2,800 aprotic CH3CN 3.92 38 5,000 aprotic POLAR PROTIC SOLVENTS (polar and ability to be H-bond donor)

have dipoles due to polar bonds can H atoms that can be donated into a H-bond examples are the more common solvents like H2O and ROH remember basicity is also usually measured in water anions will be solvated due to H-bonding, inhibiting their ability to function as Nu POLAR APROTIC SOLVENTS (polar but no ability to be H-bond donor) have dipoles due to polar bonds don't have H atoms that can be donated into a H-bond examples are acetone, acetonitrile, DMSO, DMF anions are not solvated and are "naked" and reaction is not inhibited

Overall

All nucleophiles will be more reactive in aprotic than protic solvents Those species that were most strongly solvated in polar protic solvents will "gain" the most reactivity in polar aprotic (e.g. F-). Polar aprotic solvents are typically only used when a polar protic solvent gives poor results due to having a weak Nu, (esp. F-, -CN, RCO2-)