亲核试剂和亲电试剂.pptxVIP

Electrophiles(亲电试剂) Electron-deficient molecules are called electrophiles (electron-loving) and react with nucleophiles. ;Anions（阴离子）;Some ions (e.g. the carboxylate ion) are able to share the negative charge between two or more atoms through a process known as delocalization. In this case, the negative charge is shared between both oxygen atoms and so both of these atoms are nucleophilic centers;Cations（阳离子）;Some molecules (e.g. the allylic cation) are able to delocalize their positive charge between two or more atoms in which case all the atoms capable of sharing the charge are electrophilic centers;Polar bonds（极性键）;Relative nucleophilicity;Nucleophilic (δ-) and electrophilic (δ+) centers in neutral inorganic molecules.;Nucleophilic strength;The relative nucleophilic strengths of these atoms is explained byIf hydrogen fluoride acts as a nucleophile, then the fluorine atom gains a positive charge. Since the fluorine atom is strongly electronegative, it does not tolerate a positive charge. Therefore, this reaction does not take place. Oxygen is less electronegative and is able to tolerate the positive charge slightly better, such that an equilibrium is possible between the charged and uncharged species. Nitrogen is the least electronegative of the three atoms and tolerates the positive charge so well that the reaction is irreversible and a salt is formed. ;HF, H2O, and NH3 are weaker nucleophiles than F-, OH- and NH2-;Fei非极性;13;14;15;Dipole moment (?) - Net molecular polarity, due to difference in summed charges;18;Bond Polarity Electronegativity;;Definition;Curly arrows;The following rules are worth remembering when drawing arrows:;x;Half curly arrows;heterolytic cleavage（异裂）;Definition;mineral acids(无机酸）;functional groups contain hydrogens which are potentially acidic;base is a molecule which can form a bond to a proton.;;2;pKa;;pKa=- log10 Ka;CH3CH2NH2;Inductive effects(诱导效应）;inductive effect explains the relative acidities;Resonance（共振）;with the