Ch_322a_3.06

Ch_322a_3.06 - group (Lewis acid). direction of electron...

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The Reactivity of Chemical Intermediates Carbocations as Electrophiles Since carbocations are electron-deficient in the valence level, they are strong Lewis acids . Carbocations react rapidly with Lewis bases, species that are capable of donating electrons. Carbocations are called electrophiles . C + a carbocation (an electrophile) + :B - -C:B -C-B An Example C + + :O-H H : Lewis base -C-O-H H + -H + -C-O-H an alcohol
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Carbanions as Nucleophiles Carbanions are Lewis bases. They donate an electron pair to Lewis acids such as H + and other electropositive atoms and groups. Carbanions are called nucleophiles . -C: - carbanion (a nucleophile) + H-A Lewis acid ! + !" -C:H + :A - -C: - + -C-L !" ! + Lewis acid -C-C- + :L -
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The Curved Arrow Formalism The curved arrow begins at an electron pair (bonding or nonbonding) and moves towards an electron-deficient atom or
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Unformatted text preview: group (Lewis acid). direction of electron flow nucleophile electrophile Examples The above bonding changes are illustrated with a formalism called curved arrows where the arrow shows the direction of electron flow from nucleophile to electrophile . C=C + H Cl !" ! + C C H + Cl nucleophile electrophile-+ CH 3 C = O O H !" ! + + O H H : : CH 3 C O O :: : + O H H : H nucleophile electrophile +-Quiz 3.06 In the reaction below, use the curved arrow formalism to show movement of an electron pair. C 6 H 5 CH 2 + + CH 3 OH : C 6 H 5 CH 2-OCH 3 H + Identify the electrophile and nucleophile in the reaction. electrophile nucleophile Identify the Lewis acid and Lewis base in the reaction. Lewis acid Lewis base...
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Ch_322a_3.06 - group (Lewis acid). direction of electron...

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