Orgo Unit 4.2 Discussion

Orgo Unit 4.2 Discussion - nucleophiles can act as bases In...

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2) Define "nucleophile." What electronic features characterize a nucleophile? According to Fessenden and Fessenden (in Organic Chemistry – 6 th Edition ), nucleophile literally translates to “nucleus lover.” Nucleophiles are molecules that are attracted to positive centers. Accordingly, nucleophiles are Lewis Bases, and many are anions (e.g., OH- or CH3O-). Some neutral polar molecules can also act as nucleophiles (e.g., H2O, CH3OH, or CH3NH2). Neutral nucleophiles contain unshared electrons that can be used to form sigma bonds. One of the interesting discussions provided in Chapter 5 (pg. 187) of the Fessenden and Fessenden textbook includes a discussion on this idea of Basicity versus Nucleophilicity. I thought I would provide a summary of this section to add to our discussion. Fessenden and Fessenden have noted that in some situations, all bases can act as nucleophiles, or all
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Unformatted text preview: nucleophiles can act as bases. In either case, these reagents react by donating a pair of electrons to form sigma bonds. Basicity indicates a molecule’s/atom’s ability to accept a proton in an acid-base reaction. Consequently, we can determine the strength of a base by assessing its degree of ionization of water. The basicity for the following are listed in increasing order: I- < Br- < Cl- < R-OH < H2O < -CN < -OH < -OR. Meanwhile, nucleophilicity measures a molecule’s/atom’s ability to cause a substitution reaction (according to Fessenden and Fessenden). The following molecules are listed in order of increasing nucleophilicity: H2O < R-OH < Cl- < Br- < -OH < -OR < I- < -CN. Stronger bases are typically better nucleophiles....
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This note was uploaded on 04/10/2011 for the course AAS 410.302.81 taught by Professor Thompson during the Spring '11 term at Johns Hopkins.

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