radicals_key

radicals_key - O W L S : R a d ic a ls 1. (a) Contributors:...

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OWLS: Radicals Solutions 1. (a) Contributors : H 2 C CH 2 H 2 C CH 2 Hybrid : H 2 C CH 2 δ δ Contributors : CH 2 CH 2 CH 2 CH 2 Hybrid : CH 2 δ δ δ δ Contributors : Same as the given structure, because lone pairs cannot provide resonance stabilization of an adjacent unpaired electron. See answer 2(c) below. Hybrid : Same as the one resonance contributor. (b) Resonance contributor preference rules for radicals: The most significant radical resonance contributor places the unpaired electron where it is most stable (most substituted carbon, and/or with pi bond resonance). Example: Primary radical Tertiary radical Less significant More significant The most significant radical resonance contributor has the least number of unpaired electrons. Example: H 2 C CH 2 H 2 C CH 2 Three unpaired electrons One unpaired electron Less significant More significant
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OWLS: Radicals Solutions 2 2. (a) Number of carbons bonded to the carbon bearing the unpaired electron : In a radical, the carbon bearing the unpaired electron has seven valence electrons and an open octet so it is electron deficient. Alkyl groups are weak electron donors. They can release electron density to a neighboring carbon atom with an open octet, thereby stabilizing the radical. Increasing the number of alkyl groups adjacent to the radical carbon increases the stability of the radical. H C H H < H C CH 3 H < H 3 C C CH 3 H < H 3 C C CH 3 CH 3 Methyl Least stable Primary (1 o ) Secondary (2 o ) Tertiary (3 o ) Most stable Carbocations also have an electron-deficient carbon, so carbocation stability is influenced in a similar manner. H
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radicals_key - O W L S : R a d ic a ls 1. (a) Contributors:...

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