Ch_322a_9.07

Ch_322a_9.07 - which is more electronegative than the sp 3...

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Examples of ! -Electron Anisotropic Effects The H chemical shifts are compared to the proton resonance in ethane where there are no electronegative nor ! -electron influences. CH 3 CH 3 " 0.88 CH 3 ! 2.34 toluene The methyl group is in the deshielding sector of the induced magnetic field due to the ring current. CH 3 + + _ _ _ + + _ _ Much larger downfield shifts are observed with aromatic H . H ! 7.27 benzene A second influence reinforces the anisotropy of the " -electrons. The aryl H is attached to an sp 2 hybridized carbon
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Unformatted text preview: which is more electronegative than the sp 3 carbon in ethane. Examples of !-Electron Anisotropic Effects 2-bromopropene C=C H H CH 3 Br diasteriotopic H ! 4-5 ! 2.27 as two resonances The CH 3 group is deshielded by the !-electrons and the electronegative Br ( "-effect). The resonances of the two vinyl H are more downfield because of the additional factor of bonding to an sp 2 carbon. C=C + + _ _ _ _ _ _ anisotropy of b generated by the !-electrons...
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Ch_322a_9.07 - which is more electronegative than the sp 3...

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