Dolbier HW Solutions 240

Dolbier HW Solutions 240 - 234 CONJUGATION IN ALKADIENES...

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Comparison of the mirror-image forms of 2-chloro-2,3-pentadiene reveals that they are not superposable. 2-Chloro-2,3-pentadiene is a chiral allene. 10.9 Both starting materials undergo b -elimination to give a conjugated diene system. Two minor prod- ucts result, both of which have isolated double bonds. 10.10 The best approach is to work through this reaction mechanistically. Addition of hydrogen halides always proceeds by protonation of one of the terminal carbons of the diene system. Protonation of C-1 gives an allylic cation for which the most stable resonance form is a tertiary carbocation. Pro- tonation of C-4 would give a less stable allylic carbocation for which the most stable resonance form is a secondary carbocation. Under kinetically controlled conditions the carbocation is captured at the carbon that bears the great-
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This note was uploaded on 09/26/2011 for the course CHM 2210 taught by Professor Reynolds during the Fall '01 term at University of Florida.

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