CHEM267 Lecture : Substitution & elimination reactions.pdf
12 Dec 2012
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Ch2 ch2 c functional group functional group functional group. Hs thiolate 126,000 br bromide 10,000 ch3coo acetate. Summary: all unhindered strong bases are good nucleophiles (i. e. ch3o )and weak polarizable bases are good nucleophiles (i. e. br ), however small none polarizable weak bases (i. e. good nucleophiles (i. e. br ), however small none polarizable weak bases (i. e. ch3oh) are poor nucleophiles and bulky hindered strong bases (i. e. (ch3)3c o ) are poor nucleophiles, unhindered electrophiles favor sn2 reactions and hindered electrophiles favor sn1 reactions. This is because in the transition state, as the hydrogen and bromine atoms are leaving the carbons are changing hybridization from sp3 to sp2 and for a new bond to form the developing p orbitals must be in the same plane. 3-bromoprop-1-ene or allyl bromide (bromomethyl)benzene or benzyl bromide. Thus the order of reactivity of alkyl halides is: stabilized by hyperconjugation - inductive electron donation.
