Question

1) State which of the electrophiles given below will react preferentially by i) SN1, ii) by SN2, or iii) capable of reacting by either of the two mechanisms depending on the given conditions. How can you affect those conditions to favour SN1 or SN2? Reason your
predictions based on the structures of the compounds.

Br-CH3, Br-CH2CH3, Br-CH(CH3)2, Br-C(CH3)3, Br-CH2-C5H6; C5H6 = phenyl

6) Using orbitals, draw the transition state of the SN2 reaction between sodium cyanide and bromomethane. Which orbitals are interacting with which? Why is the bond breaking? Why is the orientation important? Is there another angle besides backside attack that could theoretically work based on orbital geometry? Why doesn’t this happen?

Answer 1

D CH₂ Br SN2 in Br-elto-cth in Br-CH (Ctr) 2 SN SNI & SN2. NOTES: Notes: w Br -e (CH3)-> SNA 1 7 Broth-6to SNI & SN2

сHз н 7 сHз NEC! Vc Br H + - 4 - 1 Y. NEC ............BE transition state CH3 N=C—CS :B7

Sigma Orbitals PIEC RA R C- X o orbital bonding R o * orbital antibonding Orbital Orientations in the Sn2 Reaction L QUOTG L-33333 Nuo Nu---C--EX - Nu Nu- RR Nu: Transition State Reactants Products