Question

A student attempted to carry out a substitution reaction using molecule as the substrate. The resulting product was molecule. Which nucleophilic substitution occurred --- S_N1 or S_N2 How can you tell The molecule here cannot be used as a substrate for an E2 reaction, but can be for an E1 reaction. Explain why. Be specific --- explain why an E2 reaction cannot occur and how an E1 reaction could occur. Where does the nucleophile attack in an S_N2 reaction Backside Frontside Both sides Sideways Identify the alkyl halide that reacts the fastest in an S_N1 mechanism. CH_3Cl CH_3CH_2Cl (CH_3)_2CHCL (CH_3)_3CCl Why can't CH_3Br undergo the E2 reaction Bromide is a poor leaving group. The base cannot attack. CH_3Br is solvated in the solvent. Two carbons are needed to make a double bond.

Answer 1

30. This is an SN1 type of reaction. The L first leaves generating a secondary carbocation, which rearranges to a more stable tertiary carbocation.

31. The molecule shown here is (a) sterically crowded and (b) there is no beta hydrogen for the base to pick under an E2 elimination reaction. It is thus an E2 elimination reaction for this substrate.

32. In an SN2reaction the nulceophile attacks the carbon from,

a) backside

33. Under SN1 condition, the alkyl haldie that would be fastest to react would be,

d) (CH3)3CCl

As crowding around the carbon center having the leaving group increases, the rate of SN1 reaction also increases.

34. CH3Br does not have any beta hydrogen to loose and hence it cannot undergo an E2 elimination reaction.