Part 7: MECHANISMS

Note that no other reagents are needed in order to complete any of these sequences, you should only be using what is there.

A If an alkyl chloride is heated with strong base (here it's the larger base t-butoxide), then a 1,2-elimination occurs to give an alkene. Alkyl halide eliminations are typically E2. This prefers an anti arrangement of the C-H and C-LG bonds. The top reaction is going to be faster because with the Cl and the large T-butyl substituent being cis and the t-butyl group needing to be in an equatorial position (due to its size) then the Cl will be axial in the most stable conformation. Thus it is already set for the E2 to occur. In the lower scheme, the Cl will the equatorial and therefore not in the favourable position and the ring flip is prevented by the size of the t-butyl group.

DIAGRAM TO FOLLOW

B SN1 reaction of an alkyl bromide with the weak nucleophile water.

DIAGRAM TO FOLLOW

C Ethers react with strong acids like HI via an nucleophilic substitution mechanism.

DIAGRAM TO FOLLOW

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