In each reaction box, place the best reagent and conditions from the list below.
Problem:
In each reaction box, place the best reagent and conditions from the list below.
Solution:
Note that the condition of the double bond changed. The moving functionality includes optional addition and elimination reactions.
- When given an alkene: start with the addition
- When given RX or ROH: start with the elimination

Step 1: We’re given an alkene which means the first step should be addition.
We can do hydrohalogenation (which follows Markovnikov’s rule) using HBr.
Step 2: The alkene went from disubstituted to trisubstituted, which corresponds to a Zaitsev elimination. This can be done using a small strong base such as CH3CH2O– (ethoxide ion, an alkoxide).
Therefore, the best reagents and conditions are:
- HBr (hydrohalogenation)
- CH3CH2O– (elimination)
In each reaction box, place the best reagent and conditions
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