1. The problem statement, all variables and given/known data I have these compounds, and I have to predict which one will undergo unimolecular substitution reaction the fastest. And which one will undergo it the slowest. 3 bromo cyclohexene 1 bromo cyclohexene 4 bromo cyclohexene 2 bromo hexane (not cyclohexane/ene) The solvent is a combination of Ethanol and Silver Nitrate. So I'm definately sure this reaction will proceed SN1. I am also unsure of this: what causes the leaving group to leave in a SN1 reaction? . I know a good leaving group is stable because it's large. And in SN2 a leaving group 'leaves' because you have a backside attack by a nucleophile. 2. Relevant equations None. 3. The attempt at a solution Fastest: I'm guessing 2 bromo hexane will react the fastest, because when you get it's carbocation, the carbon bearing that cation is 2* substituted. The rest: I'm not sure about the others. You get a cycloalkene carbocation in each one. But they all have six carbons. They all seem to be 2* substitued.