Friday, December 28, 2018

organic chemistry - Rates of hydrolysis in bicyclic and monocyclic compounds




Which of the following compounds, 1-bromo-1-methylcyclohexane 1 or 1-bromobicyclo[2.2.2]octane 2, hydrolyzes faster (under comparable conditions)? It may be acid catalyzed or base catalyzed hydrolysis, but the conditions must remain the same for each pair.


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In my view because of the steric hindrance in first compound, hydrolysis should be easier for second, but I am not sure about it.


See part one of my question here.



Answer



Both hydrolysis reactions will almost certainly occur by $\mathrm{S_N1}$, forming carbocation intermediates. I'm not sure if sterics will play the biggest role here. One thing you should consider is the actual conformations of these molecules. The bicyclic is slightly more rigid and may not adjust to the trigonal planar geometry of a carbocation as easily as the cyclohexane, and this will likely be the deciding factor. Here are the conformations, as I hope you know.


enter image description here


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