1) Which Compound 2-bromo-2-methylpropane or 2-chloro-2-methylpropane, should re
ID: 855967 • Letter: 1
Question
1) Which Compound 2-bromo-2-methylpropane or 2-chloro-2-methylpropane, should react faster in an Sn1 experiment? Why?
2) Which Compound, 2-bromo-2-methylpropane or 2-bromopropane, should react faster in an Sn1 experiment? How are the reactives of 2-bromo-2-methylpropane and 2-bromopropane related to the stabilities of the Carbocations produced as intermediates in the reaction?
3) In which of the 2 solvent mixtures should 2-bromo-2-methylpropane react faster? Explain in terms of the effect of solvent polarity on the rate-determining step in the Sn1 reaction?
Explanation / Answer
1. The given compounds are both tertiary alkyl halides. So, the preferred reaction is SN1.
One of them contains Br as leaving group and the other contains Cl as leaving group.
We know the order of leaving group as
F < Cl < Br < I .
So, Br is better leaving group.
And Cl is the poor leaving group.
So, 2-bromo-2-methyl propane reacts faster than 2-chloro-2-methyl propane.
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2. Alkyl halides when react via SN1 reaction proceed through two steps.
The first step is the formation of carbocation.
The carbocation produced from 2-bromo-2-methyl propane (tertiary alkyl halide) is a tertiary carbocation.
The carbocation produced from 2-bromo propane ( secondary alkyl halide) is a secondary carbocation.
As we know that the reactivity order of carbocations is
tertiary > seconday > primary
So, as tertiary carbocations react faster, the compound 2-bromo-2-methyl propane reacts faster than 2-bromo propane.
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3.
Polar protic solvents actually speed up the rate of the unimolecular substitution reaction because the large dipole moment of the solvent helps to stabilize the transition state.
So, 2-bromo-2-methyl propane reacts faster with the polar solvents.
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