Question

Treatment of tert-butyl alcohol with concentrated HCl gives tert-butyl chloride.

When the concentration of H⁺ is doubled, the reaction rate doubles. When the concentration of tert-butyl alcohol is tripled, the reaction rate triples. When the chloride ion concentration is quadrupled, however, the reaction rate is unchanged. Write the rate equation for this reaction.

Accepted Answer

Step 1: Analyze the reaction mechanism. The reaction involves tert-butyl alcohol reacting with concentrated HCl to form tert-butyl chloride and water. This is a substitution reaction, likely proceeding via an SN1 mechanism due to the tertiary alcohol structure. Step 2: Examine the rate dependence on reactants. The problem states that doubling the concentration of H+ doubles the reaction rate, and tripling the concentration of tert-butyl alcohol triples the reaction rate. This indicates that both tert-butyl alcohol and H+ are involved in the rate-determining step. Step 3: Consider the role of chloride ion (Cl⁻). The problem states that increasing the concentration of Cl⁻ does not affect the reaction rate. This suggests that Cl⁻ is not involved in the rate-determining step but participates in a subsequent step. Step 4: Write the rate equation based on the observations. Since the rate depends on the concentrations of tert-butyl alcohol and H+, the rate equation can be expressed as: rate = k[tert-butyl alcohol][H⁺], where k is the rate constant. Step 5: Confirm the SN1 mechanism. In an SN1 reaction, the rate-determining step is the formation of the carbocation intermediate, which depends on the concentration of the substrate (tert-butyl alcohol) and the acid catalyst (H⁺). The chloride ion then reacts with the carbocation in a fast step to form tert-butyl chloride.

비슷한 문제에 대한 검증된 영상 답변:

주요 개념

Reaction Rate

Rate Law

Order of Reaction