For the reactions of 2-methyl-2-propanol ( tert -butyl alcohol) on p. 1 with hyd

Question

For the reactions of 2-methyl-2-propanol (tert-butyl alcohol) on p. 1 with hydrobromic acid (HBr) and sulfuric acid (H2SO4), both reactions have the identical mechanism up to the formation of the tertiary carbocation.

Which two factors favor elimination with sulfuric acid (H2SO4) to give 2-methylpropene (isobutene), instead of substitution?

Acidity of sulfuric acid (H2SO4)

Basicity of hydrogen sulfate (HOSO3-)

Low nucleophilicity of hydrogen sulfate (HOSO3-)

Temperature of 100 oC instead of 20 oC

Acidity of sulfuric acid (H2SO4)

Basicity of hydrogen sulfate (HOSO3-)

Low nucleophilicity of hydrogen sulfate (HOSO3-)

Temperature of 100 oC instead of 20 oC

Explanation / Answer

Two conditions that favor the elimination reaction over substitution reaction are as given below.

1) Basicity of hydrogen sulfate (HOSO3-) ion. The basicity of hydrogen sulfate (HOSO3-) ion is higher than its nucleophilicity. This favors elimination reaction.

2) Temperature of 100 oC instead of 20 oC. At low temperature, thermodynamically controlled substitution product is favored and at high temperature kinetically controlled elimination product is formed.

Related Questions

Navigate

• Browse (All)
• Browse F
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.