# What would be the correct mechanism for hydration of ethene?

Given above is the mechanism that I drew but my textbook puts it a bit differently. It says that the ethene is dissovled in the concentrated $\ce{H2SO4}$ to form ethyl hydrogen sulphate $\ce{CH3-CH2OSO3H}$ which when diluted with water reacts to form ethanol and the acid $$\ce{CH3CH2OSO3H + H-OH -> CH3CH2OH + H2SO4}$$ So which mechanism is true?

• I think that the first mechanism occurs when a solution of sulphuric acid in water is reacted with ethene. The second mechanism occurs if you first add conc. H2SO4 to ethene, and then add water. I am not fully sure, though. I will answer if I get a reference to back my claim. – Shoubhik R Maiti Dec 3 '17 at 9:09

at first i thought your mechanism was very comprehensive but upon closer inspection i think it has some flaws because in this reaction conc sulphuric acid is used as a catalyst and it must be regenerated at the end and in the above mechanism only ethanol is generated

This must be the mechanism shown in your book.

• Hmm, yes but no but yes but no … – Jan Oct 25 '19 at 8:07

Firstly hydration of alkene is equilibrium process.

When there is excess of water then water attacks directly therefore Et-HSO4 forms in less amount. If acid is concentrated the Et-HSO4 formation is more likely.

• So both happen? – Sillysack Buttowski Dec 4 '17 at 13:27
• Yes, in beaker every possible reaction occurs, difference in rate arises from kinetics and thermodynamics. – tejasvi88 Dec 5 '17 at 16:33
• Which one would take place at the most significant rate in terms of product formation and reaction rate? – Sillysack Buttowski Dec 8 '17 at 14:17