Question

Can you draw out the mechanisms of 1-butanol, 2-butanol, and 2-methyl-2-propanol with the HCl ZnCl2 reagent? I need full structures.

Answer 1

Lucas Test

: This test is for low molecular weight alcohols and it distinguishes the rates of reaction of

Lucas reagent is a solution of zinc chloride in concentrated hydrochloric acid. Zinc chloride acts as catalyst on the reaction of hydrochloric acid reacts with the alcohols.
The equation for reaction with secondary butanol is as follows.
C?H?-CHOH-CH? + HCl ? C?H?-CHCl-CH? + H?O
The secondary butyl chloride is insoluble in water and causes cloudiness of the solution after a few minutes.

It should be noted that all alcohols reacts with Lucas' reagent in that way:
R-OH + HCl ? R-Cl + H?O

The difference between the three classes of alcohols is the speed of the reaction, which allows to identify the type of alcohol.
- no visible reaction: primary alcohol
- solution turns cloudy in 3-5 minutes: secondary alcohol
- solution turns cloudy immediately, and/or phases separate: tertiary, allyl, or benzyl alcohol

Actually 1-butanol reacts with Lucas reagent but it takes too much time for the product formation.

Lucas reagent is used to differentiate between primary, secondary and tertiary alcohols. The primary alcohol i.e., 1-butanol in this case on reaction, produces a primary carbocation which is less stable compared to the tertiary and secondary carbocations. Hence the rate determining step for 1-butanol is the slowest step compared to the formation of secondary and tertiary carbocations. Hence it seems as if the reaction has not occured but it takes time.

The order is Tertiary carbocation> sec carbocation> primary carbocation.