Lucas Test Alcohols class 12 chemistry mechanism HCl anhydrous zinc chloride IIT JEE NEET MCQ скачать в хорошем качестве

Lucas Test Alcohols class 12 chemistry mechanism HCl anhydrous zinc chloride IIT JEE NEET MCQ

#lucas_test #lucasreagent #iitjeechemistry ‪@AdiChemAdi‬ Welcome, students. In this presentation, we'll explore how to distinguish primary, secondary, and tertiary alcohols using the Lucas test. This test is a simple yet essential tool in organic chemistry. I'm Aditya Vardhan from adichemistry.com, and I encourage you to ask any questions in the comments section. ============ Without wasting time, let's dive into the details of Lucas test. It involves using Lucas reagent, a mixture of anhydrous zinc chloride and HCl, to differentiate primary, secondary and tertiary alcohol types. When this reagent is added, the alcohols transform into corresponding alkyl chlorides. We distinguish between these alcohols by observing the different rates of alkyl chloride formation. Tertiary alcohols quickly form chlorides,............ while secondary alcohols take 2-3 minutes,............In the case of primary alcohols formation of the alkyl chloride requries heating. Keep in mind that, in primary alcohols, the alcohol group is attached to the primary carbon, which in turn is linked to only one carbon. Secondary alcohols have the alcohol group attached to a secondary carbon, which is connected to two carbon atoms. In case of tertiary alcohols, there is tertiary carbon that is connected to three other carbons. ============== Here's how you perform the test: Place primary, secondary, and tertiary alcohols in separate test tubes. Now add Lucas reagent to each test tube. In the case of tertiary alcohols, the solution becomes turbid or cloudy immediately. Keep in mind that, since the alkyl chlorides are immiscible liquids with alcohols, we observe this turbidity. In the case of secondary alcohols, the solution turns turbid after 2 to 3 minutes. Whereas, in the case of primary alcohols, there is no change at room temperature. The reaction mixture turns cloudy only after heating the reaction mixture. ============== Now, let's discuss the underlying principle. When alcohols react with Lucas reagent, they undergo nucleophilic substitution, replacing the OH group with a chloride ion. This reaction involves two key steps: The first step involves, departure of OH group to form a carbocation. This step is the rate-determining one. Then The carbocation then combines with a chloride ion to form an alkyl chloride. The rate of the reaction, depends on the rate of formation of carbocation. Which in turn depends on the stability of carbocation. Since the stability of carbocation decreases from tertiary to secondary to primary, the rate of the reaction also reflects the same order. ================