Question

The following questions are from an experiment titled Friedel-Crafts Alkylation for Organic Chemistry II Lab. There are pictures attached of the lab manual.

2) Is this method a good route for the preparation of p-sec-butyltoulene? Give reasons for your answer.

3) Why do you use a large excess of toulene. What are its functions?

4) What is the purpose for adding the hydrochloric acid to the water in the separatory funnel in step 5? Hint: If no acid is added, some solid may not dissolve.

5) What gas is produced when aluminum chloride reacts with water?

8) Describe a simple method for determining which layer in step 6 is actually the aqeuous phase?

9) Why is it important to work quickly when weighing out the aluminum chloride in step 1?

LAB Friedel-Crafts Alkylation c Dimculty Level Intermediate Key Words Lewis Acid Arenes Friedel-Crafts Reaction Decant Acyl Benzene Acylation Alkylation Exotherm Head Temperature Carbonyl Group Background Arenes (alkylbenzenes) are an important class of compounds. Toluene, for example, is produced commercially in huge amounts and is used as a solvent and as a starting material in the production of explosives, plastics, and drugs Arenes may be prepared in the laboratory by using either a Friedel-Crafts alkylation reaction, or by a two-step process that involves acylation followed by reduction of the carbonyl group. In the Friedel-Crafts reaction, an alkyl halide is used along with a Lewis acid catalyst, typically aluminum chloride. In alkylation reactions, the use of alkyl halides other than methyl or ethyl may lead to products that consist of a mixture of arenes with Isomerized alkyl groups. The second process (acylation) is used when straight chain alkyl groups are desired. Here, the initial acyl benzene, which is formed without rearrangement, is reduced to the desired arene. In this experiment, the primary halide (1-chlorobutane) is used as a reactant, but the butyl toluene formed will contain mainly the rearranged secondary butyl group. SYNTHESIS OF SEC-BUTYLTOLUENE Cits + CH CH.CH.CH.C + AICI, O CH,CHCH.CH, Materials Toluene Aluminum chloride (anhydrous) Hydrochloric acid (concentrated) 1-Chlorobutane Calcium chloride (anhydrous) L XC Priedel-Craft Alkylation

Answer 1

Answer:

2) This given method is preferable for the preparation of the p-sec butyl toulene. So, the answer is Yes. The reaction will proceed by the electrophilic addition to the derivative of benzene. As the given alkyl chloride is butyl chloride and so it's stable electrophilic form is secondary form, the addition of the secondary butyl is more stable to takes place and hence, the butyl group is preferentially adds in the para position only.

3) Large excess of toluene is used because toluene acts as the starting material as well as acts as a solvent.

4) In the step 5, when AlCl3 reacts with water a steamy cloud of HCl gas is produced. First, a drop of water is placed on the solid sample of AlCl3. This solid AlCl3 still splutters in the excess of water. If HCl is not added some solid sample of AlCl3 will remain in the solution and it will not dissolve. That's why we add some HCl in water to dissolve this solid AlCl3.

(5) The violent fumes of the hydrogen chloride gas (HCl) is evolved when aluminium chloride (AlCl3) reacts with the water.

8) Step-6 is not mentioned anywhere.

9) As it is known that AlCl3 has the hygroscopic property and hence, it absorbs water due to hygroscopic nature and gets hydrolysed. Therefore, it is required to be weighed quickly.

Thank you!!!