Question

13 SN1: Synthesis of tert-Butyl Chloride Alkyl halides can be prepared from their corresponding alcohols via an acid catalyzed substitution reaction. The mechanism of these acid catalyzed substitution reactions are labeled as Syl (substitution, nucleophilic, unimolecular) and S2 (substitution, nucleophilic, bimolecular). Tertiary alcohols follow the Snl route, primary alcohols follow the S2 route, and secondary alcohols can follow either path. Under acidic conditions, the mechanism (Figure 1) of the Sul reaction involves rapid protonation of the alcohol, followed by the loss of water as the rate-determining step. This generates a relatively stable carbocation which is then attacked by the halide ion to form the alkyl halide. Syl reactions are favored by tertiary alcohols because they tend to form more stable carbocations. CH₂ H HC OH- - HO CH₂ a Cho CH HC OH нус 2 HC HC Figure / Conversion of t-butanol into t-butyl chloride by an Syl mechanism The product will be verified by gas chromatography by comparing the chromatograms of the starting material, tert-butyl chloride standard, and your product. Confirmation of your product, Tert-butyl chloride, can also be performed by reacting the product with a solution of silver nitrate in ethanol. The tertiary alkyl halide will react by means of an Snl mechanism with the silver nitrate to form an insoluble silver halide. The appearance of a precipitate indicates a positive result indicating the presence of a tertiary alkyl halide. OBJECTIVES In this experiment, you will • Synthesize tert-butyl chloride via an Sxl reaction. • Confirm the presence of a tertiary alkyl halide using the silver nitrate test • Verify the product by gas chromatography. MATERIALS Part Synthesis of tert-Butyl Chloride 25 ml graduated cylinder 10 mL graduated cylinder 50 mL beaker 250 mL beaker 125 mL Erlenmeyer flask separatory funnel apparatus glass funnel disposable Pasteur pipets and bulb two 10 mL glass vials and caps hydrochloric acid, concentrated tert-butanol, reagent grade saturated sodium bicarbonate solution saturated sodium chloride solution sodium sulfate, anhydrous DI water ice

Answer 1

3.

A functional group is an atom or group of atoms with characteristic chemical and physical properties. A functional group contains either heteroatoms or π-bonds. Heteroatoms have lone pairs and create electron deficient or electron rich sites on a molecule. These heteroatoms either take part in chemical reaction or they influence the reactions that take place in the compound.

4.

When there are more than one functional groups in a compound, some of the reactions can happen in more than one sites. If precautions are not taken, more than one product will be formed and desired product needs separated and purified. Consequently the yield will be also be low. Therefore it is important to protect and deprotect one or more of the possible sites to get the desired product.

7.

a) A concerted reaction is a chemical reaction in which all bond breaking and bond making occurs in a single step.

b) S_N² reaction is an example of concerted nucleophilic reaction.

8.

a) Carbocation is a carbon species carrying a positive charge

b) S_N¹ reactions involve the formation of carbocations.

c) The first step in S_N¹ reaction leads to the formation of carbocations.

d) The formation of carbocations in S_N¹ reaction is the rate determining step.