Act. 1 Flashcards
What is the title of the activity?
Nucleophilic Substitution reaction: Sythesis of Tert-butyl Chloride
What does this experiment illustrate?
We prepare an alkyl halide from an alcohol, which is one of the most general methods available for making alkyl halides.
Other sources for halides aside from alcohols? According to Robets 1974
Phosphorus trihalides or thionyl halides
What type of alkyl halides do these other sources make? And why?
Primary halides, not tertiary bacause elimination reaction predominates.
What reaction is used here?
SN1 (unimolecular nucleophilic substitution)
What is the halogen acid used?
Hydrochloric acid because it reacts readily with tert-butyl alcohol
Explain the stages in the reaction
Stage 1:
Formation of carbocation intermediate, and it is stabilized by hyperconjugation and inductive effects.
Stage 2:
Formation of tert-butyl chloride. This is when the positive carbocation is attached with the negative chloride ion.
What is tert-butyl regarded since its in aqueous solution?
It is regarded as “wet”, hence a drying agent is needed
What is a drying agent?
This usually an inorganic compound that reacts irreversibly with water, or it is capable of forming one or more hydrates.
How do you select the drying agent?
It must be exercised with care because it may form a complex with the organic compound or solvent, or hav other reaction
What are the commonly used drying agent? Which drying agent is used in this experiment?
Calcium chloride, magnesium sulfate, and, sodium sulfate. CaCl2 is used in this experiment due to its fast action and high capacity to remove water
List down proper execution of adding drying agent
A. Place wet liquid in erlenmeyer flask with a sealed cork.
B. Add a sufficient amount which could cover the bottom of the flask.
C. Add a stopper to the flask and let it stand. Swirling the mixure increases the rate of drying.
D. In most cases, an hour of contact is the minimum time for thorough drying.
E. The drying agent is usually removed by Gravity filtration followed by distillation.
F. Carefull filtration process is needed to avoid the hydrated salt go along with the crude liquid
What is the final product? What are its uses?
Tert-butyl chloride is the product, mainly used as an alkylating agent in laboratory preparations.
What chemicals are needed for the experiment?
- Tert-butyl alcohol
- Concentrated HCl
- Saturated aqueous NaCl solution
- Saturated aqueous NaHCO₃ solution
- Anhydrous CaCl₂ or Na₂SO₄
- 2% ethanolic AgNO₃ solution
What safety precautions should be observed?
Concentrated HCl is corrosive and a poison; wear protective clothing and gloves when handling. HCl is rated as a poison. Both the alcohol and alkyl halide are flammable.
What is the first step in the procedure?
Place 5 mL of tert-butyl alcohol in a 50-mL Erlenmeyer flask.
What should be added to the flask after the tert-butyl alcohol?
Add a stir bar and commence stirring.
How much concentrated HCl should be cautiously added?
Add 13 mL of concentrated HCl (12N).
How long should the reaction mixture be stirred?
Stir the reaction mixture for 15 minutes or until the solution becomes colorless.
Where should the mixture be transferred after stirring?
Transfer the mixture to a 100-mL separatory funnel and allow to stand until two clear layers have separated.
How should the aqueous layer be treated?
- Remove the aqueous layer.
- Wash the organic layer first with 6 mL of saturated aqueous NaHCO₃ solution.
- Then wash it with 6 mL of saturated aqueous NaCl solution.
- Save the organic layer.
What precaution must be taken with the reaction between residual HCl and NaHCO₃?
- Care must be taken NOT to confine the gas in the funnel.
- Swirl the mixture initially in the UNSTOPPERED upright funnel.
- Then invert the funnel and vent IMMEDIATELY into the hood.
- Shake the funnel gently and briefly between periods of venting until the evolution of gas subsides.
How should the organic layer be dried?
Dry the organic layer over anhydrous CaCl₂.
How should the drying agent be removed?
Remove the drying agent by decantation.
