Making designer Chemicals
Conversion of an Alcohol to a Halogenoalkane Reactants: Alcohol and Hydrogen Halide (HCl,
HBr, or HI) Predicted Product: Halogenoalkane
Proposed Method:
1. Set up a round-bottom flask with a reflux condenser and a drying tube.
2. Add the alcohol (e.g., ethanol) to the flask.
3. Slowly add the concentrated hydrogen halide (e.g., concentrated HCl gas) to the
reaction mixture.
4. Heat the mixture under reflux for a specific time (e.g., 1-2 hours).
5. Allow the reaction mixture to cool to room temperature.
Actual Reaction Conditions: Reactants: Ethanol and concentrated HCl gas Temperature: Reflux
(boiling point of the alcohol) Time: 1-2 hours
Health and Safety Assessment:
Ensure proper ventilation in the laboratory or perform the reaction under a fume hood.
Wear appropriate protective equipment, including gloves and safety goggles.
Handle concentrated hydrogen halide with care as it is corrosive and toxic.
Purity and Quantity Assessment:
Perform a simple distillation to separate the halogenoalkane from the reaction mixture.
Measure the boiling point of the obtained product and compare it with the literature
value to assess its purity.
Calculate the percentage yield of the halogenoalkane by dividing the actual yield by the
theoretical yield and multiplying by 100.
Explanation:
The reaction involves the substitution of the hydroxyl group (-OH) of the alcohol with a halogen
atom (X) from the hydrogen halide. The balanced chemical equation for the reaction between
ethanol and concentrated HCl is as follows: C2H5OH + HCl → C2H5Cl + H2O
The functional groups involved are the hydroxyl group (-OH) in the alcohol and the halogen
atom (X) in the halogenoalkane. The reaction mechanism proceeds through an S<sub>N</sub>1
or S<sub>N</sub>2 mechanism, depending on the nature of the alcohol and reaction
conditions.
Importance of Reaction Conditions:
Temperature: Refluxing the mixture ensures that the reaction occurs at the boiling point
of the alcohol, providing sufficient energy for the reaction to proceed.
, Time: Allowing the mixture to reflux for a specific time allows for complete conversion
of the alcohol to the desired halogenoalkane.
Evaluation and Recommendations:
The chosen reaction conditions are suitable for converting alcohols to halogenoalkanes.
To improve the yield and purity, drying agents can be added to remove any residual
water before the addition of the hydrogen halide.
Optimizing the reaction time and temperature based on the specific alcohol used can
lead to improved yields.
Preparation 2: Conversion of an Alcohol to an Aldehyde Reactants: Alcohol and Oxidizing Agent
(PCC, Chromic Acid, or KMnO4) Predicted Product: Aldehyde
Proposed Method:
Set up a round-bottom flask with a reflux condenser and a drying tube.
Add the alcohol (e.g., ethanol) to the flask.
Slowly add the oxidizing agent (e.g., pyridinium chlorochromate, PCC) to the reaction
mixture.
Heat the mixture under reflux for a specific time (e.g., 1-2 hours).
Allow the reaction mixture to cool to room temperature.
Actual Reaction Conditions: Reactants: Ethanol and PCC Temperature: Reflux (boiling point of
the alcohol) Time: 1-2 hours
Health and Safety Assessment:
Ensure proper ventilation in the laboratory or perform the reaction under a fume hood.
Wear appropriate protective equipment, including gloves and safety goggles.
Handle oxidizing agents with care as they can be hazardous.
Purity and Quantity Assessment:
Perform a distillation or extraction to isolate the aldehyde from the reaction mixture.
Measure the boiling point of the obtained product and compare it with the literature
value to assess its purity.
Calculate the percentage yield of the aldehyde by dividing the actual yield by the
theoretical yield and multiplying by 100.
Explanation:
The reaction involves the oxidation of the alcohol, resulting in the conversion of the hydroxyl
group (-OH) to an aldehyde functional group (-CHO). The balanced chemical equation for the
oxidation of ethanol using PCC is as follows: C2H5OH + [O] → CH3CHO + H2O
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