Synthesis of 2,2,2 - Trichloroethanol from Chloral Hydrate

Introduction:

The purpose of this experiment is to prepare 2,2,2 - Trichloroethanol from chloral hydrate using a hydride reduction reaction. 2,2,2 – Trichloroethanol is a sedative and hypnotic agent that can be distributed as chloral hydrate, and therefore is often used to treat insomnia. The chemical process involves the reduction of a carbonyl group to the corresponding alcohol. Sodium borohydride (NaBH4) is the key reagent for carrying out this reduction reaction.

The mechanism of the reaction can be described as follows:

The reaction involves the reduction of chloral hydrate to 2,2,2 - Trichloroethanol using sodium borohydride as the reducing agent.

Materials and Method:

10.13g of chloral hydrate was weighed out and dissolved in 10ml of water in a 50ml beaker. The chloral hydrate solution was cooled using an ice bath. Simultaneously, 0.83g of sodium borohydride was weighed out and dissolved in 10ml of water in a smaller beaker.

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The sodium borohydride solution was then added into the chloral hydrate solution using a dropping funnel while maintaining the solution temperature between 20 to 30 degrees Celsius. After 10 minutes at room temperature, 10% HCl was added to the mixture to neutralize any remaining borohydride. The mixture was poured into a separatory funnel, and 40ml of ether was added to facilitate the separation of 2,2,2 - Trichloroethanol from the aqueous layer. The aqueous layer was removed, leaving the ether layer, which was collected in a conical flask.

A small amount of anhydrous magnesium sulfate was added to the conical flask with the ether layer to remove any remaining water. The solution was swirled, and if it remained non-translucent, more anhydrous magnesium sulfate was added. The mixture was then filtered using filter paper to remove the magnesium sulfate, and the ether was collected in a clean beaker. A total of 117.5ml of ether solution was obtained from four groups combining their solutions. The distillation apparatus was set up, and distillation was carried out at temperatures ranging from 120 to 153 degrees Celsius. 8.5ml of distillate was collected during the distillation.

Results:

For the first part of the experiment, approximately 30.5ml of filtrate was collected. When four groups combined their ether solutions, a total of 117.5ml of ether solution was obtained. During distillation, 8.5ml of distillate was collected. Since there were four groups, each group obtained 2.125ml of distillate.

The molar mass of chloral hydrate is 165.6g/mol, and for trichloroacetaldehyde, it is 147.5g/mol. Based on the reaction, 165.5g/mol of chloral hydrate produces 147.5g/mol of trichloroacetaldehyde.

Theoretical Yield Calculation:

The theoretical yield of trichloroacetaldehyde is calculated to be 9.1507g.

The molar mass of trichloroacetaldehyde is 147.5g/mol, NaBH4 is 37.83g/mol, and trichloroacetaldehyde is 149.5g/mol. Based on the reaction, 147.5g/mol of trichloroacetaldehyde reacts with 37.83g/mol of NaBH4 to produce 598g of trichloroethanol. Therefore, it is clear that trichloroacetaldehyde is the limiting reagent.

Actual Yield Calculation:

The actual yield of trichloroethanol is calculated to be 3.29375g.

Percentage Yield Calculation:

Percentage Yield = (Actual Yield / Theoretical Yield) × 100

Percentage Yield = (3.29375 / 9.1507) × 100 = 35.99% (approximately 36%)

Discussion and Conclusion:

The synthesis of 2,2,2 - Trichloroethanol from chloral hydrate using sodium borohydride as a reducing agent was successful. The reaction proceeded as expected, with chloral hydrate being converted to trichloroacetaldehyde and further reduced to trichloroethanol. The limiting reagent in the reaction was found to be trichloroacetaldehyde.

Theoretical yield calculations predicted the formation of 9.1507g of trichloroethanol, while the actual yield obtained was 3.29375g. This resulted in a percentage yield of approximately 36%. The lower than expected yield could be attributed to various factors, including incomplete reaction conversion, losses during the transfer and separation processes, and experimental errors.

In conclusion, this experiment successfully demonstrated the synthesis of 2,2,2 - Trichloroethanol from chloral hydrate using sodium borohydride as a reducing agent. While the percentage yield was not ideal, it provided valuable insights into the efficiency of the reaction and potential areas for improvement in future experiments. Overall, this synthesis has practical applications in the production of sedative and hypnotic agents, contributing to the field of pharmaceutical chemistry.