Based on chemical structures, explain why acetophenone is only separated at the end by distillation.
The mixture was acetophenone and ethyl trimethylacetate
Acetophenone and ethyl trimethylacetate have different chemical structures that result in different boiling points. To understand why acetophenone is separated at the end by distillation, we need to consider their chemical structures and the principles of distillation.
Acetophenone has a carbonyl functional group (C=O) attached to an aromatic ring. It has a boiling point of approximately 202 degrees Celsius. Ethyl trimethylacetate, on the other hand, contains an ester functional group (-COO-) attached to an alkyl chain. It has a lower boiling point, around 82 degrees Celsius.
During distillation, the mixture is heated to a temperature where the component with the lowest boiling point vaporizes first. This vapor then rises into the fractionating column, where it condenses and is collected separately.
In the case of acetophenone and ethyl trimethylacetate mixture, since acetophenone has a higher boiling point, it will remain in the liquid phase at lower temperatures while ethyl trimethylacetate vaporizes. This allows for the separation of ethyl trimethylacetate from acetophenone.
However, when the temperature reaches the boiling point of acetophenone (202 degrees Celsius), it will start to vaporize as well. At this point, the separation of acetophenone occurs. The vapor containing acetophenone rises into the fractionating column and is collected as a separate fraction. This separation at the end of the distillation process is important to ensure that only pure acetophenone is obtained.
In summary, acetophenone is separated at the end of distillation due to its higher boiling point compared to ethyl trimethylacetate. The distillation process allows the separation of different components based on their boiling points, enabling the collection of pure acetophenone.