CHEM 2242 Extraction (Lab 4)
m-nitroaniline
Basic
Be able to...
-Complete and understand a flow diagram (know solvents, in notes) -Write out reactions for steps in flow chart -Mathematically prove double extractions are more efficient -Find volume of solvent needed to remove a percentage of compound
What are the advantages and disadvantages of using ether as an extraction solvent?
Advantages: 1. It is a great solvent. It can dissolve most of the organic compounds. 2. It has low boiling point. It can be distilled over easily 3. It is chemically inert. Disadvantage: 1. Highly flammable 2. Toxic
What criteria must be considered when selecting a solvent for extraction?
The solvent must dissolve the substance being extracted and be sparingly soluble in the substance that is being extracted from.
What are the advantages of using dichloromethane (higher density) over diethyl ether (lower density) for extracting organic compounds from an aqueous solution using a separatory funnel?
Because dichloromethane is denser than water, it can be drained off of the aqueous layer allowing a second layer of solvent to be used in the next extraction. This reduces the product lost in the transfer between containers.
Why must the stopper of the seperatory funnel be removed before liquid can be withdrawn through the stopcock?
The stopper must be removed so that the air pressure will help push the liquid out of the funnel. If not, the flow of liquid is obstructed.
What differences in the chemical properties of carboxylic acid and phenol make extraction with aqueous sodium bicarbonate and an organic solvent possible?
Phenol remains in the aqueous layer and the salt formed with carboxylic acid dissolves in the aqueous layer.
Calcium Chloride
Drying agent, removes water from the organic layer
Partition Coefficient
K = C2/C2, where C1 and C2 are the concentrations at equilibrium of solute A in solvent 1 and in solvent 2, respectively.
Why are multiple extractions more efficient?
Larger volume determined by the partition coefficient-determines what percentage of the material is going to diffuse into the organic layer vs. the aqueous layer.
Miscible
Liquids that dissolve freely in one another in any proportion
Naphthalene
Neutral
What safety precautions should one take when using chlorinated solvents for extractions?
The lab should be well ventilated, there should be no flames, and gloves should be worn.
What are the advantages of having a solvent be more dense than water when extracting an organic compound from an aqueous solution in a seperatory funnel?
Two distinct layers form, allowing for easy separation.
