Question

Hi, I'm having trouble with answering these organic chemistry lab questions. Please give full answers in your own words. Thanks in advance

1. Which of the following solvents: acetone, diethly ether, dichloromethane, pentane, THF, form upper layers or lower layers and which are miscible or immiscible with water during an extraction?

2. What is the consequence of only cooling the recrystallization solution to room temperature instead of 0 degrees celsius.

3. What is the consequence of only cooling the recrysyallization solution to quickly?

4. A mixture of carboxylic acid and a phenol can often be seperated by extracting with aqueous sodium bicarbonate and a suitable organic solvent. What difference in cehmical properties of the carboxylic acid and the phenol make this seperation possible?

5. What is the practical advatnage of using dichloromethane over diethly ether for extracting organic compounds from an aqueous solution using a seperatory funnel? What are the advantages and disadvantages of using diethly ether as an extraction solvent?

Answer 1

Solution :-

1. Which of the following solvents: acetone, diethly ether, dichloromethane, pentane, THF, form upper layers or lower layers and which are miscible or immiscible with water during an extraction?

Solution :- Out of the given solvents only dichloromethane have the greater density than the water therefore the only dichloromethane forms the upper layer and other forms upper layer.

THF is miscible with water but the others are not miscible with water.

2. What is the consequence of only cooling the recrystallization solution to room temperature instead of 0 degrees celsius.

Solution :- The solubility of the solid increases as the temperature increases therefore the solute will have higher solubility at room temperature than at 0 C, therefore this will make less crystallization if the temperature is kept at room temperature instead at 0 C

3. What is the consequence of only cooling the recrytyallization solution to quickly?

Solution :-

If the recrystallization done by quick cooling then it may form the perfect crystals of the solute.

4. A mixture of carboxylic acid and a phenol can often be seperated by extracting with aqueous sodium bicarbonate and a suitable organic solvent. What difference in cehmical properties of the carboxylic acid and the phenol make this seperation possible?

Solution :- Carboxylic acid is the acid containing the COOH group which reacts with the sodium bicarbonate to form the carboxylate salt and H2CO3 acid then H2CO3 decomposes to the CO2 and H2O

This makes the carboxylic acid to become soluble in the aqueous layer and gets separated in the form of the carboxylate salt in aqueous layer in contrast phenol do not react with the sodium bicarbonate and remain soluble in the organic layer which can be separated from the organic layer.

5. What is the practical advatnage of using dichloromethane over diethly ether for extracting organic compounds from an aqueous solution using a seperatory funnel? What are the advantages and disadvantages of using diethly ether as an extraction solvent?

Solution :- Dichloromethane is the denser solvent than water therefore organic layer remains at the bottom which can be easily separated. Also the boiling point of the dichloromethane is lower than the diethyl ether therefore it is easy to evaporate the dichloromethane than diethyl ether. Also dichloromethane is non flammable but diethyl ether is highly flammable.