What is the purpose of the drying tubes?
What is the purpose of the drying tubes?
A drying tube or guard tube is a tube-like piece of apparatus used to house a disposable solid desiccant, wherein at one end the tube-like structure terminates in a ground glass joint for use in connecting the drying tube to a reaction vessel, for the purpose of keeping the vessel free of moisture.
What is a drying tube and why is it used in the Grignard reaction YOUR performed?
The set-up for this experiment is shown in Figure 12.3. Grignard reagents are very strong bases and are very sensitive to water and humid air. We need to use a calcium chloride drying tube. The purpose of the tube is to remove moisture from the atmosphere.
Why do we use guard tube?
Guard tube is used to remove moisture for gases. The guard tube contains anhydrous calcium chloride. When the gas is passed through the guard tube, the calcium chloride absorbs the water molecules, thus reducing moisture content of the gas.
What is the blue substance in the drying tube?
Dry (blue) Wet (wet) Magnesium sulfate (n=7, e=2.8 mg/L) is a slightly acidic drying agent. It works well in solvents like diethyl ether, but not as well for ethyl acetate. It is a fast drying agent, in part because it comes as a fine powder with a large surface area.
Why must a Grignard reaction be kept dry?
After reaction, the desired product (an alcohol, as shown here) is formed after acidic hydrolysis. You must keep your reaction apparatus and reagents completely dry because water functions as an acid, and would cleave the Grignard reagent producing benzene. All glassware must be thoroughly clean and dry.
How does CaCl2 dry a compound?
Calcium chloride in its anhydrous form is an economical drying agent and very important for drying processes in laboratories. Those are for example: drying of liquids and neutral gases. Calcium chloride has a drying capacity up to 98%. It binds the water through crystallization and can be regenerated by warming.
What is the purpose of the ether extraction Grignard reaction?
Diethyl ether is an especially good solvent for the formation of Grignard reagents for two reasons. The Grignard carbon is highly basic and reacts with the acidic protons of polar solvents like water to form an alkane. Ether has no acidic protons, so Grignard reagents are stable in ether.
Why is dry ether used in Grignard reagent?
q Diethyl ether is an especially good solvent for the formation of Grignard reagents because ethers are non-acidic (aprotic). Water or alcohols would protonate and thus destroy the Grignard reagent, because the Grignard carbon is highly nucleophilic. This would form a hydrocarbon.
Why guard tube containing CaCl2 is used?
If we see how hydrogen chloride gas is prepared, we will see that the gas is usually passed through a guard tube (also known as a drying tube) containing anhydrous calcium chloride. The reason behind why anhydrous calcium chloride is used in guard tubes is because it is considered as a very good drying agent.
Why calcium chloride is used to dry the gas?
Calcium chloride is deliquescent. Deliquescence is the property of some salts to be so highly hygroscopic, that they end up dissolving in their own absorbed water. Therefore, calcium chloride is widely used as a desiccant (humidity remover).
What is the difference between dehydrating agents and drying agents?
Dehydrating agents remove water which is chemically bound to a substance for e.g water of crystallization. While on the other hand a drying agent simply removes excess water present in a substance which is not chemically bound to it.
How does MgSO4 remove water?
For the most common drying agents such as sodium sulfate or magnesium sulfate, the crystals form larger clumps when they absorb water. After standing for a short period the crystals are removed by filtration or decantation, and the solution is then relatively free of water.
What is the function of a drying tube?
A drying tube or guard tube is a tube-like piece of apparatus used to house a disposable solid desiccant, wherein at one end the tube-like structure terminates in a ground glass joint for use in connecting the drying tube to a reaction vessel, for the purpose of keeping the vessel free of moisture. The tube-like structure is…
What is a guard tube used for in chemistry?
A drying tube or guard tube is a tube-like piece of apparatus used to house a disposable solid desiccant, wherein at one end the tube-like structure terminates in a ground glass joint for use in connecting the drying tube to a reaction vessel, for the purpose of keeping the vessel free of moisture.
When should I replace the desiccant in a drydrying tube?
Drying tubes are often prepared in advance and the desiccant can be replaced when exhausted. Reactions which are being heated, or which evolve gases, must never be sealed because an overpressure may shatter the vessel.
How do you fill a drying tube with calcium chloride?
In use, the drying tube is filled with a rechargeable desiccant such as calcium chloride, and the open end of drying tube is partially blocked (e.g. with wool, glasswool or a bung/cork which has a small bore made in it) and the drying tube is connected to the apparatus to be kept dry via the ground glass joint.
