Home >
Community >
Cracking of dicyclopentadiene - was my simple Liebig condenser distillation setup adequate?
Upvote
29
Downvote
+ Distillation
Posted by
Marc Roussel
Cracking of dicyclopentadiene - was my simple Liebig condenser distillation setup adequate?
The Friedrichs condenser is for refluxing dicyclopentadiene (bp ~170 C). It's kept at 50 C to let the cyclopentadiene (bp ~40 C) pass without condensing.
The Friedrichs condenser is for refluxing dicyclopentadiene (bp ~170 C). It's kept at 50 C to let the cyclopentadiene (bp ~40 C) pass without condensing.
I see. Since I had my oil bath temp. at 180 °C, I ran the risk of distilling some "uncracked" dicyclopentadienes together with the cyclopentadiene. I speculate that it probably worked because the head temperature in all likelihood was below the bp of dicyclopentadiene (cant say for sure, as I didnt measure temperature there). - Edit: looking at my own foto, I notice that I actually did have a thermometer there, but I never read it :-(More
Upvote
VOTE
Downvote
I agree the setup is a bit much. The way I viewed the above diagram the receiving flask is on the left, hence the Friedrich's condenser is used to rapidly condense the hot, cracked cyclopentadiene rapidly. As such it gets the cold water, and the other condenser gets the hot water to help the reflux. Its a good idea to keep it cold at this point since low temp slows the dimerization. When Ive done it in the past I've had my setup under flowing N2 to keep it dry, but the drying tube could work depending on how pure you need it. Also I would freeze the collected cyclopentadiene during collection and storage. Things typically react slower in the solid phase. J. Chem. Educ., 1987, 64 (10), p 898
I agree the setup is a bit much. The way I viewed the above diagram the receiving flask is on the left, hence the Friedrich's condenser is used to rapidly condense the hot, cracked cyclopentadiene rapidly. As such it gets the cold water, and the other condenser gets the hot water to help the reflux. Its a good idea to keep it cold at this point since low temp slows the dimerization. When Ive done it in the past I've had my setup under flowing N2 to keep it dry, but the drying tube could work depending on how pure you need it. Also I would freeze the collected cyclopentadiene during collection and storage. Things typically react slower in the solid phase. J. Chem. Educ., 1987, 64 (10), p 898
Youve got it wrong. Read the description above the sketch: "technical Dicyclopentadiene ...placed in two-necked flask equipped with thermometer and Friedrichs condenser (..50°C)". Also why would you put a thermometer in the receiving flask?More
You put a thermometer in the educt to make sure youre not overheating it, most importantly. Does that publication you cite give a rate constant for the dimerisation (and at what temperature)? I somehow doubt that extra cooling is really necessary.More
Your right I just looked at the picture and wondered why someone would put a thermometer above the condenser on the receiving flask side. Perhaps a thermometer In the receiving flask is to make sure the cracked product stays sufficiently cooled.More
Upvote
VOTE
Downvote
That setup in the drawing is way over the top, and you'll never get a drop of destillate with it. The Cyclopendadiene will fully condense in the bridge and all flows back into the Friedrichs. Ten degrees temperature difference to the dew point will never get it over 20 centimeters of glass tube.
However you should attach a drying tube to the exit near the receiving flask to avoid condensing water into it, especially if you do that nonsense with the dry ice/acetone. Typical for organic chemists, I'm sorry to say. A simple ice bath would help as much. Just keep the receiving flask as cold as the water in the cooler.
And 180 dC is a bit much, I'd just stay under the boiling point of the dimer. I remember adding some iron powder was supposed to speed up the retro-Diels-Alder reaction, i guess by lowering the effective concentration of the monomer through complexion.
That setup in the drawing is way over the top, and you'll never get a drop of destillate with it. The Cyclopendadiene will fully condense in the bridge and all flows back into the Friedrichs. Ten degrees temperature difference to the dew point will never get it over 20 centimeters of glass tube.
However you should attach a drying tube to the exit near the receiving flask to avoid condensing water into it, especially if you do that nonsense with the dry ice/acetone. Typical for organic chemists, I'm sorry to say. A simple ice bath would help as much. Just keep the receiving flask as cold as the water in the cooler.
And 180 dC is a bit much, I'd just stay under the boiling point of the dimer. I remember adding some iron powder was supposed to speed up the retro-Diels-Alder reaction, i guess by lowering the effective concentration of the monomer through complexion.
The Friedrichs condenser is for refluxing dicyclopentadiene (bp ~170 C). It's kept at 50 C to let the cyclopentadiene (bp ~40 C) pass without condensing.
The Friedrichs condenser is for refluxing dicyclopentadiene (bp ~170 C). It's kept at 50 C to let the cyclopentadiene (bp ~40 C) pass without condensing.
More
VOTE
VOTE
I agree the setup is a bit much. The way I viewed the above diagram the receiving flask is on the left, hence the Friedrich's condenser is used to rapidly condense the hot, cracked cyclopentadiene rapidly. As such it gets the cold water, and the other condenser gets the hot water to help the reflux. Its a good idea to keep it cold at this point since low temp slows the dimerization. When Ive done it in the past I've had my setup under flowing N2 to keep it dry, but the drying tube could work depending on how pure you need it. Also I would freeze the collected cyclopentadiene during collection and storage. Things typically react slower in the solid phase. J. Chem. Educ., 1987, 64 (10), p 898
I agree the setup is a bit much. The way I viewed the above diagram the receiving flask is on the left, hence the Friedrich's condenser is used to rapidly condense the hot, cracked cyclopentadiene rapidly. As such it gets the cold water, and the other condenser gets the hot water to help the reflux. Its a good idea to keep it cold at this point since low temp slows the dimerization. When Ive done it in the past I've had my setup under flowing N2 to keep it dry, but the drying tube could work depending on how pure you need it. Also I would freeze the collected cyclopentadiene during collection and storage. Things typically react slower in the solid phase. J. Chem. Educ., 1987, 64 (10), p 898
More
VOTE
VOTE
VOTE
VOTE
That setup in the drawing is way over the top, and you'll never get a drop of destillate with it. The Cyclopendadiene will fully condense in the bridge and all flows back into the Friedrichs. Ten degrees temperature difference to the dew point will never get it over 20 centimeters of glass tube.
However you should attach a drying tube to the exit near the receiving flask to avoid condensing water into it, especially if you do that nonsense with the dry ice/acetone. Typical for organic chemists, I'm sorry to say. A simple ice bath would help as much. Just keep the receiving flask as cold as the water in the cooler.
And 180 dC is a bit much, I'd just stay under the boiling point of the dimer. I remember adding some iron powder was supposed to speed up the retro-Diels-Alder reaction, i guess by lowering the effective concentration of the monomer through complexion.
That setup in the drawing is way over the top, and you'll never get a drop of destillate with it. The Cyclopendadiene will fully condense in the bridge and all flows back into the Friedrichs. Ten degrees temperature difference to the dew point will never get it over 20 centimeters of glass tube.
However you should attach a drying tube to the exit near the receiving flask to avoid condensing water into it, especially if you do that nonsense with the dry ice/acetone. Typical for organic chemists, I'm sorry to say. A simple ice bath would help as much. Just keep the receiving flask as cold as the water in the cooler.
And 180 dC is a bit much, I'd just stay under the boiling point of the dimer. I remember adding some iron powder was supposed to speed up the retro-Diels-Alder reaction, i guess by lowering the effective concentration of the monomer through complexion.
More
VOTE