May 20, 2022, 01:23:35 PM
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Topic: What is the purpose of applying grease to the cone of the condenser of apparatus  (Read 12260 times)

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Offline Chaste

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It is a conventional simple reflux set up for the synthesis of ligand bpm(bis(pyrazolyl)methane).

I'm guessing it acts as a lubricant? to reduce friction but what is its significance?

Offline discodermolide

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It is a conventional simple reflux set up for the synthesis of ligand bpm(bis(pyrazolyl)methane).

I'm guessing it acts as a lubricant? to reduce friction but what is its significance?

It is used to stop the ground glass joints freezing together. Just don't use too much or it will end up in your product.
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Offline Chaste

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It is a conventional simple reflux set up for the synthesis of ligand bpm(bis(pyrazolyl)methane).

I'm guessing it acts as a lubricant? to reduce friction but what is its significance?

why don't we use it always?

It is used to stop the ground glass joints freezing together. Just don't use too much or it will end up in your product.

Offline Doc Oc

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By "the cone" I'm assuming you mean the glass joint where it fits into the flask.

The reason is the joint between condenser and flask isn't airtight.  So once you get your solvent boiling it can escape through that joint and then your flask will dry out if you leave it for long enough.  Greasing the joint makes it airtight and prevents the solvent from evaporating out (also prevents air and moisture from getting in if you need to be concerned about that).

Offline Chaste

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By "the cone" I'm assuming you mean the glass joint where it fits into the flask.

The reason is the joint between condenser and flask isn't airtight.  So once you get your solvent boiling it can escape through that joint and then your flask will dry out if you leave it for long enough.  Greasing the joint makes it airtight and prevents the solvent from evaporating out (also prevents air and moisture from getting in if you need to be concerned about that).

I get it now. Thanks for the explanation!

Offline discodermolide

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By "the cone" I'm assuming you mean the glass joint where it fits into the flask.

The reason is the joint between condenser and flask isn't airtight.  So once you get your solvent boiling it can escape through that joint and then your flask will dry out if you leave it for long enough.  Greasing the joint makes it airtight and prevents the solvent from evaporating out (also prevents air and moisture from getting in if you need to be concerned about that).

Even without greasing I have never had solvent loss through the joint, but without greasing I've had plenty of frozen joints. I guess it fulfills both functions.
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Offline Chaste

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sorry, I don't understand what's frozen? does it mean the condenser and the flask becomes stuck and difficult to separate from each other at the end of the refluxing?

Offline discodermolide

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sorry, I don't understand what's frozen? does it mean the condenser and the flask becomes stuck and difficult to separate from each other at the end of the refluxing?
Exactly that!
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Offline Modestus

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I haven't ever lost product through that joint either; however J-bone is right, for some reactions, such as the formation of a Grignard reagent, where water will prevent product formation, it is imperative for the air tight seal, unless you're conducting the reaction in the Sahara, then by all means, use no grease!

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