Recrystallization
Summary
TLDRThis video demonstrates the process of recrystallizing an organic compound. The necessary equipment includes a flask with the compound, a hot plate, recrystallizing solvent, boiling chips, and a filtration setup. The process involves dissolving the compound in a heated solvent, adding activated charcoal to remove impurities, filtering, and cooling the solution to form crystals. The crystals are then collected using vacuum filtration and washed with cold solvent. Finally, the crystals are dried by pulling air through them, completing the recrystallization process.
Takeaways
- 🧪 The video demonstrates the recrystallization process of an organic compound.
- 🔥 Essential equipment includes a pipette, flasks, hot plate, boiling chips, and a filtration assembly.
- 💡 The recrystallizing solvent is heated until it is just barely boiling, ensuring it's near the solvent's boiling point.
- 🌀 Small portions of solvent are added to dissolve the compound, aiming to create a saturated solution with minimal excess.
- 🖤 Activated charcoal can be used to remove color impurities after slight cooling of the solution.
- 🔄 Insoluble impurities and charcoal are filtered out using fluted filter paper and a warm flask.
- ❄️ After filtering, the solution is allowed to cool to room temperature and then placed in an ice bath to enhance crystallization.
- 💧 Crystals are collected using vacuum filtration with a Buechner funnel and cold recrystallizing solvent.
- 🧊 The crystals are washed with cold solvent to remove any remaining supernatant liquid.
- 💨 The drying process starts by pulling air through the crystals, followed by letting them dry completely in open air.
Q & A
What equipment is required for the recrystallization process demonstrated in the video?
-The required equipment includes a Pasteur pipette, a flask containing the compound to be recrystallized, a hot plate, a flask with recrystallizing solvent, boiling chips, a stemless funnel, fluted filter paper, and another flask for receiving the filtrate.
Why is it important to adjust the hot plate to just barely boil the recrystallizing solvent?
-It is important to adjust the hot plate so the recrystallizing solvent is just barely at a boil to prevent rapid boiling, which can cause solvent loss and potential degradation of the compound. The goal is to keep everything near the solvent's boiling point to effectively dissolve the material.
What is the purpose of adding small portions of solvent to the compound during the recrystallization process?
-Small portions of solvent are added to the compound to create a saturated solution, ensuring that the compound dissolves. The goal is to add just enough solvent for saturation and then a little excess to prevent undissolved impurities.
What should you do if the solution has a slightly yellow cast?
-If the solution has a yellow cast, activated charcoal is added to the solution to remove the color. The solution is then swirled and warmed again on the hot plate before filtering out the impurities.
What is the purpose of using activated charcoal in the recrystallization process?
-Activated charcoal is used to remove color impurities from the solution, which may be present due to impurities in the compound or solvent.
Why is it important to keep the filtration apparatus warm during the hot filtration step?
-The filtration apparatus is kept warm to prevent premature crystallization in the filter or funnel, which can trap the desired compound along with the impurities.
How do you complete the recrystallization process after room temperature cooling?
-After cooling the solution to room temperature and observing crystal formation, the flask is placed in an ice water bath to further complete the crystallization process by enhancing crystal growth.
What is the role of vacuum filtration in the recrystallization process?
-Vacuum filtration is used to collect the recrystallized crystals. It involves using a Büchner funnel, filter paper, and a vacuum source to separate the crystals from the remaining solvent and impurities.
Why is cold recrystallizing solvent used to wash the crystals during filtration?
-Cold recrystallizing solvent is used to wash the crystals during filtration to prevent them from dissolving again, while removing any remaining impurities or supernatant liquid adhering to the crystals.
How are the crystals dried after filtration?
-The crystals are dried by pulling air through them using the vacuum for a few minutes, and then they are transferred to a watch glass and left in open air to dry completely.
Outlines
🧪 Demonstration of Organic Compound Recrystallization
This paragraph introduces the demonstration of the recrystallization process for an organic compound. The required equipment includes a Pasteur pipette, a flask with the compound, a hot plate, recrystallizing solvent, boiling chips, and a setup for hot filtration. The paragraph describes how to warm the crystallizing solvent and filtration apparatus, aiming for a gentle boil in the solvent. The process involves adding solvent to dissolve the compound, making a saturated solution while avoiding excess solvent. Some impurities may remain undissolved, and care should be taken not to overuse the solvent.
🔍 Removing Impurities with Filtration and Activated Charcoal
This paragraph focuses on removing color impurities using activated charcoal. Once the solution has dissolved, but with a yellow hue, activated charcoal is added to decolorize it. The solution is slightly cooled, and charcoal pellets are added before reheating. Then, the solution is filtered using fluted filter paper to remove insoluble impurities and charcoal pellets. The filter is rinsed with hot solvent, ensuring no impurities remain. The solution is then allowed to cool to room temperature before being moved to an ice bath to enhance crystallization.
🔬 Collecting and Washing Crystals via Vacuum Filtration
This section explains how to collect the recrystallized compound using vacuum filtration. The tools needed include a Buechner funnel, filter flask, cold recrystallizing solvent, and stirring rod. The Buechner funnel is fitted with filter paper and wetted to form a tight seal. Crystals are scraped off the flask’s bottom, forming a slurry with the solvent, which is poured into the funnel. The remaining crystals are rinsed from the flask with cold solvent, ensuring all material is transferred.
🌀 Drying the Recrystallized Crystals
The final paragraph outlines the process of washing and drying the crystals. The crystals are rinsed in the Buechner funnel with a small volume of cold solvent to remove any remaining liquid. To initiate drying, air is pulled through the crystals for several minutes using the vacuum. Afterward, the crystals are transferred to a watch glass and left exposed to the air for complete drying over time.
Mindmap
Keywords
💡Recrystallization
💡Solvent
💡Boiling Chips
💡Hot Filtration
💡Fluted Filter Paper
💡Activated Charcoal
💡Vacuum Filtration
💡Buechner Funnel
💡Saturated Solution
💡Crystallization
Highlights
Introduction to recrystallization process and its importance in purifying organic compounds.
The required equipment includes a Pasteur pipette, hot plate, flasks, boiling chips, funnel, and filter paper.
Proper temperature control for recrystallization solvent is crucial; solvent should be near boiling but not rapid boiling.
Step-by-step addition of solvent to the compound until saturation is achieved, ensuring no excess solvent is used.
Impurities may be insoluble; careful monitoring is needed to avoid adding too much solvent while dissolving the solid.
Activated charcoal is used to remove any color impurities from the solution after initial dissolution.
The solution is filtered through fluted filter paper to remove insoluble impurities and charcoal.
Rinsing the filter paper with hot recrystallizing solvent ensures complete removal of impurities.
The solution is left to cool to room temperature, allowing the crystallization process to begin.
Crystals begin to form after 10 minutes of cooling at room temperature and further crystallization occurs in an ice bath.
Crystals are collected using vacuum filtration with a Büchner funnel and filter flask.
Cold recrystallizing solvent helps wash and purify the crystals during the filtration process.
The crystals are washed to remove any residual supernatant liquid for higher purity.
The drying process involves pulling air through the crystals and then allowing them to dry in open air.
Final step includes transferring the dried crystals to a watch glass for full drying, completing the recrystallization.
Transcripts
in this video we'll see a demonstration
of the recrystallization of an organic
compound the equipment we need consists
of a passed your pipette a flask
containing the compound to be
recrystallized a hot plate a flask with
recrystallizing solvent and a couple
boiling chips and in assembly for doing
a hot filtration this consists of a
stemless funnel some fluted filter paper
and another flask for receiving the
filtrate we begin by warming the
crystallizing solvent and the filtration
apparatus on the hot plate we want to
adjust the hot plate so that the
recrystallizing solvent is just barely
at a boil notice here that there are
bubbles starting to form in the bottom
of the flask but it's not boiling
rapidly working on the hot plate so that
we keep everything near the boiling
point of the solvent we had a couple
portions of the solvent to our compound
you can use a folded paper towel to hold
the neck of the hot flask swirl the
flask way you keep it in contact with a
hot plate to help dissolve the material
continue adding small portions of the
solvent until the solid dissolves the
goal is to add just enough solvent to
make a saturated solution and then a
little excess some impurities may be
completely insoluble so don't add too
much solvent in trying to dissolve the
last bit of solid
you
at this point we're almost ready to
filter the solution to remove the
insoluble impurities but it has a
slightly yellow cast to it we can remove
this color by treating the solution with
activated charcoal letting the solution
cool slightly
we'll add some activated charcoal
pellets to our solution and swirl this
and warm it again on the hot plate
next we filter out the insoluble
impurities and the nor I pellets through
the fluted filter paper into the warm
flask on the hot plate
you
after most of the solution is drained
through the filter paper use a couple
small portions of the hot
recrystallizing solvent to rinse the
paper
you
now the solution is removed from the hot
plate and allowed to cool to room
temperature
you
after about 10 minutes the flask is
reached room temperature and we have a
reasonable crop of crystals will
transfer this to a nice water bath to
complete the crystallization process
we'll collect our crystals by vacuum
filtration to do this we'll need a
Buechner funnel a filter flask which
we've clamped to the ring stand and
attached to the aspirator at the
workbench some cold recrystallizing
solvent which we've chilled in the ice
bath and a stirring rod we fit the
Buechner funnel with the neoprene
adapter and then add the correct size
filter paper one that will fit flat on
the bottom of the viewer funnel and just
cover all the holes we turn on the
vacuum source and then wet the paper
with the recrystallizing a solvent to
pull it tight over the holes in the
funnel
use a stirring rod to break the crystals
free from the bottom of the flask and
create a slurry of the crystals in the
solvent pour the slurry of crystals in
the solvent into the funnel we can rinse
the remaining crystals out of the flask
with a little cold solvent
you
wash the crystals in the Buechner funnel
with a small amount of cold
recrystallizing solvent one or two
milliliters depending upon the amount of
crystals to remove any supernatant
liquid adhering to them
we initiate the crystal drying process
by pulling air through them for a few
minutes after that they're transferred
to a watch class and left in the open
air for a time to dry completely
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