Recrystallization

Summary

This 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

00:00

🧪 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.

05:03

🔍 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.

Keywords

💡Recrystallization

Recrystallization is a method used in chemistry to purify organic compounds. In the video, the process is demonstrated using a solvent to dissolve the compound and then slowly cooling it to allow pure crystals to form. This method is useful for removing impurities that do not dissolve well or remain dissolved in the solution.

💡Solvent

A solvent is a liquid in which substances (solutes) are dissolved. In the context of the video, a recrystallizing solvent is carefully heated to dissolve the organic compound. The choice and use of the solvent are critical, as it must dissolve the compound at high temperatures but allow it to recrystallize upon cooling.

💡Boiling Chips

Boiling chips are small, porous stones added to a liquid to ensure smooth boiling by preventing superheating and bumping. In the video, they are used while heating the recrystallizing solvent to maintain a steady and controlled boiling point, ensuring that the solvent doesn’t boil too vigorously.

💡Hot Filtration

Hot filtration is a technique used to separate insoluble impurities from a solution while keeping the desired compound dissolved at a high temperature. The video demonstrates the use of hot filtration with a stemless funnel and fluted filter paper to remove impurities, ensuring that the solution remains hot to prevent premature crystallization.

💡Fluted Filter Paper

Fluted filter paper is a special type of filter paper folded in such a way that it increases the surface area for filtration, speeding up the process. In the video, it is used during hot filtration to efficiently separate impurities from the dissolved compound, ensuring that the process is both fast and effective.

💡Activated Charcoal

Activated charcoal is used to adsorb colored impurities from a solution. In the video, the solution has a yellow tint, so activated charcoal pellets are added to remove these color impurities, helping to clarify the final crystallized compound. The charcoal binds to the impurities, which are later filtered out.

💡Vacuum Filtration

Vacuum filtration is a technique used to separate solid crystals from the liquid solution using reduced pressure. In the video, a Buechner funnel and an aspirator are employed to quickly collect and dry the crystals after recrystallization, with the vacuum assisting in drawing the solution through the filter paper.

💡Buechner Funnel

A Buechner funnel is a laboratory apparatus used in vacuum filtration to separate solids from liquids. In the video, it is used along with filter paper to collect the recrystallized product. The funnel's design, with holes at the bottom, allows for efficient filtration when connected to a vacuum source.

💡Saturated Solution

A saturated solution is one where the solvent contains the maximum amount of dissolved solute at a given temperature. In the video, the goal is to create a saturated solution by adding just enough solvent to dissolve the compound, followed by a little excess to ensure a proper recrystallization process.

💡Crystallization

Crystallization is the process by which a solid forms from a solution as the solvent cools. In the video, the compound is dissolved in a hot solvent and then allowed to cool, first to room temperature and then in an ice bath, causing pure crystals to form as the solution becomes supersaturated.

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