NECT Gr 12 Making Esters
Summary
TLDRIn this chemistry lab video, John McBride and Joy Sparkles demonstrate the process of making esters through esterification, a reaction between alcohols and carboxylic acids. They emphasize safety precautions, especially when handling concentrated sulfuric acid, which acts as a catalyst. The video showcases the preparation of two esters: one from ethanoic acid and ethanol, and another from salicylic acid and methanol. The esters are separated from the reaction mixture using sodium carbonate, and their distinct smells are described, with one resembling enamel paint and the other, wintergreen.
Takeaways
- 🧪 Esterification is the reaction between an alcohol and a carboxylic acid to produce an ester and water.
- 🌸 Esters are known for their pleasant aromas and are used in the perfume and deodorizing industries.
- 🔬 Concentrated sulfuric acid acts as a catalyst in esterification reactions, speeding up the process without being consumed.
- ⚠️ Safety is paramount when handling concentrated sulfuric acid due to its corrosive and dehydrating nature.
- 🥼 Proper protective gear such as gloves and safety goggles is essential when conducting chemical reactions.
- 🌡 The reaction is often carried out in a water bath to control the temperature and prevent overheating.
- 💧 Sodium carbonate is used to separate the ester from the reaction mixture by neutralizing the acid.
- 🌬 The process involves careful addition of reagents and catalysts to avoid violent reactions.
- 🌡️ Heating the reaction mixture helps to speed up the reaction rate.
- 📝 It's important to let the reaction mixture cool before adding sodium carbonate to observe the ester formation.
- 📖 Students are encouraged to record observations and complete a worksheet as part of their school-based assessment.
Q & A
What are esters and what are they commonly used for?
-Esters are fragrant substances that are volatile and have low boiling points. They are used in the perfume and deodorizing industry to manufacture artificial fragrances.
What is the esterification reaction?
-Esterification is the reaction between an alcohol and a carboxylic acid that produces an ester and water.
What role does sulfuric acid play in the esterification reaction?
-Sulfuric acid acts as a catalyst in the esterification reaction, speeding up the rate of reaction without being chemically changed during the process.
Why is safety important when handling concentrated sulfuric acid?
-Concentrated sulfuric acid is a powerful dehydrating agent and is corrosive. It can cause severe chemical burns if it comes in contact with skin, so it must be handled with care.
What is the proper way to smell chemicals in a laboratory?
-One should never smell chemicals by putting them under the nose and sniffing. Instead, the odor should be wafted towards the nose with the hand.
What are the reactants used in the first experiment described in the script?
-In the first experiment, ethanoic acid and ethanol are used as reactants.
How is the reaction mixture heated in the experiment?
-The reaction mixture is heated in a water bath, where a Bunsen burner is used to heat the water until it boils.
What is the purpose of adding sodium carbonate at the end of the reaction?
-Sodium carbonate is added to separate the unreacted acid and the ester from the reaction mixture.
What is the difference between the reactions involving ethanoic acid and salicylic acid?
-Ethanoic acid is a liquid, while salicylic acid is a crystalline solid. The method of adding the reactants and the catalyst differs slightly due to the solid state of salicylic acid.
What is the chemical formula of salicylic acid?
-The chemical formula of salicylic acid is C7H6O3.
How is the reaction progress monitored in the experiment?
-The reaction progress is monitored by observing changes in temperature, the formation of bubbles, and the appearance of an oily layer which indicates the formation of the ester.
Outlines
🧪 Introduction to Esterification in Organic Chemistry
The video begins with John McBride and Joy Sparkles introducing the topic of esterification, the chemical process of making esters by reacting alcohol and carboxylic acid. Esters are fragrant substances often used in the perfume industry. The reaction is catalyzed by concentrated sulfuric acid, which speeds up the process without being consumed. Safety precautions are emphasized, particularly when handling corrosive concentrated sulfuric acid, as it can cause severe burns. The use of gloves and goggles is stressed for protection.
⚗️ Demonstrating Esterification with Ethanoic Acid and Ethanol
The experiment begins with the esterification of ethanoic acid (vinegar-like smell) and ethanol. Two milliliters of ethanoic acid are mixed with 20 drops of ethanol in a test tube, followed by the careful addition of concentrated sulfuric acid as a catalyst. The mixture starts to heat up, and the test tube is placed in a water bath heated by a Bunsen burner to accelerate the reaction. The reaction mixture begins to bubble as the water boils. After heating, the test tube is allowed to cool down, and the esters formed in the reaction are separated using sodium carbonate.
🌫️ Observing and Describing the Ester Formation
Once the esterification reaction cools, the unreacted acid and ester are separated by adding sodium carbonate. This step causes fizzing, indicating the reaction has occurred. The mixture produces an oily layer, which is the ester. The participants describe the smell of the ester, noting that it no longer smells like vinegar but has a strong, paint-like odor. They conclude that other esters may have more pleasant aromas and encourage recording the smell as part of the experiment’s data.
🧴 Esterification Using Salicylic Acid and Methanol
In the next experiment, salicylic acid (a crystalline solid) is used as the carboxylic acid, reacting with methanol. After adding 0.5 grams of salicylic acid to a clean test tube, 3 milliliters of methanol are used to dissolve the acid. The mixture doesn’t dissolve completely, but swirling helps. Concentrated sulfuric acid is again added carefully to catalyze the reaction. As before, the test tube is placed in a water bath, heated until the reaction completes. The mixture is cooled before moving to the final stage of the experiment.
👃 Identifying the Smell of Wintergreen from the Second Ester
After the reaction cools, sodium carbonate is added to the mixture to separate the ester. This ester, formed from methanol and salicylic acid, has a pleasant odor reminiscent of wintergreen or athletic rubs used for sore muscles. The participants discuss the distinctive, refreshing smell and note it as a significant characteristic of this particular ester. The video concludes with instructions for students to complete their worksheets and record observations as part of their school assessment.
Mindmap
Keywords
💡Esterification
💡Ester
💡Catalyst
💡Concentrated Sulfuric Acid
💡Alcohol
💡Carboxylic Acid
💡Volatile
💡Safety Precautions
💡Reaction Mixture
💡Distillation
💡Fragrance
Highlights
Introduction to making esters through organic chemistry.
Esterification reaction explained: alcohol + carboxylic acid produces ester + water.
Esters are volatile and fragrant, used in perfume and deodorizing industries.
Concentrated sulfuric acid acts as a catalyst in esterification reactions.
Safety precautions when handling concentrated sulfuric acid.
Proper method for smelling chemicals in a lab to avoid direct inhalation.
Experiment starts with ethanoic acid reacting with ethanol.
Ethanoic acid smells like vinegar.
Use of a water bath to control the reaction temperature.
Observation of the reaction mixture heating up and the importance of not boiling over.
Cooling the reaction mixture before proceeding.
Separating unreacted acid and ester using sodium carbonate.
Observation of the ester as an oily layer on top of the reaction mixture.
Smelling the ester produced from ethanol and ethanoic acid.
Experiment continues with a crystalline carboxylic acid, salicylic acid.
Salicylic acid is also known as two hydro benzoic acid.
Method for reacting a solid acid with methanol.
Observation of the reaction with salicylic acid producing a pleasant odor.
Final steps include cooling and adding dilute sodium carbonate to the reaction mixture.
Smelling the ester produced from methanol and salicylic acid, which has a pleasant odor.
Assignment details for students to complete the worksheet independently.
Conclusion and encouragement for students to succeed in their experiment.
Transcripts
[Music]
[Music]
[Music]
hydrate twelve I'm John McBride and I'm
joy sparkles today we are putting
organic chemistry into practice we are
making esters oh yes although you won't
be able to smell these freaking
compounds you will be able to see the
process of making them in small
quantities the reaction between an
alcohol and a carboxylic acid produces
an ester and water we call this type of
reaction esterification esters are
fragrant substances that are volatile
and they have low boiling points many
esters have beautiful aromas in fact
esterification reactions are used in the
perfume and deodorizing industry to
manufacture artificial fragrances the
reaction of a carboxylic acid and
alcohol to produce an ester is speeded
up by the presence of concentrated
sulfuric acid sulfuric acid acts as a
catalyst in the reaction a catalyst is a
substance which speeds up the rate of
reaction without being chemically
changed during the reaction so at the
end of the reaction between an alcohol
and the carboxylic acid sulfuric acid is
still present in the reaction mixture
and this is a point worth noting because
concentrated sulfuric acid must be
handled with care
concentrated sulphuric acid is a
powerful dehydrating agent and it's
corrosive it can cause severe chemical
burns if it comes in contact with your
skin we will wear gloves and safety
goggles let's put those on now okay
[Music]
looking cool today we use ethanol and
methanol as our alcohols and ethanoic
acid and salicylic acid as our
carboxylic acid as you can see all of
these substances are liquid except for
salicylic acid which is a crystalline
solid there is one very important
precaution which you need to take very
seriously never smell any chemicals by
putting them under your nose and then
sniffing many substances and specially
organic substances give off very
poisonous and toxic fumes ethanol is a
case in point the ethanol that is used
in a chemical laboratory is 99% pure
alcohol its fumes are so toxic that you
could lose your sight permanently if you
gave it a direct sniff so we walked the
odor of the substance gently towards us
and take a sniff of the fragrance right
we are ready to make the first esters we
are using ethanoic acid reacting with
ethanol in this first investigation
right let's get our test tube ready and
we're going to add 2 mils of ethanoic
acid to this test tube thanks Joyce
using the prepare there we go beautiful
now ethanoic acid smells just like
vinegar that's important to take note
next we're going to take 20 drops of
ethanol it's about 2 mils of the ethanol
into the test tube and away we go let's
swirl it around there we've got our
carboxylic acid and alcohol you need to
add our catalyst the catalyst is
concentrated sulfuric acid so we need to
work very carefully now so only two or
three drops of concentrated sulfuric
acid
going to run it down the side of the
test tube and hopefully that will get
the reaction going there its sliding
down it's one drop
lovely lovely swirl it it doesn't look
like much is happening but this mixture
is starting to get hot I'm going to rest
it in the test tube in this beaker over
here for a moment while we get our water
bath ready
so we've already added about 10 moles of
water into this beaker and we're going
to now take our test tube with our
reaction mixture and place it into that
beaker it's time to light the Bunsen
burner and get the heat going
[Music]
now we put the beaker on the gooseneck
and we heat the water until it boils
[Music]
we're gaining some bubbles inside the
reaction vessel and the water looks like
it's almost boiling there we go
water's boiling turning off the Bunsen
flame I'm going to let it cool down for
a minute while it stands on the gauze
mat here the reaction is going quite
nicely be very careful at this stage if
the contents of the test ship starts to
boil take the test trip out of the hot
water and let it cool down slightly
before returning it to the hot water
[Music]
after about a minute in the hot water we
take the test tube out of the hot water
and put it into a empty beaker to cool
down
[Music]
now the reaction mixture is cool and so
we are ready to do the last part of the
experiment we need to separate the
unreacted acid and the ester that's in
here and the unreacted alcohol this is
the last part of the process so Joyce
won't you break some sodium carbonate
from there
yeah fill the beaker with sodium
carbonate looking beautiful and now
we're going to get some reaction let's
see what happens just slowly slowly add
the reaction mixture to sodium carbonate
look what's happening
that fizzing stuff is an important thing
to take note of and you know a choice I
can already smell something happening
here the layer of oily substance
floating on the top is the ester have a
waft in this mixture it doesn't smell
like vinegar does it not at all hmm
remember that in any laboratory
chemicals are smelled by a wafting the
order to watch the nose with their hand
like like this Oh beautiful beautiful
now you never put your nose over the
reaction mixture when you smell anything
this particular mixture mmm I can't
quite place it but it certainly doesn't
smell of vinegar what do you feel what
do you think it smells like I think it
smells like enamel paint paint finish
that's it yeah yeah oh no it's not very
pleasant I think we should find another
more pleasant smelling actually yeah
good it's a very distinctive smell but
I'm sure there are other esters that
have a much better smell before that
lenez you should record the fragrance of
this as deformed by the reaction of
ethanol and ethanoic acid later on you
can complete the other questions on the
worksheet but meanwhile we are moving on
to prepare another step
[Music]
this time we use a crystalline
carboxylic acid and reacted with
methanol salicylic acid is a crystalline
solid it's are you pack name is two
hydro benzoic acid here is its chemical
formula
[Music]
when we work with a solid asset we need
to change our method slightly of course
we first start with a dry clean tissue
here it is we have measured 0.5 grams of
salicylic acid to use in this reaction
so we'll add the silly silly s it to the
test shoot I tell you what let's take
some of the methanol and let's rinse it
out out the rest of the acid there so
take 3 moles of the methanol add it to
the boiling tube there we go
shake it around now make sure that it
follows down so we can get all of that
stuff that's it beautiful lovely okay
you'll see that the acid hasn't totally
dissolved but I'm swirling it more or
less dissolved alright what should we do
next choice finally we add the catalyst
we carefully add a few drops of
concentrated sulfuric acid to the
mixture dripping it down the sides of
the test tube here we go it's one drop
two drops and another one to make sure
everything reacts
a couple of bubbles there it looks like
it might even be reacting sulfuric acid
heats up when we add two other liquids
like alcohol or acid the increase in
temperature helps speed up the reaction
rate right the water bath is ready
John please put the test ship in the
water and let's keep the mixture now
we're lighting the Bunsen burner and
there we go
[Music]
okay the water's starting to boil so
we're going to turn off the bouncing
burner but we're going to keep the
reaction mixture in the hot water watch
carefully
so it doesn't over boil okay it's been
about a minute that the reaction
mixtures been in the hot water we're
going to take it out and put it in a
empty beaker and allow it to cool for a
little while right let's check this
reaction mixture is cooled down nicely
so let's get ready let's add dilute
sodium carbonate in here and now I'm
going to pour in the reaction mixture
oh isn't that great right
Lester bit no choice there's no need to
let it stand for a short while I can
smell something have a waft
what phrase mister has a very
distinctive smell you know what it
reminds me of athletes the change room
is the one that we used to treat sore
muscles that's right as well as sprint
angles that's right
it's called wintergreen this is a very
pleasant odor
Nonna's record the fragrance of this
ester formed by the reaction of methanol
and salicylic acid it is now time for
you to answer the questions in your
worksheet the work is set for you to
tackle by yourself without any help or
discussion with your peers alright
remember to hand in the completed
worksheet to teacher before you leave
the classroom this assignment forms part
of your school based assessment from the
trip right learners it's over to you now
we wish you all the success in
completing this top
[Music]
you
تصفح المزيد من مقاطع الفيديو ذات الصلة
5.0 / 5 (0 votes)