NECT Gr 12 Making Esters

Summary

In 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

00:00

🧪 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.

05:02

⚗️ 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.

10:07

🌫️ 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.

Keywords

💡Esterification

Esterification is a chemical reaction that produces an ester and water from an alcohol and a carboxylic acid. It is a key process in organic chemistry and is central to the video's theme of demonstrating how esters are made. In the script, esterification is the main reaction being performed, with examples including the reaction between ethanoic acid and ethanol to produce an ester.

💡Ester

An ester is an organic compound that is formed by the reaction of an acid and an alcohol. They are characterized by a sweet or fruity smell and are often used in perfumes and deodorizers. In the video, esters are the desired products of the esterification reaction, and the script describes their properties and uses.

💡Catalyst

A catalyst is a substance that increases the rate of a chemical reaction without being consumed in the process. In the context of the video, concentrated sulfuric acid acts as a catalyst for the esterification reaction, speeding up the process without being chemically changed. The script emphasizes the importance of using a catalyst and the need for careful handling of sulfuric acid.

💡Concentrated Sulfuric Acid

Concentrated sulfuric acid is a highly corrosive and dehydrating chemical used as a catalyst in the esterification reaction. The script describes its role in the reaction and the precautions that need to be taken when handling it, such as wearing gloves and safety goggles.

💡Alcohol

In the context of organic chemistry, alcohols are organic compounds with one or more hydroxyl (-OH) groups. Ethanol and methanol are used as alcohols in the video's esterification reactions. The script mentions their use and the process of adding them to the reaction mixture.

💡Carboxylic Acid

A carboxylic acid is an organic compound containing a carboxyl group (-COOH). In the video, ethanoic acid and salicylic acid are used as carboxylic acids in the esterification process. The script describes their role in the reaction and how they react with alcohols to form esters.

💡Volatile

Volatile substances are those that easily vaporize or evaporate. In the script, esters are described as volatile compounds with low boiling points, which contributes to their use in fragrances and deodorizers.

💡Safety Precautions

Safety precautions are measures taken to prevent harm or accidents in a laboratory setting. The script emphasizes the importance of safety when handling chemicals, such as smelling substances by wafting rather than directly sniffing, and wearing appropriate protective gear.

💡Reaction Mixture

A reaction mixture is a combination of substances that are undergoing a chemical reaction. In the video, the reaction mixture consists of an alcohol, a carboxylic acid, and a catalyst. The script describes the process of preparing and observing the reaction mixture during the esterification process.

💡Distillation

Distillation is a process used to separate components of a mixture based on differences in their boiling points. In the script, distillation is not directly mentioned, but the concept is implied when separating the ester from the reaction mixture by cooling and adding sodium carbonate.

💡Fragrance

Fragrance refers to the pleasant or distinctive smell of a substance. The script discusses how esters, which are the products of the esterification reaction, are used to create artificial fragrances in the perfume and deodorizing industry.

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

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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

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now we put the beaker on the gooseneck

and we heat the water until it boils

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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

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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

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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

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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

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you