Test for Carboxylic Acids

Summary

This educational video explores carboxylic acids, organic compounds found in citrus fruits and vinegar, and demonstrates various tests to identify them. It categorizes acids into aliphatic and aromatic, showcasing examples like formic, acetic, benzoic, citric, and tartaric acids. The video conducts tests including the litmus test, sodium bicarbonate reaction, ester formation, and a fluorescein test specific to dicarboxylic acids. It also acknowledges the support of Patreon backers in facilitating these experiments.

Takeaways

• 🔬 Carboxylic acids are organic compounds with the COOH functional group.
• 🍇 Carboxylic acids occur naturally in citrus fruits like grapes and green apples.
• 🧪 Vinegar is a dilute solution of acetic acid, which is a type of carboxylic acid.
• 📦 The video presents samples of carboxylic acids, including formic acid and acetic acid.
• 🌿 Aromatic carboxylic acids like benzoic acid are also discussed, with a link to a synthesis video in the description.
• 🍊 Citric acid is highlighted as commonly found in grocery stores, and tartaric acid is noted in tamarind fruit.
• 🧪 The litmus test is demonstrated to show the acidic property of carboxylic acids, turning blue litmus paper red.
• ⚗️ The sodium bicarbonate test produces a carboxylate salt and carbon dioxide, observed as effervescence.
• 🍸 The ester test involves a reaction between carboxylic acid and alcohol to produce esters with a fruity smell.
• 🌈 The fluorescein test is a special confirmatory test for dicarboxylic acids, resulting in a red color and green fluorescence under UV light.
• 🙏 The video creator thanks their Patreon supporters for helping to fund the materials needed for these experiments.

Q & A

What are carboxylic acids?

Carboxylic acids are organic compounds characterized by the presence of the -COOH functional group. They occur naturally in citrus fruits and are exemplified by acetic acid found in vinegar.

How are carboxylic acids classified?

Carboxylic acids are classified into aliphatic and aromatic acids based on their structure.

What is the difference between aliphatic and aromatic carboxylic acids?

Aliphatic carboxylic acids are those with an open chain structure, like formic and acetic acids. Aromatic carboxylic acids have a benzene ring in their structure, such as benzoic acid.

What is the purpose of the litmus test in the context of carboxylic acids?

The litmus test is used to demonstrate the acidic property of carboxylic acids. When carboxylic acid is dropped onto blue litmus paper, it turns red.

How does the sodium bicarbonate test work with carboxylic acids?

In the sodium bicarbonate test, carboxylic acids react with sodium bicarbonate to produce a carboxylate salt and release carbon dioxide, which is observed as effervescence.

What is the ester test and how is it performed?

The ester test involves reacting a carboxylic acid with an alcohol in the presence of concentrated sulfuric acid and heat to produce an ester, which has a fruity smell. This is done by mixing the acid with alcohol, adding sulfuric acid, and then heating the mixture.

What is the purpose of the fluorescein test for carboxylic acids?

The fluorescein test is a confirmatory test for dicarboxylic acids. It involves the reaction of the dicarboxylic acid with resorcinol and concentrated sulfuric acid to form fluorescein, which shows green fluorescence under ultraviolet light.

Why is the fluorescein test specific to dicarboxylic acids?

The fluorescein test is specific to dicarboxylic acids because it relies on the reaction of two carboxylic acid groups with resorcinol to form the fluorescent compound fluorescein.

What precautions are taken during the ester test?

During the ester test, the mixture is not directly sniffed to avoid inhaling the volatile compounds. Instead, the air above the beaker is gently wafted towards the nose to detect the fruity smell.

How is the alkalinity of the solution checked after the fluorescein test?

The alkalinity of the solution after the fluorescein test is checked using red litmus paper, which turns blue in an alkaline solution.

What is the final observation when testing for fluorescein under normal white light?

Under normal white light, the presence of fluorescein shows a green fluorescence in the reflected light, and the transmitted light appears deep red.

Outlines

00:00

🧪 Chemistry of Carboxylic Acids

The script introduces carboxylic acids, organic compounds with the COOH functional group, found in nature like citrus fruits and vinegar. It explains the division into aliphatic and aromatic acids and presents examples such as formic, acetic, benzoic, citric, and tartaric acids. The video demonstrates various tests for carboxylic acids, including the litmus test, which turns blue litmus paper red, indicating acidity; the sodium bicarbonate test, where the acid reacts to produce a carboxylate salt and releases carbon dioxide; and the ester test, where the acid reacts with alcohol to form esters with a fruity smell. A special test for dicarboxylic acids, the fluorescein test, is also mentioned.

05:00

🔬 Testing Carboxylic Acids: The Fluorescein Test

The script details the fluorescein test for dicarboxylic acids, using phthalic acid as an example. It describes the process of dehydrating phthalic acid with sulfuric acid to form phthalic anhydride, which then reacts with resorcinol to produce fluorescein. The test involves adding sodium hydroxide to make the solution alkaline, which is confirmed by the change of red litmus paper to blue. The presence of fluorescein is indicated by green fluorescence under normal light and deep red transmitted light. The script concludes with a demonstration of fluorescein's bright green fluorescence under ultraviolet light, confirming the presence of dicarboxylic acids.

Keywords

💡Carboxylic Acids

Carboxylic acids are organic compounds characterized by the presence of a carboxyl functional group (-COOH). They are found naturally in various fruits and are the main component of vinegar. In the video, the focus is on demonstrating tests for carboxylic acids, highlighting their reactivity and properties. Examples given include formic acid, acetic acid, and benzoic acid.

💡Functional Group

A functional group is a specific group of atoms within a molecule that is responsible for the characteristic chemical reactions of that molecule. In the context of the video, the carboxyl group (-COOH) is the functional group that defines carboxylic acids and influences their acidic properties.

💡Aliphatic Acids

Aliphatic acids are carboxylic acids with open-chain structures, meaning they do not have a benzene ring. The video script mentions formic and acetic acids as examples of aliphatic carboxylic acids.

💡Aromatic Acids

Aromatic acids are carboxylic acids that contain a benzene ring in their structure. Benzoic acid is given as an example in the script, highlighting the diversity of carboxylic acids.

💡Acetic Acid

Acetic acid is a specific type of carboxylic acid and is the main component of vinegar. It is mentioned in the script as an example of a naturally occurring carboxylic acid and is used in the sodium bicarbonate test to demonstrate its acidic properties.

💡Litmus Test

The litmus test is a simple chemical test used to determine the acidity or alkalinity of a solution. In the video, the litmus test is used to demonstrate the acidic nature of carboxylic acids by turning blue litmus paper red.

💡Sodium Bicarbonate Test

This test involves reacting a carboxylic acid with sodium bicarbonate to produce a carboxylate salt and carbon dioxide, which is observed as effervescence. The script describes this test to show the reactivity of carboxylic acids.

💡Ester Test

The ester test is used to demonstrate the formation of esters, which are fruity-smelling compounds. In the video, carboxylic acids react with alcohol in the presence of concentrated sulfuric acid and are heated to produce esters, showcasing the esterification reaction.

💡Fluorescein Test

The fluorescein test is a specific test for dicarboxylic acids, which have two carboxyl functional groups. It involves a series of reactions that result in the formation of fluorescein, which emits green fluorescence under ultraviolet light. The script describes this test using phthalic acid as an example.

💡Resorcinol

Resorcinol is an organic compound used in the fluorescein test to react with phthalic anhydride, formed from脱水phthalic acid in the presence of concentrated sulfuric acid, to produce fluorescein. The script mentions resorcinol as part of the procedure for the fluorescein test.

💡Phthalic Acid

Phthalic acid is a dicarboxylic acid used in the fluorescein test as a substrate to demonstrate the formation of fluorescein. It is mentioned in the script as the starting material for the test.

Highlights

Carboxylic acids are organic compounds with the COOH functional group.

Carboxylic acids occur naturally in citrus fruits like grapes and green apples.

Vinegar is a dilute solution of acetic acid, which is a type of carboxylic acid.

Carboxylic acids can be subdivided into aliphatic and aromatic acids.

Formic acid and acetic acid are examples of aliphatic carboxylic acids.

Benzoic acid is the simplest aromatic carboxylic acid.

Citric acid is commonly found in grocery stores.

Tartaric acid is found in fruits like tamarind.

Heparic acid is excreted through urine with increased consumption of phenolic products.

The litmus test is used to demonstrate the acidic property of carboxylic acids.

Sodium bicarbonate test produces carboxylate salt and carbon dioxide from carboxylic acids.

Ester test involves the reaction of carboxylic acid with alcohol to produce esters.

Fluorescein test is specific for dicarboxylic acids.

Phthalic acid is used in the fluorescein test to confirm the presence of dicarboxylic acids.

Resorcinol is used in the fluorescein test along with concentrated sulfuric acid.

Fluorescein is formed by the reaction of phthalic anhydride with resorcinol.

The fluorescein test solution turns alkaline, indicated by blue litmus paper.

Fluorescein exhibits green fluorescence under normal white light and deep red transmitted light.

Under ultraviolet light, fluorescein shows bright green fluorescence.

The video acknowledges Patreon supporters for their financial contributions to the experiments.

Transcripts

[Music]

the following video is for academic

purposes only

it demonstrates the various tests for

carboxylic

acids

carboxylic acids are organic compounds

with the cooh

functional group they occur naturally in

citrus fruits

like grapes and green apple vinegar is a

dilute solution of acetic acid which is

also a carboxylic acid

here we have few samples of carboxylic

acids

they can be subdivided into aliphatic

and aromatic acids

here i have formic acid in this beaker

and in the glass bottle i have acetic

acid

now for some aromatic carboxylic acids

the simplest one is the benzoic acid

and i have a synthesis video of benzoic

acid you can check the

description for the link and this is

citric acid

citric acid is commonly available in

grocery stores

this is tartaric acid tartaric acid is

seen plenty in the fruit

tamarind and this is heparic acid which

is normally excreted through urine when

you have an increased consumption of

phenolic products like

fruit juices and wine these are the

various tests for the carboxylic acid

the litmus test sodium bicarbonate test

ester test and fluorescein test which is

specific for dicarboxylic acids that are

compounds with 2coh functional group

let's start with the litmus test

when carboxylic acid is dropped on a

blue litmus paper

it turns red it indicates that the

compound have acidic property

sodium hydrogen carbonate or sodium

bicarbonate test

we have taken three milliliters of

saturated solution of sodium hydrogen

carbonate in the test tube

into that we add few milliliters of the

carboxylic acid

carboxylic acid behave like any other

acid

producing the specific carboxylate salt

and carbon dioxide is released which is

observed as the

brisk effervescence

the next test is the ester test

for that we take a clean and dry test

tube

and into that we add one milliliter of

the carboxylic acid

then i add equal volume that is one ml

of ethyl alcohol then we mix the

compounds by shaking

now add three to four drops of

concentrated

sulphuric acid into the test tube and

mix the test tube well

now we place the test tube in hot water

bath

for few minutes what's happening here is

carboxylic acid reacts with alcohol

in acidic medium to produce fruity

smelling compounds called esters

the contents of the test tube is then

poured into 30 milliliters of cold

distilled water the fruity smell of a

stir could be identified by gently

wafting the air from the beaker to the

nose

do not directly put your nose in the

beaker

now for the special test there is the

fluorescent test which is a confirmatory

test for dicarboxylic acids like talic

acid and succinic acid

for this test i am using phthalic acid

we need hundred milligram of phthalic

acid

200 milligram of resource in all three

dots of concentrated sulphuric acid

and hundred milliliter of five molar

sodium hydroxide

we start by taking a clean and dry test

tube and then we add hundred milligrams

of phthalic

acid

next we add 200 milligrams of resource

in all

the amount of resulcinol should be

roughly double the amount of phthalic

acid sociometrically

after that we shake the contents to mix

them evenly

now we add three drops of concentrated

sulphuric acid over it

do not add too much of acid

now we gently heat the chest tube over

the bunsen burner flame

the compound melts and attains a deep

red color

what's happening here is stalic acid

gets dehydrated by the presence of

sulfuric acid to form phthalic

anhydride which then reacts with

resource synol to form fluorescein

now pour the contents to 5 molar sodium

hydroxide solution

i tried to pour my contents but it

immediately got solidified

so instead i added sodium hydroxide into

the test tube

either way we want the resultant

solution to be alkaline

we can test whether our resultant

solution is alkaline or not by using a

red litmus paper

and in this case it is alkaline as it

turned blue now this solution has a high

concentration of fluorescein in it

now to test the presence of fluorescein

on passing the normal white light

the reflected light shows a green

fluorescence and the transmitted light

is deep red in color

in the presence of ultraviolet right add

some fluorescein into distilled water

and observe the bright

green fluorescence by this we conclude

the test for carboxylic acids

i would like to take this opportunity to

thank my patreon supporters who have

financially supported me

so that i could get the materials

required for doing all these experiments

thank you so much for watching this

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video

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