Aldehyde & Ketone Reactions Experiment

Summary

This educational video script details a chemistry experiment exploring the reactions of aldehydes and ketones with Tollens' reagent and iodine. The presenter demonstrates the preparation of Tollens' reagent and its application to various compounds, expecting a silver mirror from aldehydes and no reaction from ketones. Unexpected results with benzaldehyde lead to further investigation using sodium bisulfite. Additional experiments with enolate ions and the haloform reaction showcase the formation of precipitates and the identification of carbonyl compounds. The script provides a hands-on approach to understanding organic chemistry concepts.

Takeaways

• 🔬 The script describes a chemistry experiment involving Tollens' reagent, which is used to test for the presence of aldehydes.
• 📝 The preparation of Tollens' reagent involves mixing silver nitrate, sodium hydroxide, and ammonium hydroxide until a clear solution is obtained.
• 🧪 Five test tubes are prepared with equal amounts of the reagent, and different compounds are added to each: benzaldehyde, acetone, pentanone, formalin, and acetylaldehyde.
• 🔍 The experiment expects a silver mirror to form in the test tubes with aldehydes due to the oxidation reaction, while ketones should not react.
• 💡 The script highlights the importance of observing the reaction and the formation of a silver mirror as an indicator of a positive result for aldehydes.
• 🌡️ The experiment includes a step where a test tube with benzaldehyde is placed in warm water to check for any reaction that might have been missed.
• ⚗️ Another part of the script involves the use of sodium bisulfite and acetone to form a precipitate, which is then filtered and weighed.
• 📊 The script describes an experiment to identify enolate ions using various compounds and iodine, looking for the formation of a yellow precipitate.
• 📝 It is noted that the presence of a carbonyl group does not always result in a reaction, as seen with isopropyl alcohol which did not form a precipitate.
• 🔥 The script mentions a 'Haldol condensation' experiment where heating the mixture results in a yellow precipitate and a pungent odor.
• 📋 The importance of recording observations, such as the color of precipitates and the presence or absence of reactions, is emphasized for data documentation.

Q & A

What is the purpose of the Tollens' reagent in the experiment described in the script?

The Tollens' reagent is used to test for the presence of aldehydes. It undergoes an oxidation reaction with aldehydes to form a silver mirror on the inner surface of the test tube, indicating a positive reaction.

How is the Tollens' reagent prepared according to the script?

The Tollens' reagent is prepared by combining silver nitrate, sodium hydroxide, and ammonium hydroxide. Initially, a dark precipitate forms, which clears upon the addition of ammonium hydroxide until the solution becomes transparent.

What is the expected outcome when benzaldehyde is added to the Tollens' reagent?

Benzaldehyde, being an aldehyde, is expected to react with the Tollens' reagent and produce a silver mirror due to the oxidation reaction.

What happened with the benzaldehyde test tube in the experiment?

Contrary to expectations, the benzaldehyde did not produce a silver mirror, indicating that it did not undergo the oxidation reaction as it should have.

What was the reaction observed when formalin was added to the Tollens' reagent?

Upon the addition of formalin, which contains formaldehyde, the solution turned a dark color, indicating a reaction with the Tollens' reagent.

What is the purpose of adding sodium bisulfite to the flask after the Tollens' reagent experiment?

Sodium bisulfite is added to react with any remaining aldehydes or ketones, preventing further reactions and facilitating the observation of the precipitate formed by the reaction with acetone.

What is the expected product of the reaction between acetone and sodium bisulfite?

The reaction between acetone and sodium bisulfite is expected to form a precipitate, which is observed as cloudiness in the solution.

What is the iodine test for in the script?

The iodine test is used to identify the presence of carbonyl compounds. A yellow precipitate indicates the presence of a carbonyl group in the compound being tested.

What was the result of the iodine test for acetone?

The iodine test for acetone resulted in a yellow precipitate, confirming the presence of a carbonyl group in acetone.

What is the purpose of the halogen addition reaction (Haldol condensation) described in the script?

The halogen addition reaction, or Haldol condensation, is used to test for the presence of a carbonyl group. The formation of a yellow precipitate after heating indicates a positive result.

What odor was noticed during the halogen addition reaction?

During the halogen addition reaction, a faint almond-like odor was initially noticed, which became stronger and more pungent after heating.

Outlines

00:00

🔬 Tollens Reagent Test with Various Organic Compounds

The script describes an experiment using Tollens reagent to test various organic compounds for aldehydes, which are expected to undergo oxidation and form a silver mirror. The process begins with the preparation of Tollens reagent by mixing silver nitrate, sodium hydroxide, and ammonium hydroxide. The reagent is then divided among test tubes, each containing a different compound: benzaldehyde, acetone, pentanone, formalin, and acetylaldehyde. The expectation is that only aldehydes will react to form the silver mirror. The experiment observes immediate color changes with formalin and acetylaldehyde, but not all expected reactions occur, prompting a discussion about potential discrepancies and the importance of recording accurate observations.

05:02

🌡️ Investigating Reaction Outcomes with Warm Water and Sodium Bisulfite

This paragraph details the continuation of the chemical testing process, where the lack of reaction with benzaldehyde in Tollens reagent is addressed by placing the test tube in warm water to see if it stimulates a reaction. After confirming no reaction occurs, the script shifts to a new experiment involving the reaction of acetone with sodium bisulfite, resulting in the formation of a precipitate. The process includes cooling, adding acetone, and filtering to isolate the precipitate, which is then weighed to determine the mass of the product formed. The paragraph also includes the setup for another experiment with enolate ions using various compounds and iodine, observing precipitate formation as an indicator of a reaction.

10:05

🧪 Haldol Condensation and Precipitate Observation

The final paragraph of the script outlines the Haldol condensation process, where sodium hydroxide and another chemical component are combined, heated, and observed for precipitate formation and odor. The experiment notes the initial faint almond-like odor, which intensifies after heating, becoming more pungent. The description emphasizes the importance of careful observation and recording of both visual and olfactory outcomes, as well as the chemical reactions' results, to understand the behavior of the compounds involved.

Keywords

💡Tollens Reagent

Tollens Reagent, also known as silver ammonia solution, is a chemical reagent used in organic chemistry to test for the presence of aldehydes. In the video, it is prepared using silver nitrate, sodium hydroxide, and ammonium hydroxide. The reagent's ability to create a 'silver mirror' is a positive indication of an aldehyde's presence, as seen when it reacts with benzaldehyde and acetylaldehyde but not with ketones like acetone and pentanone.

💡Oxidation Reaction

An oxidation reaction involves the loss of electrons or an increase in oxidation state. In the context of the video, aldehydes undergo oxidation when they react with Tollens Reagent, leading to the formation of a silver mirror. The script emphasizes that ketones do not undergo this reaction, distinguishing between the reactivity of aldehydes and ketones.

💡Benzaldehyde

Benzaldehyde is an organic compound with the functional group of an aldehyde, which is characterized by a carbonyl group (C=O) bonded to a hydrogen and a benzene ring. In the video, benzaldehyde is expected to react with Tollens Reagent to form a silver mirror, indicating its aldehyde nature. However, the experiment shows no reaction, which is an anomaly that requires further investigation.

💡Acetylaldehyde

Acetylaldehyde is another aldehyde compound that contains a carbonyl group bonded to two hydrogen atoms and an ethyl group. The script describes its reaction with Tollens Reagent, resulting in a silver mirror, which confirms its aldehyde identity and reactivity in oxidation reactions.

💡Ketones

Ketones are organic compounds with a carbonyl group (C=O) bonded to two other carbon atoms. The video script explains that ketones do not react with Tollens Reagent, unlike aldehydes, showcasing the difference in reactivity between these two functional groups in organic chemistry.

💡Acetone

Acetone is a common ketone and a solvent widely used in various applications. In the video, it is tested with Tollens Reagent and does not produce a silver mirror, aligning with the general behavior of ketones. However, it is later used in an enolate ion reaction, demonstrating its versatility in different chemical contexts.

💡Enolate Ions

Enolate ions are a type of carbanion that forms when a ketone or aldehyde loses a proton to a base. In the video, reactions involving enolate ions are demonstrated using acetone and propanone (isopropyl alcohol), among others, to show the formation of precipitates with iodine, indicating the presence of enolate ions.

💡Precipitate

A precipitate is a solid that forms in a solution when it is insoluble and separates from the liquid phase. In the script, the formation of a precipitate is observed when enolate ions react with iodine, and it is used as an indicator of a successful chemical reaction.

💡Iodine

Iodine is a chemical element used in the video for its reactivity with enolate ions, leading to the formation of a yellow precipitate. The script describes adding iodine to various solutions to test for the presence of carbonyl compounds and the formation of enolate ions.

💡Sodium Bisulfite

Sodium bisulfite is a reducing agent used in the video to react with Tollens Reagent, preventing the formation of a silver mirror. This demonstrates the ability of sodium bisulfite to reduce the silver ions back to metallic silver, thus stopping the oxidation reaction.

💡Haldol Condensation

The Haldol condensation is a specific type of chemical reaction mentioned in the script, involving the combination of two components with sodium hydroxide to form a new compound. The reaction is characterized by the formation of a yellow precipitate and a pungent odor, indicating the successful formation of the desired product.

Highlights

Preparation of Tollens reagent using silver nitrate, sodium hydroxide, and ammonium hydroxide.

Dispersal of Tollens reagent into five test tubes for testing with different compounds.

Addition of benzaldehyde, acetone, pentanone, formalin, and acetyl aldehyde to the test tubes for oxidation reaction observation.

Expectation of a silver mirror in positive reactions, indicating aldehyde oxidation.

Demonstration of the Tollens reagent's ability to create a silver mirror.

Process of decanting to separate the liquid from the precipitate for cleaner testing.

Observation of immediate color change with formalin and acetyl aldehyde, indicating a reaction.

Ten-minute waiting period for reactions to occur in the test tubes.

Identification of a silver mirror in the last two test tubes with formalin and acetyl aldehyde.

Unexpected lack of reaction with benzaldehyde, despite it being an aldehyde.

Introduction of sodium bisulfite to the reaction with benzaldehyde to investigate the lack of reaction.

Weighing and recording the mass of filter paper for the subsequent precipitation reaction.

Formation of a precipitate upon addition of acetone, indicating a new product formation.

Filtration and drying of the precipitate to determine the mass of the product formed.

Description of the precipitate as white crystals resembling a tight texture.

Testing reactions of enolate ions with acetone, propanone, isopropyl alcohol, pentanone, and formalin.

Observation of yellow precipitates in some test tubes indicating the presence of carbonyl compounds.

No reaction observed in the test tube with too much iodine added, despite the presence of a carbonyl compound.

Haldol condensation experiment with sodium hydroxide and iodine, resulting in a yellow precipitate and a pungent odor.

Final assessment of the experiment's results and the importance of recording accurate data.

Transcripts

and ketone reactions the first thing I'm

going to do is I'm going to make the

tollens reagent using silver nitrate

sodium hydroxide then ammonium hydroxide

I'm going to take the stat solution once

I make it following the directions I'm

going to disperse it into five test

tubes equally and to the first test tube

I'm going to add benzaldehyde second

acetone third three pentanone fourth

formalin and the last one acetyl

aldehyde now remember on a tollens

reagent we're talking about it being an

oxidation reaction and we do know that

aldehydes undergo oxidation in this

reaction and ketones do not so we're

looking for a silver mirror when we have

a positive reaction in fact you can see

me reflecting inside of this you're not

going to make this much of a sample and

I'm not either we're going to put this

in a medium test tube but I wanted you

to see that the tollens reagent makes a

beautiful silver mirror again it's an

oxidizing reaction only aldehydes will

undergo this reaction and ketones will

not so to make this easier to see

actually doubled the recipe and right

now I have in here silver nitrate and my

sodium hydroxide I'm gonna go ahead and

mix this so I'm going to go ahead and

mix this we have a dark precipitate

going on in here and then the directions

say add just enough ammonium hydroxide

till the precipitate goes away so I'm

going to add a couple of drops

let's mix that see if it goes away not

yet been a couple more drops about five

drops there I'd say

we've got a lot of the precipitate

notice how it's going to the bottom and

then I it's much more clear at the top

I'm gonna go ahead and add about five

more drops so I don't want to put too

much in there and then I'm going to

actually transfer by decanting I'm gonna

transfer just the liquid so I'm going to

allow the solid to settle to the bottom

and then I'm gonna use a transfer

pipette and I'm gonna go ahead and put

it in this so I have a little easier

time to go ahead and put it in my test

tubes all right I'm gonna go ahead and

transfer just the liquid not to

precipitate that remained on the bottom

and this is called decanting because i

let the solids settle the bottom and i'm

only removing the liquid from the top

all right now I'm gonna go ahead and it

looks like I had almost 10 mils I'm

gonna cut about a mil into each one of

these in fact I'm using the transfer

pipette I'm using actually has a

milliliter mark on it makes it a little

easier for me to go ahead and measure

and it looks like we did good all right

I'm gonna go ahead and add a few more

drops than the directions said the

directions say to add two to three but I

have notes four five six seven to add

about seven drops so I add in my

benzaldehyde to the first one it has a

beautiful aromatic odor as we know it

benzaldehyde so I'm gonna go ahead

and mix that and then let that set I'm

gonna go ahead and add acetone three

pentanone formalin an acetyl aldehyde

and then they need to rest a bit and

we'll see what happens with our results

so I'm going to go ahead and let these

set for a little bit so they can go

ahead and process but right off the bat

I saw a big big difference on from

formalin which is a form of formaldehyde

immediately when I put in the drops it

turn this dark color and the same thing

with acetyl aldehyde these other three

we're gonna see what happens all right

it's been about ten minutes I know it's

kind of hard to see but there's actually

a bit of a silver disc to the last two

here so the four meld formalin and

acetyl aldehyde did get a silver bear I

know we have the gray in there so it's a

little hard to tell but let me know it

did have it the other two the other

three this one is benzaldehyde it should

have reacted it should have made a

silver mirror because it is now died now

these other two aren't aldehydes so they

shouldn't react and let's take a look so

neither one of them reacted so that's

good

so I'm gonna put this one in some warm

water and if we put it in warm water

we're gonna see if it's gonna help it to

actually react so I'm gonna put it in

some warm water here I'm going to let it

sit for a couple minutes and I'll come

back and we'll see if it does react or

not it's been almost ten minutes in the

warm bath nothing happened so for a day

that we're gonna have to say that

benzaldehyde had no reaction now here's

the thing we know it's supposed to

because it's now behind so that means

when you write your conclusion you need

to make sure that you include the fact

that benzaldehyde did not react but it

should have

for the edition we actually we're going

to put five mils of sodium bisulfite

inside of this flask we're gonna let it

cool for five minutes while we're

waiting for it to cool when I go ahead

and weigh the filter paper and after

it's all done we're going to be adding

five mils of acetone to it we're going

to get a precipitate and we're going to

filter it in the same way we did on our

previous experiment so I'm going to go

ahead and make sure that our balance is

tared and on our first paper and we're

going to record the mass

all right so I had this in an ice bath

for about five to seven minutes and it

actually made some crystals I guess that

was pretty cold I'm gonna go ahead and

add the five mils of acetone to this and

we're hoping for a precipitate so we

need to mix this pretty good we got a

little colder than I think it expected

let me mix this and how do we know what

a precipitate is formed what are we

looking for any bit of cloudiness now

let's take a look at this I know I'm

kind of using the test tube technique

take a look at this I'm actually forming

a precipitate see how it's cloudy that

means we have a precipitate a new

product was formed so I'm going to go

ahead and turn on the aspirator I'm

gonna get my precipitate out of here

collect it and then we're going to weigh

it and figure out how much we made

so we have some beautiful crystals here

that are going to live beyond the

filtration apparatus for a little bit

longer so it dries out a little bit more

to describe the product it produced

almost looks like white crystals almost

looks like tights so the next time I

feel will be giving you the mass to this

stuff all right here's our crystals

here's our weight I did tear out the

weight of the watch glass so you are

going to record three point one one four

four zeros fine and then don't forget to

remove the weight of the filter paper to

get the actual weight that you recovered

so we're looking at the reactions of

enolate ions and we are going to use

acetone to propanone also known as

isopropyl alcohol to pentanone three

pentanone and formaldehyde in the form

of formalin i've already added the first

part which was the three milliliters of

the 5% sodium hydroxide I'll be adding

the drops of each of these and then I'm

going to go ahead and add the iodine all

right I've already added the five drops

of each of these they go from left to

right acetone on the last soaking form

one I'm going to be adding the potassium

iodide to them mixing them and it does

say that some of them might take a

little bit more milliliters so we'll go

ahead and see what happens on that

alright I'm adding iodine to the first

one I'm already seeing a precipitate

there let's go ahead and mix this up I

see a yellow precipitate for the first

one let me add a few drops to iodine

here this is the second one this is the

isopropyl alcohol or propanol the color

I do have a little bit of yellow in that

ones this one is the two pentanone I'm

seeing a yellow precipitate in that one

this is the one that it said it might

take a few more milliliters because we

do know that this one definitely has a

carbonyl compound in it so I'm just

gonna add quite a bit like that up

what color of iodine is still there we

need the pillar of iodine to not be

there we actually have no precipitating

this one it's a little bit more I'm

seeing the yellow remember it said it

could take about a few minutes

hope I didn't add too much there is

definitely there actually I had done I

think I went too far so we're gonna call

that a no reaction we saw that one step

at which it was no reaction I

accidentally added too much the rest of

these needed about five drops I would

say this one is formal in formaldehyde

to mix really well the color iodine is

gone I do not see any precipitate I want

to double check by making sure that it

enough because it does have a carbonyl

group but it looks like this one is not

going to react so we're looking for a

yellow precipitate so our results our

acetone did give us a yellow precipitate

bring them closer that is not closer

there we go

our first one acetone did give us a

yellow precipitate the second one

isopropyl did it does not have a

carbonyl compound so we need to take

note of that our third one which is to

pension oh did give us yellow

precipitate remember I'd added too much

iodine to this to check it but at that

one point we saw it had no reaction so

we're gonna call this no reaction and

also our last one no reaction so that's

how you're going to record your data

it's time for the Haldol condensation

I've already added one mil of 5% sodium

hydroxide to my beaker I'm going to be

adding the three mils of the 18% to the

beaker and then I'm going to shake it

I'm going to notice the odor and then

boil it for three minutes and then we'll

be back so after adding both components

there's no precipitate let's go ahead

and heat it up so I did take notice of

the odor it has a very faint I would say

almost almond odor to it so we're going

to go ahead and heat this up and we'll

see what happens

alright it's been three minutes

definitely have a yellow precipitate let

me whack this and see if we have a

pungent odor so it does have a stronger

odor and I would say it is not as

pleasant as the almond and the idea

behind the word pungent means it's not

as desirable of an odor so go ahead and

say it I would say a medium pungent odor

wasn't real harsh and it wasn't mild the

almond oh the very beginning was a very

mild background :

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