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Topic: Reactions of aldehydes and ketones with sodium hydroxide  (Read 21656 times)

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Offline highflier

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Reactions of aldehydes and ketones with sodium hydroxide
« on: January 08, 2011, 05:14:35 AM »
1.)  What is the principle involved, type equation, sample equation, and brief explanation involved in adding drops of FORMALDEHYDE, BENZALDEHYDE, ACETALDEHYDE and ACETONE to SODIUM HYDROXIDE?

2.) A test tube with 2ml of 40% NaOH solution is added with 5 drops of bezaldehyde then  submerging this tube in a water bath for 10 mins. upon removing it in water bath, we acidified it with 6N HCl.

What is the purpose of acidification of a sample with HCl?

Anyone please answer me you may submit LINKS, or anything :'( THANK YOU!
I would be grateful if you can answer atleast one of my questions  :)

« Last Edit: January 03, 2012, 06:54:51 AM by Dan »

Offline StuffedMatt

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Re: Reactions of aldehydes and ketones with sodium hydroxide
« Reply #1 on: January 08, 2011, 10:21:51 AM »
We have the same problem. :/ From what section are you?
« Last Edit: January 03, 2012, 06:55:09 AM by Dan »

Offline discodermolide

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Re: Reactions of aldehydes and ketones with sodium hydroxide
« Reply #2 on: January 08, 2011, 10:27:15 AM »
1.)  What is the principle involved, type equation, sample equation, and brief explanation involved in adding drops of FORMALDEHYDE, BENZALDEHYDE, ACETALDEHYDE and ACETONE to SODIUM HYDROXIDE?

2.) A test tube with 2ml of 40% NaOH solution is added with 5 drops of bezaldehyde then  submerging this tube in a water bath for 10 mins. upon removing it in water bath, we acidified it with 6N HCl.

What is the purpose of acidification of a sample with HCl?

Anyone please answer me you may submit LINKS, or anything :'( THANK YOU!
I would be grateful if you can answer atleast one of my questions  :)

Look up the Canizzaro reaction and the aldol reaction.
in question 2; HCl is used to neutralise the excess base and re-protonate one of the products.


« Last Edit: January 03, 2012, 02:21:59 PM by Dan »
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Offline highflier

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Re: Reactions of aldehydes and ketones with sodium hydroxide
« Reply #3 on: January 08, 2011, 09:01:09 PM »
Look up the Canizzaro reaction and the aldol reaction.
in question 2; HCl is used to neutralise the excess base and re-protonate one of the products.

THANKS SIR.  :)
« Last Edit: January 03, 2012, 06:55:41 AM by Dan »

Offline Zwrei

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Re: Reactions of aldehydes and ketones with sodium hydroxide
« Reply #4 on: January 03, 2012, 06:31:36 AM »
Guys, I still can't understand this. I'm sorry but can someone please answer this questions for me? It can only be an idea or something. I'll appreciate that. :)
« Last Edit: January 03, 2012, 06:56:02 AM by Dan »

Offline discodermolide

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Re: Reactions of aldehydes and ketones with sodium hydroxide
« Reply #5 on: January 03, 2012, 06:59:00 AM »
Guys, I still can't understand this. I'm sorry but can someone please answer this questions for me? It can only be an idea or something. I'll appreciate that. :)

Look at the answer above:

http://www.chemicalforums.com/index.php?topic=46051.0

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Offline orgopete

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Re: Reactions of aldehydes and ketones with sodium hydroxide
« Reply #6 on: January 03, 2012, 03:10:23 PM »
Deleted, I misunderstood question.
Author of a multi-tiered example based workbook for learning organic chemistry mechanisms.

Offline selym2

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Re: Reactions of aldehydes and ketones with sodium hydroxide
« Reply #7 on: December 29, 2012, 06:59:34 AM »
I have the same problem too, can anyone please help me  :(

Offline discodermolide

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Re: Reactions of aldehydes and ketones with sodium hydroxide
« Reply #8 on: December 29, 2012, 08:46:13 AM »
Read the thread above!
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Offline selym2

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Re: Reactions of aldehydes and ketones with sodium hydroxide
« Reply #9 on: December 30, 2012, 09:12:17 AM »
E. Reactions of the Aldehydes and Ketones with Sodium Hydroxide

Objective:

•   To determined what physical and chemical changes happen to Aldehydes and Ketones as it react with the Sodium Hydroxide

Procedures:

1.   Prepare 5 clean and dry test tubes
2.   Label the first 3 tubes and place 2 ml 40% NaOH solution
3.   Label the remaining test tubes 4 and 5 and place 2 ml of 10% NaOH solution
4.   Transfer 10 drops of the following samples: tube 1- formaldehyde, tube 2- benzaldehyde, tube 3 & 4 acetaldehyde and in tube 5 acetone
5.   Transfer all tubes in a boiling water bath for 10 minutes: Note for the following changes:
6.   Place some 6N HCl in tube 2 after acidification
7.   Record all of your observation

Results:

Tube Sample   NaOH   Observations
Formaldehyde   40%   Foul smell
Benzaldehyde   40%   White precipitate, yellow oil on the surface of the solution
Acetaldehyde   40%   Dark Orange solution with dark resin
Acetaldehyde   10%   Orange Solution with red Precipitate
Acetone   10%   Viscous colorless Solution

Interpretation of Results:

After adding
Reagents used:

•   Sodium Hydroxide solution
•   HCl


a.)   State the function of the sodium hydroxide in the test

b.)   What are the principles involved in the test? What is its purpose

•   Cannizzaro reaction is a redox reaction in which two molecules of an aldehyde are reacted to produce a primary alcohol and a carboxylic acid using a hydroxide base. It involves a reaction with aldehydes which have no alpha hydrogen atoms

Aldol Condesation is an organic reaction in whichan enolate ion reacts with a carbonyl compound to form a β-hydroxyaldehyde or β-hydroxyketone, followed by dehydration to give a conjugated enone
•   
c.)   Provide the type equation used in the test

d.)   Show the sample equations involved in the reaction between:

•   40% Sodium Hydroxide and your samples which gave a positive result
•   10% Sodium Hydroxide and your samples which gave a positive result

e.)   Provide a possible explanation for

•   Positive result obtained with your sample


•   Negative results obtained with your samples

f.)   What is the purpose of acidification with HCL

HCl is used to neutralize the excess base and to re-protonate one of the products

please answer the following, im begging all of you.please don't ignore this.  :'(  :'(

Offline discodermolide

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Re: Reactions of aldehydes and ketones with sodium hydroxide
« Reply #10 on: December 30, 2012, 10:02:29 AM »
Why should we do all the work for you?
Forum rules state you must show your own attempt.
I suggest you start with one question at a time, otherwise the whole thing will get very confusing.
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