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Chemistry: Post your doubts here!

Xaptor16

Xaptor16

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nehaoscar said:
Ok so i know the fehling's and tollens tests and what results you get and all
but i need what the actual reaction takes place
like sometimes it asks you to write the product that is formed with the reaction with fehlings and tollens
So can someone give me a example please and state what the product would be? :)
Click to expand...
so you should know that only aldehydes react with Fehling's and Tollen's reagent. what happens it that the aldehyde is oxidized to carboxylic acid in both cases. In case of Tollen's reagent, the Ag+ ions act as a mild oxidizing agent and oxidize the aldehyde, and reduce themselves to Ag atoms, which form the silver mirror. so if they say what will be the product when CH3CH2CHO reacts with tollen's reagent, it'll be CH3CH2COOH. same goes for fehling's reagent. the Cu2+ ions act as a mild oxidizing agent and oxidize the aldehyde to a carboxylic acid, and reduce themselves to Cu+ ions, giving the orange color as a precipitate of copper (I) oxide forms.
please do correct me if I've got anything wrong :)
 
Metanoia

Metanoia

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Midnight dream said:
thnkss.. but i was actually asking whether H2 with platinium catalyst reduce the aldehyde or not?
i know NaBH4 will do it..:)
Click to expand...
Yes. H2 will reduce ketone and aldehyde, not sure why the ms says otherwise.

nehaoscar said:
Ok so i know the fehling's and tollens tests and what results you get and all
but i need what the actual reaction takes place
like sometimes it asks you to write the product that is formed with the reaction with fehlings and tollens
So can someone give me a example please and state what the product would be? :)
Click to expand...

You'll get the carboxylate salt RCOO- with Cu2O (red brown ppt) for Fehlings.
And carboxylate salt with Ag ( silver mirror) with Tollens.
 
Lola_sweet

Lola_sweet

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wht are the products formed when a i) Ketone ii) Carboxylic Acid
reacts with LiAlH4 in dry ether

One is the alcohol ofc as its a reducing agent
but do i need to knw other products?
 
nehaoscar

nehaoscar

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Xaptor16 said:
so you should know that only aldehydes react with Fehling's and Tollen's reagent. what happens it that the aldehyde is oxidized to carboxylic acid in both cases. In case of Tollen's reagent, the Ag+ ions act as a mild oxidizing agent and oxidize the aldehyde, and reduce themselves to Ag atoms, which form the silver mirror. so if they say what will be the product when CH3CH2CHO reacts with tollen's reagent, it'll be CH3CH2COOH. same goes for fehling's reagent. the Cu2+ ions act as a mild oxidizing agent and oxidize the aldehyde to a carboxylic acid, and reduce themselves to Cu+ ions, giving the orange color as a precipitate of copper (I) oxide forms.
please do correct me if I've got anything wrong :)
Click to expand...
Metanoia said:
Yes. H2 will reduce ketone and aldehyde, not sure why the ms says otherwise.



You'll get the carboxylate salt RCOO- with Cu2O (red brown ppt) for Fehlings.
And carboxylate salt with Ag ( silver mirror) with Tollens.
Click to expand...
Thanks to both of you!
 
S

Studydayandnight

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After Y, when concentrated. H2SO4, is added why is the OH group removed? Why not the COOH? :s because the formula that I came up with is: CH2=CHCH(OH)CO2H
 

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qwertypoiu

qwertypoiu

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Studydayandnight said:
After Y, when concentrated. H2SO4, is added why is the OH group removed? Why not the COOH? :s because the formula that I came up with is: CH2=CHCH(OH)CO2H
Click to expand...
This is dehydration of alcohol. OH group must be removed, along with H from a carbon next-door
 
S

Studydayandnight

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When a mixture of ethanal and propanal is reacted under the same conditions as in step I above, a similar reaction occurs with the formation of compound S, C5H10O2.

CH3CHO + CH3CH2CHO ----> C5H10O
Suggest a structural formula for S.

http://www.franklychemistry.co.uk/GCE_Papers/CIE/2009/June/9701_s09_qp_2.pdf

It's the fifth question in the second variant.

I need the structure because the answer isn't there in the mark scheme for this last part.
 
asadalam

asadalam

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Studydayandnight said:
When a mixture of ethanal and propanal is reacted under the same conditions as in step I above, a similar reaction occurs with the formation of compound S, C5H10O2.

CH3CHO + CH3CH2CHO ----> C5H10O
Suggest a structural formula for S.

http://www.franklychemistry.co.uk/GCE_Papers/CIE/2009/June/9701_s09_qp_2.pdf

It's the fifth question in the second variant.

I need the structure because the answer isn't there in the mark scheme for this last part.
Click to expand...
The ans is given in the ms:

CH3CH2CH(OH)CH2CHO
or
CH3CH(OH)CH(CH3)CHO
allow
CH3CH(OH)CH2CH2CHO
 
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