yousefshah77
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I've been confused on this question, the answer is A but I don't understand why ? :

A compound, Q, gives an orange precipitate with 2,4dinitrophenylhydrazine.
Compound Q is resistant to oxidation.On reduction, Q gives a product made up of a pair of optical isomers.
Which of the following compounds could be compound Q?

A) CH3CH2CH2COCH3

B) CH3CH=CHCH(OH)CH3

C) CH3CH2CH2CH2CHO

D) CH3CH2COCH2CH3

All help would be greatly appreciated
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EierVonSatan
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Go through it one by one...

orange precipitate with 2,4dinitrophenylhydrazine.
What does this test for? Which, if any, of the compounds can you rule out as a result?

Compound Q is resistant to oxidation
Which functional groups can be oxidised? A is a ketone, B has an alcohol + alkene, C is an aldehyde and D is a ketone.

Can any more be ruled out, now?
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Girling1996
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As it reacts 2,4 dnp so is an aldehyde or ketone.
As wont oxidises further, must be a ketone or 3rd alcohol.
So is A, as A is a ketone.


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yousefshah77
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(Original post by EierVonSatan)
Go through it one by one...



What does this test for? Which, if any, of the compounds can you rule out as a result?



Which functional groups can be oxidised? A is a ketone, B has an alcohol + alkene, C is an aldehyde and D is a ketone.

Can any more be ruled out, now?
I understand it now ! Thanks mate
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yousefshah77
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(Original post by Girling1996)
As it reacts 2,4 dnp so is an aldehyde or ketone.
As wont oxidises further, must be a ketone or 3rd alcohol.
So is A, as A is a ketone.


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Thanks for the help , appreciate it !
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Spudgunhimself
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(Original post by yousefshah77)
Thanks for the help , appreciate it !
This answer wouldn't get all the marks though. Compound D is also a ketone and wouldn't oxidise further, you would need to say that as the reduced version of compound D would not form optical isomers as no carbon has 4 distinct groups, and therefore are no chiral centres, whereas in the reduced version of compound A, there are 4 distinct groups attached to a carbon atom, therefore there is a chiral centre
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