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Reductiion of Aldehydes

The reaction I'm interested in is highlighted by the red box.

Hydrogen in the presence of a catalyst should turn an alkene into an alkane, hence option E is selected.

Hydorgen in the presence of a catalyst should also reduce an aldehyde to a primary alcohol and a ketone to a secondary alcohol.

Hence, C and D are correct.

The issue arises since the mark scheme (a handwritten one by the board) states only Option E as the correct answer.
(edited 13 years ago)
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Original post by Ari Ben Canaan
The reaction I'm interested in is highlighted by the red box.

Hydrogen in the presence of a catalyst should turn an alkene into an alkane, hence option E is selected.

Hydorgen in the presence of a catalyst should also reduce an aldehyde to a primary alcohol and a ketone to a secondary alcohol.

Hence, C and D are correct.

The issue arises since the mark scheme (a handwritten one by the board) states only Option E as the correct answer.


Catalytic hydrogenation does not reduce aldehydes and ketones - where did you get that from?
Original post by charco
Catalytic hydrogenation does not reduce aldehydes and ketones - where did you get that from?


http://www.elmhurst.edu/~chm/vchembook/703reduction.html
Original post by Ari Ben Canaan


Yup, after a little research it clearly is possible, but more difficult than with double bonds.
Original post by charco
Yup, after a little research it clearly is possible, but more difficult than with double bonds.


So who is correct ? The markscheme or me ?

Remember, this is a pretty old paper and the markscheme is handwritten indicating corrections may have been made later.
Original post by charco
Yup, after a little research it clearly is possible, but more difficult than with double bonds.


:shock:

:wink:
Reply 7
Avatar for shengoc
shengoc
12
Original post by Ari Ben Canaan
So who is correct ? The markscheme or me ?

Remember, this is a pretty old paper and the markscheme is handwritten indicating corrections may have been made later.


as usual, don't take mark scheme for granted but yet don't overcomplicate a question than it needs to be.

most common answer is obviously the catalystic hydrogenation of an alkene, write that down.

then judge the rest by what you have read and researched a bit more to be true, ie read from one source might not be the correct one, ie the more resources you have, the more reliable your knowledge is, the idea of "averaging", i suppose:biggrin:
Original post by shengoc
as usual, don't take mark scheme for granted but yet don't overcomplicate a question than it needs to be.

most common answer is obviously the catalystic hydrogenation of an alkene, write that down.

then judge the rest by what you have read and researched a bit more to be true, ie read from one source might not be the correct one, ie the more resources you have, the more reliable your knowledge is, the idea of "averaging", i suppose:biggrin:


I have an A level study guide that also states the catalytic hydrogenation of ketones and aldehydes is possible.... I see what you mean though.

I HATE having to look into the Examiner's mindset. -_-

EDIT : Why on earth was I negged ?
(edited 13 years ago)
Reply 9
Avatar for shengoc
shengoc
12
Original post by Ari Ben Canaan
I have an A level study guide that also states the catalytic hydrogenation of ketones and aldehydes is possible.... I see what you mean though.

I HATE having to look into the Examiner's mindset. -_-

EDIT : Why on earth was I negged ?


different years have different examiners, so i would have thought. they might have come from different background(years) when common methods were used, so different sorts of mark schemes could have been drafted. all the best though

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