[Las]

Does anyone know whether the oxidation of an alcohol to an aldehyde is a reaction that is used in the edexcel AL syllabus?

If so what would be the conditions and the reactants?

For my local A level examinations,we learnt that the reaction is feasible under controlled conditions, but it was all a big mess in conversions..Can anyone please help me out?

It is apparantly feasible but the yield is very low,so its not used that much..that's what my teacher said anyway..Any help?

[macman104]

Alcohol to aldehyde is very easy to accomplish, and with fairly high yields.  I'm not familiar with the A level system, so I can't say whether you should know them.  But to name the two most common ones are swern oxidation or PCC (Pyridinium Chlorochromate) Oxidation

[Las]

oh wow..I dont think I'm supposed to know them..lol..I'll check the edexcel syllabus again..Thanks:)

[cliverlong]

Note: Primary alcohol > Aldehyde

Secondary alcohol > Ketone

I think the problem is removing the aldehyde as soon as it is formed before the product is further oxidized to carboxylic acid

See Partial oxidation to aldehydes in
http://www.chemguide.co.uk/organicprops/alcohols/oxidation.html#top

Yes this is in EdExcel A-Level

Learn the tests to distiguish aldehydes and ketones using the various strangely named reagents

Clive

[Las]

you mean 2,4-dnp and stuff right?? I think that's alright..it was about not letting it get oxidised to carboxylic acid...

and thanks:)

[cliverlong]

you mean 2,4-dnp and stuff right?? I think that's alright..it was about not letting it get oxidised to carboxylic acid...

and thanks:)

I'm a bit confused by your post.

If by 2,4-dnp and stuff you mean 2,4-dinitrophenylhydrazine then that is a reagent that provide a fairly specific test for various aldehydes and ketones. Whereas your original quesiton is about the preparation of aldehydes from primary alcohol avoiding further oxidation to carboxylic acid - I believe my previous post attempted to address that question - basically, excess alcohol and get the aldehyde out,  by distillation, as quickly as it is produced.

Clive

[Las]

Learn the tests to distiguish aldehydes and ketones using the various strangely named reagents

I was replying to this...we have 2,4-dinitrophenylhydrazine,iodoform test, Tollens and Fehlinng's..

And thanks again, I understood the first time:)

[macman104]

Cliverlong that technique seems antiquated.  You don't need to worry about distilling off quickly.  There are reagents that are selective, and stop at the aldehyde step.  Those are the reagents I mentioned above.

[Las]

I've heard of swern's..not the other one though..anyway I dont think I'm supposed to know either..so I guess I'll have to go with distillation..

[cliverlong]

Cliverlong that technique seems antiquated.  You don't need to worry about distilling off quickly.  There are reagents that are selective, and stop at the aldehyde step.  Those are the reagents I mentioned above.

Hello Macman

That's the great thing about this forum, apart from contributing, one picks up new information all the time.

Clive

[super_kaka1402]

I am a new guy here, i see you guys talk a lot with the word "Edexcel syllabus" so i am wondering what is it ?
cause i am from a country that's not use english, so thanks !

[cliverlong]

I am a new guy here, i see you guys talk a lot with the word "Edexcel syllabus" so i am wondering what is it ?
cause i am from a country that's not use english, so thanks !

EdExcel is a UK-based examination board offering vocational and pre-University examinations taken mainly in the UK but also in other countries.
EdExcel is a subsidiary of the Pearson company whereas other (all other?) UK-based examination boards are charities.

Clive

[macman104]

It seems surprising to me that you don't need to know those reagents.  Those are things taught to first semester organic chemistry students in the US.  Seems like it's fairly introductory.

[Las]

I dont know...Its not mentioned anywhere..I know why its not there in the Sri Lankan local syllabus ofcourse..our syllabus has not been revised in 20years..maybe those reagents were discovered within those 20years..lol..

But I dunno why its not there in edexcel syllabus..anyway edexcel is gonna be a breeze after that horrible local exam, so I dont really mind not having one reagent..