OCehm Reagent CrO3 vs. K2Cr207 :)

[A6project]

Hi, I was wondering if anyone can help me with that. 🙂))

well, KMnO4 and K2Cr2O7/heat makes a primary OH to a carboxylic acid.
However, CrO3, Pyr just make the primary OH to an aldehyde.

I understand that K2Cr2O7 is more complicated and is quite different from CrO3, but aren't they pretty much the same??? (both has a lot of oxygens and carries oxdiatizing reactions.) QUESTION#1

And, are there any cases where KMnO4 and K2Cr2O7 makes a primary OH to an aldehyde??? QUESTION#2

Thanks so much guys!!!

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[UndergradGuy7]

Hi, I was wondering if anyone can help me with that. 🙂))

well, KMnO4 and K2Cr2O7/heat makes a primary OH to a carboxylic acid.
However, CrO3, Pyr just make the primary OH to an aldehyde.

I understand that K2Cr2O7 is more complicated and is quite different from CrO3, but aren't they pretty much the same??? (both has a lot of oxygens and carries oxdiatizing reactions.) QUESTION#1

And, are there any cases where KMnO4 and K2Cr2O7 makes a primary OH to an aldehyde??? QUESTION#2

Thanks so much guys!!!

K2Cr2O7 (actually it is H2CrO4 which is made by reaction from K2Cr2O7 + acid) is just a stronger oxidizing agent. So it can oxidize to carboxylic acids (depending on the type of alcohol). A primary alcohol will go to carboxylic acid always. A secondary will stop at ketone. Tertiary will not react.

Also by the way CrO3, pyridine is more commonly known as PCC. (there is also a reagent called PDC it does the same thing). It can only reduce to aldehyde/ketone and not further.

 

[A6project]

lets just say that if the reagent is K2Cr2O7 or KMnO4, you always assume that a primary alcohol will be a carboxylic acid. It will never be an aldehyde?

 

[UndergradGuy7]

Yes.

 

[A6project]

thank you!!!!

 

[SuperCool101]

CrO3 is a STRONG OXIDIZING AGENT!! Therefore it would oxidize a primary alcohol into a carboxylic acid not aldehyde!!

CrO3 is not the same as PCC.

CrO3 is called Jones Reagent.

Both CrO3 and K2CrO7 are strong oxidizing agents.

 

[lex1489]

CrO3, H2SO4/quinoline is Jones' Reagent. I'm not sure what PCC actually is.

 

[jirotrom]

CrO3 is a STRONG OXIDIZING AGENT!! Therefore it would oxidize a primary alcohol into a carboxylic acid not aldehyde!!

CrO3 is not the same as PCC.

CrO3 is called Jones Reagent.

Both CrO3 and K2CrO7 are strong oxidizing agents.

really... i had thought that PCC and Jones reagent had the same relative strength

 

[Ibracadabra]

K2Cr2O7 (actually it is H2CrO4 which is made by reaction from K2Cr2O7 + acid) is just a stronger oxidizing agent. So it can reduce to carboxylic acids (depending on the type of alcohol). A primary alcohol will go to carboxylic acid always. A secondary will stop at ketone. Tertiary will not react.

Also by the way CrO3, pyridine is more commonly known as PCC. (there is also a reagent called PDC it does the same thing). It can only reduce to aldehyde/ketone and not further.

Woah.. that sentence confused me a bit here.. lol
I guess you were talking about the reagent itself.. since an alcohol->carboxylic acid is an oxidation reaction.

 

[SuperCool101]

really... i had thought that PCC and Jones reagent had the same relative strength

Nope, they are not the same

PCC (Pyridinium Chlorochromate) is weaker oxidizing agent

CrO3 (Jones Reagent) is stronger oxidizing agent

I am 100% positive 🙂

 

[chromosome21]

CrO3 is a STRONG OXIDIZING AGENT!! Therefore it would oxidize a primary alcohol into a carboxylic acid not aldehyde!!

CrO3 is not the same as PCC.

CrO3 is called Jones Reagent.

Both CrO3 and K2CrO7 are strong oxidizing agents.

I believe Undergradguy is right.

CrO3, pyridine is actually PCC. The meaning of PCC is Pyridinium ChloroChromate.

John's reagent, however, is not the same as PCC. It's CrO3 + HCl (or H2SO4) + acetone.

PCC is a weak oxidizing agent which will turn primary alcohol to aldehyde.
John's reagent is a strong oxidizing agent and it will turn primary alcohol to carboxylic acid.

 

[UndergradGuy7]

Woah.. that sentence confused me a bit here.. lol
I guess you were talking about the reagent itself.. since an alcohol->carboxylic acid is an oxidation reaction.

Typo. It was late.

I believe Undergradguy is right.

CrO3, pyridine is actually PCC. The meaning of PCC is Pyridinium ChloroChromate.

John's reagent, however, is not the same as PCC. It's CrO3 + HCl (or H2SO4) + acetone.

PCC is a weak oxidizing agent which will turn primary alcohol to aldehyde.
John's reagent is a strong oxidizing agent and it will turn primary alcohol to carboxylic acid.

^^^ I was a little confused at the CrO3, pyridine too since I always call it PCC.

 

[orgohacks]

Typo. It was late.




^^^ I was a little confused at the CrO3, pyridine too since I always call it PCC.

[nitpick] It's not *quite* PCC, it's called the Collins reagent (you don't need to know that BTW) but you are right that for your purposes they can be thought of as being the same.

PCC = pyridinium chlorochromate (the HCl salt of pyridine + CrO3).

/nitpick

 

[vindicate]

KMn04, if its dilute and cold, will add syn -oh to alkenes.