Jones Reagent

[Baylor2011]

So this isn't in either one of my Organic books..weird, but I did google it..just want some confirmation

It says it's a solution of Chromium (VI) Oxide in aqueous H2SO4 with acetone. Then it says it can be prepared with the dichromate derivatives as well.

Does the acetone change the reactivity at all? Because I know about CrO3/H2SO4 as an oxidant, but I've never heard it referred to as the Jones Reagent anywhere except Destroyer.

Shedding any amount of light on this would be appreciated, thanks!

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[toothfairy05]

So this isn't in either one of my Organic books..weird, but I did google it..just want some confirmation

It says it's a solution of Chromium (VI) Oxide in aqueous H2SO4 with acetone. Then it says it can be prepared with the dichromate derivatives as well.

Does the acetone change the reactivity at all? Because I know about CrO3/H2SO4 as an oxidant, but I've never heard it referred to as the Jones Reagent anywhere except Destroyer.

Shedding any amount of light on this would be appreciated, thanks!

Acetone is just a solvent. Don't worry about it. What you should be concerned with is if you see Cr03 combined with water/aqueous H2SO4 or not. If there is water, it is called Jones reagent and it is considered a strong oxidizing agent since it can oxidize an alcohol directly into a carboxylic acid. This happens as a second oxidation event with an addition of water to the aldehyde to form a carboxylic acid.

If there no water with Cr03, then the alcohol is oxidized to an aldehyde. This is called PCC (pyridinian chlorochromate), which is a mild oxidizing agent and anhydrous. Hope that helps!

 

[gigawatt]

I've been wondering this, too. It looks like using acetone as a solvent protects the substrate from the strong acid. Acetone isn't a reactive component of the reagent, though.

http://www.organic-chemistry.org/chemicals/oxidations/jones-reagent.shtm

Although the reagent is very acidic, the substrate in acetone is essentially titrated with the oxidant solution and only very acid-sensitive groups are incompatible. For example esters, even tert-butyl esters, remain unchanged. The concentration of sulfuric acid can be decreased to minimize side reactions, although the oxidation power increases too.

 

[Baylor2011]

If there no water with Cr03, then the alcohol is oxidized to an aldehyde. This is called PCC (pyridinian chlorochromate), which is a mild oxidizing agent and anhydrous. Hope that helps!

1. PCC is a completely different compound...
2. Isn't there automatically some water in solution since H2S04 is aqueous, so would it really matter if they put H2O or not?

 

[toothfairy05]

1. PCC is a completely different compound...
2. Isn't there automatically some water in solution since H2S04 is aqueous, so would it really matter if they put H2O or not?

When I say water, i mean aqueous solution (H+ source). Yes, you're actually right PCC is different, but it's the mild version of Jones and it's anhydrous.

 

[Baylor2011]

Ah ok, thanks =]

 

[Troyvdg]

1. PCC is a completely different compound...
2. Isn't there automatically some water in solution since H2S04 is aqueous, so would it really matter if they put H2O or not?

not the thread jack, but, I've been coming across problems with Jones as CrO3 and as Na2Cr2O7...so which one is correct?

In my Ochem class PCC was always CrO3 and Jones was always Na2Cr2O7

 

[Baylor2011]

Well pyridinium chlorochromate is a complete different compound...does have a Cr+6 group though. It's a reduced (more specific) oxidant versus dichromate will oxidize everything

The website I looked at said Jones can be made with Chromium (VI) oxide or with the dichromate salts...so just know that Jones can be any of those 3, and PCC is different, and less reactive

 

[Troyvdg]

Well pyridinium chlorochromate is a complete different compound...does have a Cr+6 group though. It's a reduced (more specific) oxidant versus dichromate will oxidize everything

The website I looked at said Jones can be made with Chromium (VI) oxide or with the dichromate salts...so just know that Jones can be any of those 3, and PCC is different, and less reactive

oh ok, thanks.
I've had people tell me, that when they do use PCC, the simply put PCC, rather than the reagents

 

[Ibraiz]

So Jones reagent is a mild oxidizing agent unless it is used with water as an solvent?

If it is not used with water as a solvent, would it act similar to PCC?
If it is used with water as a solvent, would it act similar to KMNO4 as a strong oxidizing agent?

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