Remove aldehyde moiety (wrong word?) from aryl compound

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Discussion Overview

The discussion revolves around the conversion of 3,5-dimethyl-4-nitro-benzaldehyde to 2,6-dimethyl-nitrobenzene, specifically focusing on the removal of the aldehyde moiety. Participants explore various chemical methods, including oxidation and the Cannizzaro reaction, while addressing concerns about preserving other functional groups in the molecule.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Jeff expresses a desire to remove the aldehyde group without affecting the methyl groups, indicating a lack of experience in organic chemistry.
  • Some participants suggest that mild oxidation might not affect the methyl groups, proposing reagents like PCC or silver ammonium nitrate.
  • There is a discussion about the correct nomenclature for the compound in question, with Jeff acknowledging a mistake and seeking clarification.
  • One participant proposes the Cannizzaro reaction followed by decarboxylation as a potential method for achieving the desired conversion.
  • Concerns are raised about the possibility of concentrated base in the Cannizzaro reaction affecting the methyl groups, with some participants expressing doubt about this outcome.
  • Another participant clarifies the advantages and disadvantages of the Cannizzaro reaction, emphasizing its oxidizer-free nature but noting potential yield issues.
  • There is a reiteration of the Cannizzaro reaction process, with a focus on producing an alcohol and a carboxylic acid, and the subsequent steps to remove the acid while preserving the methyl groups.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the best method for removing the aldehyde group, with multiple competing views on the effectiveness and safety of suggested reactions, particularly regarding the Cannizzaro reaction and oxidation methods.

Contextual Notes

Participants express uncertainty about the nomenclature and the specific reagents involved, indicating a reliance on various chemical reactions that may have different outcomes based on conditions and assumptions.

Who May Find This Useful

Individuals interested in organic chemistry, particularly those exploring functional group transformations and reaction mechanisms, may find this discussion relevant.

JeffEvarts
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Presuming I have 3,5-dimethyl-4-nitro-benzaldehyde, and what I want is 2,6-methyl-nitrobenzene (same molecule, minus the -COH) is there a straightfortward way to do this conversion? Oxidizing it away seems risky: I don't want the -CH3 groups to go all -COOH on me, but I'm not an experienced enough as an O-chemist to know other ways to "address" an unwanted-aldehyde problem.

Any suggestions gratefully accepted.

BTW: Not interested in any help from the illicit-pharmaceuticals quadrant. My life is complicated enough without dabbling in anything illegal. :)

Thank you, and happy holidays 2017!
-Jeff
 
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JeffEvarts said:
2,6-methyl-nitrobenzene

That nomenclature is not correct.

JeffEvarts said:
Oxidizing it away seems risky: I don't want the -CH3 groups to go all -COOH on me,

I don't think mild oxidation will oxidise -CH3; something like PCC or [Ag(NH3)2]NO3 might work.
 
Thanks for your reply!
Sorry about the nomenclature. Please tell me the correct term so I can use it in the future.

I see "silver ammonium nitrate" (AgN2H4O3) But not the complex you list. What's the name for that compound?

Lastly, Pyridinium Chlorocromate ( which is the PCC I am familiar with) is the "kinder, gentler" chromic acid, and generally converts alcohols TO aldehydes.

I want to make sure I'm being clear: I'm trying to take a substituted benzene (1:nitro,2:methyl,4:aldehyde,6:methyl) and convert it to (1:nitro, 2:methyl, 6:methyl) by removing the aldehyde at position 4. If oxidation is the way to go, please let me know. If there's a better way to do it, please let me know.

Thanks Buffu
 
Argh... nvm on the nomenclature.

2,6-dimethyl-nitrobenzene.

-Jeff
 
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Cannizzaro reaction then decarboxylation?
 
JeffEvarts said:
I see "silver ammonium nitrate" (AgN2H4O3) But not the complex you list. What's the name for that compound?

Tollens reagent.

TeethWhitener said:
Cannizzaro reaction then decarboxylation?

I think concentrated base in Cannizzaro will eat the methyl group also.
 
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In an effort to clarify, a diagram may be worth a thousand posts.

Rxn1.png


Buffu and Teethwhitener have suggested some stronger and milder oxidization reactions. (Thank you!)

Any help with this reaction would be greatly appreciated.

-Jeff
 

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Buffu said:
I think concentrated base in Cannizzaro will eat the methyl group also.
I seriously doubt this will happen in the absence of an oxidizer (cf. toluene pKa ~ 41). The advantage of Cannizzaro is that it’s oxidizer-free. The disadvantage is yield.
 
TeethWhitener said:
I seriously doubt this will happen in the absence of an oxidizer (cf. toluene pKa ~ 41). The advantage of Cannizzaro is that it’s oxidizer-free. The disadvantage is yield.

So to be clear, you're suggesting a Canizzaro reaction to produce the alcohol and the carboxilic acid, separating out the acid, and... heating with a strong alkali to drive it off as carbon dioxide? This should leave the methyl groups in place?
 
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JeffEvarts said:
So to be clear, you're suggesting a Canizzaro reaction to produce the alcohol and the carboxilic acid, separating out the acid, and... heating with a strong alkali to drive it off as carbon dioxide? This should leave the methyl groups in place?
Yes. You sacrifice yield for a non-oxidizing environment.