Modification of Riemer Tieman reaction

  • Thread starter harini_5
  • Start date
  • #1
36
0

Main Question or Discussion Point

I’ve learnt the modification of Riemer Tieman reaction in which carbon tetra chloride is added to phenol to get aromatic acids. What is the electrophile attacking phenol?
 

Answers and Replies

  • #2
GCT
Science Advisor
Homework Helper
1,728
0
Although I don't know a lot about this reaction my guess is that it's the carbon tetra chloride with respect to the positively charged carbon.
 
  • #3
36
0
But carbontetrachloride as such is very stable and so it is very unreactive.So it possibly cannot attack phenol.It is due to this low reactivity that it is used as a solvent in most cases
 
  • #4
GCT
Science Advisor
Homework Helper
1,728
0
The molecule does not have an overall dipole moment yet there's still that positive charge on the carbon - I've known of carbon chloride compounds which are useful for addition of carbon on the benzene although I am not recalling any at the moment.

P
 
  • #5
1,104
25
I’ve learnt the modification of Riemer Tieman reaction in which carbon tetra chloride is added to phenol to get aromatic acids. What is the electrophile attacking phenol?
What are the exact conditions and reagents used in this reaction?
 
  • #6
chemisttree
Science Advisor
Homework Helper
Gold Member
3,239
183
Although I don't know a lot about this reaction my guess is that it's the carbon tetra chloride with respect to the positively charged carbon.
The four chloro groups are pulling the electrons away from the carbon in carbon tet. That carbon cannot be nucleophilic. The missing reagent is a strong base, sometimes KOH and copper powder. Reimar and Tiemann placed phenol, sodium hydroxide, chloroform and some ethanol/water solution into a sealed tube and heated for 3 days at 100C to generate the mixture of o- and p-hydroxybenzoic acids. The KOH reacts with the phenol, deprotonating it and activating the ortho/para carbon on the ring to behave as a nucleophile. The KOH also reacts with the carbon tet to generate :CCl2. This is the electrophile or the substrate upon which the intermediate ion (o- or p-phenolate anion) adds to. The resulting dichloromethyl-substituted phenolate ion can further react with OH- to generate the aldehyde and ultimately the carboxylic acid.
 
  • #7
GCT
Science Advisor
Homework Helper
1,728
0
I mentioned it as an electrophile not a nucleophile and I'm not quite certain why it has to be nucleophilic as you've pointed out since the dichlorocarbene is electrophilic. Regardless what a bizarre mechanism I just referenced it

http://en.wikipedia.org/wiki/Reimer-Tiemann_reaction

You've got
electrophilic aromatic substitution (technical name)
An SN reaction
carbenes
cyclic rearrangements

........all in "one pot"
 
  • #8
chemisttree
Science Advisor
Homework Helper
Gold Member
3,239
183
The four chloro groups are pulling the electrons away from the carbon in carbon tet. That carbon cannot be nucleophilic. The missing reagent is a strong base, sometimes KOH and copper powder. Reimar and Tiemann placed phenol, sodium hydroxide, chloroform and some ethanol/water solution into a sealed tube and heated for 3 days at 100C to generate the mixture of o- and p-hydroxybenzoic acids. The KOH reacts with the phenol, deprotonating it and activating the ortho/para carbon on the ring to behave as a nucleophile. The KOH also reacts with the carbon tet to generate :CCl2. This is the electrophile or the substrate upon which the intermediate ion (o- or p-phenolate anion) adds to. The resulting dichloromethyl-substituted phenolate ion can further react with OH- to generate the aldehyde and ultimately the carboxylic acid.
Sorry, that should have been carbon tet, not chloroform. What happened to the edit function?
 
  • #9
GCT
Science Advisor
Homework Helper
1,728
0
It should be located on the top right of your section - strange - it's not there.
 
  • #10
Borek
Mentor
28,326
2,713
What happened to the edit function?
Looks like you no longer can edit posts already answered.
 
  • #11
Borek
Mentor
28,326
2,713
No, it is slightly different situation. You can edit your posts only for 30 minutes since posting. So even if you have wrote "wether" instead of "whether" you can't correct it if you have waited for too long :frown:
 

Related Threads for: Modification of Riemer Tieman reaction

Replies
1
Views
646
  • Last Post
Replies
7
Views
1K
  • Last Post
Replies
0
Views
2K
  • Last Post
Replies
4
Views
711
  • Last Post
Replies
5
Views
4K
  • Last Post
Replies
2
Views
20K
  • Last Post
Replies
18
Views
7K
Top