[cjohnston]

Hi,

I was stuck with my project. If anyone could please help me. thanks. I am making hydroxychalcone using acid catalysed aldol reaction.


http://www.jpsr.pharmainfo.in/Documents/Volumes/Vol1Issue3/pdf/jpsr01030902.pdf

Procedure [6]
To a stirred mixture of acetophenone
(0.01mol) and benzaldehyde
(0.01mol) in absolute ethanol (5ml),
add thionyl chloride (0.05ml)
dropwise and continue stirring for
two hour at room temperature. Allow
to stand reaction mixture for 12hr.
Precipitate the reaction mixture by
addition of water. Filter the product,
wash with cold ethanol.


So acetophenone, benzaldehyde and ethanol were stirred first then thionyl chloride was added to produce HCl environment that is required.

What if thionyl chloride was added to ethanol first and stirred and then acetophenone and benzaldehyde added. Would this produce better HCl environement??


In the method it says adding thionyl chloride drop wise. If I didnt do this and added it all at once, would this be a problem??


Also, hydroxychalcones require protection of phenolic groups when in basic conditions, why don't we need that in acid catalysed reaction.




Your help will be much appreciated.

[Dan]

I was stuck with my project.

Can you clearly state what you are trying to do and what is going wrong?

[cjohnston]

I was stuck with my project.

Can you clearly state what you are trying to do and what is going wrong?

Basically, I am making 2'5'-dihydroxychalcone. I initially used THP (tetrahydropyranal) to protect the OH in the structure.

So I tried to make 2'5'-dihydroxychalcone using the link I posted before. Now as it is acid catalysed reaction, I don't need to protect the OH groups.

But, for my project my tutor told me to change the order I added the excepients.

First exp.: I added 2'5'-dihydroxyacetophenone and benzyaldehyde in ethanol. Then I added thionyl chloride.

Second exp.: I added thionyl chloride to ethanol first. then after a while I added 2'5'-dihydroxyacetophenone and benzyaldehyde.


From my current knowledge, thionyl chloride reacts with ethanol to produce HCl environement.


So I want to learn if this makes any different to the reaction, (it must be as my tutor made me do it). Does it effect the HCl environment.


Is the first exp better or the second where thionyl chloride was added to ethanol first.




Sorry I am new to this forum.
Hope this is clear

[Dan]

And the problem is what? What were the results of the experiments?

[cjohnston]

And the problem is what? What were the results of the experiments?

Thionyl chloride reacts with ethanol to form alkyl chloride.

So I want to know that is Exp 1 better or Exp 2 (in terms of which would give the ideal HCl environment)


Reminder

First exp: I added 2'5'-dihydroxyacetophenone and benzyaldehyde in ethanol. Then I added thionyl chloride.

Second exp: I added thionyl chloride to ethanol first. then after a while I added 2'5'-dihydroxyacetophenone and benzyaldehyde.

[cjohnston]

Does Thionyl Chloride react with either :

- hydroxyacetophenone (is a ketone)

or

-Benzaldehyde (is a aldehyde)


I know it does with carboxylic acid but not sure on the above.

[Dan]

Thionyl chloride reacts with ethanol to form alkyl chloride.

So I want to know that is Exp 1 better or Exp 2 (in terms of which would give the ideal HCl environment)

It is very unlikely to make a difference, thionyl chloride will react much faster with EtOH than anything else in your mixture. That said, there is no harm in premixing the thionyl chloride and the EtOH (that is how I would do it).

Have you actually run either of these reactions?

I'd watch out for flavanone side products with your substrate.
Have you actually done the experiment

[cjohnston]

Yes I have.

First exp: I added 2'5'-dihydroxyacetophenone and benzyaldehyde in ethanol. Then I added thionyl chloride.

Yield was 0.32g



Second exp: I added thionyl chloride to ethanol first. then after a while I added 2'5'-dihydroxyacetophenone and benzyaldehyde.

Yield was 0.23g


How would the flavone be formed (micahel addition...), i.e. at what stage?

[cjohnston]

Would thionyl chloride react with hydroxyacetophenone. (has a phenolic group)

[Dan]

You should give yields as a percentage, otherwise we can't tell if they are high or low. Are these reactions run on 0.010 mol - i.e. around 10-15% yield?

Is low yield the problem you are trying to solve?

Would thionyl chloride react with hydroxyacetophenone. (has a phenolic group)

It will react with the EtOH solvent much faster. I don't think any discrepancy in yield is due to the order of addition of reagents.

How would the flavone be formed (micahel addition...), i.e. at what stage?

Yes, acid catalysed intramolecular Michael addition after formation of the chalcone. I don't know how easy that process is, and the conditions you're using are mild so maybe it's not an issue. I had a similar problem a couple of weeks ago on a related system (but the conditions were much harsher).

I take it you have confirmed by NMR that your isolated product is the chalcone?

[zsinger]

Chalcones can be formed via a solid state reaction .  Ever look into that?
                     -Zack

[cjohnston]

Chalcones can be formed via a solid state reaction .  Ever look into that?
                     -Zack

Ermm yeh I've heard of it. After having a quick think, was wondering that is it possible to
make 2',5'-dihydroxychalcone ??

Usually, we need to use a protection method (in basic condition) and I have tried acid catalysed (SOCl2/ethanol)

So wasnt sure about the solid state reaction??

Have u ever made hydroxychalcones with it?

[zsinger]

Nah, never done it.  I wrote a paper on it in undergrad once .