[AlphaScent]

Hello all and happy hump day,

I am wondering if any of you have ever purified alcohols by making a solid derivative using 3,5-dinitrobenzoyl chloride?  I have this task in front me and was wondering if there are any tricks or procedural techniques that may be useful to me.  I have never done this reaction before.  Can I do it neat?  Add the chloride to the alcohol i assume?  Best solvent to recrystallize from?

Thanks in advance!!

Cheers!

[AlphaScent]

I forgot to add, I found this

PROCEDURE: Place 800 mg of 3,5-dinitrobenzoyl chloride, 0.20 mL (or 200 mg) of the unknown
alcohol, 2.0 mL of dry pyridine, and a boiling stone in a 5-mL round-bottomed flask. Attach an aircooled condenser and heat the mixture at reflux on an aluminum block or in a sand bath at 140°C for 15–20 min. Put 5 mL of water in a 10-mL Erlenmeyer flask and pour the reaction mixture slowly into the water. Cool the solution in an ice-water bath until the product precipitates. Scratching the walls of the flask with a stirring rod may be necessary to induce crystallization. Collect the crystals by vacuum filtration on a Hirsch funnel. Transfer the crystals to a small beaker and stir them thoroughly with 3 mL of 5% sodium carbonate solution to remove the excess 3,5-dinitrobenzoic acid that may be present. Again collect the solid by vacuum filtration on a Hirsch funnel and wash it with 1 mL of cold water. Recrystallize the derivative from a mixture of ethanol and water.

Source: http://www2.volstate.edu/chem/2020/labs/qualitative_organic_analysis.pdf

[AlphaScent]

Since I know my alcohol and was doing this as a purification technique, I used 1.3 eq of the acid chloride and used enough pyridine to make a 1 M soln.  I think when this is done on a larger scale, stoichiometric amounts of pyridine could be used.  I only heated to 70 degrees and after 2 hours it was done by TLC. 

KCCO!
Cheers!!

[PhDoc]

AS,

What alcohol are you attempting to purify? Is it a single alcohol or a mixture of alcohols? If a mixture, what are the components?

Typically another reaction is to be avoided if column chromatography can suffice.

Dr. J

[orgopete]

I did this years ago. I had followed the Shriner and Fuson (old textbook) method. I used whatever solvent they suggested. I probably wouldn't now. I'd just check several solvent/mixtures and use whatever worked, the watch glass technique (old school). The objective of making a crystalline derivative was two-fold, get a melting point or mixed melting point and purification. I had a mixture of inseparable isomers so I isolated one of them by crystallization.

I've done many purifications where I had a mixture that couldn't be separated by chromatography. This can be faster and easier than a regio or stereo specific synthesis.

[AlphaScent]

The problem is that I have 75 g of material.  I am trying to avoid running a column.  Specifically a silver nitrate on silica column.  I am still working to find a suitable recrystallization solvent.  I am trying to purify a conjugated diene alcohol.  C5 and C7 dodecen1-ol.  The NMR shows that there is only one alcohol peak.  The impurity is a olefin of some type.