Hi Míra,

I guess to get it really dry it is difficult, you could try to form the Aldehyde from the hemiacetal or acetal species under water-free conditions. I added a few links to give an incentive.

Marcus

http://www.sigmaaldrich.com/catalog/product/aldrich/390321

http://www.sigmaaldrich.com/catalog/product/aldrich/cds001466

http://www.masterorganicchemistry.com/2010/05/28/on-acetals-and-hemiacetals/

Hi Mira,

Try drying over P2O5.

Meanwhile, see the following article. That also might help.

Braid, Milton; Iserson, Hyman; Lawlor, Francis E. Journal of the American Chemical Society (1954), 76, 4027.

Good luck.

Prof Ramin Zibaseresht

Hi Mira, 

I do not think you have to dehydrate fluoral hydrate over P2O5-H2SO4 as suggested. A better approach would be to generate anhydrous fluoral in-situ. The Mukayama aldol condensation involves TiCl4 as catalyst. You may use excess of TiCl4 which will react with fluoral hydrate to afford anhydrous fluoral , TiO2 and HCl. To neutralize HCl you can use N,N-diisopropylethylamine (Hunig base). Alternatively, isobutylene oxide will neutralize instantaneously the released HCl to afford the chlorohydrin. Other Lewis acid catalysts used in excess in presence of hindered amine bases should work as well, for example Bu2BOTf or Sn(OTf)2. 

Rgds, y@b

for a review of the Mukayama Aldol see: http://medchem.rutgers.edu/mc504/pdfs/mukaiyama.pdf

Thanks for all advices, I was able to do it with clasic H2SO4/P2O5 but it was a bit messy and with bad yields. I will deffinitely try the hemiacetal instead of hydrate as well.