formaldehyde - Sciencemadness Dot Org

6S
FORMALDEHYDE
sodium sulfate, and isolating the polyoxymethyiene glycols in the acetone
solution thus obtained by fractional precipitation with petroleum ether.
Another procedure involved as a starting material the polyoxymethyiene
glycol gel obtained by an ether extraction of strong aqueous formaldehyde.
Homologs containing 6 to 3 formaldehyde units per molecule were isolated
when the wax-like solid, obtained on cooling a hot 80 per cent formaldehyde
solution, was allowed to stand at room temperature for 2 to 3 weeks. This
solid was first treated with a little acetone and filtered. The filter residue
was then separated into fractions which, were soluble in cold acetone, warm
acetone, and boiling acetone. From the cold acetone fraction, hexa- and
heptaoxymethylene glycols were precipitated with petroleum ether. Homologs
containing 8 to 12 formaldehyde units were isolated from the other
extracts by fractional crystallization.
The lowest fraction isolated was a mixture of di- and trioxymethylene
glycols, HOCH2OCH2OH and HOCH,OCH2OCH2OE5 which melted at
82-85°C and was highly soluble in cold acetone. Tetraoxymethylene
glycol; HO- (CHsOVH, was somewhat less soluble and melted at 95-105°C,
with decomposition. Hexa- and heptaoxymethylene glycol fractions were
fairly soluble in cold acetone. Oeto-oxymethylene glycol was very soluble
in hot acetone and melted at 115-120 C C, with decomposition. Acetone
solubility decreased progressively for higher polyoxymethyiene glycols,
dodecaoxyniethylene glycol being only sparingly soluble in the boiling
solvent. The purity of these fractions was indicated by the fact that
further fractionation produced little or no change in physical properties or
chemical composition.
Because of the chemical instability of the lower polyoxymethyiene glycols,
Staudinger was unable to obtain a complete structural identification
of his purified fractions. Cryoscopic molecular weight determinations
could not be made and attempts at conversion to the corresponding methyl
ethers and acetates resulted in decomposition, so that a series of derivatives
was obtained rather than a single product. However, since the homologous
dimethyl ethers and diacetates, which are more stable, have been
successfully isolated and identified, there is little reason, for doubting their
structure.
The octo-oxymethylene glycol fraction described by Staudinger is a
typical representative of the group. This product, HO-(CH20)a-HT contained
93.0 per cent CHsO and was apparently unchanged by further recrystallization
from hot acetone. It dissolved readily in the hot solvent
and crystallized on cooling in almost quantitative yield. It could also be
recrystallized from chloroform, dioxane, and pjTidine. By quick manipulation,
it could even be recrystallized from water. Dilute acids and alkalies
caused decomposition in a short time, even at low temperatures* 3 .