[Rutherford]

Why has diethyl ether a bigger solubility in water than butanal? Both oxygen and hydrogen from butanal can produce hydrogen bonds with water molecules, while in diethyl ether only the oxygen can do it.

[Dan]

Why has diethyl ether a bigger solubility in water than butanal?

As far as I know, this is not true. What is your source?

Solubility of diethyl ether in water ~1.5 wt%
Source: J. Am. Chem. Soc. http://pubs.acs.org/doi/abs/10.1021/ja01150a531

Solubility of diethyl ether in water ~7.1 wt%
Source: Dow chemicals specification sheet

[Rutherford]

Found on wikkipedia:
http://en.wikipedia.org/wiki/Diethyl_ether -Solubility in water 14.68 g/L (25 °C)
http://en.wikipedia.org/wiki/Butyraldehyde -Solubility in water 7.6 g/100 mL (20 °C)

The temperature difference is relatively low and I thought that at the same temperature diethyl ether will be more soluble anyway. WHat you posted is solubility of water in diethyl ether.
I still don't know which one is actually more soluble.