Hexamethylenetetramine (77 g., 0.55 mole) is dissolved in
200 ml. of chloroform, and
88 g. (0.5 mole) of 3-thenyl bromide (p.921) is added as rapidly as possible with shaking (Note
1). A
reflux condenser is attached, and the mixture is refluxed over a
steam bath for 30 minutes. After being cooled, the mixture of
chloroform and crystalline product (Note
2) is poured into 250 ml. of water and stirred until all the salt dissolves. The
chloroform layer is separated and washed twice with 125-ml. portions of water, and the combined water extracts are steam-distilled. When the distillate comes over clear (about 1 l. of distillate is usually collected), it is acidified with a little
hydrochloric acid (Note
3) and extracted with three
100-ml. portions of ether. After drying over
Drierite, the
ether is evaporated, and the residue is distilled.
3-Thenaldehyde is collected at
72–78°/12 mm. or
195–199°/744 mm.,
nD20 = 1.5860 (Note
4). The yield is
30–40 g. (
54–72%).