Organic Syntheses, CV 4, 323
Submitted by Herman Stone and Harold Shechter
1.
Checked by T. L. Cairns, B. C. McKusick, and G. V. Mock.
1. Procedure
In a
1-l. three-necked flask, equipped with a
short reflux condenser, a
sealed mechanical Hershberg stirrer, and a
thermometer, is placed
65 g. (0.46 mole) of phosphoric anhydride, and
231 g. of 85% orthophosphoric acid (135 ml., 2 moles) is added (Note
1). After the stirred mixture has cooled to room temperature,
332 g. (2 moles) of potassium iodide and
59 g. (0.5 mole) of recrystallized 1,6-hexanediol (Note
2), (Note
3), and (Note
4) are added. The mixture is stirred and heated at 100–120° for 3–5 hours, during which time the homogeneous solution separates into two phases, and finally a dense oil settles through the acid layer. The stirred mixture is cooled to room temperature, and 150 ml. of water and
250 ml. of ether are added (Note
5). The
ether layer is separated, decolorized by shaking with
50 ml. of 10% sodium thiosulfate solution, washed with
200 ml. of cold saturated sodium chloride solution, and dried with
50 g. of anhydrous sodium sulfate. The
ether is removed by distillation on a
steam bath, and the product is distilled from a
modified Claisen flask under reduced pressure. The fraction boiling at
123–128°/4 mm. is collected. The yield of
1,6-diiodohexane is
140–144 g. (
83–85%),
nD15 1.585, m.p.
10° (Note
6) and (Note
7).
2. Notes
5. Usually one extraction of the reaction product with
ether is sufficient to remove the color from the acid layer.
6. Slightly yellow
1,6-diiodohexane crystallizes as white needles when cooled in an ice-water mixture. The addition of a few drops of
mercury to the yellow product produces a nearly colorless liquid.
7. The submitters reported yields of
93–95% and a melting point of
8.5–9.0°.
3. Discussion
This preparation is referenced from:
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