Spontaneous polymerization of acetaldehyde to polyacetaldehyde at close to dry-ice temperature
✍ Scribed by K. K. Georgieff
- Book ID
- 102733971
- Publisher
- John Wiley and Sons
- Year
- 1966
- Tongue
- English
- Weight
- 543 KB
- Volume
- 10
- Category
- Article
- ISSN
- 0021-8995
No coin nor oath required. For personal study only.
✦ Synopsis
Polyacetaldehyde has been prepared in the liquid and vapor phases without the addition of a catalyst by storing undiluted acetaldehyde in the dark at a temperature of -68°C. for 3-6 months. When acetaldehyde was stored in an untreated Pyrex flask, 20% high polymer, 55% paraldehyde, and less than 1% metaldehyde were obtained. The polymer was an elastomeric solid with a low to moderate degree of crystallinity and an intrinsic viscosity of 0.63 dl./g. When the sample was stored in a Pyrex flask which had been pretreated wit.h alcoholic potassium hydroxide followed by a water wash, 16-17% high polymer and 6% paraldehyde were obtained. Some polymer formed on the unwetted glass above the liquid. It was slightly elastic, a t least moderately crystalline, and had an intrinsic viscosity of 1.6 dl./g. It is suggested t,hat the formation of this polymer was initiated by basic active sites on the Pyrex surface which acted by an anionic mechanism. This material was an amorphous, highly viscoiis oil with an intrinsic viscosity of 0.28 dl./g. It was probably formed by a cationic mechanism. It is also suggest,ed that a relatively small amount of paraldehyde was formed in the alkali-treated flask in the liquid phase due to neutralization of the Brfinsted acid sites and possibly some of the Lewis acid sites on the surface of the flask.