Α-Methylstyrene Explained

α-Methylstyrene (AMS) is an organic compound with the formula C₆H₅C(CH₃)=CH₂. It is a colorless oil.

Synthesis and reactions

AMS is formed as a by-product of the Cumene process. In this procedure, cumene is converted to its radical, through a reaction with oxygen.

Normally these cumene radicals are converted to cumene hydroperoxide, however they can also undergo radical disproportionation to form AMS.

Although this is only a minor side reaction, the cumene process is run at such a large scale that the recovery of AMS is commercially viable and satisfies much of the global demand. AMS can also be produced by dehydrogenation of cumene.

The homopolymer obtained from this monomer, poly(α-methylstyrene), is unstable, being characterized by a low ceiling temperature of 65 C.^{[1] [2]}

Side Effects in Humans

The American Conference of Governmental Industrial Hygienists (2009) defined occupational exposure limits of 10 ppm for airborne concentrations of a-methylstyrene.^[3] based on allergic reactions, and effects on the central nervous system.^{[3] [4]}

Notes and References

1. Book: Stevens, Malcolm P.. Polymer Chemistry an Introduction. 1999. Oxford University Press. New York. 978-0-19-512444-6. 193–194. 3rd. 6.
2. 10176471 . 2023 . Jones . G. R. . Wang . H. S. . Parkatzidis . K. . Whitfield . R. . Truong . N. P. . Anastasaki . A. . Reversed Controlled Polymerization (RCP): Depolymerization from Well-Defined Polymers to Monomers . Journal of the American Chemical Society . 145 . 18 . 9898–9915 . 10.1021/jacs.3c00589 . 37127289 .
3. Morgan . D. L. . Mahler . J. F. . Kirkpatrick . D. T. . Price . H. C. . O'Connor . R. W. . Wilson . R. E. . Moorman . M. P. . February 1999 . Characterization of inhaled alpha-methylstyrene vapor toxicity for B6C3F1 mice and F344 rats . Toxicological Sciences. 47 . 2 . 187–194 . 10.1093/toxsci/47.2.187 . 1096-6080 . 10220856. free .
4. Web site: OSHA . α-METHYL STYRENE† .