4-Methylbenzophenone

Chemical Properties

white to beige crystalline powder or crystals

Uses

4-Methylbenzophenone may be used as a reference standard for the determination of the analyte in breakfast cereals, paperboard food packaging and packed milk by various chromatography techniques.

Uses

4-Methylbenzophenone is used as clear coatings for wood, plastic and metal, overprint varnish.

Uses

Benzophenone estrogenicity toxicity structure activity.

Synthesis Reference(s)

Journal of the American Chemical Society, 82, p. 1223, 1960 DOI: 10.1021/ja01490a047
Tetrahedron Letters, 40, p. 3109, 1999 DOI: 10.1016/S0040-4039(99)00476-1
Synthesis, p. 776, 1977 DOI: 10.1055/s-1977-24573

General Description

4-Methylbenzophenone is a photo-initiator for printing inks, mainly applied to the cardboard boxes used for packing. It is reported to be a non-genotoxic carcinogen. However, it can contaminate foodstuffs when it comes in contact with the package contents.

Flammability and Explosibility

Not classified

Safety Profile

Poison by intraperitoneal route. A flammable liquid. When heated to decomposition it emits acrid smoke and irritating fumes.

Purification Methods

Crystallise the ketone from MeOH, Et2O (m 58-59o) or pet ether. The cis-oxime has m 154o(153-156o) (from EtOH), and the trans-oxime has m 114-116o (from pet ether). [Beilstein 7 H 440, 7 III 2127, 7 IV 1403.]

Structure and conformation

4-Methylbenzophenone was one of the first organic compounds for which polymorphism was observed. It crystallizes in two modifications, the stable monoclinic α-form (mp 59°C) and a metastable trigonal β-form (mp 55 ℃). The metastable β-form is rather stable and almost indefinitely preserved if not subjected to severe mechanical load or brought into contact with the stable form. If it converts into a stable form, the crystal becomes milky white and non-transparent due to micro-cracking. There are no conditions under which the β-form is more stable than the α-form. 4-Methylbenzophenone crystallizes in a monoclinic stable form (mp 59 ℃) with a = 5.70 Å, b = 13.89 Å, c = 14.08 Å, p = 95.18° and space group P2_1/c, and a trigonal metastable form (mp 55°C) with a = 9.12 Å, c = 11.28 Å and space groups P3₁, or P3₂[1].

References

[1] H. Kutzke,  H. Klapper,  M. Al-Mansour. "Stable and metastable crystal phases of 4-methylbenzophenone." Journal of Molecular Structure 374 1 (1995): 129–135.