Michler's ketone

Michler's Ketone
Other names 4,4'-bis(N,N-dimethylamino)benzophenone, 4,4'-bis(Dimethylamino)benzophenone; bis(p-(N,N-dimethylamino)phenyl)ketone; Michler ketone; Michler's Ketone
Identifiers
CAS number	90-94-8
KEGG	C19266 Y
Properties
Molecular formula	C17H20N2O
Molar mass	268.36 g/mol
Appearance	colorless solid
Hazards
MSDS	External MSDS
EU classification	not listed
Related compounds
Related compounds	Benzophenone
Y ketone (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Michler’s ketone is an organic compound with the formula of [(CH₃)₂NC₆H₄]₂CO. This electron-rich derivative of benzophenone is an intermediate in the production of dyes and pigments, for example Methyl violet. It is also used as a sensitizer.^[1] It is named after the German chemist Wilhelm Michler.

Synthesis

The ketone is prepared today as it was originally by Michler^[2] using the Friedel-Crafts acylation of dimethylaniline (C₆H₅NMe₂) using phosgene (COCl₂) or equivalent reagents such as triphosgene (Me = methyl):

COCl₂ + 2 C₆H₅NMe₂ → (Me₂NC₆H₄)₂CO + 2 HCl

The related tetraethyl compound (Et₂NC₆H₄)₂CO, also a precursor to dyes, is prepared similarly.

Uses

Michler’s ketone is an intermediate in the synthesis of dyes and pigments for paper, textiles, and leather. Condensation with various aniline derivatives gives several of the dyes called methyl violet, such as crystal violet.

Condensation of Michler's ketone with N-phenyl-1-naphthylamine gives the dye Victoria Blue B (CAS#2580-56-5, CI Basic Blue 26), which is used for coloring paper and producing pastes and inks for ballpoint pens.

Michler’s ketone is commonly used as an additive in dyes and pigments as a sensitizer for photoreactions because of its absorption properties. Michler’s ketone is an effective sensitizer provided energy transfer is exothermic and the concentration of the acceptor is sufficiently high to quench the photoreaction of Michler’s ketone with itself. Specifically Michler’s ketone absorbs intensely at 366 nm and effectively sensitizes photochemical reactions such as the dimerization of butadiene to give 1,2-divinylcyclobutane.^[3]

Related compounds

Auramine O, a dye, is a salt of the iminium cation [(CH₃)₂NC₆H₄]₂CNH₂⁺. Michler's thione, [(CH₃)₂NC₆H₄]₂CS, is prepared by treatment of Michler's ketone with hydrogen sulfide in the presence of acid or sulfideing auramine O.^[4]

References

1. ^ Kan, Robert O. "Organic Photochemistry" McGraw-Hill, New York, 1966.
2. ^ W. Michler (1876). "Synthese aromatischer Ketone mittelst Chlorkohlenoxyd". Berichte der deutschen chemischen Gesellschaft 9: 716–718. doi:10.1002/cber.187600901218. 
3. ^ Charles D. DeBoer, Nicholas J. Turro, and George S. Hammond (1973), "cis- and trans-1,2-Divinylcyclobutane", Org. Synth., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=CV5P0528 ; Coll. Vol. 5: 528 
4. ^ R. M. Elofson, Leslie A. Baker, F. F. Gadallah, R. A. Sikstrom "The Preparation of Thiones in the Presence of Anhydrous Hydrogen Fluoride" J. Org. Chem., 1964, volume 29, pp 1355–1357. doi:10.1021/jo01029a020