Michler's ketone is an

organic compound Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...

with the formula of CH₃)₂NC₆H₄sub>2CO. This electron-rich derivative of

benzophenone Benzophenone is a naturally occurring organic compound with the formula (C6H5)2CO, generally abbreviated Ph2CO. Benzophenone has been found in some fungi, fruits and plants, including grapes. It is a white solid with a low melting point and ros ...

is an intermediate in the production of dyes and pigments, for example

Methyl violet Methyl violet is a family of organic compounds that are mainly used as dyes. Depending on the number of attached methyl groups, the color of the dye can be altered. Its main use is as a purple dye for textiles and to give deep violet colors in pain ...

. It is also used as a

photosensitizer Photosensitizers are light absorbers that alter the course of a photochemical reaction. They usually are catalysts. They can function by many mechanisms; sometimes they abstract an electron from the substrate, and sometimes they abstract a hydro ...

. It is named after the German chemist Wilhelm Michler.

Synthesis

The ketone is prepared today as it was originally by Michler using the Friedel-Crafts

acylation In chemistry, acylation is a broad class of chemical reactions in which an acyl group () is added to a substrate. The compound providing the acyl group is called the acylating agent. The substrate to be acylated and the product include the foll ...

dimethylaniline ''N'',''N''-Dimethylaniline (DMA) is an organic chemical compound, a substituted derivative of aniline. It is a tertiary amine, featuring a dimethylamino group attached to a phenyl group. This oily liquid is colourless when pure, but commercial ...

(C₆H₅NMe₂) using

phosgene Phosgene is an organic chemical compound with the formula . It is a toxic, colorless gas; in low concentrations, its musty odor resembles that of freshly cut hay or grass. It can be thought of chemically as the double acyl chloride analog of ...

(COCl₂) or equivalent reagents such as

triphosgene Triphosgene (bis(trichloromethyl) carbonate (BTC)) is a chemical compound with the formula OC(OCCl3)2. It is used as a solid substitute for phosgene, which is a gas and diphosgene, which is a liquid. Triphosgene is stable up to 200 °C. Triphosge ...

:COCl₂ + 2 C₆H₅NMe₂ → (Me₂NC₆H₄)₂CO + 2 HCl → salt 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 Methyl violet is a family of organic compounds that are mainly used as dyes. Depending on the number of attached methyl groups, the color of the dye can be altered. Its main use is as a purple dye for textiles and to give deep violet colors in pain ...

, such as

crystal violet Crystal violet or gentian violet, also known as methyl violet 10B or hexamethyl pararosaniline chloride, is a triphenylmethane, triarylmethane dye used as a histological stain and in Gram staining, Gram's method of classifying bacteria. Crystal ...

. 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 In thermodynamics, an exothermic process () is a thermodynamic process or reaction that releases energy from the system to its surroundings, usually in the form of heat, but also in a form of light (e.g. a spark, flame, or flash), electricity (e ...

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 1,3-Butadiene () is the organic compound with the formula CH2=CH-CH=CH2. It is a colorless gas that is easily condensed to a liquid. It is important industrially as a precursor to synthetic rubber. The molecule can be viewed as the union of two ...

to give 1,2-divinylcyclobutane.

Related compounds

''p''-Dimethylaminobenzophenone is related to Michler's ketone, but with only one amine. Auramine O, a dye, is a salt of the iminium cation CH₃)₂NC₆H₄sub>2CNH₂⁺. Michler's thione, CH₃)₂NC₆H₄sub>2CS, is prepared by treatment of Michler's ketone with

hydrogen sulfide Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is toxic, corrosive, and flammable. Trace amounts in ambient atmosphere have a characteristic foul odor of rotten eggs. Swedish chemist ...

in the presence of acid or sulfideing auramine O.{{cite journal , doi = 10.1021/jo01029a020 , title = The Preparation of Thiones in the Presence of Anhydrous Hydrogen Fluoride , year = 1964 , last1 = Elofson , first1 = R. M. , last2 = Baker , first2 = Leslie A. , last3 = Gadallah , first3 = F. F. , last4 = Sikstrom , first4 = R. A. , journal = The Journal of Organic Chemistry , volume = 29 , issue = 6 , pages = 1355 Hydride reduction of Michler's ketone gives 4,4'-bis(dimethylamino)benzhydrol.

References

Printing Benzophenones Anilines Dimethylamino compounds