Pinacyanol (1,1'-diethyl-2,2'-carbocyaniniodide) is an organic compound , a polymethine dye with the chemical formula C 25 H 25 N 2 I, which belongs to the group of symmetric carbocyanines. Synthesized in 1905 by Benno Homolka , used as an optical sensitizer for the red range. The properties of pinacianol allowed to begin production of photographic materials, called panchromatic , with sensitivity to the entire spectrum range visible to humans.
| Pinacyanol | |
|---|---|
| Are common | |
| Chem. formula | C₂₅H₂₅IN₂ |
| Physical properties | |
| Molar mass | 480.38 g / mol |
| Thermal properties | |
| T. melt. | 295 ° C |
| Classification | |
| Reg. CAS number | |
| Pubchem | |
| Reg. EINECS number | |
| Smiles | |
| Inchi | |
| Chebi | |
| Chemspider | |
| Security | |
| GHS pictograms |  |
| NFPA 704 |  0 four 0 |
Trade names: quinaldine blue , sensitol red ( United Kingdom, Ilford ), CI 808 .
Content
History
At the beginning of the 20th century, Dr. Ernst Koenig , who directed research on the production of photographic sensitizers in the Höchst laboratory, as well as a number of his colleagues, obtained a significant number of compounds that allowed sensitizing photographic materials up to the orange range of visible radiation. But works on sensitization to the red range ran into a number of problems that did not allow obtaining high-quality sensitization. These problems were resolved by the production of Pinacianol Benno Homolka in 1905. The resulting dye gave a strong and high-quality sensitization to red rays. To obtain pinacyanol, Homolka carried out a condensation reaction similar to that used to obtain ethyl red , but in the presence of formaldehyde or chloroform [1] .
Due to the strong difference in properties between the old dyes and pinacyanol, it was obvious that it belongs to the new group of cyanine dyes, but only Mills and Hammer, in works published in 1920, precisely determined the dye structure. The group was called carbocyanins and, unlike previous cyanine dyes linked by a monomethine chain = CH-, had a connection between quinoline nuclei consisting of a trimethine chain = CH-CH = CH- [1] [2] .
The first photographic plates , known as panchromatic , were released to the market in 1906 by Wratten and Wainwright, Ltd. They were sensed by a mixture of pinacianol and pinachrome , had a significantly higher photosensitivity than the previous generation plates, and allowed photographs to be taken in red light with a short shutter speed [1] .
Physical and chemical properties
Dark green powder. Soluble in ethanol and benzene. The molar mass is 480.38 g / mol, the melting point is 295 ° C. The alcohol solution has a blue color, with a maximum absorption λ max = 604 nm, while the dye itself and its solutions quickly decolorize under the influence of light. It has a sensitizing effect on the photographic emulsion with a maximum in the region of 570-660 nm [3] [4] [5] [6] .
A mixture of pinacianol and pinaflavol in a ratio of 10: 1 gives an overlapping area of sensitization, and also exhibits supersensitizing properties, expressed in the mutual expansion of the areas of sensitization and increased sensitivity in both areas [6] .
The introduction of diethoxy substituents at positions 6.6 'gives another sensitizing dye - pinachrome blue [3] .
Getting
Obtained by the interaction of quinaldine iodoethylate and triethyl orthoformate [3] .
Another method was proposed, which quickly lost its practical application. In it, pinacianol was obtained by the interaction of a mixture of quinoline and quinaldine iodoethylates with formalin , while quinoline iodoethylate was not involved in the reaction, but its use increased the yield [2] [7] .
Application
It was used in photography as a sensitizer for the red part of the spectrum. Unsuitable in mixtures intended for sensitization to green light, in addition to red, as it desensitizes in this area. Instead, in these cases, violet pinachrome can be used, the sensitization spectrum of which is similar to that produced by pinacyanol [8] .
For sensitization of bromide photographic emulsions, concentrations of the order of 0.05% by weight of silver bromide are used [6] .
In microscopy, it is used for staining histological preparations [5] .
Security
Highly toxic by inhalation, toxic in contact with skin. Causes skin and eye irritation. NFPA rating 704 : health hazard: 4, flammability: 0, instability: 0 [4] .
Notes
- ↑ 1 2 3 Mees, 1942 , p. 972.
- ↑ 1 2 Venkataraman, 1957 , p. 1313-1314.
- ↑ 1 2 3 Venkataraman, 1957 , p. 1314.
- ↑ 1 2 Sigma-Aldrich .
- ↑ 1 2 Freistatt, 1980 , p. 313-314.
- ↑ 1 2 3 Baker, 1941 , p. 111.
- ↑ Wise, 1919 , p. 461.
- ↑ Joffe, 1929 , p. 333-335.
Literature
- Venkataraman K. Chemistry of synthetic dyes. - L .: State Scientific and Technical Publishing House of Chemical Literature, 1957. - T. 2.
- Technique of a physical experiment / ed. Ioffe A. F. - M., L .: State Publishing House, 1929.
- Freistat D.S. Reagents and preparations for microscopy. - M .: Chemistry, 1980 .-- 480 p.
- Baker TT Photographic emulsion technique. - Boston: American photography publishing Co., 1941.
- Mees, CEK The theory of photographic process . - New York: The Macmillan Company, 1942.
- Wise LE, Adams EQ, Steward JK, Lund CH Synthesis of photosensitizing dyes: pinaverdol and pinacyanol (Eng.) // The journal of industrial and engineering chemistry: journal. - 1919. - Issue. 11 . - No. 5 . - S. 460-463 . - DOI : 10.1021 / ie50113a026 .
Links
- 1,1′-Diethyl-2,2′-carbocyanine iodide MSDS . Sigma-Aldrich .