Reichardt dye

Structural formula
General
Surname	Reichardt dye
other names	2,6-diphenyl-4- (2,4,6-triphenyl-1-pyridinio) phenolate; 2,6-diphenyl-4- (2,4,6-triphenylpyridinio) phenolate; Reichardt's dye; Reichardts Betaine Dye No. 30;
Molecular formula	C 41 H 29 NO
Brief description	crystalline color: dark purple
External identifiers / databases
PubChem	2754438
Wikidata	Q23069154
properties
Molar mass	551.68 g mol −1
Physical state	firmly
density	No data available
Melting point	271-275 ° C
safety instructions
GHS hazard labeling ; no classification available
GHS hazard labeling ; no classification available
	As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Reichardt dye ( betaine 30 ) (2,6-diphenyl-4- (2,4,6-triphenyl-1-pyridinio) phenolate), is an organic dye from the group of azomerocyanine betaines . It is notable for its solvatochromic property. This means that it can change its color with the solvent in which it is dissolved. It has one of the largest known solvatochromic effects with colors that cover the entire visible spectrum . This large color shift was used to create a scale, the -scale. It was derived from spectroscopic data and is defined as the transition energy of the longest-wave Vis / NIR absorption band of Reichardt dye under normal conditions in kcal · mol ⁻¹ . If you define the polarity of tetramethylsilane to 0 and that of water to 1, you get the normalized -values, the -values. ${\ displaystyle E _ {\ tau} (30)}$ ${\ displaystyle E _ {\ tau} (30)}$ ${\ displaystyle E _ {\ tau} ^ {N}}$

Solutions of the Reichardt dye Betain 30 in different solvents show different colors

history

The Reichardt dye is named after Christian Reichardt , who synthesized it during his doctoral thesis under Karl Dimroth and who discovered its properties. In some sources, the dye is therefore also referred to as Dimroth-Reichardt dye . In some cases, derivatives are also called this, especially those which have tert-butyl groups in the para position .

Occurrence

The Reichardt dye does not occur naturally and can only be produced synthetically.

Extraction and presentation

A more recent synthesis is as follows:

2,6-Diphenylphenol is nitrated in the 4-position with dilute HNO ₃ and then reduced to the amine with sodium dithionite . This amine is reacted with 2,4,6-triphenylpyrylium hydrogen sulfate in the presence of sodium acetate to form the hydrogen sulfate of the dye, from which the betaine form of Reichardt dye is produced with NaOH .

properties

Reichardt's dye is a dark purple crystalline solid. In addition to solvatochromism, it has the properties of thermochromism ( the color change in phenol from orange-yellow at room temperature to orange, red-orange, red, violet to blue at the boiling point ), piezochromism and halochromism is impressive .

use

Due to its solvatochromism, the Reichardt dye can be used to estimate the polarity of solvents by measuring its absorption spectrum in the respective solvents; the wavelength of the maximum absorption bands in water (453 nm) and in diphenyl ether (810 nm). The following formula can then be used to calculate the value for the respective solvent based on the wavelength (or wave number) . This corresponds to the molar electronic excitation energy: ${\ displaystyle E _ {\ tau} (30)}$

${\ displaystyle E _ {\ tau} (30) = hcN_ {A} {\ tilde {\ nu}} _ {max} = {{119627 ~ kJ \ cdot nm \ cdot mol ^ {- 1}} \ over {\ lambda _ {max}}} = {{28572 ~ kcal \ cdot nm \ cdot mol ^ {- 1}} \ over {\ lambda _ {max}}}}$

${\ displaystyle h}$ : Planck's quantum of action

${\ displaystyle c}$ : Speed of light

${\ displaystyle N_ {A}}$ : Avogadro's constant

${\ displaystyle {\ tilde {\ nu}} _ {max}}$ : Wave number at absorption maximum,: wavelength at absorption maximum ${\ displaystyle \ lambda _ {max}}$

The value is the E _T (30) value normalized to the polarity extremes tetramethylsilane (= 0) and water (= 1) . ${\ displaystyle E _ {\ tau} ^ {N}}$

Alternatively, Brookers merocyanine can be used.

literature

C. Reichardt: Solvents and Solvent Effects in Organic Chemistry . 3. Edition. Wiley-VCH Verlag, Weinheim 2003, doi : 10.1002 / 3527601791 ( archive.org - first edition: 1979).
- 4th edition; with T. Welton, 2010, doi: 10.1002 / 9783527632220 .

Individual evidence

↑ ^a ^b ^c Datasheet Reichardt's dye from Sigma-Aldrich , accessed on April 10, 2016 ( PDF ).

↑ This substance has either not yet been classified with regard to its hazardousness or a reliable and citable source has not yet been found.

↑ Bruce R. Osterby, Ronald D. McKelvey: Convergent Synthesis of Betaine-30, a Solvatochromic Dye: An Advanced Undergraduate Project and Demonstration . In: J. Chem. Educ. . 73, No. 3, 1996, pp. 260-261. doi : 10.1021 / ed073p260 .

↑ Vanderlei Gageiro Machado, Clodoaldo Machado: An Easy and Versatile Experiment to Demonstrate Solvent Polarity Using Solvatochromic Dyes . In: J. Chem. Educ. . 78, No. 5, 2001, pp. 649-651. doi : 10.1021 / ed078p649 .

^ Alan R. Katritzky, Dan C. Fara, Hongfang Yang, Kaido Tämm et al .: Quantitative Measures of Solvent Polarity In: Spectroscopic Measurements. P. 183.

^ Christian Reichardt: Solvatochromic Dyes as Solvent Polarity Indicators . In: Chem Rev.. . 94, No. 8, 1994, pp. 2319-2358. doi : 10.1021 / cr00032a005 .

↑ Manfred A. Kessler, Otto S. Wolfbeis: An Improved Synthesis of the Solvatochromic Dye ET-30 . In: Synthesis . tape 1988 , no. January 8 , 1988, pp. 635-636 , doi : 10.1055 / s-1988-27662 .

↑ Karl Dimroth, Christian Reichardt, Armin Schweig: On the thermochromism of pyridinium-N-phenol-betaines . In: Justus Liebig's Annals of Chemistry . tape 669 , no. 1 , November 8, 1963, p. 95-105 , doi : 10.1002 / jlac.19636690111 .

↑ Christian Reichardt: Polarity of ionic liquids determined empirically by means of solvatochromic pyridinium N-phenolate betaine dyes . In: Green Chemistry . tape 7 , no. 5 , 2005, p. 339-351 , doi : 10.1039 / B500106B .

↑ Guido Heckenkemper: Synthesis and UV / Vis spectroscopic properties of new solvatochromic 2-, 3- and 4-pyridyl-substituted pyridinium-N-phenolate betaine dyes and their application for the investigation of aqueous ionophore solutions Dissertation, Chemie, 1999, Chapter 1, ( archiv.ub .uni-marburg.de ).

↑ Karl Dimroth, Christian Reichardt, Theodor Siepmann, Ferdinand Bohlmann: About pyridinium-N-phenol-betaine and their use to characterize the polarity of solvents . In: Justus Liebig's Annals of Chemistry . tape 661 , no. 1 , February 18, 1963, ISSN 1099-0690 , p. 1-37 , doi : 10.1002 / jlac.19636610102 .

[Sigma-1] Datasheet Reichardt's dye from Sigma-Aldrich , accessed on April 10, 2016 ( PDF ).

[NV-2] This substance has either not yet been classified with regard to its hazardousness or a reliable and citable source has not yet been found.

[3] Bruce R. Osterby, Ronald D. McKelvey: Convergent Synthesis of Betaine-30, a Solvatochromic Dye: An Advanced Undergraduate Project and Demonstration . In: J. Chem. Educ. . 73, No. 3, 1996, pp. 260-261. doi : 10.1021 / ed073p260 .

[4] Vanderlei Gageiro Machado, Clodoaldo Machado: An Easy and Versatile Experiment to Demonstrate Solvent Polarity Using Solvatochromic Dyes . In: J. Chem. Educ. . 78, No. 5, 2001, pp. 649-651. doi : 10.1021 / ed078p649 .

[5] Alan R. Katritzky, Dan C. Fara, Hongfang Yang, Kaido Tämm et al .: Quantitative Measures of Solvent Polarity In: Spectroscopic Measurements. P. 183.

[6] Christian Reichardt: Solvatochromic Dyes as Solvent Polarity Indicators . In: Chem Rev.. . 94, No. 8, 1994, pp. 2319-2358. doi : 10.1021 / cr00032a005 .