What are the properties of Z stilbenes

Stilbene

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Stilbene (1,2-diphenylethene) is an unsaturated hydrocarbon that can be seen as a symmetrical diphenyl derivative of ethene. It exist with that cis- and trans-Stilben two configurational isomeric compounds. The asymmetric diphenyl derivative of ethene is the constitutional or structural isomer 1,1-diphenylethene.

The name Stilben comes from the French chemist Auguste Laurent in 1845 and refers to the Greek word stilbein for shine, similar to the pearlescent mineral stilbit.[6]

Presentation and extraction

The synthesis of trans-Stilbene is achieved by reacting benzaldehyde with diethyl benzylphosphonate in a Horner-Wadsworth-Emmons reaction.[7] The alkylated phosphonic acid ester can be obtained by a Michaelis-Arbuzov reaction of diethyl phosphite with benzyl bromide.[7]

An alternative production variant is the reaction of benzaldehyde with benzyl magnesium bromide.[8] The technical production of trans-Stilbene occurs through a catalyzed oxidative dimerization of toluene or through a reductive dimerization of benzylidene chloride.[6]

The manufacture of cis-Stilbene occurs through a photochemical isomerization of trans- styles.[9][10][11] The isomerization reaction is reversible. A Reisomerization to the trans-Stilben is possible thermally.[12]

The synthesis of pure cis-Stilbene can also be achieved by metalation of diphenylacetylene with lithium and subsequent reaction with methanol at −78 ° C.[13] Another production possibility is the decarboxylation of 1-phenylcinnamic acid.[6]

properties

Physical Properties

trans-Stilben forms colorless shiny crystals that melt at 125 ° C. The enthalpy of fusion is 27.37 kJ mol−1, the entropy of fusion is 68.8 J mol−1· K−1.[4] The molar heat capacity has a value of 235.0 J mol at 25 ° C−1· K−1.[4] A molar enthalpy of combustion of -7360.8 ± 3.9 kJ mol−1 and a molar enthalpy of formation of 136.7 kJ mol−1 certainly.[14][15]

cis-Stilbene is a colorless liquid which crystallizes to a solid below the melting point at 5.85 ° C.[5] A boiling point of 135 ° C. was observed under a reduced pressure of 13 hPa.[6] The enthalpy of vaporization is 66 ± 1 kJ mol−1.[16] A molar enthalpy of combustion of -7404.05 ± 0.75 kJ mol−1 certainly.[17]

Chemical properties

cis-Stilbene can be cyclized photochemically to 4a, 4b-dihydrophenanthrene.[18] The cyclization product is thermodynamically unstable and easily forms the cis-Style back.[19] In the presence of oxidizing agents, in the simplest case of atmospheric oxygen, the thermodynamically stable phenanthrene is formed quickly.

use

trans-Stilbene can be used as a monomer additive in copolymerizations. The crystals are suitable as scintillator materials.[6]cis-Stilbene is often used as an olefinic test substance to elucidate the mechanism and stereospecificity of organic syntheses. It can also be used as a starting substance in heterocycle synthesis and in cyclopropanation.[6]

Stilbene derivatives

Occurrence

Stilbene derivatives are found in plants and are the product of two different biosynthetic pathways. One part comes from the shikimic acid route, the other from polyketide biosynthesis, a phenylpropanide building block being used as a starter unit for the iterative PKS synthesis of PKS III.

Other stilbene derivatives are resveratrol, which is associated with the health-promoting effects of red wine, rhaponticin, a phytoestrogen that can be isolated from rhubarb, and pinosylvin, a 3,5-stilbene diol found in the heartwood of pine trees.[8]

use

A number of stilbene derivatives have hormone-like effects. The substance diethylstilbestrol (diethylstilbestrol, DES) was the first commercial oral estrogen preparation. Due to its anabolic effect, DES was used as a fattening aid in cattle and pig fattening until the early 1980s. However, DES is carcinogenic. This is why the use of stilbene and its derivatives in food-producing animals is prohibited in the EU. In Germany this is legally in the Ordinance on substances with a pharmacological effect regulated.[20] In connection with hormone meat scandals, these stilbene derivatives were often referred to as “stilbenes” in media reports.

Stilbene derivatives are often used as optical brighteners, especially in textiles made from polymer materials, and as laser dyes. The special feature of stilbene compared to other aromatics and polyenes is exploited in that it fluoresces despite the double bond that characterizes the absorption. This is due to the strong change in the bond conditions in the excited state; In the excited S1 state, the double bond has a strong single bond character, whereas the single bonds to the rings have a double bond character. This greatly attenuates the torsional vibrations of the rings, which have a strong fluorescence-quenching character in other compounds with a similar structure, which results in the comparatively strong fluorescence quantum yield of stilbene.

literature

Individual evidence

  1. ↑ data sheet trans-stilbene at Merck, accessed December 9, 2010.
  2. ↑ data sheet cis-stilbene at Merck, accessed December 9, 2010.
  3. 3,03,13,23,3CRC Handbook of Chemistry and Physics. 87th edition. (CD-Rom version 2007), Taylor and Francis, Boca Raton (FL) 2007.
  4. 4,04,14,2J.C. Van Miltenburg, J.A. Bouwstra: Thermodynamic properties of trans-azobenzene and trans-stilbene in J. Chem. Thermodyn. 16 (1984) 61-65, doi: 10.1016 / 0021-9614 (84) 90075-2.
  5. 5,05,1S. Frisch, H. Hippler, J. Troe: UV Absorption Spectra and Formation Rates of Silibene in the High Temperature Kinetics of Benzyl Radicals in Z. Phys. Chem. (Munich) 188 (1995), pp. 259-273, doi: 10.1524 / zpch.1995.188.Part_1_2.259.
  6. 6,06,16,26,36,46,56,6Thieme Römpp Online. Georg Thieme Verlag, Stuttgart, accessed on January 26, 2011.
  7. 7,07,1Organikum. 21st edition. Wiley-VCH 2001, ISBN 3-527-29985-8.
  8. 8,08,1Römpp Lexikon Chemie, 10th edition Georg Thieme Verlag 1999
  9. ↑ H. Goerner, H. J. Kuhn: Cis-Trans Photoisomerization of Stilbenes and Stilbene-Like Molecules in Adv. Photochem. 19 (1995) pp. 1-117, doi: 10.1002 / 9780470133507.ch1.
  10. ↑ J. Saltiel, J. T. D’Agostino, E. D. Megarity, L. Metts, K. R. Neuberger, M. Wrighton, O. C. Zafiriow: Org. Photochem. 3 (1973) 1.
  11. ↑ F.A. Carey, R.J. Sunberg: Advanced Organic Chemistry - Part A: Structure and Mechanisms. 5th edition. Springer, 2008, ISBN 978-0-387-68346-1, pp. 1085-1091.
  12. ↑ C. Bastianelli, V. Caia, G. Cum, R. Gallo, V. Mancini: Thermal isomerization of photochemically synthesized (Z) -9-styrylacridines. An unusually high enthalpy of Z → E conversion for stilbene-like compounds. In: J. Chem. Soc .. Perkin Trans. 2, 1991, pp. 679-683, doi: 10.1039 / P29910000679.
  13. ↑ G. Levin, J. Jagur-Grodzinski, M. Szwarc: Simple and quantitative method of preparation of cis-stilbene and its deuterated analog, Ph-CD: CD-Ph. In: J. Org. Chem. 35 (1970), p. 1702, doi: 10.1021 / jo00830a109.
  14. ↑ p. Marantz, G.T. Armstrong: Heats of combustion of trans-stilbene and trans-2,2 ', 4,4', 6,6'-hexanitrostilbene (HNS) in J. Chem. Eng. Data 13 (1968) 118-121, doi: 10.1021 / je60036a036.
  15. ↑ p. Marantz, G.T. Armstrong: Heats of combustion of trans-stilbene and trans-2,2 ', 4,4', 6,6'-hexanitrostilbene (HNS) (correction) in J. Chem. Eng. Data 13 (1968) 455, doi: 10.1021 / je60038a902.
  16. ↑ D.S. Brackman, P.H. Plesch: Some physical properties of cis-stilbene in J. Chem. Soc. 1952, 2188-2190, doi: 10.1039 / JR9520002188.
  17. ↑ K. Yates, R.S. MC Donald: A thermochemical probe into the mechanism of electrophilic addition to olefins in J. Am. Chem. Soc. 93 (1971) 6297-6299, doi: 10.1021 / ja00752a066.
  18. ↑ F. B. Mallory, C. W. Mallory: Photochemistry of stilbenes. VI. Steric effects on the photocyclizations of some m-substituted stilbenes. In: J. Am. Chem. Soc .. 95 (1972), doi: 10.1021 / ja00772a017, pp. 6041-6048.
  19. ↑ L. Liu, B. Yang, T. J. Katz, M. K. Poindexter: Improved methodology for photocyclization reactions. In: J. Org. Chem. 56 (1991), doi: 10.1021 / jo00012a005, pp. 3769-3775.
  20. ↑ Federal Ministry of Justice: Ordinance on substances with a pharmacological effect.

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