18-Crown-6

Dibenzo-18-crown-6 changed 477209292 18-Crown-6 18-c-6.png skin-invert 150px Skeletal formula 18-Crown-6-from-xtal-1980-Mercury-3D-balls.png bg-transparent Ball-and-stick model Sample 18-crown-6.jpg sample 1,4,7,10,13,16-Hexaoxacyclooctadecane 1/C12H24O6/c1-2-14-5-6-16-9-10-18-12-11-17-8-7-15-4-3-13-1/h1-12H2 XEZNGIUYQVAUSS-UHFFFAOYAP 28557 C1COCCOCCOCCOCCOCCO1 correct EBI 155204 correct chemspider 1S/C12H24O6/c1-2-14-5-6-16-9-10-18-12-11-17-8-7-15-4-3-13-1/h1-12H2 correct chemspider XEZNGIUYQVAUSS-UHFFFAOYSA-N correct CAS 17455-13-9 correct FDA 63J177NC5B O1CCOCCOCCOCCOCCOCC1 correct chemspider correct EBI 32397 26563 241-473-5 1619616 4535 C12H24O6 264.315 g/mol 1.237 g/cm3 37 to 40 116 (0.2 Torr) 75 g/L 07 Warning 302 315 319 335 261 264 270 271 280 301+312 302+352 304+340 305+351+338 312 321 330 332+313 337+313 362 403+233 405 501 Dibenzo-18-crown-6TriglymeHexaaza-18-crown-6 18-Crown-6 is an organic compound with the formula [C2H4O]6 and the IUPAC name of 1,4,7,10,13,16-hexaoxacyclooctadecane. It is a white, hygroscopic crystalline solid with a low melting point. Supramolecular Chemistry 2nd Jonathan W. Steed Jerry L. Atwood Wiley 2009 978-0-470-51233-3 Like other crown ethers, 18-crown-6 functions as a ligand for some metal cations with a particular affinity for potassium cations (binding constant in methanol: 106 M−1). The point group of 18-crown-6 is S6. The dipole moment of 18-crown-6 is solvent- and temperature-dependent. Below 25 °C, the dipole moment of 18-crown-6 is 2.76 ± 0.06 D in cyclohexane and 2.73 ± 0.02 in benzene.Caswell Lyman R. Savannunt Diana S. Temperature and solvent effects on the experimental dipole moments of three crown ethers J. Heterocyclic Chem. January 1988 25 1 73–79 10.1002/jhet.5570250111 The synthesis of the crown ethers led to the awarding of the Nobel Prize in Chemistry to Charles J. Pedersen. Synthesis This compound is prepared by a modified Williamson ether synthesis in the presence of a templating cation:Gokel George W. Cram Donald J. Donald J. Cram Liotta Charles L. Harris Henry P. Cook Fred L. 1977 18-Crown-6 Org. Synth. 57 30 10.15227/orgsyn.057.0030 free (CH2OCH2CH2Cl)2 + (CH2OCH2CH2OH)2 + 2 KOH → (CH2CH2O)6 + 2 KCl + 2 H2O It can be also prepared by the oligomerization of ethylene oxide. It can be purified by distillation, where its tendency to supercool becomes evident. 18-Crown-6 can also be purified by recrystallisation from hot acetonitrile. It initially forms an insoluble solvate. Rigorously dry material can be made by dissolving the compound in THF followed by the addition of NaK to give [K(18-crown-6)]Na, an alkalide salt.10.1002/9781118744994.ch24 Inorganic Syntheses: Volume 36 36 127–134 2014 Jilek Robert E. Fischer Paul J. Ellis John E. Bis(1,2-Bis(Dimethylphosphano)Ethane)Tricarbonyltitanium(0) and Hexacarbonyltitanate(2−) 9781118744994 Crystallographic analysis reveals a relatively flat molecule but one where the oxygen centres are not oriented in the idealized 6-fold symmetric geometry usually shown.J. D. Dunitz P. Seiler 1,4,7,10,13,16-Hexaoxacyclooctadecane Acta Crystallogr. 1974 B30 11 2739 10.1107/S0567740874007928 The molecule undergoes significant conformational change upon complexation. Reactions thumb|left|upright=0.6|The complex of H3O+ with 18-crown-6 18-Crown-6 has a high affinity for the hydronium ion H3O+, as it can fit inside the crown ether. Thus, reaction of 18-crown-6 with strong acids gives the cation [H3O·18-crown-6]+. For example, interaction of 18-crown-6 with HCl gas in toluene with a little moisture gives an ionic liquid layer with the composition [H3O·18-crown-6]+[HCl2]−·3.8C6H5Me, from which the solid [H3O·18-crown-6]+[HCl2]− can be isolated on standing. Reaction of the ionic liquid layer with two molar equivalents of water gives the crystalline product (H5O2)[H3O·18-crown-6]Cl2.Atwood Jerry L. Bott Simon G. Coleman Anthony W. Robinson Kerry D. Whetstone Stephen B. Means C. Mitchell The oxonium cation in aromatic solvents. Synthesis, structure, and solution behavior of [H3O+·18-crown-6][Cl-H-Cl] Journal of the American Chemical Society December 1987 109 26 8100–8101 10.1021/ja00260a033Atwood Jerry L. Bott Simon G. Means C. Mitchell Coleman Anthony W. Zhang Hongming May Michael T. Synthesis of salts of the hydrogen dichloride anion in aromatic solvents. 2. Syntheses and crystal structures of and the related Inorganic Chemistry February 1990 29 3 467–470 10.1021/ic00328a025 left Applications thumb|left|upright=0.6|18-crown-6 complex with potassium ion 18-Crown-6 binds to a variety of small cations, using all six oxygens as donor atoms. Crown ethers can be used in the laboratory as phase transfer catalysts.Liotta C. L. Berknerin J. 18-Crown-6 Encyclopedia of Reagents for Organic Synthesis L. Paquette 2004 J. Wiley & Sons New York 10.1002/047084289X.rc261 0471936235 Salts which are normally insoluble in organic solvents are made soluble by crown ether.Wynn etal David The Solubility of Alkali-Metal Fluorides in Non-Aqueous Solvents With and Without Crown Ethers... Talanta 1984 31 11 1036–1040 10.1016/0039-9140(84)80244-1 18963717 For example, potassium permanganate dissolves in benzene in the presence of 18-crown-6, giving the so-called "purple benzene", which can be used to oxidize diverse organic compounds. Various substitution reactions are also accelerated in the presence of 18-crown-6, which suppresses ion-pairing.Cook Fred L. Bowers Chauncey W. Liotta C. L. Chemistry of naked anions. III. Reactions of the 18-crown-6 complex of potassium cyanide with organic substrates in aprotic organic solvents The Journal of Organic Chemistry November 1974 39 23 3416–3418 10.1021/jo00937a026 The anions thereby become naked nucleophiles. For example, using 18-crown-6, potassium acetate is a more powerful nucleophile in organic solvents: [K·(18-crown-6)]+AcO− + C6H5CH2Cl → C6H5CH2OAc + [K·(18-crown-6)]+Cl− The first electride salt to be examined with X-ray crystallography, [Cs(18-crown-6)2]+·e−, was synthesized in 1983. This highly air- and moisture-sensitive solid has a sandwich molecular structure, where the electron is trapped within nearly spherical lattice cavities. However, the shortest electron-electron distance is too long (8.68 Å) to make this material a conductor of electricity. References External links [https://www.sigmaaldrich.com/US/en/search/18-crown-6?focus=products&page=1&perpage=30&sort=relevance&term=18-crown-6&type=product ISBNcrowndocx Category:Crown ethers Category:Macrocycles