15-Crown-5

15-Crown-5 is a crown ether with the formula (C2H4O)5. It is a cyclic pentamer of ethylene oxide that forms complex with various cations, including sodium (Na+)[2] and potassium (K+),[3] however, it is complementary to Na+ and thus has a higher selectivity for Na+ ions.

15-Crown-5
Names
Systematic IUPAC name
1,4,7,10,13-Pentaoxacyclopentadecane[1]
Identifiers
3D model (JSmol)
1618144
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.046.694
EC Number
  • 251-379-6
3897
MeSH 15-Crown-5
RTECS number
  • SB0200000
Properties
C10H20O5
Molar mass 220.265 g·mol−1
Appearance Clear, colorless liquid
Density 1.113 g cm−3 (at 20 °C)
Boiling point 93–96 °C (199–205 °F; 366–369 K) at 0.05 mmHg
log P -0.639
1.465
Thermochemistry
Std enthalpy of
formation (ΔfH⦵298)
 -881.1--877.1 kJ mol−1
Std enthalpy of
combustion (ΔcH⦵298)
 -5.9157--5.9129 MJ mol−1
Hazards
Safety data sheet msds.chem.ox.ac.uk
GHS pictograms
GHS Signal word Warning
GHS hazard statements
 H302, H315, H319
P305+351+338
NFPA 704 (fire diamond)
Flammability code 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oilHealth code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
1
2
0
Flash point 113 °C (235 °F; 386 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Properties

Analogous to 18-crown-6, 15-crown-5 binds to sodium ions. Thus, when treated with this complexing agent, sodium salts often become soluble in organic solvents.

First-row transition metal dications fit snugly inside the cavity of 15-crown-5. They are too small to be included in 18-crown-6. The binding of transition metal cations results in multiple hydrogen-bonded interactions from both equatorial and axial aqua ligands, such that highly crystalline solid-state supramolecular polymers can be isolated. Metal salts isolated in this form include Co(ClO4)2, Ni(ClO4)2, Cu(ClO4)2, and Zn(ClO4)2. Seven coordinate species are most common for transition metal ions complexes of 15-crown-5, with the crown ether occupying the equatorial plane, along with 2 axial aqua ligands.[4]

The structure of the complex [Co(15-crown-5)(H2O)2]2+.

15-crown-5 has also been used to isolate salts of oxonium ions. For example, from a solution of tetrachloroauric acid, the oxonium ion [H7O3]+ has been isolated as the salt [(H7O3)(15-crown-5)2][AuCl4]. Neutron diffraction studies revealed a sandwich structure, which shows a chain of water with remarkably long O-H bond (1.12 Å) in the acidic proton, but with a very short OH•••O distance (1.32 Å).[4]

Structure of [(H7O3)(15-crown-5)2]+ ion

A derivative of 15-crown-5, benzo-15-crown-5, has been used to produce anionic complexes of carbido ligands as their [K(benzo-15-crown-5)2]+ salts:[4]

(Ar2N)3MoCH + KCH2Ph + 2 (15-crown-5) → [K(15-crown-5)2]+[(Ar2N)3MoC]− + CH3Ph
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See also
  • Host guest chemistry
  • Phase transfer catalyst

References
  1. "15-crown-5 - Compound Summary". PubChem Compound. USA: National Center for Biotechnology Information. 16 September 2004. Identification and Related Records. Retrieved 11 October 2011.
  2. Takeda, Y.; et al. (1988). "A Conductance Study of 1:1 Complexes of 15-Crown-5, 16-Crown-5, and Benzo-15-crown-5 with Alkali Metal Ions in Nonaqueous Solvents". Bulletin of the Chemical Society of Japan. 61 (3): 627–632. doi:10.1246/bcsj.61.627.
  3. Chen, Chun-Yen; et al. (2006). "Potassium ion recognition by 15-crown-5 functionalized CdSe/ZnS quantum dots in H2O". Chem. Comm. (3): 263–265. doi:10.1039/B512677K.
  4. Jonathan W. Steed; Jerry L. Atwood (2009). Supramolecular Chemistry, 2nd edition. Wiley. ISBN 978-0-470-51233-3.

Further reading
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