12-Crown-4
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12-Crown-4 can be synthesized using a modified Williamson ether synthesis, using LiClO4 as a templating cation:
- (CH2OCH2CH2Cl)2 + (CH2OH)2 + 2 NaOH → (CH2CH2O)4 + 2 NaCl + 2 H2O
It also forms from the cyclic oligomerization of ethylene oxide in the presence of gaseous boron trifluoride.
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Properties
Like other crown ethers, 12-crown-4 complexes with alkali metal cations. The cavity diameter of 1.2-1.5 Å gives it a high selectivity towards the lithium cation (ionic diameter 1.36 Å)
Its point group is S4. The dipole moment of 12-crown-4 varies with solvent and temperature. At 25 °C, the dipole moment of 12-crown-4 was determined as 2.33 ± 0.03 D in cyclohexane and 2.46 ± 0.01 D in benzene.