recognition” have implications for how enzymes recognize their substrates, how
hormones cause their effects, how antibodies recognize antigens, how
neurotransmitters propagate their signals, and many other aspects of
biochemistry.
- When crown ethers coordinate with a metal cation, they thereby convert the metal
ion into a species with a hydrocarbonlike exterior.
- The 18-crown-6 coordinates very effectively with potassium ions because the
cavity size is correct and because the six oxygen atoms are ideally situated to
donate their electron pairs to the central ion.
- Crown ethers render many salts soluble in nonpolar solvents.
- Salts such as KF, KCN, and CH 3 CO 2 K can be transferred into aprotic solvents
by using catalytic amounts of 18-crown-6.
- In the organic phase the relatively unsolvated anions of these salts can carry out
a nucleophilic substitution reaction on an organic substrate.
RCH 2 X + K+CN− 18-cbenzenerown-6 RCH 2 CN + K+X−
(100%)
C 6 H 5 CH 2 Cl+ K+F− 18-cbenzerownen-6 C 6 H 5 CH 2 F+ K+Cl−
+
dicyclohexano-18-crown-6
benzene
(90%)
KMnO 4
HO 2 C
O
O
O
O
O
O
O
Dicyclohexano-18-crown-6
