(in benzene) aqueous KMnO^4 , 3^5
oC
(99%)
CH 3 (CH 2 ) 5 CH CH 2 R^4 N
+Br−
CH 3 (CH 2 ) 5 CO 2 H+HCO 2 H
i) Potassium permanganate can be transferred to benzene by quaternary
ammonium salts to give “purple benzene” which can be used as a test reagent
for unsaturated compounds ⇒ the purple color of KMnO 4 disappears and the
solution becomes brown (MnO 2 ).
11.20A CROWN ETHERS
- Crown ethers are also phase-transfer catalysts and are able to transport ionic
compounds into an organic phase.
- Crown ethers are cyclic polymers of ethylene glycol such as 18-crown-6:
O
O
O
O
O
O
O
O
O
O
O
O
K+
18-Crown-6
K+
2) Crown ethers are named as x-crown-y where x is the total number of atoms in the
ring and y is the number of oxygen atoms.
3) The relationship between crown ether and the ion that is transport is called a
host-guest relationship.
i) The crown ether acts as the host, and the coordinated cation is the guest.
- The Nobel Prize for Chemistry in 1987 was awarded to Charles J. Pedersen
(retired from DuPont company), Donald J. Cram (retired from the University of
California, Los Angeles), and Jean-Marie Lehn (Louis Pasteur University,
Strasbourg, France) for their development of crown ethers and other molecules
“with structure specific interactions of high selectivity”.
- Their contributions to our understanding of what is now called “molecular
