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Crown ether

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Crown ether, also known as "crown compound" because of its crown-like shape, is a class of compounds with a special property of complexation which was newly developed after 1970s. It’s a class of macrocyclic polyether composed of [CH2CH2Y] n (n> 2) units, wherein Y is a heteroatom such as O, N, S, or P. Crown ether narrowly refers to macrocyclic polyether in which Y is O, such as 18-crown-6 and dicyclohexyl-18-crown-6. They are named after the order of non-ring substituents, the number of the ring atoms, class name (crown) and the number of the ring hetero atoms according to the customary nomenclature, such as dibenzo-18-crown-6. Saturated crown ether is a colorless viscous liquid or low melt solid while aromatic ring-containing crown ether is a colorless crystal. Aromatic ring-containing crown ethers are insoluble in water, alcohol and common organic solvents at room temperature but more soluble in dichloromethane, chloroform, pyridine and formic acid. Crown ethers containing cyclohexyl have a higher solubility than the corresponding benzo crown ether in water, alcohols and aromatic hydrocarbons, also in petroleum ether.

Crown ether generally has a good thermal stability. However its ether bonds are susceptible to oxidation when melted or at a high temperature. The aromatic ring in the molecule can take part in bromination, nitration, esterification and ozonization, as well as form a polymer with formaldehyde in condensation. Crown ether can form a complex substance called crypate rendering many salts soluble in non-polar organic solvent, so that many of difficult reactions can be easily carried out. The stronger its lipophilic is, the greater catalytic activity it has. Furthermore, the reaction is selective since its fixed space can only accommodate ion of the corresponding size. The stability of formed by crown ethers and positive ions is mainly dependent on the relative size of the polyether ring and positive ions; and the stability constant is generally small for this crypate was formed by electrostatic interactions. What makes the reaction convenient is that the complexing can be easily broken down by adding water, dilute acid or through heat decomposition.

Preparation: Williamson (Williamson) ether synthesis is generally adopted. But in order to prevent a chain polymerization, high dilution method, fractional condensation and template reaction are recommended.

Currently the most widely used also the most readily available crown ethers are 18-crown-6, dibenzo-18-crown-6 and dicyclohexyl-18-crown-6. It is an important characteristic of crown ethers that it forms complexes with metal cations, which is utilized in phase transfer catalysis in organic synthesis.

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Structure:
Chemical Name:
1,4,7-Triazacyclononane
CAS:
4730-54-5
MF:
C6H15N3
Structure:
Chemical Name:
18-Crown-6
CAS:
17455-13-9
MF:
C12H24O6
Structure:
Chemical Name:
Cyclen
CAS:
294-90-6
MF:
C8H20N4
Structure:
Chemical Name:
2,5-DIMETHOXYCINNAMIC ACID
CAS:
161282-95-7
MF:
C40H46O8
Structure:
Chemical Name:
DOTA
CAS:
60239-18-1
MF:
C16H28N4O8
Structure:
Chemical Name:
1,4,7,10-TETRAAZACYCLODODECANE TETRAHYDROCHLORIDE
CAS:
10045-25-7
MF:
C8H21ClN4
Structure:
Chemical Name:
1,4,8,11-TETRAAZACYCLOTETRADECANE
CAS:
295-37-4
MF:
C10H24N4
Structure:
Chemical Name:
Dicyclohexano-18-crown-6
CAS:
16069-36-6
MF:
C20H36O6
Structure:
Chemical Name:
Kryptofix 222
CAS:
23978-09-8
MF:
C18H36N2O6
Structure:
Chemical Name:
1,4,7-Triazacyclononane trihydrochloride
CAS:
58966-93-1
MF:
C6H18Cl3N3
Structure:
Chemical Name:
4'-Aminobenzo-15-crown-5-ether
CAS:
60835-71-4
MF:
C14H21NO5
Structure:
Chemical Name:
1,4,7-TRIMETHYL-1,4,7-TRIAZACYCLONONANE
CAS:
96556-05-7
MF:
C9H21N3
Structure:
Chemical Name:
4,13-Diaza-18-crown 6-ether
CAS:
23978-55-4
MF:
C12H26N2O4
Structure:
Chemical Name:
1,4,7,10,13,16-HEXAAZACYCLOOCTADECANE
CAS:
296-35-5
MF:
C12H30N6
Structure:
Chemical Name:
4-NITROBENZO-15-CROWN-5
CAS:
60835-69-0
MF:
C14H19NO7
Structure:
Chemical Name:
2,3-(4-METHOXYCARBONYLBENZO)-1,4,7,10,13-PENTAOXACYCLOPENTADEC-2-ENE
CAS:
56683-56-8
MF:
C16H22O7
Structure:
Chemical Name:
4'-ACETYLBENZO-18-CROWN 6-ETHER
CAS:
41855-35-0
MF:
C18H26O7
Structure:
Chemical Name:
4'-FORMYLBENZO-18-CROWN 6-ETHER
CAS:
60835-74-7
MF:
C17H24O7
Structure:
Chemical Name:
DIBENZO-30-CROWN-10
CAS:
17455-25-3
MF:
C28H40O10
Structure:
Chemical Name:
1,4,8,12-TETRAAZACYCLOPENTADECANE
CAS:
15439-16-4
MF:
C11H26N4
Structure:
Chemical Name:
2-HYDROXYMETHYL-15-CROWN-5
CAS:
75507-25-4
MF:
C11H22O6
Structure:
Chemical Name:
1,3-DIISOPROPOXYCALIX[4!ARENECROWN-6, 97
CAS:
161282-96-8
MF:
C44H54O8
Structure:
Chemical Name:
Aza-15-crown-5
CAS:
66943-05-3
MF:
C10H21NO4
Structure:
Chemical Name:
1,4,7-TRIOXA-10-AZACYCLODODECANE
CAS:
41775-76-2
MF:
C8H17NO3
Structure:
Chemical Name:
1,4,7,10,13,16,19,22-OCTAOXACYCLOTETRACOSANE
CAS:
33089-37-1
MF:
C16H32O8
Structure:
Chemical Name:
1,4,8,11-TETRATHIACYCLOTETRADECANE
CAS:
24194-61-4
MF:
C10H20S4
Structure:
Chemical Name:
DIBENZO-15-CROWN-5
CAS:
14262-60-3
MF:
C18H20O5
Structure:
Chemical Name:
1,4,7,10,13-PENTAOXACYCLOPENTADECANE-2-METHANAMINE
CAS:
83585-56-2
MF:
C11H23NO5
Structure:
Chemical Name:
4-Vinylbenzo-18-crown-6
CAS:
39557-71-6
MF:
C18H26O6
Structure:
Chemical Name:
15-CROWN-4 [4-(2,4-DINITROPHENYLAZO)PHENOL]
CAS:
81238-57-5
MF:
C20H22N4O9
Structure:
Chemical Name:
4'-BROMOBENZO-18-CROWN-6
CAS:
75460-28-5
MF:
C16H23BrO6
Structure:
Chemical Name:
BIS(1,4-PHENYLENE)-34-CROWN 10-ETHER
CAS:
53914-95-7
MF:
C28H40O10
Structure:
Chemical Name:
N,N'-DIBENZYL-1,4,10,13-TETRAOXA-7,16-DIAZACYCLOOCTADECANE
CAS:
69703-25-9
MF:
C26H38N2O4
Structure:
Chemical Name:
4-NITROBENZO-18-CROWN-6
CAS:
53408-96-1
MF:
C16H23NO8
Structure:
Chemical Name:
N-PHENYLAZA-15-CROWN 5-ETHER
CAS:
66750-10-5
MF:
C16H25NO4
Structure:
Chemical Name:
Dibenzo-24-crown-8
CAS:
14174-09-5
MF:
C24H32O8
Structure:
Chemical Name:
BENZO-12-CROWN-4
CAS:
14174-08-4
MF:
C12H16O4
Structure:
Chemical Name:
2,3-(4-CARBOXYBENZO)-1,4,7,10,13,16-HEXAOXACYCLOOCTADEC-2-ENE
CAS:
60835-75-8
MF:
C17H24O8
Structure:
Chemical Name:
18-CROWN-5 [4-(2,4-DINITROPHENYLAZO)PHENOL]
CAS:
81238-58-6
MF:
C22H26N4O10
Structure:
Chemical Name:
1,4,8,11-TETRAMETHYL-1,4,8,11-TETRAAZACYCLOTETRADECANE
CAS:
41203-22-9
MF:
C14H32N4
Structure:
Chemical Name:
Dicyclohexano-24-crown-8
CAS:
17455-23-1
MF:
C24H44O8
Structure:
Chemical Name:
(+)-(18-CROWN-6)-2,3,11,12-TETRACARBOXYLIC ACID
CAS:
61696-54-6
MF:
C16H24O14
Structure:
Chemical Name:
1,5,9-TRIAZACYCLODODECANE
CAS:
294-80-4
MF:
C9H21N3
Structure:
Chemical Name:
1,4,7,10,13,16-hexaazacyclooctadecane hexahydrochloride
CAS:
58105-91-2
MF:
C12H30N6.6HCl
Structure:
Chemical Name:
4'-BROMOBENZO-15-CROWN 5-ETHER
CAS:
60835-72-5
MF:
C14H19BrO5
Structure:
Chemical Name:
2-(HYDROXYMETHYL)-12-CROWN 4-ETHER
CAS:
75507-26-5
MF:
C9H18O5
Structure:
Chemical Name:
4'-Aminobenzo-18-crown-6
CAS:
68941-06-0
MF:
C16H25NO6
Structure:
Chemical Name:
1,7-DIAZA-12-CROWN-4
CAS:
294-92-8
MF:
C8H18N2O2
Structure:
Chemical Name:
(BENZO-15-CROWN 5-ETHER)-4'-CARBOXYLIC ACID
CAS:
56683-55-7
MF:
C15H20O7
Structure:
Chemical Name:
[2,5]-DIBENZO-21-CROWN-7
CAS:
14098-41-0
MF:
C22H28O7
Structure:
Chemical Name:
2-(ALLYLOXYMETHYL)-18-CROWN 6-ETHER
CAS:
84812-04-4
MF:
C16H30O7
Structure:
Chemical Name:
1,4,7,10,13-PENTAOXA-16-AZACYCLOOCTADECANE
CAS:
33941-15-0
MF:
C12H25NO5
Structure:
Chemical Name:
1,4,10-TRIOXA-7,13-DIAZACYCLOPENTADECANE
CAS:
31249-95-3
MF:
C10H22N2O3
Structure:
Chemical Name:
4'-ACETYLBENZO-15-CROWN 5-ETHER
CAS:
41757-95-3
MF:
C16H22O6
Structure:
Chemical Name:
4-ACRYLAMIDOBENZO-18-CROWN-6, 98
CAS:
68865-32-7
MF:
C19H27NO7
Structure:
Chemical Name:
4'-NITRO-5'-(PICRYLAMINO)BENZO-18-CROWN-6
CAS:
74305-50-3
MF:
C22H25N5O14
Structure:
Chemical Name:
1,3-DIOCTYLOXYCALIX[4!ARENECROWN-6, 97
CAS:
161282-97-9
MF:
C54H74O8
Structure:
Chemical Name:
4-TERT-BUTYLBENZO-15-CROWN-5
CAS:
15196-73-3
MF:
C18H28O5
Structure:
Chemical Name:
2,3-NAPHTHO-15-CROWN-5
CAS:
17454-47-6
MF:
C18H22O5
Structure:
Chemical Name:
4-Aminobenzo-15-crown-5 hydrochloride
CAS:
111076-66-5
MF:
C14H21NO5.ClH
Structure:
Chemical Name:
CYCLOHEXANO-18-CROWN-6
CAS:
17454-53-4
MF:
C16H30O6
Structure:
Chemical Name:
4-T-BUTYLCYCLOHEXANO-15-CROWN-5
CAS:
17454-49-8
MF:
C18H34O5
Structure:
Chemical Name:
4',4''(5'')-DI-TERT-BUTYLDICYCLOHEXANO-18-CROWN-6
CAS:
28801-57-2
MF:
C28H52O6
Structure:
Chemical Name:
POLY(DIBENZO-18-CROWN-6)
CAS:
53660-42-7
MF:
C21H26O7
Structure:
Chemical Name:
4-AMINOBENZO-18-CROWN-6 SESQUIHYDRATE HYDROCHLORIDE, 99
CAS:
205504-06-9
MF:
C16H25NO6.ClH.H2O
Structure:
Chemical Name:
4',4''(5'')-DI-TERT-BUTYLDIBENZO-18-CROWN-6
CAS:
29471-17-8
MF:
C28H40O6
Structure:
Chemical Name:
CYCLOHEXANO-15-CROWN-5
CAS:
17454-48-7
MF:
C14H26O5
Structure:
Chemical Name:
4'-AMINO-5'-NITROBENZO-15-CROWN-5
CAS:
77001-50-4
MF:
C14H20N2O7