9-Benzylidene-9H-fluorene Derivatives Linked to Monoaza-15-crown-5: Synthesis and Metal Ion Sensing was written by Cao, Jing;Li, Yang;Feng, Junxiang. And the article was included in Chinese Journal of Chemistry in 2012.SDS of cas: 66943-05-3 This article mentions the following:
Two kinds of novel styryl chemosensory 2-FMNC and 3-FMNC, were designed and synthesized by an appropriate introduction of 9-benzylidene-9H-fluorene group as fluorophore with the aim at avoiding photoisomerization. These 9-benzylidene-9H-fluorene derivatives showed the similar selectivity and sensitivity upon addition of metal ions. The sensitivity of FMNC to alk. earth metal ions was Ba2+ > Sr2+ > Ca2+≈Mg2+. In the experiment, the researchers used many compounds, for example, 1,4,7,10-Tetraoxa-13-azacyclopentadecane (cas: 66943-05-3SDS of cas: 66943-05-3).
1,4,7,10-Tetraoxa-13-azacyclopentadecane (cas: 66943-05-3) belongs to ethers. The oxygen atom in ethers are more electronegative than carbon, thus the hydrogens which are alpha to the ethers are more acidic than the simple hydrocarbons. Ethers feature bent C–O–C linkages. In dimethyl ether, the bond angle is 111° and C–O distances are 141 pm. The barrier to rotation about the C–O bonds is low. The bonding of oxygen in ethers, alcohols, and water is similar. In the language of valence bond theory, the hybridization at oxygen is sp3.SDS of cas: 66943-05-3
Referemce:
Ether – Wikipedia,
Ether | (C2H5)2O – PubChem