Ethere hydrogen bonding

Hydrogen bonding Because there is no 0—H bond in an ether, hydrogen bonding does not occur between ether molecules. Ethers can accept hydrogen bonding from water molecules. 

There are several examples of crown ether complexes where yttrium is not bound to the crown ether. [Y(H20)8]C13 (15-crown-5) has a [Y(H20)8]3+ cation (distorted dodecahedron) with the crown ether and chloride hydrogen bonded to the coordinated water molecules.58,225 An aqueous solution containing yttrium triflate and 18-crown-6 produces crystals of [Y(CF3-COO)2(H20)6](CF3COO),(18-crown-6) which have the crown ether hydrogen bonded to the coordinated water molecules.226 The complex [Y(N03)3(H20)3] (dibenzo-24-crown-8) has a nine-coordinate yttrium formed by bonding to three bidentate nitrate groups and three water molecules. The crown ether is hydrogen bonded to the water molecules.227... 

As already mentioned, the starting point is the combination of one of the thermodynamic frameworks of Appendix 2.A with the above hydrogen bonding formalism. For simplicity of presentation we use the LF framework and we confine ourselves to the case of one self-associated (e.g., OH=OH) and one cross-associated (e.g., 0H=0(ether)) hydrogen bonding interaction. 

Polyurethane EO copolymer N-H—ether hydrogen bonding noted 298... 

As shown m Figure 16 1 however the presence of an oxygen atom permits ethers to participate m hydrogen bonds to water molecules These attractive forces cause ethers to dissolve m water to approximately the same extent as comparably constituted alco hols Alkanes cannot engage m hydrogen bonding to water... 

Ethers tend to dissolve in alcohols and vice versa Represent the hydrogen bonding interaction between an alcohol molecule and an ether molecule J... 

Section 16 3 The carbon-oxygen bond of ethers is polar and ethers can act as proton acceptors m hydrogen bonds with water and alcohols... 

But ethers lack OH groups and cannot act as proton donors in forming hydrogen bonds... 

Podates AcycHc analogues of crown ethers /coronands and cryptands (podands, eg, (11) (30) are also capable of forming inclusion compounds (podates) with cations and uncharged organic molecules, the latter being endowed with a hydrogen bond fiinctionahty. Podates normally are less stable than coronates and cryptates but have favorable kinetics. 

Bond dissociation energies (BDEs) for the oxygen—oxygen and oxygen— hydrogen bonds are 167—184 kj/mol (40.0—44.0 kcal/mol) and 375 kj/mol (89.6 kcal/mol), respectively (10,45). Heats of formation, entropies, andheat capacities of hydroperoxides have been summarized (9). Hydroperoxides exist as hydrogen-bonded dimers in nonpolar solvents and readily form hydrogen-bonded associations with ethers, alcohols, amines, ketones, sulfoxides, and carboxyhc acids (46). Other physical properties of hydroperoxides have been reported (46). 

Association Complexes. The unshared electron pairs of the ether oxygens, which give the polymer strong hydrogen bonding affinity, can also take part in association reactions with a variety of monomeric and polymeric electron acceptors (40,41). These include poly(acryhc acid), poly(methacryhc acid), copolymers of maleic and acryflc acids, tannic acid, naphthoHc and phenoHc compounds, as well as urea and thiourea (42—47). 

Poly(vinyhdene chloride) also dissolves readily in certain solvent mixtures (82). One component must be a sulfoxide or A/,Al-diaIk5lamide. Effective cosolvents are less polar and have cycHc stmctures. They include aUphatic and aromatic hydrocarbons, ethers, sulfides, and ketones. Acidic or hydrogen-bonding solvents have an opposite effect, rendering the polar aprotic component less effective. Both hydrocarbons and strong hydrogen-bonding solvents are nonsolvents for PVDC. 

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