Proton affinity dimethyl ether

Molecular orbital calculations predict that oxirane forms the cyclic conjugate acid (39), which is 30 kJ moF stabler than the open carbocation (40) and must surmount a barrier of 105kJmoF to isomerize to (40) (78MI50500). The proton affinity of oxirane was calculated (78JA1398) to be 807 kJ mol (cf. the experimental values of 773 kJ moF for oxirane and 777-823 kJ moF for dimethyl ether (80MI50503)). The basicity of cyclic ethers is discussed in (B-67MI50504). 

The polarization potential provides the energy due to electronic reorganization of the molecule as a result of its interaction with a point positive charge. The sum of the electrostatic and polarization potentials provides a better account of the energy of interaction of a point positive charge than available from the electrostatic potential alone. It properly orders the proton affinities of trimethylamine, dimethyl ether and fluoromethane. 

These studies were extended briefly to a number of other Lewis bases, including dimethyl ether to look for trends relating to base strength or proton affinity (74). The major spectral features of the complexes were shifted vibrational modes of the base, but these shifts were much less substantial than for H2O or NH3, and very little information about the nature or structure of the complex could be extracted. 

Proton affinity (PA) acetaldehyde, 123 acetone, 123 acrolein, 123 butenone, 123 dimethyl ether, 123 dimethylacrolein, 123 formaldehyde, 123 methanol, 123 methyl acetate, 123 methyl acrylate, 123 (Aj-mcthylacrolein, 123 oxetane, 123 table of, 123 tetrahydrofuran, 123 water, 123... 

---