A comparative AIM study of alkyl monoethers and their protonated forms

The effects of the protonation on the atomic and bond properties of the oxygen atom were studied in a series of unbranched alkyl monoethers of formula CH3(CH2)nO(CH2)mCH3 (n,m=0,1,2,3,4) using MP2/6-31++G∗∗//MP2/6-31G∗∗ wave functions. The different character of oxygen in methylethers and the remaining dialkylethers and the charge transfer dominant part in the protonation process are supported by two different linear correlations (one for methoxyethers and another for the remaining ethers) between proton charges and protonation energies. The atomic energy of the proton accounts for more than 93% of the protonation energy.