Formation of CH₃CH₂OCH₃^+˙ and ^˙CH₂⁺OHCH₂CH₃ from ionized 2‐ethoxyethanol and theoretical and experimental studies of the reactions of ^˙CH₂⁺OHCH₂CH₃

Abstract

It is concluded that C3H80+' formed by dissociation of ionized 2ethoxyethanol (8) is a mixture of CH,CH,OCHl' (7) and 'GH,+OHCH,CH, (2). Formation of 7 and CH3CH2+0HCH3 (12) is attributed to dissociations of species formed by the hydrogen transfers [ CH,CH20CH2+ 'CH,OHI + [CH,CH,OCHi' CH,Ol -+ [CH,CH,+OHCH, HCO]. Production of 7 competes weakly with dissociation to CH,CH,+OCH, (13) and to 12. The low abundance of 7 is attributed to the simple dissociation 8 + 13 being both energetically and entropically favored, and a second H-transfer to give 12 being energetically favored. The threshold for forming 7 is 45 kJ mol-' above that for dissociation directly to 13, so formation of 7 is the first ion-neutral complex-mediated elimination found to have a threshold above that for the competing simple dissociation. The low abundance of 7 also demonstrates that ion-neutral complexes can be intermediates without obviously revealing their presence by direct dissociation. Experimental results suggest that 2 isomerizes to CH,CH2CHz0H+' (5) and then dissociates by eliminating water. Ab initio results support the feasibility of 2 + CH,+OHCH,CH,' (1) and 2 + 5. However, experimental observations suggest that 2 + 1 does not occur. This is attributed to strong competition from dissociation and isomerization to 5. The transition state for 2 + 5 resembles [ CH,CH, CH,OHI +., and a cyclic transition state for 2 + 5 is ruled out. When the ethyl-oxygen bond in 2 is simply lengthened, the charge is initially concentrated on ethyl, but it switches to CH,OH in a curve crossing at an apparent transition state for C -0 bond breaking. 45

Unimolecular and Bimolecular Reactions of the .beta.-Distonic Ion CH3CH2OH+CH2CH2.bul.: An Experimental and Theoretical Study

“…(1 -1') and (1 -2), which correspond to the intramolecular 13-and 1,4-H migrations, respectively, involve high and similar barriers: the energies of the associated transition states differ by only 2 kJ/mol and the most stable transition state lies 98 kJ/mol above 1. In a similar system, CH30H+CH2CH2*, McAdoo et al 26 have obtained, at the UMP2/ 6-31G** level, a barrier for the intramolecular 1,4-H transfer similar to ours: 117 kJ/mol.…”