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The heats of formation of some protonated olefinic carbonyl compounds: [C 5 H 9 O] + and [C 4 H 7 O 2 ] + ions
Author(s) -
Bouchoux G.,
Hoppilliard Y.,
Jaudon P.,
Houriet R.
Publication year - 1984
Publication title -
organic mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 0030-493X
DOI - 10.1002/oms.1210190808
Subject(s) - protonation , chemistry , mndo , ion , standard enthalpy of formation , proton , proton affinity , metastability , ion cyclotron resonance , medicinal chemistry , analytical chemistry (journal) , molecule , organic chemistry , cyclotron , physics , quantum mechanics
The proton transfer equilibrium reactions involving 3‐penten‐2‐one, 3‐methyl‐3‐buten‐2‐one, crotonic acid and methacrylic acid were carried out in an ion cyclotron resonance (ICR) spectrometer. The semiempirical method MNDO, used to estimate the heats of formation for 14 protonated [C 5 H 9 O] + and [C 4 H 7 O 2 ] + ions and the energetic aspect of the fragmentations of metastable [C 6 H 12 O] +. and [C 6 H 12 O 2 ] +. ions, leads to the conclusion that the ions corresponding to protonation at the carbonyl oxygen are the most stable. Thus the experimentally determined heats of formation of protonated olefinic carbonyl compounds can be attributed to the following structures: [CH 3 COHCHCHCH 3 ] + (δH f = 490 KJ mol −1 ), [CH 3 COHC(CH 3 )CH 2 ] + (δH f = 502 KJ mol −1 ), [HOCOHCHCHCH 3 ] + (δH f = 330 KJ mol −1 ) and [HOCOHC(CH 3 )CH 2 ] + (δH f = 336 KJ mol −1 ).