TY - JOUR
T1 - Possible Intermediacy of Cyclopropane Complexes in the Isomerization of Aliphatic Amine Radical Cations
AU - Nielsen, Christian B. O.
AU - Pedersen, Anders H.
AU - Hammerum, Steen
PY - 2019/2/28
Y1 - 2019/2/28
N2 - The isomerization of aliphatic amine radical cations via intermediate [cyclopropane-NH 3 ] + and [cyclopropane-amine] + ion-neutral complexes was studied experimentally with double-focusing mass spectrometers and computationally with composite ab initio methods. The results examine and extend Audier's suggestion that primary amine radical cations with alkyl substituents at the β- and/or -carbon atoms isomerize via transient complexes of NH 3 and alkyl cyclopropanes; these are formed by ring closure of the easily accessible -distonic isomers. Ionized amines with substituents at the α-carbon may react analogously when trialkyl cyclopropane complexes can be formed. Isomerization via complex intermediates is a major reaction pathway when the internal energy of the amine radical cation is less than that required for simple CC-bond cleavage. Complexes of unsubstituted or monosubstituted ionized cyclopropanes rarely contribute to the isomerization reactions. Secondary and tertiary amine radical cations do not undergo isomerization via cyclopropane intermediates, whereas aliphatic ether radical cations do.
AB - The isomerization of aliphatic amine radical cations via intermediate [cyclopropane-NH 3 ] + and [cyclopropane-amine] + ion-neutral complexes was studied experimentally with double-focusing mass spectrometers and computationally with composite ab initio methods. The results examine and extend Audier's suggestion that primary amine radical cations with alkyl substituents at the β- and/or -carbon atoms isomerize via transient complexes of NH 3 and alkyl cyclopropanes; these are formed by ring closure of the easily accessible -distonic isomers. Ionized amines with substituents at the α-carbon may react analogously when trialkyl cyclopropane complexes can be formed. Isomerization via complex intermediates is a major reaction pathway when the internal energy of the amine radical cation is less than that required for simple CC-bond cleavage. Complexes of unsubstituted or monosubstituted ionized cyclopropanes rarely contribute to the isomerization reactions. Secondary and tertiary amine radical cations do not undergo isomerization via cyclopropane intermediates, whereas aliphatic ether radical cations do.
U2 - 10.1021/acs.jpca.8b10523
DO - 10.1021/acs.jpca.8b10523
M3 - Journal article
C2 - 30698964
SN - 1089-5639
VL - 123
SP - 1548
EP - 1557
JO - Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory
JF - Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory
IS - 8
ER -