Characterization by theory of H-transfers and onium reactions of CH₃CH₂CH₂N⁺H=CH₂

Abstract

H-transfers by 4-, 5-, and 6-membered ring transition states to the -bonded methylene of CH 3 CH 2 CH 2 NH ϩ ϭCH 2 (1) are characterized by theory and compared with the corresponding transfers in cation radicals. Four-membered ring H-transfers converting 1 to CH 3 CH 2 CHϭN ϩ HCH 3 (2) and CH 3 N ϩ HϭCH 2 to CH 2 ϭNH ϩ CH 3 are high-energy processes involving rotation of the source and destination RHCϭ groups (R ϭ H or C 2 H 5 ) to near bisection by skeletal planes; migrating hydrogens move near these planes. The H-transfer 1 ¡ CH 3 C ϩ HCH 2 NHCH 3 (3) has a higher energy transition-state than 1 ¡ 2, in marked contrast to the corresponding relative energies of 4-and 5-membered ring H-transfers in cationradicals. Six-membered ring H-transfer-dissociation (1 ¡ CH 2 ϭCH 2 ϩ CH 2 ϭN ϩ HCH 3 ) is a closed shell analog of the McLafferty rearrangement. It has a lower energy transition-state than either 1 ¡ 2 or 1 ¡ 3, but is still a much higher energy process than 6-membered ring H-transfers in aliphatic cation radicals. In contrast to the stepwise McLafferty rearrangement in cation radicals, H-transfer and CC bond breaking are highly synchronous in 1 ¡ CH 3 N ϩ HϭCH 2 ϩ CH 2 ϭCH 2 . H-transfers in propene elimination from 1 are ion-neutral complex-mediated:Intrinsic reaction coordinate tracing demonstrated that a slight preference for H-transfer from the methyl containing the carbon from which CH 2 ϭNH is cleaved is due to CH 2 ϭNH passing nearer this methyl than the other on its way to abstracting H, i.e., some memory of the initial orientation of the partners accompanies this reaction. (J Am Soc Mass Spectrom 2007, 18, 270 -278)

1,2-Eliminations from (CH3)2NH+CH2CH3 and (CH3)2NH2+: Guided dissociations

“…The existence of two pathways from 1 to CH 2 ϭCH 2 elimination adds to evidence that reactions between incipient partners can follow distinct trajectories, as we have reported elsewhere [41]. Although the reorientation criterion appears to be satisfied by the movement of the partners around each other in this reaction, the two CH 2 ϭCH 2 elimination pathways probably would not be distinct if the partners reorient freely relative to each other in the course of those reactions.…”

Formation of chlorobenzenes by oxidative thermal decomposition of 1,3-dichloropropene

“…Under our reaction conditions, it is far more likely that radical cyclisation is responsible for chlorobenzene formation, as proposed by Hudson et al [38]. In the case of chlorobenzenes, radical cyclisation would The PES for cyclisation of 1,6-dichlorohexatriene-derived radical IM5 is shown in Fig.…”

Studies of the Interesting Gas‐phase Rearrangement Reactions of 2‐Pyrimidinyloxy‐N‐arylbenzylurea Promoted by Urea‐Carbamimidic Acid Tautomerism by ESI‐MS/MS and Theoretical Computation

“…Before the final departure, the interaction between the two partners within the complex could lead to various chemical reactions including transfer from the charged to the neutral species of the proton. [22][23][24] In the ion-neutral complex pathway, the proton shifts from benzylamine to the dipropylamine of urea inducing cleavage of urea bond to form the ion at m/z 413. In such process, the relative energy of the proton transfer is 95.1 kJ/mol and the energy barrier for dissociation of the urea bond is 86.2 kJ/mol.…”