CAS Number: 1724-44-3
Allyl cation
Allyl cations are important chemical intermediates in various organic reactions. They play a crucial role in the biosynthesis of many carbocyclic and heterocyclic compounds
Product Information
HM Chemical Trading GmbH supplies industrial-grade specialty chemicals and raw materials with reliable international logistics support.
References
-
Dissociating C3H5Br+ ions: Almost all roads lead to the allyl cation
The dissociative photoionization of five C3H5Br isomers—cis-1-bromopropene, trans-1-bromopropene, 2-bromopropene, 3-bromopropene (allyl bromide), and bromocyclopropane—was investigated using imaging photoelectron photoion coincidence (iPEPICO) spectroscopy, revealing that bromine loss is the sole dissociation channel in the measured energy range. Experimental onsets, supported by ab initio calculations, show that four isomers (allyl bromide, cis- and trans-1-bromopropene, and bromocyclopropane) dissociate to form the allyl cation (CH2CHCH2?), while the 2-bromopropene cation yields the less stable 2-propenyl cation (CH3C?=CH2) due to a high interconversion barrier. The 0 K appearance energies for allyl cation formation range from 10.211 ± 0.005 eV (bromocyclopropane) to 10.581 ± 0.014 eV (cis-1-bromopropene), while that for the 2-propenyl cation from 2-bromopropene is 10.930 ± 0.015 eV. Using a combined theoretical and experimental thermochemical network, the 0 K heats of formation for the five neutral isomers were determined. The study highlights that, although several isomers lead to the same allyl cation product, the dissociation mechanisms differ: the 1-bromopropene cations isomerize to the allyl bromide cation prior to dissociation, whereas 2-bromopropene follows a distinct pathway, demonstrating that "almost all roads lead to the allyl cation" except for the 2-bromopropene route.
DOI: 10.1016/j.ijms.2012.08.014