Ethyl cation transfer from diethylchloronium to alkyl aromatics studied by high pressure mass spectrometry

Abstract

Diethylchloronium ((C2H5)2Cl+) has been formed in a high pressure (2-4 Tori-) ion source using a C2H5Cl/CH4 mixture.(C2H5)2CI+ reacts with CzH5Cl (E, = 22 + 2 kcal mol-') at temperatures above 500 K to give t-C4HL The reaction of (C2H5)2Cl+ with B (B = benzene, toluene, isopropylbenzene, mesitylene) yields mainly C2H5B+ at temperatures below 500 K but BH+ is also formed at higher temperatures. The further reactions of C2H5B+ include proton transfer to B yielding BH+ (mesitylene), hydride transfer from B (isopropylbenzene), and reaction with C2H5CI yielding ( C 2 H &~+ (toluene and benzene) and (C2H5),~+ (benzene). The rate constants for the reaction (C2H5)2CI+ + B + C2H5B+ + C2H5CI increase in the order of increasing reaction exothermicity (mesitylene > isopropylbenzene > toluene > benzene). Mesitylene has a negative temperature coefficient, isopropylbenzene has no temperature coefficient, and toluene and benzene show positive temperature coefficients of reaction rate constants consistent with the double well potential theory for gas phase SN2 reactions. isopropylbenztne > tolukne > benztne). Pour ce qui est des coefficients de temperature des constantes des vitesses de reaction, celui du mCsitylkne. est ntgatif alors que l'isopropylbenzkne n'en a pas et que ceux du toldne et du benzkne sont positifs; ces rtsultats sont en accord avec la thCorie du potentiel A double puits pour les reactions SN2 en phase gazeuse.[Traduit par la revue]

An ICR mass spectrometry study of ion/molecule reactions between ethyl chloride and alkylamines

“…In contrast, Mathews and Stone reported that the C2H5+ transfer from diethylchloronium ion, (C2H5),C1+, to these aromatics is slower than CH3' transfer from dimethylchloronium species (7). Our results are in agreement with those of Mathews and Stone (7).…”

“…Such alkylation processes are bimolecular nucleophilic displacement reactions and are usually highly exothermic for bases such as dimethyl ether, ethanol, ammonia, and many aromatic bases (5,7,8). The observed relative rates for many of these reactions (5,7) reveal a negative temperature dependence, which strongly supports evidence for a double well potential model as summarized by Magnera and Kebarle (9).…”

“…In 1.4 mixture these two ions have almost the same fractional intensities, and in 1:8 mixture the rnlz = 100 ion species become the major product. This trend indicates that ethyl chloride is an essential compound for the formation of cSH14N+ (rnlz = 88) species, and the main channel for the formation of this ion is reaction [7]:…”

“…The comparison of rate constant values show that the rates of methylation or ethylation of C,-C3 alkylamines (reactions 111, [4], [7], and [9]) are comparable, being around 115 of the collision rate estimated by trajectory calculation (16). The high uncertainty of the rate constant of reaction [ l ] results from the occurrence of reactions [2] and [3] the contributions of which are not easy to estimate.…”

“…Dialkylhalonium ions have been used as alkylating agents in both gas and liquid phase reactions (3)(4)(5)(6)(7), and it is expected that diethylchloronium ions will react similarly. Such alkylation processes are bimolecular nucleophilic displacement reactions and are usually highly exothermic for bases such as dimethyl ether, ethanol, ammonia, and many aromatic bases (5,7,8).…”