Gaseous tetramethylenechloronium ion

Abstract

Thus the stabilization energy due to the second cyclopropane in quadricyclyl should be no greater than 0.11/0.52 = 0.21 of the initial stabilization In nortrlcyclyl. This fraction Is reduced still further since | --jJ < | AEi-sl (I.e., the methyl cation LUMO is lower than the cyclopropyl carbinyl LUMO). This simple perturbation theory result is to be compared with the experimental relative rates (12) This species is stabilized yet further, of course, because of relief of angle strain at the cationic center. It is the intention of this paper to focus on only electronic effects, however. (13) Using the procedure of ref 11, (HL_h)2 " 0.47 for the interaction of cyclopropane with the already strongly stabilized cyclopropyl allyl cation; this represents 90% of the stabilization due to interaction of cyclopropane with methyl cation. ( 14) M.

Metastable ion characteristics. XXXVII. Structure and formation of stable C3H6O.+ ions

“…Ions of structure e are also formed from ethyl propenyl ether, consistent (Scheme V) with hydrogen rearrangement to the oxygen Scheme V + HO e atom18 as found for vinyl ethers. 3 Allyl Derivatives. From ionization potential data Meyerson and McCollum18 proposed that the abundant C3H6O•4" ions from allyl ethers had the ionized allyl alcohol structure h. Extensive deuterium labeling19 showed that this process involves a nonspecific hydrogen transfer, again consistent with H transfer to the saturated oxygen atom to form h. The CA data for three allyl ethers and allyl acetate (Table I) are consistent with the initial formation of allylalcohol ions h, although these presumably have rearranged to e ions in the 10-5 sec delay before measurement of their CA spectra (vide supra).…”

Rearrangement of 3-Membered 1,1,2-Trifluorobromonium and Iodonium Ions and Comparison of Trifluorochloronium to Fluorocarbenium Ions

“…Reaction of chlorine (Cl 2 ) with 1 cannot provide experimental evidence for a five-membered-ring intermediate since migration of the 4-chloro-substituent cannot be discerned because intermediates 4 and 5 (Scheme , X = Y = Z = Cl) each react with chloride ion to give the same product 1,2,4-trichloro-1,1,2-trifluorobutane ( 8 ). The parent hydrocarbon tetramethylene chloronium ion has been reported in the gas phase, in superacid media, and for the addition of trifluoroacetic acid to 5-chloro-1-hexene . The five-membered trifluorochloronium ion 5 (Scheme , X = Y = Z = Cl) is 19.7 kcal/mol more stable than the open-chloronium ion A (Table , run 1).…”

“…The three strong electron-withdrawing vinyl fluorine atoms on alkenes 1 , 2 , and 3 attenuate the neighboring group effect since we did not find evidence for a neighboring group effect when the number-4 substituent is chlorine (alkene 1 ). This is in contrast to the hydrocarbon where five-membered-ring tetramethylene chloronium ions are readily formed. – For halogen substituents on the number-4 carbon of 1,1,2-trifluoroterminal alkenes, iodine participates in neighboring group rearrangement better than bromine and the involvement of chlorine is not indicated. Quantum chemical calculations show that the chloronium ions from alkenes 1 , 2 , or 3 are unbridged and open-ions that form β-chlorocarbenium ions are similar to those reported by Ohta in super acid .…”

Gas phase bimolecular chemistry of isomeric C3H6Br+ cations

“…These cychc alkylenebromomum ions were detected experimentally for the first time 30 years later by Olah and Bolmger [2] via proton magnetic resonance spectroscopy of the cyclic tetramethylethylenehalonium ions, formed through ionization of 2,3-&-halo-2,3-dimethylbutanes in condensed superacldic media. Since then the experimental evidence for cyclic alkylenehalonium ions has been accumulating m the condensed phase [3][4][5][6][7][8][9] as well as in the gas phase [10][11][12][13][14][15][16][17][18][19]. Theoretical approaches predict that several cyclic alkylenehalonium ions can be equally or even more stable than the corresponding open halocarbocatlons [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35].…”