Thermochemistry and structures of solvated SN2 complexes and transition states in the gas phase: experiment and theory

Bogdanov, Bogdan; McMahon, T. B.

doi:10.1016/j.ijms.2004.12.018

Cited by 36 publications

(50 citation statements)

References 74 publications

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“…Methyl halides (CH 3 X, X=F, Cl, Br, I) are frequently employed as model compounds in gas‐phase reactions1 to study at a molecular level mechanistic aspects of CH and CX bond activation. These ion/molecule reactions can be classified in four different types: 1) nucleophilic substitution when CH 3 X is reacted with anions resulting in the formation X − ;1b,d,e,i,n,p,q,r,x,z 2) halide atom abstraction by metal cations1t–v or anions;1p 3) proton, hydride or hydrogen‐atom abstraction by anions1b,k,x or cations,1v respectively; 4) dehydrogenation or dehydrohalogenation promoted by metal cations 1v. In all these processes, only one or two bonds of the methyl halide are activated.…”

Section: Branching Ratios [%] Reaction Rate Constants (K) and Reactmentioning

confidence: 99%

Evaluating the Thermal Vinylcyclopropane Rearrangement (VCPR) as a Practical Method for the Synthesis of Difluorinated Cyclopentenes: Experimental and Computational Studies of Rearrangement Stereospecificity

Orr

Percy

Tuttle

et al. 2014

Chemistry A European J

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Vinyl cyclopropane rearrangement (VCPR) has been utilised to synthesise a difluorinated cyclopentene stereospecifically and under mild thermal conditions. Difluorocyclopropanation chemistry afforded ethyl 3-(1'(2'2'-difluoro-3'-phenyl)cyclopropyl) propenoate as all four stereoisomers (18a, 18b, 22a, 22b) (all racemic). The trans-E isomer (18a), prepared in 70 % yield over three steps, underwent near quantitative VCPR to difluorocyclopentene 23 (99 %). Rearrangements were monitored by (19) F NMR (100-180 °C). While cis/trans cyclopropane stereoisomerisation was facile, favouring trans-isomers by a modest margin, no E/Z alkene isomerisation was observed even at higher temperatures. Neither cis nor trans Z-alkenoates underwent VCPR, even up to much higher temperatures (180 °C). The cis-cyclopropanes underwent [3,3]-rearrangement to afford benzocycloheptadiene species. The reaction stereospecificity was explored by using electronic structure calculations, and UB3LYP/6-31G* methodology allowed the energy barriers for cyclopropane stereoisomerisation, diastereoisomeric VCPR and [3,3]-rearrangement to be ranked in agreement with experiment.

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Section: Branching Ratios [%] Reaction Rate Constants (K) and Reactmentioning

confidence: 99%

Evaluating the Thermal Vinylcyclopropane Rearrangement (VCPR) as a Practical Method for the Synthesis of Difluorinated Cyclopentenes: Experimental and Computational Studies of Rearrangement Stereospecificity

Orr

Percy

Tuttle

et al. 2014

Chemistry A European J

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“…These results are also in line with the identical experimental results obtained with the same reactions carried out in solvents of different polarity (THF and toluene). [24] B3LYP versus MP2 methods: Different studies have shown that DFT methods in general, and B3LYP in particular, fail in determining some thermochemistry parameters such as reaction enthalpies so MP2/6-31 + G* or MP2/6-31 + G*//B3LYP/6-31 + G* level studies are recommended. [25a,b] It has also been shown that B3LYP fails to describe the M···p interactions, although it does well in the case of electrostatic M + n ···p interactions.…”

Section: Solvent Effectmentioning

confidence: 99%

“…However, it has been evocated [26] that DS°values contain errors, owing to the low frequency intermolecular vibrational modes and the neglect of their anharmonic character. The energy differences between equivalent species (between transition states or between enolates) vary by less than 1 kcal mol À1 , owing to the entropic effects, meaning that the agreement with the experimental results is not affected.…”

Section: Energiesmentioning

confidence: 99%

“…b (major diastereomer): GC: R t = 9.52 min; 1 H NMR (250 MHz, CDCl 3 ): d = 0.88 (t, 3 H, 3 J = 7.4 Hz), 1.09 (d, 3 H, 3 J = 6.7 Hz), 1.26-1.68 (m, 2 H), 2.31 (m, 1 H), 4.11 (m, 1 H), 4.62 (m, 1 H), 5.09 (m, 1 H), 6.02 (m, 1 H), 7.18-7.39 ppm (m, 5 H); 19 F NMR (235.35 MHz, CDCl 3 ): d = À77.84 ppm (m, 3 F); MS: m/z (%): 301 (M + , 52), 273(5), 217(15), 203 (27), 188 (56), 148 (36), 120 (31), 104(24), 85 (51), 57 (100).…”

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confidence: 99%

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Fluorine⋅⋅⋅ and π⋅⋅⋅Alkali Metal Interactions Control in the Stereoselective Amide Enolate Alkylation with Fluorinated Oxazolidines (Fox) as a Chiral Auxiliary: An Experimental and Theoretical Study

Sini¹,

Tessier

Pytkowicz

et al. 2008

Chemistry A European J

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The alpha-alkylation of amide enolates by using a pseudo-C(2) symmetry trans 4-phenyl-2-trifluoromethyloxazolidine (trans-Fox) as a chiral auxiliary occurs with an extremely high diastereoselectivity (>99 % de). The origin of this excellent stereocontrol was investigated by an experimental and theoretical (DFT) study. With this trans chiral auxiliary, both F...metal and pi...metal interactions compete to give the same diastereomer through Re face alkylation of the enolate. A 5.5 kcal mol(-1) energy difference found between the Re face and the Si face attack transition states is consistent with the complete diastereoselectivity that has been experimentally achieved. On the other hand, in the case of the cis chiral auxiliary (cis-Fox) the competition between the F...metal and pi...metal interactions is unfavourable to the diastereoselectivity. In this case, the Re face and the Si face attack transition states were found to be nearly isoenergetic (0.3 kcal mol(-1) difference), which is in good agreement with the very low diastereoselectivity observed.

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“…Gas phase S N 2 reactions of halide ions with trifluoromethyl halides have been investigated using HPMS and theoretical calculations (Bogdanov & McMahon, 2006). In addition, thermochemistry and structures of solvated S N 2 complexes and transition states in the gas phase have been studied experimentally and theoretically (Bogdanov & McMahon, 2005).…”

Section: G S N 2 Reactionsmentioning

confidence: 99%

Structures, energetics, and dynamics of gas phase ions studied by FTICR and HPMS

McMahon

2009

Mass Spectrometry Reviews

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Both Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) and high-pressure mass spectrometry (HPMS) are very powerful tools in the field of gas phase ion chemistry. Many experimental method developments based on FTICR-MS and HPMS are summarized, including the coupling of a high-pressure external ion source to a FTICR mass spectrometer, blackbody infrared radiative dissociation (BIRD), coupling laser desorption ionization with HPMS, infrared multiple photon dissociation (IRMPD), radiative association and bimolecular routes to gas phase cluster ion formation. An abundance of thermochemical data, such as proton affinities, gas phase acidities, methyl cation affinities and metal cation affinities, have been obtained. Some of these data are the basis of the standard data listed in the NIST thermochemical databases. Ion-molecule interactions, energetics, reactivities, and structures of molecules have been extensively investigated using the methods developed based on HPMS and FTICR mass spectrometric techniques.

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Thermochemistry and structures of solvated SN2 complexes and transition states in the gas phase: experiment and theory

Cited by 36 publications

References 74 publications

Evaluating the Thermal Vinylcyclopropane Rearrangement (VCPR) as a Practical Method for the Synthesis of Difluorinated Cyclopentenes: Experimental and Computational Studies of Rearrangement Stereospecificity

Evaluating the Thermal Vinylcyclopropane Rearrangement (VCPR) as a Practical Method for the Synthesis of Difluorinated Cyclopentenes: Experimental and Computational Studies of Rearrangement Stereospecificity

Fluorine⋅⋅⋅ and π⋅⋅⋅Alkali Metal Interactions Control in the Stereoselective Amide Enolate Alkylation with Fluorinated Oxazolidines (Fox) as a Chiral Auxiliary: An Experimental and Theoretical Study

Structures, energetics, and dynamics of gas phase ions studied by FTICR and HPMS

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