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Negative Ion Rearrangements in the Gas Phase

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Negative Ion Rearrangements in the Gas Phase r5.Y.q2 Negative Ion Rear{angements rn the Gas Phase A thesis presented for the degree of Doctor of Philosophy by Peter Charles Hans EICHINGER B.Sc. (Hons.) Deparhent of Organic Chemistry The University of Adelaide Sept., t99L Contents List of Fisures v1 List of Tables xiii - Statement xvu Acknowledeements XVlU Abstract xx 1, Introduction. L - 1.1 Generation of Negative lons. 2 7.2 Formation of Negative lons. J 1,.2.1,. Primary Formation. 3 7.2.L.7 Resonance Capture (Electron Capture). 3 1,.2.1,.2 Dissociative Resonance Capture (Electron Dissociative Attachment). 4 L.2.1.3 lon-Pair Formation. 5 1.2.2 Secondary lons. 6 7.2.2.I Proton Transfer. 7 7.2.2.2 Charge Exchange. 7 1.2.2.3 Nucleophilic Addition. 8 I.2.2.4 Nucleophilic Displacement. 8 1.3. Collisional Activation 9 1.4 Mass Analysed Ion Kinetic Energy Spectrometry ( MrKES ). 10 1.5 Detection of Negative Ions. 11 1.6 Vacuum Generators ZAB 2HF Reversed Geometry Mass Spectrometer. 74 1.7 Structural Identification of Ions. 76 1..71 Charge Reversal. 18 L.72 Neutralisation - Reionisation Mass Spectrometry 22 7.73 IonDissociation Characteristics. 25 1..74 Kinetic Energy Release. 28 1.8 Rules for Fragmentation of Anions. 32 1.8.1 Simple homolytic cleavage. 33 7.8.2 Formation of an ion- neutral complex. 33 1.8.3 Proton transfer preceding ion - neutral complex formation. 34 7.8.4 Rearrangement, preceding fragmentation 34 1..9 Rearrangement reactions. 35 1.10 Intrinsic Reactivity 37 1.11.1 Solvent 38 1,.11.2 Volume of Activation ÂV# 39 1.11.3 pKa 40 7.17.4 Counter Ions 47 1.11.5 Ion Pairing 43 1,.11.6 Aggre gregation 50 L The Wittig Rearrangement. 2.1, Introduction. 64 2.1.1. The Condensed Phase Wittig Rearrangement. 64 2.L.2 The Gas Phase Wittig Rearrangement. 73 2.1.2.1Atkyl- and Aryl Benzyl Ethers. 74 2.1..2.2 Diallyl Ether. 79 111 2.7.2.3 Absence of the Wittig Rearrangement from Allyl Alkyl Ethers. 83 2.2 Results and Discussion 85 2.2.1 Dibenzyl Ether. 85 2.2.2 Allyl Phenyl Ether. 87 2.2.3 Allyl Benzyl Ether. 97 2.2.4 A Reinvestigation of the Condensed Phase Rearrangements of Deprotonated Allyl Benzyl Ether. 111 2.2.5 Diphenylmethyl Phenyl Ether. 772 2.2.6 Vinyl Alkyl Ether. 776 2.2.7 Benzyl Vinyl Ether. 130 2.2.8 Divinyl Ether. 131 2.2.9 Allyl Vinyl Ether. 133 2.3 Conclusions and Summary. 145 2.3.I The Scope of the Wittig Rearrangement in the Gas Phase. 145 2.3.2 Loss of Alkyl Radicals. 747 3. The Smiles Rearrangement. 3.1, Introduction. 159 3.2 Results and Discussion. 166 3.2.L Phenoxyalcohols. 1.66 3.2.2 Thiophenoxyalcohols. 180 3.2.3 Phenoxyalkanethiols. IU 3.3 Synthetic studies directed toward Identification of the Intermediates in the Gas Phase Rearrangement. 186 lr The Benzilic Acid Reanangement and related rearrangements. 4.1, Introduction. 190 4.2 The Gas Phase Benzilic Acid Rearrangement. 791 1V 4.3 Rearrangements of Deprotonated o - Hydroxylactate Esters. 797 4.4 Rearrangement Reactions of Deprotonated Alkyl Pyruvates. 207 å The Acvloxvacetate / Acvl hvdroxvacetate rearransement and related reanansements. 5.1 Introduction. 278 5.2 The Gas Phase Rearrangement of Acyloxyacetates. 223 5.3.1 Fragmentations of the Alkoxycarbonyl - a-Dicarbonyl Complex(L90). 231 5.3.2 Loss of Alkyl Formate. 23r 5.3.3 Fragmentations of the Alkoxycarbonyl a-Dicarbonyl Complex (19L). 237 5.4 The Gas Phase Acyloxyacetonitrile / AcyL Hydroxyacetonitrile Rearrangement. 248 6. Future Directions. 6.7 Future Directions. 256 6.2 Dissociation of the deprotonated molecule to form a radical anion -radical or anion - neutral complex. 257 6.2.7 The Wittig rearrangement. 257 6.2.2 Other Rearrangements. 259 6.3 Internal nucleophilic addition of an ion to a suitable r-System. 259 6.3.1 The Smiles Rearrangement. 259 6.3.2 Miscellaneous. 267 6.4 Nucleophilic addition of the base to yield an anionic species which may then undergo reatrangement. 262 v 6.4.7 Benzilic Acid rearrangement. 262 6.5 Solvolysis reactions. 264 6.6 Miscellaneous Reactions. 264 Exoerimental. 266 References. 296 339 vl List of Fisures. Figure Title of Figure Page Number Number 1.1 Morse curves -indicating the vertical transition on addition of an electron to a diatomic system to form a stable radical anion M-. ( resonance capfure, process a) and an unstable radical anion ( dissociative resonance capture, process b ). 6 r.2 Schematic representation of the electron multiplier commonly used to detect positive ions. 72 1.3 Schematic representation of the electron multiplier showing modifications designed to enhance the sensivity of the detector to negative ions. T4 '1..4 Simplified schematic representation of the VG ZAB 2HF Mass Specbometer. 15 1.5a Conventional Positive Ion Mass Spectrum of Flavanone at 70 eY. 20 1.5b The Charge Reversal Mass Spectrum of the Flavanone Molecular lon. 20 1..6 Schematic representation of a Neutralisation Reionisation experiment. 23 1.7 Simplified schematic representation of the Gas Collision Cell and the Effect of Applying an Electric Potential to the Collision Cell. 26 vtl 1.8 The spectrum of deprotonated benzyl ethyl ether obtained by floating the gas collision cell to +1,000V shown offset from the normal spectrum. 28 r.9 The Effects of Orientation of an Ion leading to Kinetic Energy Release. 29 1.L0a Peak Shape resulting from small Kinetic Energy 31 Release. 1.10b Peak Shape resulting from large Kinetic Energy Release. 31 2.1 The Collisional Activation Mass Spectrum of Deprotonated PhCH2OEt recorded on a VG ZAB zF{F Mass Spectrometer. 75 2.2 The Collisional Activation Mass Spectrum of Deprotonated Ph(EI)CHOH recorded on a VG ZAB zF{F Mass Spectrometer. 75 2.3 The Collisional Activation Mass Spectrum of Deprotonated Diallyl Ether recorded on a VG ZAB z}{F Mass Spectrometer. 80 2.4 The Collisional Activation Mass Spectrum of Deprotonated 5 - Hexenal recorded on a VG ZAB zH.F Mass Spectrometer. 80 2.5 Comparative Reaction Coordinates for allylic migration in the presence and absence of a Lithium Cation. 83 2.6 The Collisional Activation Mass Spectrum of PhOC-(H)CH=CH2. 89 2.7 The Collisional Activation Mass Spectrum of Ph(cH2=cH)cHo- 89 2.8 The Collisional Activation Mass Spectrum of Deprotonated g-Allyl Phenol. 96 vul 2.9 The Collisional Activation Mass Spectrum of Deprotonated Allyl Benzyl Ether. 100 2.70 The Collisional Activation Mass Spectrum of the Expected Wittig rearrangement ion Ph(CH2=CHCH2)CHO- (82). 101 2.r1. The Collisional Activation Mass Spectrum of the Expected Wittig rearrangement ion PhCH2(CHz=CH)CHO- (83). 101 2.12 The Collisional Activation Mass Spectrum of PhCD2OC-(H)CH=CHz (8a) recorded on a VG ZAB 2FIF Mass Spectrometer. 104 2.r3 The Collisional Activation Mass Spectrum of PhCD-OCH2CH=CH2 (85) recorded on a VG ZAB z}{F Mass Spectrometer. 104 2.74 The Collisional Activation Mass Spectrum of CH2=Ç- OCH2CH3 prepared by an S¡2(Si) reaction. 123 2.15 The Collisional Activation Mass Spectrum of Deprotonated Ethyl Vinyl Ether. 723 2.1.6 The Collisional Activation Mass Spectrum of the Expected Wittig Rearrangement Ion, the Butan-2-one Enolate lon. r24 2.77 Partial Spectrum of the "Collision - Induced" vs "IJnimolecular" Decompositions of Deprotonated Ethyl Vinyl Ether recorded on a VG Z.AB 2HF Mass Spectrometer. 126 2.78 The Collisional Activation Mass Spectrum of Deprotonated n-Butyl Vinyl Ether. L28 2.r9 The Collisional Activation Mass Spectrum of CH2=Çg--OBur. r29 IX 2.20 The Collisional Activation Mass Spectrum of the Flexan - 2 - one Enolate Ion. 129 2.21 Collisional Activation Mass Spectrum of Deprotonated Allyl Vinyl Ether. 137 2.22 Collisional Activation Mass Spectrum of Deprotonated Penta-1.,4-Pentadien-3-o1. 137 2.23 Charge Reversal Mass Spectrum of Deprotonated Allyl Vinyl Ether. 138 2.24 Charge Reversal Mass Spectrum of Deprotonated Penta- 1,4-dien-3-ol. 138 2.25 The Collisional Activation Mass Spectrum of Deprotonated Benzyl Diethyl Acetal [PhC-(OEt)z]. r57 3.1 Collisional Activation Mass Spectrum of PhOCH2CH218O- recorded on the VG ZAB 2HF Mass Spectrometer. 769 3.2 Collisional Activation Mass Spectrum of PhOCH2CH2CH218O- recorded on the VG ZAB 2HF Mass Spectrometer. 769 3.3 Collisional Activation Mass Spectrum of PhO(CHz)¿18O- recorded on the VG ZAB 2HF Mass Spectrometer. 170 3.4 PhO- peak (m/z = 93) from PhO(CH2)zO-. 171. 3.5 PhO- composite peak (m/z = 93) from PhO(CH2)sO-. 177 3.6 Partial Spectrum of the "Collision Induced" vs "IJnimolecular" Decompositions of PhO(CH2)3189- io., recorded on the VG ZAB 2HF Mass Spectrometer. 172 3.7 Collisional Activation Mass Spectrum of the Phenoxide Ion, recorded on a VG ZAB 2F{F instrument. 178 X 3.8 Partial Collisional Activation Mass Spectrum of the PhO- ion ( the rn/z = 64 - 66 region ). 179 3.9 Partial Collisional Activation Mass Spectrum of the 2,4,6 Dg -PhO- ion ( the m/z = 64 - 66 region ). 779 3.10 Partial Collisional Activation Mass Spectrum (the m/z = 64 - 66 region) of (Ph-1-13C)O- ion (m/z = 94). 180 3.11 Partial Collisional Activation Mass Spectrum (the m/z = 64 - 66 region) of (Ph-1-t3C)O- ion (m/z = 94) trom 2- (phenoxy - 1-13c)ethoxide ion. 180 3.72 Collisional Activation Mass Spectrum of PhSCH2CHzO- recorded on the VG ZAB 2HF Mass Spectrometer. 181 3.13 PhS- peak (m/z = 109 ) from PhS(CH2)2O-.
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