RearrangementsLeading toFragmentations ofHydrocinnamate and Analogous Nitrogen-containing Anions Upon Collision-induced Dissociation

Elizabeth A.L. Gillis, J. Stuart Grossert and Robert L. White

Department of Chemistry, Dalhousie University, 6274 Coburg Road,

PO Box 15000, Halifax, Nova Scotia, B3H 4R2, Canada

Supplementary Information 1

Table S1.Computedrelative free energies (G) of isomeric [C8H9]– and [C7H8N]– ions formed by decarboxylation of hydrocinnamate (1a) and the N-phenylglycine anion (4a), respectively, and related transition structures

Structure
[C8H9]– / G (kJ mol–1) / Equivalent Structures
[C7H8N]– / G (kJ mol–1)
B3LYP
6-31++G(2d,p) / MP2a
6-311++G(2d,p) / UCCSD(T)b
6-31+G(d,p) / MP2a
6-311++G(2d,p)
3a / 0 / 0 / 0 / 5a / 0
3b / +30 / +28 / +15 / – / –
TS3a–3b / +44 / +36 / +38 / – / –
3c / -40 / -51 / -59 / 5c / -15
TS3a–3c / +44 / +37 / +49 / TS5a–5c / +60
3d / -112 / -108 / -104 / 5d / -144
TS3a–3d / +123 / +131 / +145 / TS5a–5d / +117
– / – / – / – / TS5c–5d / +168

aComputed using B3LYP/6-31++G(2d,p) geometries.bComputed by Maclean et al. using B3LYP/6-31+G(d,p) geometries [Maclean, M.J., Walker, S., Wang, T., Eichinger, P., C.H., Sherman,P.J., Bowie, J.H.: Diagnostic fragmentations of adducts formed between carbanions and carbon disulfide in the gas phase. A joint experimental and theoretical study.Org. Biomol. Chem.8, 371–377 (2010)]

Figure S1.Energy profile for the direct conversion of deprotonated N-phenylglycine (4a) to the decarboxylated product anions 5a, 5c, 5d and 5f. Numbers in parenthesis are MP2/6-311++G(2d,p)//B3LYP-6-31++G(2d,p) free energies

FigureS2. Energy profile for the rearrangement of deprotonated N-phenylglycine (4a) to 4d and 4e, and subsequent decarboxylation to the novel delocalized anion 5e, followed by potential rearrangement of 5e to the more stable benzylic anion 5d.Computed bond lengths in Å are shown on the structure of 5e. Numbers in parenthesis are MP2/6-311++G(2d,p)//B3LYP-6-31++G(2d,p) free energies

FigureS3.Energy profile for the formation of the acetoxy radical ion 8a (m/z 58) by dissociation of deprotonated hydrocinnamic acid (1a). Numbers in parentheses are MP2/6-311++G(2d,p)//B3LYP-6-31++G(2d,p) free energies

Table S2. Relative free energies (G in kJ mol–1) computed for the formation of acetoxy ion 8a by dissociation of deprotonated hydrocinnamic acid (1a), N-phenylglycine (4a) and 3-pyridin-2-ylpopanoic acid (6a)

HydrocinnamicAcida / N-Phenylglycine / 3-Pyridin-2-ylpropanoic Acid
Species / G / Species / G / Species / G
1a / 0 / 4a / 0 / 6a / 0
TS1a–8a / 361 / TS4a–8a / 387 / TS6a-8a / 349
[8a:PhCH2•] / 227 / [8a:PhNH•] / 239 / [8a:C5H4NCH2•] / 220
8a + PhCH2• / 230 / 8a + PhNH• / 263 / 8a + C5H4NCH2• / 233

a Data also presented in Fig. S2

FigureS4. Energy profile for the formation of phenide ion (8b, m/z = 77) bydecarboxylation of hydrocinnamate (1a) and dissociation of the -phenylethyl anion 3a,as well as synchronous dual bond cleavage of hydrocinnamate (1a). The energy for detachment of an electron from 3a was computed by Maclean et al. [Maclean, M.J., Walker, S., Wang, T., Eichinger, P.C.H., Sherman, P.J., Bowie, J.H.: Diagnostic fragmentations of adducts formed between carbanions and carbon disulfide in the gas phase. A joint experimental and theoretical study.Org. Biomol. Chem. 8, 371–377 (2010)]. Other numbers in parentheses are MP2/6-311++G(2d,p)//B3LYP-6-31++G(2d,p) free energies

Table S3. Relative free energies (G in kJ mol–1) computed for the formation of hydroxycarbonyl (8c), styrene (8d), PhN=CH– (9d), C5H4NCH=CH– (10d), phenide (8b) and C5H4N–(10b) ions from hydrocinnamate (1a), N-phenylglycine (4a), and 3-pyridin-2-ylpropanoate (6a) ions

HydrocinnamicAcida / N-Phenylglycine / 3-Pyridin-2-ylpropanoic Acid
Species / G / Species / G / Species / G
1d / 97 / 4d / 52 / 6d / 76
TS1d–8c / 259 / TS4d–9c / 245 / TS6d–10c / 264
8c or [8c:PhCH=CH2] / 218 / 9c or [8c:PhN=CH2] / 239 / 10c or [8c:C5H4NCH=CH2] / 207
8c + PhCH=CH2 / 228 / 8c + PhN=CH2 / 260 / 8c + C5H4NCH=CH2 / 225
TS8c–8d / 294 / TS9c–9d / 303 / TS10c–10d / 315
[8d:HCO2H] / 282 / [9d:HCO2H] / 288 / [10d:HCO2H] / 300
8d + HCO2H / 295 / 9d + HCO2H / 312 / 10d + HCO2H / 319
TS8d–8b + HCO2H / 468 / TS9d–8b + HCO2H / 430 / TS10d–10b + HCO2H / 478
[8b:C2H2] + HCO2H / 406 / – / – / [10b:C2H2] + HCO2H / 415
8b + C2H2 + HCO2H / 429 / 8b + HCN + HCO2H / 294 / 10b + C2H2 + HCO2H / 438

aData also presented in Figure 7

FigureS5.Energy profile for -lactone formation by displacement of the anilino ion 5f (m/z 92) from deprotonated N-phenylglycine (4a).Numbers in parentheses are MP26-311++(2d,p)//B3LYP6-31+g(d) free energies

FigureS6.Energy profile for the loss of water from 3-pyridin-2-ylpropanoate (6a) via benzylic (6d) and enolate (6f) ions.Numbers in parentheses are MP26-311++(2d,p)//B3LYP6-31+g(d) free energies


Figure S7.Precursor-ion spectra (30 V cone, 5 eV CID) obtained for ions at m/z 106 (A) and m/z 104 (B) derived from 3-pyridin-2-ylpropanoate (6a, m/z 150)

FigureS8. Energy profile for the loss of dihydrogen from7e (m/z = 106),thesyn product anion formed bydecarboxylation of 3-pyridin-2-ylpropanoate (6a). The computations were done using the wB97XD/6-311++g(d,p) functional (Gaussian09; J.-D. Chai and M. Head-Gordon, Phys. Chem. Chem. Phys., 2008, 10, 6615–6620), which was developed to include long-range interactions.In this case, the optimization of structures using the B3LYP functional proved to be problematic. Numbers in parentheses are MP2/6-311++G(2d,p)//wB97XD/6-311++g(d,p)free energies

Computations starting from the anticonformerof 7e(9 kJ mol–1) yielded corresponding free energies of 158, 62, 91, 45 and 31 kJ mol–1.

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