Protonation of γ‐Butyrolactone and γ‐Butyrolactam

Abstract

γ-Butyrolactone and γ-butyrolactam were reacted in the superacidic systems XF/MF 5 (X = H, D; M = As, Sb). Salts of the monoprotonated species of γ-butyrolactone were obtained in terms of [(CH 2) 3 OCOH] + [AsF 6 ] À , [(CH 2) 3 OCOH] + [SbF 6 ] À and [(CH 2) 3 OCOD] + [AsF 6 ] À and the analogous lactam salts in terms of [(CH 2) 3 NHCOH] + [AsF 6 ] À , [(CH 2) 3 NHCOH] + [SbF 6 ] À and [(CH 2) 3 NDCOD] + [AsF 6 ] À. The salts were characterized by low temperature Raman and infrared spectroscopy and for both protonated hexafluoridoarsenates, [(CH 2) 3 OCOH] + [AsF 6 ] À and [(CH 2) 3 NHCOH] + [AsF 6 ] À , single-crystal X-ray structure analyses were conducted. In addition to the experimental results, quantum chemical calculations were performed on the B3LYP/ aug-cc-pVTZ level of theory. As in both crystal structures C•••F contacts were observed, the nature of these contacts is discussed with Mapped Electrostatic Potential as a rate of strength.

Ring Opening and Closure Reactions of β‐Propiolactone in the Superacids HF/MF5 (M=Sb, As)

“…The neighboring CO stretching vibration, belonging to the ester group, is detected at 1508 cm −1 in the respective IR spectra of ( 3 ) and ( 4 ) and in the Raman spectra at 1510 cm −1 ( 3 ) and 1515 cm −1 ( 4 ), respectively. All these frequencies are in good agreement, with reported literature data of protonated esters [17] . The ν(CC) vibrations are observed at approximately 1090 cm −1 and 1025 cm −1 in ( 3 ) and ( 4 ), which is in fair agreement to values reported in literature [22] .…”

“…The adjacent cyclic CO bonds (C1−O1, C4−O3 and C7−O5) are in the same range. These CO bond lengths are all between a formal single (1.43 Å) and double bond (1.19 Å) and in accordance with values of protonated ester groups [16,17] . The C−C bond distances in the trication are between 1.473(8) Å (C1−C2) and 1.529(9) Å (C8−C9).…”

Intermediates in Friedel‐Crafts Acylation of Fumaryl Halides

“…Aside from that, the crystal structure of 1 exhibits interactions between the cationic C4 atom tetracoordinated by nucleophilic fluorine and oxygen atoms. The distances C4⋅⋅⋅F11 (2.758(4) Å), C4⋅⋅⋅F13 ii (2.917(4) Å) and C4⋅⋅⋅F2 iii (2.786(4) Å) which are in accordance with other reported C⋅⋅⋅F contacts, [11,17–19] are below the sum of the van der Waals radii of 3.17 Å, [20] respectively. In addition, an interaction between the carbonyl group of one cation and the acylium ion side of another cation is observed, which is shown in Figure 2.…”

“…In addition, orbital interactions reinforce the attractive interaction [39] between the acylium moiety and the nucleophiles. There are reported examples of sp 2 ‐hybridized carbenium ions stabilized by fluorine bridging along the axis of the unoccupied p z orbital [17–19] . However, in the monoacyl cation the corresponding carbon atom is supposed to be sp‐hybridized.…”

“…There are reported examples of sp 2 -hybridized carbenium ions stabilized by fluorine bridging along the axis of the unoccupied p z orbital. [17][18][19] However, in the monoacyl cation the corresponding carbon atom is supposed to be sphybridized. To confirm the assumption of the sp-hybridization of the C4 atom, natural bond orbital calculations of [C 4 H 2 FO 2 ] + were performed.…”