Carbon‐13 NMR spectroscopy of acrylic monomer and Lewis acid complexes

Abstract

13C NMR spectra of acrylic monomers complexed with a Lewis acid were measured and their electronic structures discussed in relation to their alternating copolymerizability. The β‐carbon of acrylonitrile and methacrylonitrile showed a downfield shift due to the complex formation with the Lewis acid, while the α‐carbon showed an upfield shift and the nitrile carbon showed no significant shift. The degree of shift of olefinic carbons decreased in the following order: AlCl3 > EtAlCl2 > Et1.5AlCl1.5 > Et2AlCl > SnCl4, EtOAlCl2 > Et(EtO)AlCl, which seems to run parallel to the Lewis acidity and acid strength. On the other hand, the chemical shift of olefinic carbons of methyl acrylate, methyl methacrylate, and olefinic diesters was influenced little by complex formation with Lewis acids, whereas the carbonyl and alkoxyl carbons were deshielded significantly by the complex formation. These results are discussed in terms of electron distribution on the carbons and an alternating polymerization mechanism.

Enantioselective Addition of Allyltin Reagents to Amino Aldehydes Catalyzed with Bis(oxazolinyl)phenylrhodium(III) Aqua Complexes

“…Similar lower field shifts of H f and C f along with the olefinic protons H α and H β (H α = α-proton, H β = β-proton) were also observed for the mixture of i -Pr- 1 and 3e in 1 H and 13 C NMR (ΔH α = +0.27 ppm, ΔH β = +0.14 ppm, ΔH f = +0.77 ppm, ΔC f = +2.9 ppm, respectively) (Entry 5). It is widely known that chemical shifts of vinylic protons (H α and H β ), formyl proton (H f ) and carbon (C f ) of enals bound to Lewis acids by the carbonyl oxygen appear at lower field than those of free enals [ 20 , 21 , 22 ]. These lower-field shifts of H α , H β , H f and C f are also observed in the reaction of i -Pr- 1 and ( E )-cinnamaldehyde [ 16 ].…”

Living Cationic Polymerization of tert-Butyl Vinyl Ether by Organoaluminum Halides in the Presence of Added Bases

“…To find suitable conditions for the living polymerization of TBVE, the effects of temperature, acid strength of activators, 9 • 10 and basicity of added bases 2 • 11 were investigated in detail. Table I summarizes The long lifetime of growing species was further demonstrated by the sequential addition of fresh TBVE to the polymerization reaction mixture.…”

IR‐Spektroskopische Untersuchungen an EDA‐Komplexen α,β‐ungesättigter Ester mit Lewis‐ Säuren

“…Siegfried Kulpe, Akademie der Wissenschaf'ten der DDR, Zentralinstitut fur physikalische Chemie, Bereich Physikalische Methoden der analytischen Chemie, 1199 Berlin Ilt-Spektroskoptsehe Untersuchungen an EDA-Komplexen 'X,{J-ungesiittigter Ester mit Lewis-Siiuren Die EDA-Komplexbildullg des Methacrylsauremethyleaters (MASME) mit verschiedenen Lewis-Sauren wurde wegen der Einfliisse auf Polymerisationsreaktionen [1] eingehend untersucht [2], [3], [4]. In Abhangigkeit vom D:A-Verhaltnis und vom Losungsmittel bilden sich sowohl 2 :1-als auch 1 :l-Komplexe, die monomer oder dimer vorliegen konnen [5], [6], [7].…”