Electronic structure and activity of vinyltetrazoles in radical homopolymerization

Vinyltetrazoles: synthesis and properties

“…41 An insignificant (1 ± 3 ppm) upfield shift of the C b signal was observed 67 for 2-vinyltetrazole (15a) and its derivatives in comparison with the corresponding 1-vinyl derivatives. In the presence of a vinyl group in position 5, the pattern of the 13 (Dq ab ) of compound 1 is much lower than that of the 1-vinyl derivative 14a; 60,61 as a result, the difference between the chemical shifts (Dd ab ) diminishes correspondingly. 27,31,43,53 13 C NMR spectra of 2-alkyl-5-vinyltetrazoles and 1-vinyltetrazoles is shifted downfield, but the difference in the chemical shifts Dd ab is even less pronounced than in the case of unsubstituted 5-vinyltetrazole (1).…”

“…125 ± 127 The electronic structure of 5-vinyltetrazole is characterised by a smaller charge, q b , and a lower charge difference, q a q b , in comparison with 1-vinyltetrazole. 60,61 Moreover, a small reduction of the acceptor induction effect of the substituent at the double bond of 5-vinyltetrazole is accompanied by a considerable decrease in the donor mesomeric effect in comparison with 1-vinyltetrazole. Thus, the tetrazolyl substituent in the C-vinyl monomer manifests stronger acceptor properties which accounts for higher activity of 5-vinyltetrazole.…”

“…The distribution of the total charges (s + p) calculated by the SNDO/S method based on the planar structure of vinyltetrazole molecules is shown in Figure 1. 43 Calculations of total (s + p) electron densities have shown 60,61 that both carbon atoms in the vinyl group of C-vinyltetrazoles bear a negative charge, while the charge of the a-carbon atom of N-vinyltetrazoles is positive due to s-electron-withdrawing properties of the nitrogen atom at the double bond. In both cases, the total electron density on the b-carbon atom of the vinyl group is higher than that on the a-atom.…”

“…In both cases, the total electron density on the b-carbon atom of the vinyl group is higher than that on the a-atom. The p-electron distribution is characterised by reverse polarisation 60,61 (the negative p-electron charge is concentrated on the a-carbon atom of the C=C bond), which testifies to the p-electron-withdrawing effect of the tetrazolyl substituent. Polarisation of the vinyl group (Dq ba ) in N-vinyltetrazoles is more pronounced than in C-vinyltetrazoles.…”

“…The mutual effect of two unsaturated fragments in the vinyltetrazole molecule is especially pronounced in their polarographic analysis. 43,60,79 Vinyltetrazoles are polarographically active, but the mechanisms of reduction of N-and unsubstituted C-vinyl derivatives are different.…”