| Abstract: | The semiempirical CNDO/2 SCF MO method using the tight-binding approximation for polymers has been applied to poly(β-hydroxy-l-proline), β-PHP, to compare the electronic structure of β-PHP with that of poly(γ-hydroxy-l-proline), γ-PHP, which we have described in a previous publication. The results obtained show the preferred orientation of the OH group at the β-position of the pyrrolidine ring. The different situation between β-PHP and γ-PHP is briefly discussed. Analysis of the calculated results shows that the energy difference between the two species is not sufficient to deny the existence of either form. This agrees well with the experimental results. The conformational stability between the trans and cis forms of the H---:C---:O---:H group is explained by using the calculated results in connection with the previous experimental and theoretical treatments. From the analysis of the total energy, the dominant stabilizing factors are discussed. |
