About this Chemistry article
Combined NMR spectroscopy and molecular mechanics studies of OH-depleted calix[4]arenes: On the influence of OH groups on the relative stability of calix[4]arene conformers by Takaaki Harada; Fumio Ohseto; Seiji Shinkai is a Chemistry article available to read on EtoBox.
Abetrack The effects of OH groups on the relative stabilities and tbe structures of four conformers of OH-depleted calix[4Jarenes are discussed on the basis of a compu~on~ method using molecular mechanics (MM3(92)) calculations. The results are compared with various NMR spectroscopic experiments. From these studies, it is found that tbe calix[4]arene framework with no OH group in the 'lower rim &.etra-OHsLrpleted calix[4]areaes: 4a and Sb) favors a cone confom~ation with C+ symmeQy and the changes in the relative stabilities in calix[4]areaes with OH-groups are due to the formarion of stable hydrogen bonds and/or the relaxation of the steric crowding around OH-substituents in a lower rim site. NMR studies suggest that mono-OH-depleted calix[4]amne lb forms intra-and intermolecular hydrogen bonds among pheaolic OH groups, white di-and ~~H~le~ calix[4]arenes (2b and 3b) scarcely form it. They also show that the ring inversion barriers of calix[4]arenes increase with the number of OH groups in 25.26.27 or 2&position. \* 77.1 \* 76.8 73.0 \* so.7 46.5 53.6 \* 48.4 \* 44.3 \* 45.0 \* 73.6 \* 66.7 53.6 Angle Meg Phl-CH2-Ph2 \* 84.0 \* 43.2 73.0 -102.8 33.5 \* 83.8 + 44.4 74.0 \* 44.8 77.
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- Author
- Takaaki Harada; Fumio Ohseto; Seiji Shinkai
- Publisher
- Elsevier Science; Elsevier ; Elsevier Ltd.; Elsevier BV (ISSN 0040-4020)
- Published
- 1994
- Language
- EN
- Field
- Chemistry (Physical Sciences)