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The Bond‐Rotational Mobility of Guanidinium Ion
Author(s) -
Bally Thomas,
Diehl Peter,
Haselbach Edwin,
Tracey Alan S.
Publication year - 1975
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19750580819
Subject(s) - mindo , chemistry , ion , bond length , rotation (mathematics) , crystallography , single bond , anisotropy , computational chemistry , rotational energy , molecular geometry , molecule , atomic physics , group (periodic table) , crystal structure , organic chemistry , physics , geometry , mathematics , quantum mechanics
The NMR. spectrum of guanidinium ion 1 is studied in anisotropic liquid crystalline nematic solution. Assuming an HNH‐angle of 120°, the distance ratio NH / NC = 0.784 is obtained, from which using NC = 1.330 Å (from X‐ray data) NH = 1.043 Å results. An upper bound for the free energy of activation for bond rotation of Δ G + ≤ 13 kcal/mol is deduced. The bondrotational mobility of 1 is also investigated using the MINDO/3‐SCF‐procedure. The results obtained for the three conceivable consecutive activation energies for bond‐rotation indicate that the observed bond‐rotational mobility of 1 does not involve cooperative two‐ or three‐bond rotations. The ‘conjugative stabilization’ of 1 has been estimated to be of the order of 24–26 kcal/mol.
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