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Title: Electrostatic properties of L-alanine from x-ray diffraction at 23 K and ab initio calculations

Abstract

Maps of the electrostatic potential of L-alnine have been derived from single-crystal X-ray diffraction data collected at 23 (1) K and interpreted with a multipole (pseudoatoms) formalism. In the crystal, minimia in the potential of virtually identical magnitudes are observed near both oxygen atoms, in spite of their different environments. For an isolated, zwitterionic molecule constructed by assembling the pseudoatoms, a single minimum of -500 (42) kJ mol{sup {minus}1} {vert bar} e {vert bar}{sup {minus}1} is obtained. Its position, which differs from those of the minima in the crystal, is at 1.15 {angstrom} from an oxygen atom-the one that forms two hydrogen bonds in the crystal structure- and along the line connecting, in the crystal, the oxygen and hydrogen atoms involved in the shortest hydrogen bond. Theoretical maps of the electrostatic potential, calculated by self-consistent field molecular orbital (SCF MO) ab initio methods with four different basis sets, have been compared with those derived from the experiment. In the region of the carboxylate group the best agreement is obtained with maps computed with the largest basis set here employed, of double-{zeta} plus polarization quality (6-31 G**). From various multipole models adopted to analyze the X-ray data, values of 12.7 (7)-13.1more » (7) D are derived for {vert bar} {mu} {vert bar}, the magnitude of the molecular dipole moment of L-alanine in the solid state, to be compared with literature values, 12.3-17.0 D, of solution measurements. For an isolated molecule of the amino acid, the theoretical estimates of {vert bar} {mu} {vert bar} with our basis sets are in the range 12.0-12.9 D. Atomic electric field gradients (EFG) have also been derived from the results of the X-ray diffraction experiment, and the corresponding asymmetry parameters {eta} and quadrupole coupling constants (QCC) e{sup 2}qQ/h evaluated.« less

Authors:
; ;  [1]
  1. Universita di Milano (Italy)
Publication Date:
OSTI Identifier:
6751468
Resource Type:
Journal Article
Journal Name:
Journal of Physical Chemistry; (USA)
Additional Journal Information:
Journal Volume: 93:11; Journal ID: ISSN 0022-3654
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; 59 BASIC BIOLOGICAL SCIENCES; ALANINE-L; ELECTRODYNAMICS; CALCULATION METHODS; DATA ANALYSIS; EXPERIMENTAL DATA; MEASURING INSTRUMENTS; MEASURING METHODS; VERY LOW TEMPERATURE; X-RAY DIFFRACTION; ALANINE-ALPHA; ALANINES; AMINO ACIDS; CARBOXYLIC ACIDS; COHERENT SCATTERING; DATA; DIFFRACTION; INFORMATION; NUMERICAL DATA; ORGANIC ACIDS; ORGANIC COMPOUNDS; SCATTERING; 400201* - Chemical & Physicochemical Properties; 550200 - Biochemistry

Citation Formats

Destro, R, Bianchi, R, and Morosi, G. Electrostatic properties of L-alanine from x-ray diffraction at 23 K and ab initio calculations. United States: N. p., 1989. Web. doi:10.1021/j100348a015.
Destro, R, Bianchi, R, & Morosi, G. Electrostatic properties of L-alanine from x-ray diffraction at 23 K and ab initio calculations. United States. doi:10.1021/j100348a015.
Destro, R, Bianchi, R, and Morosi, G. Thu . "Electrostatic properties of L-alanine from x-ray diffraction at 23 K and ab initio calculations". United States. doi:10.1021/j100348a015.
@article{osti_6751468,
title = {Electrostatic properties of L-alanine from x-ray diffraction at 23 K and ab initio calculations},
author = {Destro, R and Bianchi, R and Morosi, G},
abstractNote = {Maps of the electrostatic potential of L-alnine have been derived from single-crystal X-ray diffraction data collected at 23 (1) K and interpreted with a multipole (pseudoatoms) formalism. In the crystal, minimia in the potential of virtually identical magnitudes are observed near both oxygen atoms, in spite of their different environments. For an isolated, zwitterionic molecule constructed by assembling the pseudoatoms, a single minimum of -500 (42) kJ mol{sup {minus}1} {vert bar} e {vert bar}{sup {minus}1} is obtained. Its position, which differs from those of the minima in the crystal, is at 1.15 {angstrom} from an oxygen atom-the one that forms two hydrogen bonds in the crystal structure- and along the line connecting, in the crystal, the oxygen and hydrogen atoms involved in the shortest hydrogen bond. Theoretical maps of the electrostatic potential, calculated by self-consistent field molecular orbital (SCF MO) ab initio methods with four different basis sets, have been compared with those derived from the experiment. In the region of the carboxylate group the best agreement is obtained with maps computed with the largest basis set here employed, of double-{zeta} plus polarization quality (6-31 G**). From various multipole models adopted to analyze the X-ray data, values of 12.7 (7)-13.1 (7) D are derived for {vert bar} {mu} {vert bar}, the magnitude of the molecular dipole moment of L-alanine in the solid state, to be compared with literature values, 12.3-17.0 D, of solution measurements. For an isolated molecule of the amino acid, the theoretical estimates of {vert bar} {mu} {vert bar} with our basis sets are in the range 12.0-12.9 D. Atomic electric field gradients (EFG) have also been derived from the results of the X-ray diffraction experiment, and the corresponding asymmetry parameters {eta} and quadrupole coupling constants (QCC) e{sup 2}qQ/h evaluated.},
doi = {10.1021/j100348a015},
journal = {Journal of Physical Chemistry; (USA)},
issn = {0022-3654},
number = ,
volume = 93:11,
place = {United States},
year = {1989},
month = {6}
}