Comparison of the molecular structures of five benzene derivatives as determined independently by gas-phase electron diffraction in two different laboratories: a perspective

Abstract

The merits and limitations of gas-phase electron diffraction as a technique for determining accurately the structures of small organic molecules are demonstrated by comparing the molecular structures of five benzene derivatives studied in two different laboratories. The existence of many possible representations of the structure of a molecule (r (a), r (g), r (alpha), r (alpha) (0) , r (e), aEuro broken vertical bar), implying differences in the physical meaning of geometrical parameters, is discussed in some detail as it may cause difficulties in a comparison. Also illustrated are different ways of estimating and expressing uncertainties in the geometrical parameters from a gas-phase electron diffraction study

Interplay of thermochemistry and Structural Chemistry, the journal (volume 21, 2010) and the discipline

“…Campanelli et al [206] in their contribution describe advantages and limitations of gas-phase electron diffraction for determining molecular structure of five different benzene derivatives, 1,4-difluorobenzene, 1,3,5-trifluorobenzene, 1,4-dichlorobenzene, 1,3,5-trichlorobenzene, and silylbenzene. The report is rather unique, as it is only rarely possible that the analyses can be repeated independently by the same technique in two different laboratories.…”

Molecular Structure of Pyrazinamide: A Critical Assessment of Modern Gas Electron Diffraction Data from Three Laboratories

“…A completely different situation is when results of two or more concurrent investigations disagree. Several publications in the past have been addressed to this problem [4][5][6][7][8][9][10]. Some of them documented significant deviations in structural parameters [4,6,10], which was an indication of relatively large systematic errors leading to biased parameters or underes-timated uncertainties.…”

“…Some of them documented significant deviations in structural parameters [4,6,10], which was an indication of relatively large systematic errors leading to biased parameters or underes-timated uncertainties. The work of Campanelli et al [10] should be mentioned due to careful comparison of molecular structures determined by GED method in different groups for a series of halogenated benzene derivatives. An expressive example from this paper is the r g length of C-C bonds in benzene ring of 1,3,5-trichlorobenzene determined to be 1.392(2) Å [11] and 1.400(1) Å [12].…”

“…Several publications in the past have addressed this problem. − Some of them documented significant deviations in structural parameters, ,, which was an indication of relatively large systematic errors leading to biased parameters or underestimated uncertainties. The work of Campanelli et al should be mentioned due to careful comparison of molecular structures determined by GED in different groups for a series of halogenated benzene derivatives. An expressive example from this paper is the r g length of C–C bonds in the benzene ring of 1,3,5-trichlorobenzene determined to be 1.392(2) Å and 1.400(1) Å .…”