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File:Lipscomb-NMR-hexaborene-B6H10.png

From Wikipedia, the free encyclopedia

Original file(1,552 × 1,232 pixels, file size: 143 KB, MIME type: image/png)

Summary

Description
Nuclear Magnetic Resonance NMR spectrum and structure of hexaborane B6H10.

NMR Interpretation of hexaborane

12.8 MHz. range (right)

A simple example of the chemical shift is the "a" and "b" doublets (pairs of peaks). "A" and "b" are two groups of boron atoms in different electronic environments, which place the "a" doublet to the right of the "b" doublet in the spectrum.

The relative peak heights of the "a" and "b" doublets suggest a 1:5 ratio of borons in one environment to borons in another environment.

This suggests, combined with the molecular weight of the molecule:

  • 5 boron atoms in one environment ("b") and
  • 1 boron atom in another environment ("a"),

which in turn suggests a pyramidal structure, which does appear in the atomic diagram.

40 MHz. range (left)

"a" suggests a hydrogen at the apex, which is in the atomic diagram sticking straight up.

"b" suggests hydrogens bonded to one boron each, which are in the atomic diagram sticking straight out from the edges.

"c" suggests other bridge hydrogens, which is to say hydrogens in the middle of a boron-hydrogen-boron bonding arrangement like a hydrogen bridge between two boron shores, which are in a ring around the atomic diagram.

(Williams1959)

History

X-ray diffraction was needed to be sure of the structure.(Hirshfeld1958)

More complex molecules are more challenging, although in some cases common subgroups of atoms produce characteristic spectral patterns, which can be recognized.

References

(Williams1959) Wiliams, R.E., Gibbins, S.G., and Shapiro, I., J. Chem. Phys, 30, 333 (1959).

(Hirshfeld1958) Hirshfeld, F. L., Eriks, K., Dickerson, R. E., Lippert, E. L., and Lipscomb, W. N., "Molecular and Crystal Structure of B6H10,” J. Chem. Phys. 28, 56 (1958).
Date
Source The two papers above, reviewed in: Eaton GR, Lipscomb, WN. 1969. NMR Studies of Boron Hydrides and Related Compounds. W. A. Benjamin, Inc.
Author See author list for the two papers above.
Permission
(Reusing this file)
Research paid for by a U.S. Government grant, in the public domain.

Licensing

Public domain
This work is in the public domain in the United States because it is a work prepared by an officer or employee of the United States Government as part of that person’s official duties under the terms of Title 17, Chapter 1, Section 105 of the US Code. Note: This only applies to original works of the Federal Government and not to the work of any individual U.S. state, territory, commonwealth, county, municipality, or any other subdivision. This template also does not apply to postage stamp designs published by the United States Postal Service since 1978. (See § 313.6(C)(1) of Compendium of U.S. Copyright Office Practices). It also does not apply to certain US coins; see The US Mint Terms of Use.

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17 February 2011

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Date/TimeThumbnailDimensionsUserComment
current16:46, 8 March 2011Thumbnail for version as of 16:46, 8 March 20111,552 × 1,232 (143 KB)JslipscombArrows show the chemical shift
23:57, 5 March 2011Thumbnail for version as of 23:57, 5 March 20111,552 × 1,232 (140 KB)JslipscombSharper, less blurry.
01:36, 18 February 2011Thumbnail for version as of 01:36, 18 February 20111,552 × 1,232 (184 KB)Jslipscomb{{Information |Description ={{en|1=Nuclear Magnetic Resonance NMR spectrum and structure of hexaborane B6H10. Research paid for by a U.S. Government grant.}} |Source =William Lipscomb |Author =WIlliam Lipscomb and Gareth Eaton, edited b
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