How Strong Is a Covalent Bond?

Science  12 Mar 1999:
Vol. 283, Issue 5408, pp. 1727-1730
DOI: 10.1126/science.283.5408.1727

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The rupture force of single covalent bonds under an external load was measured with an atomic force microscope (AFM). Single polysaccharide molecules were covalently anchored between a surface and an AFM tip and then stretched until they became detached. By using different surface chemistries for the attachment, it was found that the silicon-carbon bond ruptured at 2.0 ± 0.3 nanonewtons, whereas the sulfur-gold anchor ruptured at 1.4 ± 0.3 nanonewtons at force-loading rates of 10 nanonewtons per second. Bond rupture probability calculations that were based on density functional theory corroborate the measured values.

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