Bond dissociation energy

You don't need to be Editor-In-Chief to add or edit content to WikiDoc. You can begin to add to or edit text on this WikiDoc page by clicking on the edit button at the top of this page. Next enter or edit the information that you would like to appear here. Once you are done editing, scroll down and click the Save page button at the bottom of the page.

Please Take Over This Page and Apply to be Editor-In-Chief for this topic: There can be one or more than one Editor-In-Chief. You may also apply to be an Associate Editor-In-Chief of one of the subtopics below. Please mail us [1] to indicate your interest in serving either as an Editor-In-Chief of the entire topic or as an Associate Editor-In-Chief for a subtopic. Please be sure to attach your CV and or biographical sketch.

In chemistry, bond dissociation energy, D₀ or BDE, is one measure of the bond strength in a chemical bond. It is defined as the standard enthalpy change when a bond is cleaved by homolysis, with reactants and products of the homolysis reaction at 0K (absolute zero). For instance, the bond dissociation energy for one of the C-H bonds in ethane (C₂H₆) is defined by the process:

CH₃CH₂-H → CH₃CH₂ + H

D₀ = ΔH = 101.1 kcal/mol (423.0 kJ/mol)

The bond dissociation energy is sometimes also called the bond dissociation enthalpy (or bond enthalpy), but these terms are not strictly correct, as they refer to the above reaction enthalpy at standard conditions, and may differ from D₀ by more than 3 kcal/mol (12 kJ/mol).

The bond dissociation energy is usually different from the bond energy, which is calculated from the sum of the bond dissociation energies of all bonds in a molecule. ^[1]

For example, an O-H bond of a water molecule (H-O-H) has 493.4 kJ/mol of bond dissociation energy, and 424.4 kJ/mol is needed to cleave the remaining O-H bond. The bond energy of the O-H bonds in water is 458.9 kJ/mol, which is the average of the values.

In the same way for removing successive hydrogen atoms from methane the bond dissociating energies are 104 kcal/mol (435 kJ/mol) for D(CH₃-H), 106 kcal/mol (444 kJ/mol) for D(CH₂-H), 106 kcal/mol (444 kJ/mol) for D(CH-H) and finally 81 kcal/mol (339 kJ/mol) for D(C-H). The bond energy is thus 99 kcal/mol or 414 kJ/mol (the average of the bond dissociation energies).

Note that following dissociation, if new bonds are formed at lower enthalpy, then there is a net loss of energy, and thus an overall exothermic process.

Heterolytic bond dissociation energy is involved in chemical bond breaking by heterolysis rather than homolysis.

See also

• Bond strength
• Bond energy
• Binding energy
• Chemical bond

References

ar:طاقة تفكك رابطة ja:結合解離エネルギー

WikiDoc Help Menu Quick Start.. Get Started Here! How to Login How to Search Pages How to Start a New Page How to Edit a Page Cheat Sheet Editing basics Learning Basic Formatting How to make Links in WikiDoc & to External Sites How to Make Lists How to Ignoring Formatting Adding References or Footnotes to Articles Tracking Changes You Have Made How to Put an Article Into a Category When Multiple Topics Should Go To The Same Page (MI, Acute MI, AMI) Using Redirection Advanced editing How to Make Tables How to Insert Images and Other Media How to Add Video Help:How to Make Columns Web Colors How To Make Templates How to Move Pages Inserting Dynamic Dates and Times Inserting WikiDoc Statistics Editing the Table of Contents Communicating your edits Let others know what you changed: The importance of Edit Summaries Minor Edits Edit Conflicts Help Videos You Can Watch Getting Started Video

Acknowledgement and Attribution Regarding Sources of Content

Some of the initial content on this page may be incorporated in part from copyleft sources in the public domain including wikis such as Wikipedia and AskDrWiki. Drug information for patients came from the The National Library of Medicine. Infectious disease information may have come from the Centers for Disease Control (CDC). Differential Diagnoses are drawn from clinicians as well as an amalgamation of 3 sources: 1.The Disease Database; 2. Kahan, Scott, Smith, Ellen G. In A Page: Signs and Symptoms. Malden, Massachusetts: Blackwell Publishing, 2004:3; 3. Sailer, Christian, Wasner, Susanne. Differential Diagnosis Pocket. Hermosa Beach, CA: Borm Bruckmeir Publishing LLC, 2002:7 .