1 / 15

Bond Properties

Bond Properties. What is the effect of bonding and structure on molecular properties ?. Buckyball in HIV-protease. Double bond. Single bond. Triple bond. Bond Order # of bonds between a pair of atoms. Acrylonitrile. Bond Order.

neva
Download Presentation

Bond Properties

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Bond Properties • What is the effect of bonding and structure on molecular properties? Buckyball in HIV-protease

  2. Double bond Single bond Triple bond Bond Order # of bonds between a pair of atoms Acrylonitrile

  3. Bond Order Fractional bond ordersoccur in molecules with resonance structures. Consider NO2- The N—O bond order = 1.5

  4. 123 pm 414 kJ 110 pm 745 kJ Bond Order Bond order is proportional to two important bond properties: (a) bond strength (b) bond length

  5. Bond Length • Bond length is the distance between the nuclei of two bonded atoms.

  6. H—F H—Cl H—I Bond Length Bond length depends on size of bonded atoms. In Angstrom units where 1 A = 10-2 pm.

  7. Bond length depends on bond order. In Angstrom units where 1 A = 10-2 pm.

  8. Bond Strength • —measured by the energy required to break a bond. See Table 9.9

  9. Bond Strength The GREATER the number of bonds (bond order) the HIGHER the bond strength and the SHORTER the bond. • BOND STRENGTH (kJ/mol) H—H 436 C—C 346 C=C 602 CC 835 NN 945

  10. Bond Strength Bond Order Length Strength HO—OH O=O 1 142 pm 210 kJ/mol 2 121 494 1.5 128 ?

  11. Using Bond Energies Estimate the energy of the reaction H—H + Cl—Cl ----> 2 H—Cl Net E = ∆Hrxn ∆Hrxn = E to break bonds - E evolved from formation H—H = 436 kJ/mol Cl—Cl = 242 kJ/mol H—Cl = 432 kJ/mol

  12. Using Bond Energies H—H = 436 kJ/mol Cl—Cl = 242 kJ/mol H—Cl = 432 kJ/mol Estimate the energy of the reaction H—H + Cl—Cl ----> 2 H—Cl Sum of H-H + Cl-Cl bond energies = 436 kJ + 242 kJ = +678 kJ 2 mol H-Cl bond energies = 864 kJ ∆H = +678 kJ - 864 kJ = -186 kJ

  13. Using Bond Energies Estimate the energy of the reaction 2 H—O—O—H ----> O=O + 2 H—O—H Is the reaction exo- or endothermic? Which is larger: A) energy required to break bonds B) or energy evolved on making bonds?

  14. Using Bond Energies 2 H—O—O—H ----> O=O + 2 H—O—H Energy required to break bonds: break 4 mol of O—H bonds = 4 (463 kJ) break 2 mol O—O bonds = 2 (146 kJ) Make 1 mol O=O bonds = 498 kJ TOTAL ENERGY to break bonds = 2144 kJ (in) TOTAL ENERGY evolved on making O=O bonds and 4 O-H bonds bonds = 2350 kJ (out)

  15. Using Bond Energies 2 H—O—O—H ----> O=O + 2 H—O—H Net energy = +2144 kJ - 2350 kJ = - 206 kJ The reaction is exothermic! More energy is evolved on making bonds than is expended in breaking bonds.

More Related