This preview has intentionally blurred sections. Sign up to view the full version.
View Full DocumentThis preview has intentionally blurred sections. Sign up to view the full version.
View Full DocumentThis preview has intentionally blurred sections. Sign up to view the full version.
View Full DocumentThis preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
Unformatted text preview: Resonance Resonance Resonance Resonance Resonance Resonance Resonance Resonance Structures Reading: Gray: (214) OGN: (3.4) C C H H H H H C C C H H H H H C C C H H H H H C Resonance Structures [C 3 H 5 ] : – two structural possibilities for  however, the actual molecule is neither of the two structures: δ δ H C C H H H H H C Resonance Structures: Another Example Two structural possibilities for benzene: C C C H C C H H H H H C C C C H C C H H H H H C C C C Each C  C bond can be thought of as a 1.5electron bond in the actual structure C C H H H H H C Formal Charge Formal Charge : the difference between the number of valence shell electrons for an element and the number of electrons surrounding it in a molecule (including half of the bond electrons and all the free electrons) Example: The leftmost carbon has 3 bonds with 2 electrons each, plus 2 free electrons; so it has 5 electrons surrounding it. The formal charge equals the valence electrons minus surrounding electrons: 4  5 = –1 = Formal Charge “Reasonable” Resonance Structures 1. Form octets if possible 2. Maximize bonding 3. Distribute formal charges in a reasonable wayminimize if possiblemore negative on more electronegative atomsavoid same sign on neighboring atoms Drawing Resonance Structures Count the number of electrons available, and devise a reasonable structure having that many electrons example:[CO 3 ] 2 8e in bonds +16e as free electrons 24e total O C O O O C O O O C O O C 4e O 3(6e ) + 2 extra electrons 24 electrons total  O N N O N N N N O N N O N 2 O 2(5e ) + 6e = 16e this structure won’t work: no octets on N’s nor this one: high formal charges +2 O N N nor this one: such configurations are destabilized by “ring strain” + best structures possible Resonance Structures of N 2 O + C...
View
Full Document
 Fall '08
 Lewis
 Electron, Mole, Lewis Structure, Acids, H2CO3 HSO3H2AsO4H2PO4HClO HCO3HAsO42HPO422.30

Click to edit the document details