CH 222 Friday January 19, 2018 L08 Good Afternoon

CH 222 Friday January 19, 2018 L08Good Afternoon“These are not the bonds you’re looking for:Introduction to Resonance Structures”David R. (Randy) Sullivan and Thomas J. GreenboweDepartment of Chemistry and BiochemistryUniversity of Oregon, Eugene, Oregon 97403 USAtgreenbo@uoregon.eduObi-Wan KanobiMos Eisley, Tatooine

CH 222 Friday January 19, 2018 L08Good Afternoon“These are not the bonds you’re looking for:Introduction to Resonance Structures”David R. (Randy) Sullivan and Thomas J. GreenboweDepartment of Chemistry and BiochemistryUniversity of Oregon, Eugene, Oregon 97403 USAtgreenbo@uoregon.eduObi-Wan KanobiMos Eisley, Tatooine

Table 09.03As bond order increases, bond length .Therefore, bond energy .

Double and triple bonds are quite common,and not just something we do on paper.

Table 09.03As bond order increases, bond length .Therefore, bond energy .

Ozone, O3: average bond energy 364 kJ/molCalculate the energy per molecule. 1mol 19364kJ / mol 6.04x10J / molecule23 6.022 x10 Calculate the wavelength of light that would benecessary to break the bonds in O3.h 6.626 x 10-34J s c 3.00 x 108 m/shc (6.626 x10 34 J s)(3.00 x108 ) 7E 3.28x10m 19λ6.04 x10 J 328nm

λ 328 nm What part of the UV spectrum?in the UVA region7

UV-A 400 – 320 nmUV-B 320 – 280 nmUV-C 280 nm

When outdoors during the daylight hours, wearsunglasses that can block UV light, even on cloudydays. UV rays pass through clouds and will damageunprotected eyes.Improve your chemistry exam scores.9

Draw the Lewis structure for ozone, O3.AllatomsmustobeytheOctetRule.

Lewis Structures andResonanceStep 1:3(6) 18 valence electronsStep 2:OOOStep 4:OOOStep 3:OOOStep 5:OOO

Correct Lewis structure for ozone, O3?

Draw the Lewis Structure for O3This is the Lewisstructure wewould draw forozone, O3.How many single bonds?How many double bonds do you see?

Star Wars Episode VII and VIIIKylo Ren his real name is14

Obi-Wan Kenobi His real name isStar Wars Episode IV A New Hope15

Star Wars Episode IV A New HopeWho is the lady and what is she giving R2D2?16

Star Wars Episode IV A New Hope17

“General Kenobi. Years ago you served my father in theClone Wars. Now he begs you to help him in his struggleagainst the Empire. I regret that I am unable to present myfather's request to you in person, but my ship has fallenunder attack, and I'm afraid my mission to bring you toAlderaan has failed. I have placed information vital to thesurvival of the Rebellion into the memory systems of this R2unit. My father will know how to retrieve it. You must seethis droid safely delivered to him on Alderaan. This is ourmost desperate hour. Help me, Obi-Wan Kenobi. You're myonly hope.”18

Star Wars Episode IVhttps://www.youtube.com/watch?v 532j-186xEQ

Correct Lewis structure for ozone, O3?

Bond Enthalpy and Bond LengthBond Energy204 kJ/mol498 kJ/mol148 pm121 pm

Bond Length and Bond AngleMeasurements But this is at oddswith the true,observedstructure ofozone, Both O-O bondlengths in O3 arethe same.

Ozone But this is at odds withthe true, observedstructure of ozone, inwhich – both O—O bondshave the same bondenergy– both outer oxygenshave a charge of 1/2.– O3 does not have asingle bond and it doesnot have a double bond.

What is the bond order in ozone?Bond order is somewhere intermediate between 1 and 2.When equivalent Lewis structures can be drawn, the bondorder is calculated as:number of bonding pairs3bond order 1.5number of bonding regions 2

ResonanceJust as green is asynthesis of blue andyellow ozone is a synthesis ofthese two resonancestructures.

Draw the Lewis structure for O3

Resonance: Electron Delocalization When one Lewis structure cannot accuratelydepict a molecule like ozone. We use multiplestructures, resonance structures, to describethe molecule.In a resonance hybrid, electrons are delocalized:their density is “spread” over a few adjacent atoms.Extra stability is gained byhaving resonance structures.

Draw the Lewis structure forCO32-

Draw the Lewis structure forCO32-

Draw the Lewis Structure for CO32This is the Lewisstructure wewould draw for,CO32-How many single bonds?How many double bonds do you see?

Table 09.03Carbonate ion

All C-O bonds are 128 pm in lengthThe C-O bond energy is 528 kJ/molThe Lewis structure model is too simple to represent amolecule or ion exhibiting resonance.We need three Lewis structures to approximate therepresentation of the carbonate ion.32

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Star Wars Episode IV A New Hope . 16 Star Wars Episode IV A New Hope Who is the lady and what is she giving R2D2? 17 Star Wars Episode IV A New Hope . 18 “General Kenobi. Years ago you served my father in the Clone Wars. Now he begs you to help him in his struggle