Chem 161-2010 Lecture 21

Chem 161-2010 Lecture 21 - CHEMISTRY 161-2010 LECTURE 21...

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CHEMISTRY 161-2010 LECTURE 21 ANNOUNCEMENTS ATTENDANCE EXAMS/QUIZZES How did we do? THANKSGIVING Chem 161-2010 Lecture 21 1
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50 55 60 65 70 80 1 2 3 4 5 6 7 8 9121314151617181920212223242526272829303132333435363740415051525354 Chem 161-2010 Lecture 21 2 CHEM 161-2010 GRADES IN 3 rd HOURLY EXAM ALL SECTIONS Douglass/Cook Avg of Tavss’ sections Avg of D/C sections Avg of Rutgers/Pharm sections: SECTIONS College Ave.
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PLAN FOR TODAY : COMPLETE LECTURE 20 CHAPTER 10 – (10.3 – 10.5, 10.9) • VALENCE BOND THEORY - Hybridization of atomic orbitals - Geometric isomerism Chem 161-2010 Lecture 21 3
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Chem 161-2010 Lecture 21 4 Molecular Polarity No No No No Yes Yes Yes **Assuming bonds are polar and terminal atoms are identical. < < sp (+ 2 p orbitals non-hybridized) Hybridization sp 2 (+ 1 p orbial non-hybridized) sp 2 + (1 p orbital non-hybridized) sp 3 sp 3 sp 3 sp 3 d * Number of bonding and non-bonding electron pairs, not including π electron pairs * < effective ET: VSEPR = Valence-shell electron pair repulsion; ET: Use BeH 2 and BH 3 , CH 4 square planar and CH 4 tetrahedral as models. ET: Show models of “effective electron groups, i.e., CH 2 with a non-bonding electron pair, CH 2 -O, and CH 2 =O, demonstrating equal electron group geometry. ET: Discuss “Molecular Polarity” analogous to sled dog’s pulling in various directions in Susan Butcher’s Iditarod race in Alaska; use CH 2 O as an example.
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Chem 161-2010 Lecture 21 5 **Assuming bonds are polar and terminal atoms are identical * Number of bonding and non-bonding electron pairs, not including π electron pairs * < or square bipyramidal effective
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VSEPR OF RESONANCE STRUCTURES Considering the double bond in each resonance structure as one effective electron group, we count three electron groups around the N, making the electron group geometry and molecular geometry trigonal planar. The bond angle would be exactly 120 o , since with resonance, the double bond is delocalized uniformly among all three N-O bonds. Chem 161-2010 Lecture 21 6
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VSEPR OF MOLECULES WITH MORE THAN ONE CENTRAL ATOM If a molecule has more than one central atom, consider the geometry around each central atom separately. Acetic acid has the formula CH 3 COOH and the structure The geometry around the first carbon is tetrahedral (four bonds); the geometry around the second carbon is trigonal planar (two single bonds, one double bond, for a total of three effective electron groups); the geometry around the singly-bonded oxygen is angular (two bonds, two lone pairs). Chem 161-2010 Lecture 21 7
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VSEPR Method H&P 21. What is the VSEPR notation of the central atom in each of the following? (a) HOCl (b) SiF 4 (c) NCl 3 (a) HOCl . . . . H O Cl : AX 2 E 2 . . . . SiF 4 . . : F : . . | . . : F ―Si ― F : AX 4 . . | . . : F : . . NCl 3 . . : Cl : . . | . . : Cl ― N ― Cl : AX 3 E . . . . . . Chem 161-2010 Lecture 21 8
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CHEM 161-2000 EXAM III + ANSWERS CHAPTER 8 - BONDING: GENERAL CONCEPTS VSEPR, POLARITY AND BOND ANGLES BOND ANGLE ET: Note that double bonds don’t affect the geometry.
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This document was uploaded on 11/02/2011 for the course GEN CHEM 162 at Rutgers.

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Chem 161-2010 Lecture 21 - CHEMISTRY 161-2010 LECTURE 21...

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