1 © 2009 Brooks/Cole - Cengage Advanced Theories of Chemical Bonding Chapter 9 Atomic Orbitals...

Advanced Theories of Advanced Theories of Chemical BondingChemical Bonding

Chapter 9Chapter 9

Atomic OrbitalsAtomic Orbitals MoleculesMolecules

• MOLECULAR MOLECULAR ORBITAL THEORYORBITAL THEORY — — Robert Mullikan (1896-Robert Mullikan (1896-1986)1986)

• valence electrons are valence electrons are delocalizeddelocalized

• valence electrons are valence electrons are in orbitals (called in orbitals (called molecular orbitals) molecular orbitals) spread over entire spread over entire molecule.molecule.

Two Theories of BondingTwo Theories of BondingTwo Theories of BondingTwo Theories of Bonding

• VALENCE BOND THEORYVALENCE BOND THEORY — Linus Pauling— Linus Pauling

• valence electrons are valence electrons are localized between atoms localized between atoms (or are lone pairs).(or are lone pairs).

• half-filled atomic orbitals half-filled atomic orbitals overlap to form bonds.overlap to form bonds.

Linus Pauling, 1901-1994Linus Pauling, 1901-1994Linus Pauling, 1901-1994Linus Pauling, 1901-1994

Sigma Bond Formation by Sigma Bond Formation by Orbital OverlapOrbital Overlap

Two s orbitals Two s orbitals overlapoverlap

Sigma Bond FormationSigma Bond FormationSigma Bond FormationSigma Bond Formation

Two s Two s orbitals orbitals overlapoverlap

Two p Two p orbitals orbitals overlapoverlap

Using VB TheoryUsing VB TheoryUsing VB TheoryUsing VB TheoryBonding in BFBonding in BF33

planar triangleplanar triangleangle = 120angle = 120oo

FFFBoron configuration↑↑↓↑↓2p2s1s•••••••••••• ••••••B

Bonding in BFBonding in BF33Bonding in BFBonding in BF33

• How to account for 3 bonds 120How to account for 3 bonds 120oo apart using apart using a spherical s orbital and p orbitals that are 90a spherical s orbital and p orbitals that are 90oo apart?apart?

• Pauling said to modify VB approach with Pauling said to modify VB approach with

ORBITAL HYBRIDIZATIONORBITAL HYBRIDIZATION• — — mix available orbitals to form a new mix available orbitals to form a new

set of orbitals — set of orbitals — HYBRID ORBITALSHYBRID ORBITALS — that will give the maximum overlap — that will give the maximum overlap in the correct geometry. in the correct geometry.

Why Hybridize?Why Hybridize?

Just looking at valence electrons:

Be should form no covalent bonds

B should form one covalent bond

C should form 2 covalent bonds

But…

BeF2, BF3 and CF4

Exist! HOW?

Hybrid Orbitals: Why?Hybrid Orbitals: Why?

• To explain the bonding in molecules like BeF2, BF3 and CF4, Linus Pauling proposed that orbitals become ‘hybridized’

– Hybrid orbitals are orbitals created by mixing the s, p or d orbitals of an atom.

Hybrid Orbitals: The RulesHybrid Orbitals: The Rules

1. The number or hybrid orbitals is ALWAYS equal to the number of atomic orbitals that are combined to make the hybrid set

2. Hybrid orbital sets are always built by combining an s orbital with as many p or d orbitals necessary to accommodate the bonding and lone pairs on the central atom (Remember Electron Pair Geometry?)

3. The Hybrid Orbitals are directed TOWARDS the terminal atoms• This results in a better orbital overlap AND stronger

bonds between the central and terminal atoms

spsp Hybrid Orbitals Hybrid Orbitals

Mix an s orbital with a p orbital to create two sp orbitals

spsp22 Hybrid Orbitals Hybrid Orbitals

Mix an s orbital with 2 p orbitals to create three sp2 orbitals

spsp33 Hybrid Orbitals Hybrid Orbitals

Mix an s orbital with 3 p orbitals to create four sp3 orbitals

spsp33 Hybrid Orbitals: Examples Hybrid Orbitals: Examples

rearrange electronshydridize orbs.

unused porbital

three sp 2 hybrid orbitals

• The three hybrid orbitals are made The three hybrid orbitals are made from 1 s orbital and 2 p orbitals from 1 s orbital and 2 p orbitals 3 sp 3 sp22 hybrids.hybrids.

• Now we have 3, half-filled HYBRID orbitals Now we have 3, half-filled HYBRID orbitals that can be used to form B-F sigma bonds.that can be used to form B-F sigma bonds.

An orbital from each F overlaps one of the An orbital from each F overlaps one of the spsp22 hybrids to form a B-F hybrids to form a B-F bond. bond.

BF3, Planar Trigonal BF3, Planar Trigonal

Bonding in CHBonding in CH44

How do we account for 4 CHow do we account for 4 C

—H sigma bonds 109—H sigma bonds 109oo

apart? apart?

Need to use 4 atomic Need to use 4 atomic

orbitals — s, porbitals — s, pxx, p, pyy, and , and

ppzz — to form 4 new — to form 4 new

hybrid orbitals pointing hybrid orbitals pointing

in the correct direction.in the correct direction.

109o109o

4 C atom orbitals 4 C atom orbitals hybridize to form hybridize to form four equivalent spfour equivalent sp33 hybrid atomic hybrid atomic orbitals.orbitals.

Bonding in a Tetrahedron Bonding in a Tetrahedron Formation of Hybrid Atomic OrbitalsFormation of Hybrid Atomic Orbitals

QuickTime™ and aGraphics decompressor

are needed to see this picture.

Bonding in a Tetrahedron — Bonding in a Tetrahedron — Formation of Hybrid Atomic Formation of Hybrid Atomic

OrbitalsOrbitals

4 C atom orbitals 4 C atom orbitals hybridize to form hybridize to form four equivalent spfour equivalent sp33 hybrid atomic hybrid atomic orbitals.orbitals.

QuickTime™ and aVideo decompressor

Bonding in CHBonding in CH44Bonding in CHBonding in CH44

OCOHHHNHHsp3sp3

sp3sp2••••••C

Bonding in Bonding in GlycineGlycine

OCOHHHNHHsp3sp3

sp3sp2••••••C

OCOHHHNHHsp3sp3

sp3sp2••••••C

OCOHHHNHHsp3sp3

sp3sp2••••••C

OCOHHHNHHsp3sp3

sp3sp2••••••C

Orbital HybridizationOrbital HybridizationOrbital HybridizationOrbital Hybridization

2 e2 e-- clouds clouds

3 e- clouds3 e- clouds

Multiple BondsMultiple BondsMultiple BondsMultiple BondsConsider ethylene, CConsider ethylene, C22HH44

sp2120° C

Sigma Bonds in CSigma Bonds in C22HH44Sigma Bonds in CSigma Bonds in C22HH44

sp2120° C

ππ Bonding in C Bonding in C22HH44ππ Bonding in C Bonding in C22HH44

The unused p orbital on The unused p orbital on each C atom contains an each C atom contains an electron and this p orbital electron and this p orbital overlaps the p orbital on overlaps the p orbital on the neighboring atom to the neighboring atom to form the π bond. form the π bond.

p orb.for πbond3 sp2hybrid orbitals↑↑↑↑↑↑↑↓2p2s

ππ Bonding in C Bonding in C22HH44ππ Bonding in C Bonding in C22HH44

The unused p orbital on each C atom contains The unused p orbital on each C atom contains an electron and this p orbital overlaps the p an electron and this p orbital overlaps the p orbital on the neighboring atom to form the orbital on the neighboring atom to form the π bond.π bond.

Multiple BondingMultiple Bondingin Cin C22HH44

and and ππ Bonding in Bonding in CC22HH44

and and ππ Bonding in Bonding in CHCH22OO

Consequences of Multiple Consequences of Multiple BondingBonding

There is restricted rotation around C=C bond.There is restricted rotation around C=C bond.

Consequences of Multiple Consequences of Multiple BondingBonding

Restricted rotation around C=C bond.Restricted rotation around C=C bond.

Consequences of Multiple BondingConsequences of Multiple BondingConsequences of Multiple BondingConsequences of Multiple Bonding

Formation of IsomersFormation of Isomers

One isomer may have biological One isomer may have biological activity while the other may notactivity while the other may not

Double Bonds and Double Bonds and VisionVision

1 © 2009 Brooks/Cole - Cengage Advanced Theories of Chemical Bonding Chapter 9 Atomic Orbitals...

Documents

Transcript of 1 © 2009 Brooks/Cole - Cengage Advanced Theories of Chemical Bonding Chapter 9 Atomic Orbitals...

Copyright ©2011 Brooks/Cole, Cengage Learning Turning Data Into Information Chapter 2 1.

106 ©2013, Cengage Learning, Brooks/ Cole Publishing Chapter 7 Psychological Development in Adolescence.

©2010, Cengage Learning, Brooks/ Cole Publishing Infancy Ch. 6 Unit 3 Seminar.

Hybrid Orbitals: atomic orbitals formed by blending different orbitals together Just like with other hybrids, the characteristics of the hybrid orbitals.

Issues in Supervision and Consultation Deborah Smith, PhD Michelle March, PhD Corey, 8e, © 2011, Brooks/ Cole – Cengage Learning.

Atomic Orbitals s-orbitals p-orbitals d-orbitals.

1 Chapter 9 Orbitals and Covalent Bond. 2 Molecular Orbitals n The overlap of atomic orbitals from separate atoms makes molecular orbitals n Each molecular.

Business & Professional Ethics for Directors, Executives ... · Business & Professional Ethics for Directors, Executives & Accountants, 8e L.J. Brooks & P. Dunn, Cengage Learning,

Copyright © 2012 Brooks/Cole, a division of Cengage Learning, Inc. Professional Concerns Chapter Nine.

Copyright ©2011 Brooks/Cole, Cengage Learning Statistics Success Stories and Cautionary Tales Chapter 1 1.

Copyright 2012 Brooks/Cole, a division of Cengage Learning, Inc. Chapter 4 Planning 2016. Cengage Learning. All rights reserved.

Copyright © 2012 Brooks/Cole, a division of Cengage Learning, Inc. The Helping Process Chapter Seven.

Copyright © 2012 Brooks/Cole, a division of Cengage Learning, Inc. Early Stages in the Development of a Group 0.

Copyright ©2011 Brooks/Cole, Cengage Learning Inference about Simple Regression Chapter 14 1.

57 ©2013, Cengage Learning, Brooks/ Cole Publishing Chapter 4 Social Development in Infancy and Childhood.

€¦ · BROOKS/COLE CENGAGE Learning. John E. McMurry Organic Chemistry Chapter 10 Organohalides Hovig Kouyoumdjian

© 2009 Brooks/Cole - Cengage Thermochemistry CHAPTER 6 1.

Copyright ©2011 Brooks/Cole, Cengage Learning Testing Hypotheses about Means Chapter 13.

Thermochemistry - Chapter 6 Rev 8 - Student Version · Chapter 6 — Thermochemistry 1 © 2009 Brooks/Cole - Cengage Thermochemistry CHAPTER 6 1 2 © 2009 Brooks/Cole ... monitor

Orbitals and Mechanisms Handout 2013 - The Burton Groupburton.chem.ox.ac.uk/orbitals-and-mechanisms-2.pdf · Orbitals and Mechanism III 1 Orbitals and Mechanism III 8 Lectures, Year