1 9 Hybridized Atomic Orbitals Given the electron

1. 9 Hybridized Atomic Orbitals • Given the electron configuration for C and H, imagine how their atomic orbitals might overlap • Would such orbital overlap yield methane? Copyright 2012 John Wiley & Sons, Inc. 1 Klein, Organic Chemistry 2 e

1. 9 Hybridized Atomic Orbitals • To make methane, the C atom must have 4 atomic orbitals available for overlapping • If an electron is excited from the 2 s to the 2 p, will that make it suitable for making methane? • If four H atoms were to come in and overlap with the 2 s and 2 p orbitals, what geometry would the resulting methane have? Copyright 2012 John Wiley & Sons, Inc. 2 Klein, Organic Chemistry 2 e

1. 9 Hybridized Atomic Orbitals • The carbon must undergo hybridization to form 4 equal atomic orbitals • The atomic orbitals must be equal in energy to form four equal-energy symmetrical C-H bonds Copyright 2012 John Wiley & Sons, Inc. 3 Klein, Organic Chemistry 2 e

1. 9 Hybridized Atomic Orbitals • Should the shape of an sp 3 orbital

1. 9 Hybridized Atomic Orbitals • To make CH 4, the 1 s atomic orbitals of the H atoms will overlap with the four sp 3 hybrid atomic orbitals of C Copyright 2012 John Wiley & Sons, Inc. 5 Klein, Organic Chemistry 2 e

1. 9 Hybridized Atomic Orbitals • Draw a picture that shows the necessary atomic orbitals and their overlap to form ethane (C 2 H 6). • Draw a picture that shows the necessary atomic orbitals and their overlap to form water. • Practice with conceptual checkpoint 1. 19 Copyright 2012 John Wiley & Sons, Inc. 6 Klein, Organic Chemistry 2 e

1. 9 Hybridized Atomic Orbitals • Consider ethene (ethylene). • Each carbon in ethene must bond to three other atoms, so only three hybridized atomic orbitals are needed Copyright 2012 John Wiley & Sons, Inc. 7 Klein, Organic Chemistry 2 e

1. 9 Hybridized Atomic Orbitals • An sp 2 hybridized carbon will have three equal-energy sp 2 orbitals and one unhybridized p orbital Copyright 2012 John Wiley & Sons, Inc. 8 Klein, Organic Chemistry 2 e

1. 9 Hybridized Atomic Orbitals • The sp 2 atomic orbitals overlap to form sigma (σ) bonds • Sigma bonds provide maximum HEAD-ON overlap Copyright 2012 John Wiley & Sons, Inc. 9 Klein, Organic Chemistry 2 e

1. 9 Hybridized Atomic Orbitals • The unhybridized p orbitals in ethene form pi (π) bonds, SIDE-BY-SIDE overlap • Practice with conceptual checkpoint 1. 20 Copyright 2012 John Wiley & Sons, Inc. 10 Klein, Organic Chemistry 2 e

1. 9 Hybridized Atomic Orbitals • The unhybridized p orbitals in ethene form pi (π) bonds, SIDE-BY-SIDE overlap of p-orbitals giving both CONSTRUCTIVE and DESTRUCTIVE interference • MO theory provides a similar picture. Remember, red and blue regions are all part of the same orbital Copyright 2012 John Wiley & Sons, Inc. 11 Klein, Organic Chemistry 2 e

1. 9 Hybridized Atomic Orbitals • Why is sp 2 hybridization not appropriate for

1. 9 Hybridized Atomic Orbitals • Consider ethyne (acetylene). • Each carbon in ethyne must bond to two other atoms, so only two hybridized atomic orbitals are needed Copyright 2012 John Wiley & Sons, Inc. 13 Klein, Organic Chemistry 2 e

1. 9 Hybridized Atomic Orbitals • The sp atomic orbitals overlap HEAD-ON to form sigma (σ) bonds while the unhybridized p orbitals overlap SIDEBY-SIDE to form pi bonds • Practice with Skill. Builder 1. 7 Copyright 2012 John Wiley & Sons, Inc. 14 Klein, Organic Chemistry 2 e

1. 9 Hybridized Atomic Orbitals • Which should be stronger, a pi bond or a sigma bond? WHY? • Which should be longer, an sp 3 – sp 3 sigma bond overlap or an sp – sp sigma bond overlap? Copyright 2012 John Wiley & Sons, Inc. 15 Klein, Organic Chemistry 2 e

1. 9 Hybridized Atomic Orbitals • Explain the different strengths and lengths below. •

1. 10 Molecular Geometry • Valence shell electron pair repulsion (VSEPR theory) – Valence electrons (bonded and lone pairs) repel each other • To determine molecular geometry… 1. Determine the Steric number Copyright 2012 John Wiley & Sons, Inc. 17 Klein, Organic Chemistry 2 e

1. 10 Molecular Geometry • Valence shell electron pair repulsion (VSEPR theory) – Valence electrons (bonded and lone pairs) repel each other • To determine molecular geometry… 2. Predict the hybridization of the central atom • • • If the Steric number is 4, then it is sp 3 If the Steric number is 3, then it is sp 2 If the Steric number is 2, then it is sp Copyright 2012 John Wiley & Sons, Inc. 18 Klein, Organic Chemistry 2 e

1. 10 3 sp Geometry • For any sp 3 hybridized atom, the 4 valence electron pairs will form a tetrahedral electron group geometry • Methane has 4 equal bonds, so the bond angles are equal Copyright 2012 John Wiley & Sons, Inc. • How does the lone pair of ammonia affect its geometry? 19 • The bond angels in oxygen are even smaller, why? Klein, Organic Chemistry 2 e

1. 10 3 sp Geometry • The molecular geometry is different from the electron

1. 10 2 sp Geometry • Calculate the Steric number for BF 3 • Electron pairs that are located in sp 2 hybridized orbitals will form a trigonal planar electron group geometry • What will be the molecular geometry? Copyright 2012 John Wiley & Sons, Inc. 21 Klein, Organic Chemistry 2 e

1. 10 2 sp Geometry • How many electrons are in Boron’s unhybridized p

1. 10 2 sp Geometry Analyze the steric number, hybridization, electron group geometry and

1. 10 sp Geometry • Analyze the Steric number, the hybridization, the electron group geometry, and the molecular geometry for the following molecules • Be. H 2 • CO 2 Copyright 2012 John Wiley & Sons, Inc. 24 Klein, Organic Chemistry 2 e

1. 10 Geometry Summary • Practice with Skill. Builder 1. 8 Copyright 2012 John

1. 11 Molecular Polarity • Electronegativity Differences cause induction • Induction (shifting of electrons WITHIN their orbitals) results in a dipole moment. • Dipole moment = (the amount of partial charge) x (the distance the δ+ and δ- are separated) • Dipole moments are reported in units of debye (D) • 1 debye = 10 -18 esu ∙ cm – An esu is a unit of charge. 1 e- has a charge of 4. 80 x 10 -10 esu – cm are included in the unit, because the distance between the centers of + and – charges affects the dipole Copyright 2012 John Wiley & Sons, Inc. 26 Klein, Organic Chemistry 2 e

1. 11 Molecular Polarity • Consider the dipole for CH 3 Cl • Dipole moment (μ) = charge (e) x distance (d) – Plug in the charge and distance • μ = (1. 056 x 10 -10 esu) x (1. 772 x 10 -8 cm) – Note that the amount of charge separation is less than what it would be if it were a full charge separation (4. 80 x 10 -10 esu) • μ = 1. 87 x 10 -18 esu ∙ cm – Convert to debye • μ = 1. 87 D Copyright 2012 John Wiley & Sons, Inc. 27 Klein, Organic Chemistry 2 e

1. 11 Molecular Polarity • What would the dipole moment be if CH 3 Cl were 100% ionic? • μ = charge (e) x distance (d) – Plug in the charge and distance • μ = (4. 80 x 10 -10 esu) x (1. 772 x 10 -8 cm) – The full charge of an electron is plugged in • μ = 8. 51 x 10 -18 esu ∙ cm = 8. 51 D • What % of the C-Cl bond is ionic? • Is the C-Cl bond mostly ionic or mostly covalent? Copyright 2012 John Wiley & Sons, Inc. 1 -28 28 Klein, Organic Chemistry 2 e

1. 11 Molecular Polarity • Check out the polarity of come other common bonds

1. 11 Molecular Polarity • Why is the C=O double bond so much more

1. 11 Molecular Polarity • For molecules with multiple polar bonds, the dipole moment is the vector sum of all of the individual bond dipoles Copyright 2012 John Wiley & Sons, Inc. 31 Klein, Organic Chemistry 2 e

1. 11 Molecular Polarity • It is important to determine a molecule’s geometry FIRST before analyzing its polarity • If you have not drawn the molecule with the proper geometry, it may cause you to assess the polarity wrong as well • Would the dipole for water be different if it were linear rather than angular? Copyright 2012 John Wiley & Sons, Inc. 32 Klein, Organic Chemistry 2 e

1. 11 Molecular Polarity • Electrostatic potential maps are often used to give a

1. 11 Molecular Polarity • Practice with Skill. Builder 1. 9 Copyright 2012 John

1. 11 Molecular Polarity • Explain why the dipole moment for pentane = 0

Study Guide for sections 1. 9 -1. 11 DAY 2, Terms to know: Sections 1. 9 -1. 11 hybridized atomic orbitals, steric number, degenerate orbitals, pi bond, sigma bond, electron group geometry, molecular geometry, induction, dipole moment DAY 2, Specific outcomes and skills that may be tested on exam 1: Sections 1. 9 -1. 11 • Be able to predict what type of hybridization atomic orbitals will undergo for an atom depending on the bonding and steric number of the atom. • Be able to explain how the ratio of s and p orbitals mixed into the hybrid atomic orbitals affects the shape and energy of the resulting hydridized orbitals. • Be able to draw a picture showing the overlapping of the correct atomic orbitals for small molecules with 8 atoms or less including molecules with single, double, and triple bonds. • Be able to predict where molecules will have pi bonds and sigma bonds between atoms. • Be able to predict the steric number, hybridization, electron group geometry, molecular geometry, and approximate bond angle for atoms within molecules. • Be able to determine the direction of dipole moment for a molecule and rate its approximate magnitude. • Be able to describe how molecular geometry affects polarity or dipole. 36 Klein, Organic Chemistry 2 e

Practice Problems for sections 1. 9 -1. 11 Complete these problems outside of class until you are confident you have learned the SKILLS in this section outlined on the study guide and we will review some of them next class period. 1. 20 1. 21 1. 22 1. 23 1. 25 1. 26 1. 27 1. 29 1. 30 1. 31 1. 49 1. 50 1. 51 1. 55 1. 59 37 Klein, Organic Chemistry 2 e

Prep for day 3 Must Watch videos: https: //www. youtube. com/watch? v=cn. STs. Lvyu. Ok (dissolving) https: //www. youtube. com/watch? v=_m. WHWJi. MKXU (solubility) https: //www. youtube. com/watch? v=RP 6 AS 7 XVIC 8 (drawing organic molecules) Other helpful videos: http: //www. youtube. com/watch? v=gxmpr 09 Xk 4 Y (solvation, Brightstorm) https: //www. youtube. com/watch? v=p. Mo. A 65 Dj-zk (drawing organic molecules) Read sections 1. 12 -1. 13, 2. 1 -2. 2 38 Klein, Organic Chemistry 2 e