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01 Lecturey
Uploaded: 1 weeks ago
Contributor: lee871009
Category: Organic Chemistry
Type: Lecture Notes
Rating: N/A
Filename:   01_Lecturey.pptx (6.16 MB)
Page Count: 74
Credit Cost: 7
Views: 2
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Transcript
1st mid-term exam: October 20 (Tue.); 25% 2nd mid-term Nov. 20 (Friday): 25% 3rd mid-term: Dec 22 (Tue): 25% Final exam: June 15 (Friday): 25% The contents in handouts, exercises, and problems account for 80-90% of the questions in the exams. Attendance check: 5 times this semester; accounts for extra 10% score © 2014 Education, Inc. Chapter 1 Paula Yurkanis Bruice University of California, Santa Barbara © 2014 Education, Inc. Remembering General Chemistry: Electronic Structure and Bonding What is Organic Chemistry? © 2014 Education, Inc. Organic compounds: from living organisms (with a vital force) Inorganic compounds: from minerals (with a vital force) organic chemistry = compounds that contain carbon What Makes Carbon So Special? Atoms to the left of carbon give up electrons. Atoms to the right of carbon accept electrons. Carbon shares electrons. © 2014 Education, Inc. The Structure of an Atom Protons are positively charged. Neutrons have no charge. Electrons are negatively charged. Atomic number = # of protons Atomic number of carbon = 6 Neutral carbon has six protons and six electrons. © 2014 Education, Inc. Isotopes © 2014 Education, Inc. The Distribution of Electrons in an Atom The first shell is closest to the nucleus. The closer the atomic orbital is to the nucleus, the lower its energy. Within a shell, s < p. © 2014 Education, Inc. Relative Energies of the Atomic Orbitals © 2014 Education, Inc. © 2014 Education, Inc. -Aufbau principle: An electron goes into the atomic orbital with the lowest energy. -Pauli exclusion principle: No more than two electrons can be in an atomic orbital. -Hund’s rule: An electron goes into an empty degenerate orbital rather than pairing up. Atoms on the Left Side of the Periodic Table Lose an Electron © 2014 Education, Inc. Atoms on the Right Side of the Periodic Table Gain an Electron © 2014 Education, Inc. A Hydrogen Atom Can Lose or Gain an Electron © 2014 Education, Inc. An Ionic Bond is Formed by the Attraction Between Ions of Opposite Charge © 2014 Education, Inc. Covalent Bonds are Formed by Sharing Electrons Nonpolar covalent bond = bonded atoms are the same Polar covalent bond = bonded atoms are different © 2014 Education, Inc. How Many Bonds Does an Atom Form? Lewis Structures © 2014 Education, Inc. Bond Polarity Depends on the Difference in Electronegativity © 2014 Education, Inc. Polar Covalent Bonds © 2014 Education, Inc. Dipole Moments the greater the difference in electronegativity, the greater the dipole moment, and the more polar the bond © 2014 Education, Inc. Electrostatic Potential Maps © 2014 Education, Inc. Formal Charge © 2014 Education, Inc. Formal Charge = the number or valence electrons 1/2 the number of bonding electrons or Formal Charge = the number or valence electrons the number of bonds Neutral Carbon Forms Four Bonds if carbon does not form four bonds, it has a charge (or it is a radical) © 2014 Education, Inc. Neutral Nitrogen Forms Three Bonds Nitrogen has one lone pair. If nitrogen does not form three bonds, it is charged. © 2014 Education, Inc. Neutral Oxygen Forms Two Bonds Oxygen has two lone pairs. If oxygen does not form two bonds, it is charged. © 2014 Education, Inc. Hydrogen and the Halogens Form One Bond A halogen has three lone pairs. if hydrogen or halogen does not form one bond, it has a charge (or it is a radical) © 2014 Education, Inc. The Number of Bonds and Lone Pairs {2D5ABB26-0587-4C30-8999-92F81FD0307C} Halogen = 3 lone pairs Oxygen = 2 lone pairs Nitrogen = 1 lone pair © 2014 Education, Inc. Lewis Structures © 2014 Education, Inc. How to Draw a Lewis Structure NO3– Determine the total number of valence electrons (5 + 6 + 6 + 6 = 23). Because they are negatively charged, add another electron = 24. Avoid O–O bonds. Check for formal charges. © 2014 Education, Inc. © 2014 Education, Inc. Kekulé Structures and Condensed Structures © 2014 Education, Inc. What is an Atomic Orbital? © 2014 Education, Inc. A Standing Wave © 2014 Education, Inc. The Lobes of a p Orbital Have Opposite Phases © 2014 Education, Inc. The Three p Orbitals © 2014 Education, Inc. The Bonding in H2 © 2014 Education, Inc. © 2014 Education, Inc. Waves Can Reinforce Each Other; Waves Can Cancel Each Other © 2014 Education, Inc. Atomic Orbitals Combine to Form Molecular Orbitals © 2014 Education, Inc. . Side-to-Side Overlap of In-Phase p Orbitals Forms a π Bond © 2014 Education, Inc The p Orbital of the More Electronegative Atom Contributes More to the Bonding MO © 2014 Education, Inc. The Bonding in Methane © 2014 Education, Inc. In Order to Form Four Bonds, Carbon Must Promote an Electron © 2014 Education, Inc. Four Orbitals are Mixed to Form Four Hybrid Orbitals An sp3 orbital has a large lobe and a small lobe. © 2014 Education, Inc. The Carbon in Methane is sp3 Carbon is tetrahedral. The tetrahedral bond angle is 109.5°. © 2014 Education, Inc. The Bonding in Ethane © 2014 Education, Inc. The Bonding in Ethane © 2014 Education, Inc. End-On Overlap of Orbitals Forms a (σ) Bond © 2014 Education, Inc. Bonding in Ethene © 2014 Education, Inc. An sp2 Carbon Has Three sp2 Orbitals and One p Orbital © 2014 Education, Inc. The Carbons in Ethene are sp2 © 2014 Education, Inc. Bonding in Ethyne © 2014 Education, Inc. The Two sp Orbitals Point in Opposite Directions The Two p Orbitals are Perpendicular © 2014 Education, Inc. The Carbons in Ethyne are sp © 2014 Education, Inc. Methyl Cation and Methyl Radical are sp2 © 2014 Education, Inc. Methyl Anion is sp3 © 2014 Education, Inc. Nitrogen Has Three Unpaired Valence Electrons and Forms Three Bonds in NH3 Nitrogen does not have to promote an electron. © 2014 Education, Inc. The Bonds in Ammonia (NH3) © 2014 Education, Inc. The Ammonium Ion (+NH4) © 2014 Education, Inc. Oxygen Has Two Unpaired Valence Electrons and Forms Two Bonds in H2O Oxygen does not have to promote an electron. © 2014 Education, Inc. The Bonds in Water (H2O) © 2014 Education, Inc. The Bond in a Hydrogen Halide © 2014 Education, Inc. Overlap of an s Orbital with an sp3 Orbital © 2014 Education, Inc. The Length and Strength of a Hydrogen Halide Bond © 2014 Education, Inc. Summary of Hybridization orbitals used in bond formation determine the bond angle © 2014 Education, Inc. Single Bond: 1 σ + 1 π Double bond: 1 σ + 2 π Triple Bond: 1 σ + 2 π © 2014 Education, Inc. Hybridization of C, N, and O © 2014 Education, Inc. Bond Strength and Bond Length The shorter the bond, the stronger it is. © 2014 Education, Inc. s Character The shorter the bond, the stronger it is. © 2014 Education, Inc. The More s Character in the Orbital, the Shorter and Stronger the Bond The more s character, the shorter and stronger the bond. © 2014 Education, Inc. The More s Character in the Orbital, the Greater the Bond Angle The more s character, the greater the bond angle. © 2014 Education, Inc. Hybridization, Bond Angle, Bond Length, Bond Strength © 2014 Education, Inc. Summary © 2014 Education, Inc. The shorter the bond, the stronger it is. The greater the electron density in the region of orbital overlap, the stronger the bond. The more s character, the shorter and stronger the bond. The more s character, the larger the bond angle. A π Bond is Weaker Than a σ Bond © 2014 Education, Inc. Dipole Moments of Molecules © 2014 Education, Inc. Dipole Moments of Molecules © 2014 Education, Inc.


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