Organic Chemistry 1 Week 1 and 2 Notes
Organic Chemistry 1 Week 1 and 2 Notes CHEM 231
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This 4 page Class Notes was uploaded by Jernelle John on Sunday September 11, 2016. The Class Notes belongs to CHEM 231 at University of Maryland taught by Dr. Monique Koppel in Fall 2016. Since its upload, it has received 153 views. For similar materials see Organic Chemistry 1 in Chemistry at University of Maryland.
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Date Created: 09/11/16
Monday, September 12, y Week 1 and 2 Notes Ch.1 Aufbau Principle orbitals fill from lowest to highest energy level Pauli Principle orbitals can only contain two electrons each Hund’s Rule all orbitals of the same energy level must have one electron before any orbital could add another electron ionization potential the energy that it takes to remove an electron molecule Electronegative the degree of an atom’s attraction towards another atom Covalent bonds sharing of electrons • polar covalent bonds the unequal sharing of electrons between 0.5 to 1.9 = polar less than 0.5 = nonpolar more than 1.9 = ionic bond How to draw Lewis Structure • determine the number of valance electrons by summing the number of valance electrons of all atoms apart of the compound • determine the arrangement of atoms through an experimental procedure • bond the atoms and add lone pairs so that each atom has an octet exception: Boron and Aluminum often have an incomplete octet Formal Charge = the number of valance electrons (number of lone pairs + 1/2 the number of bonds) 1 Monday, September 12, y Molecular Orbital Theory used to calculate the energy and shape of molecular orbitals • combine atomic orbitals of the atoms apart of a compound • arrange from lowest to highest energy levels • use the same principles as atomic orbital (Aufbau, Pauli, Hund) • ground state at lowest energy • excited state state other than ground state • ionic bond bond of metal and nonmetal • Valance Bond Theory overlap of orbitals single bond a sigma bond double bond a sigma bond and a pi bond triple bond a sigma bond and two pi bonds Exception to Octet Rule • row three elements and down can have expanded octets (more the eight electrons) because of the d orbital Not all Resonance Structures are Equal Priorities from Most Important to Least Important • Full Valance Shell • Negative Charge on the most electronegative atom • Least (+) and () signs Sigma Bonds and Pi Bonds occupy hybrid orbitals Single bonds are longer than double bonds are longer than triple bonds • single bonds require more space (sp ) hybridization 2 Monday, September 12, y • the shorter the bond, the stronger it is Resonance • electrons from double bonds and lone pairs can move if the adjacent group can accept it • all electrons that participate in resonance are in a p orbital Week 2 Notes ( Ch. 4) Acid Base Reactions • Arrhenius definition (Not commonly used) acid a substance that can dissolve in water to produce H or H O+ + 3 base a substance that can dissolve in water to produce OH • BrønstedLowry definition (More commonly used) + acid a proton (H ) donor which creates a conjugate base base a proton acceptor which + creates a conjugate acid Cl (conjugate base) + H 3 (conjugate acid) ex. HCl (acid) +H O2(base) water can act as an acid or a base • A base with two receptor sites will accept the electron at its more stable site delocalization of the negative charge (resonance) is more stable is more stable than a structure without resonance • Double bonds (pi bond and sigma bond) use electrons to accept protons pi bonds serve as electron acceptor (base) • equilibrium constant measure the strength of an acid 3 Monday, September 12, y + ex. for HA + H O 2 + H O 3 • [H O ][A ] / [HA][H 0] 3 2 • the concentration of water does not change very much; therefore we can take water out of the equation to find the acid dissociation constant • Acid Dissociation Constant (K ) which is the same as K[H O] a 2 K a [H O3][A] / [HA] • pK =alog K10 a the pKa value is used to determine the strength of acids the larger the pKa value, the weaker the acid the weaker the acid, the stronger the conjugate base the larger the pKa value, the stronger the conjugate base if the pKa value is negative than most molecules of the acid are dissociated in water • in an acidbase reaction equilibrium always favors stronger acids and bases to make weaker conjugate acids and bases Hybridization • any structure that can be hybridized to a lower hybridization state due to resonance should be ex. Nitrogen is connected to three single bonds and contains a lone pair (sp 3 orbital). If an orbital can accept the lone pair on Nitrogen using resonance to make it an sp orbital than when asked on a test what is the hybridization of 2 Nitrogen, put the lower hybridization state (sp )! 2 4
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