Organic Chemistry RALO
Organic Chemistry RALO CHM 11500 - 002
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This 7 page Bundle was uploaded by Allison Notetaker on Wednesday December 9, 2015. The Bundle belongs to CHM 11500 - 002 at Purdue University taught by Dr. Roy Tasker/ Dr. Scott McLuckey in Fall 2015. Since its upload, it has received 51 views. For similar materials see General Chemistry in Chemistry at Purdue University.
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Date Created: 12/09/15
CHM 11500 Reading Assignments and Learning Objectives Fa2015 Organic Chemistry Hybridization Reading Assignm :t Sections 11.1: Valence Bond Theory and Orbital Hybridization 11.2: Modes of Orbital Overlap and the Types of Covalent Bonds Learning Object es: Concepts to Understand Describe the major tenets of valence bond theory. Basic principle: a covalent bond forms when orbitals of two atoms overlap and a pair of electrons occupy the overlap region o Their wave functions are in phase, so the amplitude between the nuclei increases 1. Opposing spins of the electron pair o the space forme by the overlapping orbitals has a maximum capacity for two electrons that have opposite spins 2. Maximum overlap of bonding orbitals o bond strength depends on the attraction between nuclei and shared electrons, so the greater the orbital overlap, the closer the nuclei are to the electrons, and the stronger the bond 3. Hybridization of atomic orbitals o the valence orbitals in the isolated atoms become new orbitals in the molecule o hybridization o hybrid orbitals 4. Features of hybrid orbitals o the number of hybrid orbitals formed equals the number of atomic orbitals mixed o the type of hybrid orbitals formed varies with the types of atomic orbitals mixed o the shape and orientation of a hybrid orbital maximize its overlap with the orbital of the other atom in the bond How atomic orbitals mix to form hybrid orbitals with different positions in space (linear, trigonal planar, tetrahedral). The number of hybrid orbitals formed equals the number of atomic orbitals mixed The type of hybrid orbtials formed varies with the types of atomic orbitals mixed The shape and orientation of a hybrid orbital maximize its overlap with the orbital of the other atom in the bond Sp o Tow nonequivalent orbitals of a central atom mix and form equivalent sp hybrid orbitals o The orbital orientations increase electron density in the bonding direction and minimize repulsions between the electrons that occupy the orbitals Sp2 o Mixing one s and two p orbitals gives three sp2 hybrid orbitals that point to the corners of an equilateral triangle How sigma and pi bonds are formed via overlap. Sigma bond CHM 11500 Reading Assignments and Learning Objectives Fa2015 o Formed from an endtoend overlap o Has its highest electron density along the bond axis o Shaped like an ellipse rotated about its long axis o All single bonds Pi bond Side to side bond Has two regions of electron density: one above and one below the pibond axis The two electrons in one pi bond occupy both lobes A double bond consists of one sigma bond and one pi bond, which increases electron density between the nuclei The two electron pairs act as one electron group because each pair occupies a different orbital, which reduces repulsions How the differing modes of overlap lead to single, double, and triple bonds. Because orbitals overlap less side to side than they do end to end, a pi bond is weaker than a sigma bond Lonepair repulsions, bond polarities and other factors affect overlap between other pairs of atoms Why pi bonding restricts rotation about double and triple bonds. Because p orbitals must be parallel to each other to overlap most effectively For this reason, distinct cis and trans structures exist for compounds Has a major effect on molecular polarity Rotation around a triple bond is not meaningful; each triplebonded C atom is bonded to one other group in a linear arrangement, so there can be no difference in the relative positions of attached groups Understand how orbital position determines bond angle. Skills to Master Use molecular shape to determine the hybrid orbitals on the central atom(s) in a molecule. Describe the types of orbitals and bonds in a molecule. Hydrocarbons and Functional Groups Reading Assignme t: Sections 15.1: The Special Nature of Carbon and the Characteristics of Organic Molecules 15.2: The Structures and Classes of Hydrocarbons 15.4: Properties and Reactivities of Common Functional Groups Learning Object es: Concepts to Understand: Oil provides our society with a vast amount of resources besides just gasoline. Identify hydrocarbons and describe how they are important when considering the composition of oil Hydrocarbons o The simplest type of organic compound o Contain only H and C atoms o Natural gas and gasoline o Ethylene, acetylene, benzene CHM 11500 Reading Assignments and Learning Objectives Fa2015 The geometries about the carbon atoms in alkanes, alkenes, and alkynes (relate to hybridization) Alkane o A hydrocarbon that contains only single bonds o Comprise a homologous series, one in which each memberdiffers from the next by a –CH2—(methylene) group o Each C is sp3 hybridized o Because each C is bonded to the maximum number of other atoms, alkanes are referred to as saturated hydrocarbons o Cyclic hydrocarbon is one that contains one or more rings o Nearly nonpolar, so we would expect their physical properties and solubility behavior to be determined by dispersion forces o Alkanes are miscible in each other and in other nonpolar solvents, but are nearly insoluble in water Alkene o A hydrocarbon that contains at least one C=C bond o General formula CnH2n o Double bonded C atoms are sp2 hybridized o Unsaturated hydrocarbons because their carbon atoms are bonded to fewer than the maximum of four atoms each o Tetrahedral geometry around each C atom, whereas the double bonded C atom in alkenes are trigonal planar o The CC bond allows rotation of bonded groups, so the atoms in an alkane continually change their relative positions, but the pi bond of the alkene C=C bond restricts rotation, so the relative positions of the atoms attached to the double bond are fixed o Geometric isomers (aka cistrans isomers) have different orientations of groups around a double bond The cis (on the same side) The trans (different sides) For a molecule to have geometric isomers, each C atom in the C=C bond must also be bonded to two different groups Have different physical properties Alkynes o Hydrocarbons that contain at least one C=C bond o General formula: CnH2ns o Each C in a C=C is sp and linear o Because of their localized pi electrons, C=C and C=C bonds are electron rich and act as functional groups o Thus, alkenes and alkynes are much more reactive than alkanes Isomer o Two or more compounds that have the same molecular formula but different properties Constitutional isomers o Those with different arrangemtns of bonded atoms o Physical roperties depend on the strength of the dispersion forces Understand the importance of functional groups and how they affect physical properties The distribution of electron density in a functional group is a key to the reactivity of the compound CHM 11500 Reading Assignments and Learning Objectives Fa2015 o The electron density can be high, as in the C=C and C=C bonds, or it can be low at one end of a bond and high at the other, as in the CCl and CO bonds o Such electronrich or polar bonds enhance the opposite charge in a polar bond of the other reactant o As a result, the reactants attract each other and begin a sequence of bondforming and bondbreaking steps that lead to a product o The intermolecular forces that affect physical properties and solubility also affect reactivity o Funcation groups with only single bonds undergo elimination or substitiution o Functional groups with double or triple bonds undergo addition o Functional groups with both single and double bonds undergo substitution Alcohol o Consists of a carbon bonded to an OH group o Common organic reactants, and the functional group occurs in many biomeolecules, including carbohydrates, sterols, and some amino acids o Physical properties of the smaller alcohols are similar to those of water They have high melting and boiling points as a result of hydrogen bondings Dissolve polar molecules and some salts Haloalkane o A halogen atom bonded to a carbon o Named by identifying the halogen with a prefix on the hydrocarbon name and numbering the C atom to which the halogen is attached Amine o Trigonal pyramidal shapes and a lone pair of electrons on a partially negative N atom Alkenes o The C=C bond is the essential portion of the alkene functional group Aldehyde o The carbonyl C is bonded to H so it occurs at the end of a chain Ketone o The carbonyl C is bonded to two other C atoms, so it occurs within the chain Organometallic compounds o Take part in a ghighly polar reaction Understand the composition of polymers Organic compounds The Structural Complexity of Organic Molecules 1. Electron configuration, electronegativity, and bonding o carbon forms covalent bonds in all its elemental forms and compounds result of its electron configuration and electronegativity 2. Catenation, bond properties and molecular shape o the number and strength of carbon’s bonds lead to its property of catenation, the ability to bond to itself repreatedly, which results in a multitude of chemically and thermally stable chain, ring and branched compounds through the process of orbital hybridization, carbon forms four bonds in virtually all its compounds, the small size of carbon allows close approach to another atom and thus greater orbital overlap, so carbon forms relatively short, strong bonds the CC bond is short enough to allow sidetoside overlap of halffilled, unhybridized p orbitals and the formation of multiple bonds CHM 11500 Reading Assignments and Learning Objectives Fa2015 these restrict rotation of attached groups, leading to additional structures Molecular stability o Carbon forms stable chains because of atomic and bonding properties Atom size and bond strength Small atomic size means shorter and stronger bond Relative enthalpies of reaction Realtively little heat is released when a C cahin reacts and one bond replaces the other Orbitals available for reaction Functional group o The central feature of most organic molecules o A specific combination of bonded atoms that reacts in a characteristic way, no matter what molecule it occurs in o The reaction of an organic compound takes place at the functional group Carbon’s small size, intermediate electronegativity, four valence electrons, and ability to form multiple bonds result in the structural complexity of organic compounds These factors lead to carbon’s ability to catenate, which creates chains, branches, and rings of C atoms. o Small size and absence of d orbitals in the valence level lead to strong chemically resistant bonds that point in a s many as four directions from each C Carbon’s ability to bond to many other elements, especially O and N, crates polar, reactive bonds, which leads to the chemical diversity of organic compounds Most organic compounds contain functional groups, specific combinations of bonded atoms that react in characteristic ways Skills to Master: Draw expanded, condensed, and carbon skeleton formulas of organic molecules Assign names for simple alkanes, alkenes, and alkynes up to 10 carbons Predict the products of combustion reactions of hydrocarbons Recognize and name key functional groups in organic molecules listed in Table 15.5, and the class of molecule to which they belong Identify cis and trans isomers from chemical structures Polymer Chemistry Reading Assignme Section 15.5: The MonomerPolymer Theme 1: Synthetic Macromolecules pp. 500504: Polymeric Materials Learning Objecti es: Concepts to Understand Describe how carbon’s atomic properties give rise to its ability to form four strong covalent bonds, multiple bonds, and chains, which results in the great structural diversity of organic compounds. Describe how addition and condensation polymers form (know what the elimination products are). Addition polymers o Form when monomers undergo an addition reaction with one another o Also called chainreaction polymers because as each monomer adds to the chain, it forms a new reactive site to continue the process Condensation Polymers o Must have two functional groups o Link when an A group on one undergoes a dehydration condensation reaction with a B group on another o Many are copolymers, those consisting of two or more different repeat units Polyamides polyesters Identify three types of biopolymers and their monomers. Describe how the “molecular architecture” of a polymer affects its physical properties. Describe how functional groups affect the physical and chemical properties of a polymer. How structures of polymers compare to structures of small organic molecules Skills to Master Determine the reactants and products of the reactions of alcohols, alkyl halides and amines. Draw an abbreviated synthetic polymer structure based in monomer structures. Identify the monomer(s) given a polymer structure. Identify the alkene monomer given a polymer structure Infrared Spectroscopy Reading Assignme t: pp. 374375: Infrared Spectroscopy Learning Objecti s: Concepts to Understand: Absorption of light in the UV and IR regions of the spectrum can be just as characteristic as visible absorption Identify the region of the electromagnetic spectrum where electronic transitions, vibrational transition, and rotational transitions are excited in a molecule Identify the region of the electromagnetic spectrum where bonds can be broken. What characteristics of molecules must be present for IR absorption to occur. The effect of mass on the vibrational frequency for a given pair of atoms. The effect of bond energy and bond order on the vibrational frequency. What types of characterizations problems can be solved by using IR spectroscopy Convert between frequency, wavelength and energy. IR absorption is based on the vibrational energy levels of a molecule.
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