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Introduction to Organic Chemistry] CHEM 102 [INTRODUCTION TO ORGANIC CHEMISTRY] CHEM 102 Introduction to Organic Chemistry Exam 1 Material Only Professor Kelly Boebinger Crafton Hills College 1 Copyright © 2015 Kelly Boebinger | Crafton Hills College CHEM 102 [INTRODUCTION TO ORGANIC CHEMISTRY] Table of Contents: Lecture Notes: Page Exam 1 Topics: 1 OCHEM Introduction, Alkanes, Cycloalkanes, Alkenes, Alkynes Exam 2 Topics: 32 Benzene, Aromatics, Alcohols, Phenols Exam 3 Topics: 53 Ethers, Thiols, Sulfides, Amines Exam 4 Topics: 67 Aldehydes, Ketones, Carbonyl Groups Final Exam Topics: All above plus: 86 Amino acids, Proteins Experiments: 1 Melting Point 97 2 Distillation 101 3 Molecular Models 105 4 Electrophilic Aromatic Substitution 111 5 The Hydroxyl Group 113 6 Chromatography 117 7 Extraction and Isolation of Caffeine 121 8 Aldehyde and Ketone Reactions 123 9 Soaps and Detergents 127 10 Milk Protein & Amino Acids 131 2 Copyright © 2015 Kelly Boebinger | Crafton Hills College CHEM 102 [INTRODUCTION TO ORGANIC CHEMISTRY] Section 1: Alkanes, Cycloalkanes, Alkenes, Alkynes What is Organic Chemistry? Organic Chemistry: The study of compounds that contain carbon. There are millions of organic compounds. Inorganic chemistry is the study of all the other elements. Organic Chemists are interested in the 1) Structure of carbon containing compounds. 2) Nomenclature (naming) of organic compounds. 3) Physical properties of organic compounds. 4) Synthesis of organic compounds. 5) Reactions of organic compounds. Structure of Organic Compounds: The Atom: Atoms contain a small, dense nucleus surrounded by electrons. The nucleus is positively charged and contains most of the mass of the atom. The nucleus contains protons, which are positively charged, and neutrons, which are neutral. The atomic number of an element is equal to the number of protons in the nucleus. The atomic weight is approximately equal to the sum of the number of the protons and neutrons in the nucleus. Electrons are concentrated in certain regions of space outside the nucleus called orbitals. The orbitals, which differ in shape, are designated by the letters s, p, d, and f. There are one s orbital, three p orbitals, five d orbitals, and seven f orbitals. Each orbital can hold two electrons maximum. BONDS: Ionic, Covalent, Multiple, Polar Covalent Ionic bonds: are formed by the transfer of one or more valence electrons from one atom to another. Because electrons are negatively charged, the atom that gives up the electrons becomes positively charged, a cation. The atom that receives the electron becomes negatively charged, and an anion. The atoms are held together by electrostatic force. Electropositive (+): atoms that tend to give up electrons, such as sodium. Electronegative (-): atoms that tend to accept electrons, such as chlorine. Carbon is neither strongly electropositive nor strongly electronegative. 3 Copyright © 2015 Kelly Boebinger | Crafton Hills College CHEM 102 [INTRODUCTION TO ORGANIC CHEMISTRY] Covalent bonds: are formed by the sharing of electron pairs. When two or more atoms are joined by covalent bonds it is known as a molecule. Carbon is tetravalent (four valence electrons): Carbon always has four bonds, (eight electrons) around it to fulfill the octet rule. These bonds are covalent. The unique property of carbon atoms is the ability to share electrons not only with different elements but also with other carbon atoms, and form multiple bonds. Multiple Bonds in Organic Compounds Carbon can form multiple bonds with a neighboring carbon. Atoms may sometimes share more than one electron pair and form multiple bonds. A double bond shares two electron pairs (4 electrons) and a triple bond shares three electron pairs (6 electrons). Single Bond Double Bond Triple Bond Organic Compounds and Polar Covalent Bonds Polar Covalent Bond: a covalent bond in which the electron pair is not shared equally between the two atoms. This occurs when there's a difference in electronegativity between the atoms. The atoms that are linked carry a partial negative and partial positive charge. = delta = polarity Dipole moment = μ CH3Cl chloromethane or methyl chloride (a substituted alkane) The electronegative chloride removes electron density from carbon, leaving it electropositive. Elements Found in Organic Compounds Other Than Carbon 1. hydrogen: almost all compounds 2. halogens: Cl, Br, ( also I & F , but are less common) 3. oxygen: alcohols, ethers, ketones, esters, and aldehydes 4. sulfur: thiols and disulfides 5. nitrogen: amines, amides, amino acids 4 Copyright © 2015 Kelly Boebinger | Crafton Hills College CHEM 102 [INTRODUCTION TO ORGANIC CHEMISTRY] Hydrocarbon: Contains only hydrogen and carbon Hydrocarbon Alkane Alkene Alkyne Bonding General Formula Saturated or Unsaturated Example Structure Name Geometry Bond Angle Hybridization Hybridization: Hybrid of s and p orbitals to form bonds. Hybridization can be determined on any atom that is bonded to 2 or more other atoms; sp, sp2, sp3 H H H H H C C H C C H H H H H H H C O C C CH C C H H C C H 2 H CH3 5 Copyright © 2015 Kelly Boebinger | Crafton Hills College CHEM 102 [INTRODUCTION TO ORGANIC CHEMISTRY] Ways to represent an organic compound: Molecular Formula: Only shows the ratio of atoms relative to each other, does not explain how atoms are connected together. For example C6H14 Structural Formulas: The most common structural formula used is a condensed structural formula, and many times simply referred to as a structural formula, omitting the word condensed. In some cases and expanded structural formula is used to emphasize features on a molecule. Expanded Structural Formula shows in two dimensions, all of the atoms in a molecule and all of the bonds connecting them. Many times this is described as showing all bonds explicitly. Condensed Structural Formula uses groupings of atoms, in which the central atoms and the atoms connected to them are written as a group, to convey molecular structural information. Line or Skeletal Structures: Perhaps the ultimate abbreviated structures are the use of lines to represent the carbon framework. Carbon at bend or end (also intersection). Often used to represent rings of carbons. Molecular CH4 C3H8 C6H14 Formula Expanded Structural Formula Condensed Structural Formula Examples of Line Structures 6 Copyright © 2015 Kelly Boebinger | Crafton Hills College CHEM 102 [INTRODUCTION TO ORGANIC CHEMISTRY] Structure of straight chain carbons: When a number of carbon atoms are connected together, they are said to be in a straight chain, even though in the actual molecule, the carbon atoms are in a zigzag pattern. Once you are aware of these dimensional structures of molecules, you do not have to explicitly show this in most cases. Three dimensional shapes of carbon compounds. Carbons at intersections. MAKE MODELS ____ out of plane “”””” behind plane in plane Solid Wedge Dashed Wedge ALKANES: are hydrocarbon molecules of carbon and hydrogen that have only single bonds. General formula for an Alkane: The formula for an alkane is CnH2n+2 where n is equal to the number of carbon atoms. Example: For an alkane, which contains five carbons. n = 5 2n + 2 = 2(5) + 2 = 12 The molecular formula is thus C5H12. This corresponds to pentane. Molecular Formula Name Number of Prefix Carbon atoms CH4 methane 1 meth- C2H6 ethane 2 eth- C3H8 propane 3 prop- C4H10 butane 4 but- C5H12 pentane 5 pent- C6H14 hexane 6 hex- C7H16 heptane 7 hept- C8H18 octane 8 oct- C9H20 nonane 9 non- C10H22 decane 10 dec- 7 Copyright © 2015 Kelly Boebinger | Crafton Hills College CHEM 102 [INTRODUCTION TO ORGANIC CHEMISTRY] Alkanes can be shown in the following way, keeping in mind that they are three- dimensional. The following represents the structures that are only straight chain, and do not include any branched alkanes which will be covered later. Draw the condensed structural formula for the following: methane hexane ethane heptane propane octane butane nonane pentane decane Conformations of Alkanes: Conformations are differing orientations of a molecule made possible by rotations around a single bond. Rotation about carbon-carbon single bonds is an important property of alkane molecules. As a result of rotation around single bonds, alkane molecules (except methane) can exist in infinite numbers of orientations, or conformations. Different conformations for C4H10 Problem: Predict if the following are isomers of each other or different conformations. CH3 CH CH a. CH2 and 3 3 CH2 CH2 CH2 CH2 CH2 CH3 CH CH3 3 b. CH3 CH CH 2 CH 3 and CH3 CH2 CH2 CH2 8 Copyright © 2015 Kelly Boebinger | Crafton Hills College CHEM 102 [INTRODUCTION TO ORGANIC CHEMISTRY] Structure of branched chain alkanes and Isomers: • If an alkane contains four or more carbon atoms, there can be branched alkanes. • Structural isomers are compounds with the same molecular formula but a different structural formula (different connections between atoms). The number of structures possible = number of isomers IUPAC system is the first name listed; it is the most current way to name compounds. The older way to name is still sometimes used, so it is necessary to know some of the old names. (Old way to name: n- meant straight chain or on carbon 1, and iso meant something is coming off carbon 2) C H has the following structural formulas: 2 structures = 2 isomers 4 10 butane (n-butane) 2-methylpropane (isobutane) C H has the following structural formulas: 3 structures = 3 isomers 5 12 pentane 2-methylbutane 2,2-dimethylpropane 9 Copyright © 2015 Kelly Boebinger | Crafton Hills College CHEM 102 [INTRODUCTION TO ORGANIC CHEMISTRY] C6H14 has the following structural formulas: 5 structures = 5 isomers hexane 2-methylpentane 3-methylpentane 2,2-dimethylbutane 2,3-dimethylbutane As the number of carbon atoms increase the number of possible isomers increase exponentially. Branched alkanes and the number of isomers: C7H16 9 isomers C8H18 18 isomers C9H20 35 isomers C10H22 75 isomers C20H24 366,319 isomers C30H26 4,111,846,763 isomers C40H28 62,491,178,805,831 isomers 10 Copyright © 2015 Kelly Boebinger | Crafton Hills College CHEM 102 [INTRODUCTION TO ORGANIC CHEMISTRY] Alkyl groups, which are attached to a carbon chain, are derived from the respective alkane.
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