General, Organic, and Biochemistry: Chapter 10 Lecture Notes PDF

GENERAL, ORGANIC, AND BIOCHEMISTRY 10TH Edition...

GENERAL, ORGANIC, AND BIOCHEMISTRY 10TH Edition Katherine J. Denniston Joseph J. Topping Danaè R. Quirk Dorr Robert L. Caret Chapter 10 An Introduction to Organic Chemistry The Saturated Hydrocarbons ©2020 McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior  10.1 Strategies for Success in Organic Chemistry Organic chemistry Rational and systematic Success depends on learning roles of naming and the principles that determine their properties and reactivity Active learning – key to successful learning ©2020 McGraw-Hill Education  Active Learning Practices Prepare for class Make the most of class time Make your study time active Review and annotate class notes Solve problems on your own and with a study group Don’t look at solutions until you solve them Talk through solutions Use flash cards, visual summaries, and concept maps ©2020 McGraw-Hill Education  10.2 The Chemistry of Carbon Why are there so many organic compounds? 1. Carbon forms stable, covalent bonds with other carbon atoms Carbon can form up to 4 covalent bonds with other carbon atoms 2. Carbon atoms form stable bonds with other elements, such as: Oxygen Nitrogen Sulfur Halogen The presence of these other elements confers ©2020 McGraw-Hill Education many new physical and chemical properties on  Why are there so many organic compounds? Reason 3 3. Carbon atoms form double or triple bonds with other atoms to produce a variety of structures with differing properties: Double Bonds: Triple Bonds: ©2020 McGraw-Hill Education  Why are there so many organic compounds? Reason 4 4. The number of ways to arrange carbon and other atoms is nearly limitless: Branched chains Ring structures Linear chains Two organic compounds may even have the same number and kinds of atoms but completely different structures and thus, different properties These are called isomers ©2020 McGraw-Hill Education  Important Differences Between Organic and Inorganic Compounds Bond type Organics have covalent bonds (electron sharing) Inorganics usually have ionic bonds (electron transfer) ©2020 McGraw-Hill Education  Structural Differences Between Organic and Inorganic Compounds Structure Organics Molecules Nonelectrolytes Inorganics Three-dimensional crystal structures Often water-soluble, dissociating into ions - electrolytes ©2020 McGraw-Hill Education  Physical Differences Between Organic and Inorganic Compounds Melting Point & Boiling Point Organics have lower melting points Intermolecular forces broken fairly easily Inorganics usually have higher melting points Ionic bonds require more energy to break Water Solubility Organics Nonpolar, water insoluble Inorganics Water-soluble, readily dissociate ©2020 McGraw-Hill Education  Comparison of Major Properties of Organic and Inorganic Compounds Table 10.1 Comparison of the Major Properties of a Typical Organic and an Inorganic Compound: Butane Versus Sodium Chloride Property Organic Compound Inorganic Compound (Butane) (Sodium Chloride) Molar Mass 58 g/mol 58.5 g/mol Bonding Covalent (C4H10) Ionic (Na+ and Cl- ions) Physical state at Gas Solid room temperature and atmospheric pressure Boiling Point Low (-0.5°C) High (1413°C) Solubility in water Insoluble High (36 g/100 mL) Solubility in High Insoluble organic solvents (e.g. hexane) Flammability Flammable Nonflammable Electrical Nonconductor Conducts electricity in conductivity ©2020 McGraw-Hill Education solution and in molten  Hydrocarbons Hydrocarbons contain only carbon and hydrogen They are nonpolar molecules Not soluble in water (water is polar) Are soluble in typical nonpolar organic solvents Toluene Pentane ©2020 McGraw-Hill Education  Substituted Hydrocarbons Hydrocarbons are constructed of chains or rings of carbon atoms with sufficient hydrogen atoms to fulfill carbon’s need for four bonds Substituted hydrocarbon is one in which one or more hydrogen atoms is replaced by another atom or group of atoms ©2020 McGraw-Hill Education  Division of the Family of Hydrocarbons ©2020 McGraw-Hill Education  Hydrocarbon Saturation Alkanes are compounds that contain only carbon-carbon and carbon-hydrogen single bonds A saturated hydrocarbon has no double or triple bonds Alkenes and alkynes are unsaturated hydrocarbons because they contain at least one carbon to carbon double or triple bond ©2020 McGraw-Hill Education  Cyclic Structure of Hydrocarbons Some hydrocarbons are cyclic Form a closed ring Aromatic hydrocarbons contain a benzene ring or related structure ©2020 McGraw-Hill Education  Common Functional Groups ©2020 McGraw-Hill Education  10.3 Alkanes The general formula for a chain alkane is CnH2n+2 In this formula n = the number of carbon atoms in the molecule Alkanes are saturated hydrocarbons Contain only carbon and hydrogen Bonds are carbon-hydrogen and carbon- carbon single bonds ©2020 McGraw-Hill Education  Formulas Used in Organic Chemistry Molecular formula - lists kind and number of each type of atom in a molecule, no bonding pattern: C2H6 C3H8 Structural formula - shows each atom and bond in a molecule ©2020 McGraw-Hill Education  Condensed and Line Formulas Condensed formula - shows all the atoms in a molecule in sequential order indicating which atoms are bonded to which CH3-CH3 CH3-CH2-CH3 Line formula - assume a carbon atom at any location where lines intersect Each carbon in the structure is bonded to the correct number of hydrogen atoms ©2020 McGraw-Hill Education  Names of First Ten Continuous- Chain Alkanes Table 10.3 Names and Formulas of the First Ten Straight- Chain Alkanes. Name Molecular Condensed Formula Formula Alkanes CnH2n+2 Methane CH4 CH4 Ethane C2H6 CH3CH3 Propane C3H8 CH3CH2CH3 Butane C4H10 CH3CH2CH2CH3 or CH3(CH2)2CH3 Pentane C5H12 CH3CH2CH2CH2CH3 or CH3(CH2)3CH3 Hexane C6H14 CH3CH2CH2CH2CH2CH3 or CH3(CH2)4CH3 Heptane C7H16 CH3CH2CH2CH2CH2CH2CH3 or CH3(CH2)5CH3 Octane C8H18 CH3CH2CH2CH2CH2CH2CH2CH3 or CH3(CH2)6CH3 Nonane C9H20 CH3CH2CH2CH2CH2CH2CH2CH2CH3 or ©2020 McGraw-Hill Education  Formulas Used in Organic Chemistry - Example Write the structural and condensed formulas for the following line formula: First, place the C Next, add the skeleton: correct number of H atoms: ©2020 McGraw-Hill Education  Writing Condensed from Structural Formula Finally, condense the structure: ©2020 McGraw-Hill Education  The Tetrahedral Carbon Atom (a)Lewis dot structure (b)The tetrahedral shape around the carbon atom (c)The tetrahedral carbon drawn with dashes and wedges (d)The stick drawing of the tetrahedral carbon ©2020 McGraw-Hill Education  Comparison of Ethane and Butane Structures ©2020 McGraw-Hill Education  Isomers Many carbon compounds exist in the form of isomers Isomers are compounds with the same molecular formula but different structures An isomer example: both are C4H10 but have different structures: Methylpropa Butane ne ©2020 McGraw-Hill Education  Physical Properties of Isomers Isomers with the same molecular formula have different physical properties: Table 10.4 Melting and Boiling Points of Five Alkanes of Molecular Formula C6H14 Name Condensed Formula Boiling Melting Point* Point* Hexane CH3(CH2)4CH3 68.8°C –95.2°C 2-Methylpentane CH3CH(CH3)(CH2)2CH3 60.9°C –153.2°C 3-Methylpentane CH3CH2CH(CH3)CH2CH3 63.3°C –118°C 2,3- CH3CH(CH3)CH(CH3)CH 58.1°C –130.2°C Dimethylbutane 3 as reported in the National Institute of Standards and *Melting and boiling points Technology 2,2- Chemistry Webbook, CH C(CH which can CH ) CH be found at http://webbook.nist.gov/ 49.8°C –100.2°C 3 3 2 2 3 Dimethylbutane ©2020 McGraw-Hill Education  Physical Properties of Hydrocarbons 1. Nonpolar molecules 2. Not water soluble; soluble in nonpolar organic solvents 3. Low melting points and low boiling points 4. Generally less dense (lighter) than water 5. As length (molecular weight) increases, melting and boiling points ©2020 McGraw-Hill Education  Carbon Classification Carbon atoms are classified according to the number of other carbon atoms to which they are attached: ©2020 McGraw-Hill Education  Alkyl Groups An alkyl group is an alkane with one hydrogen atom removed It is named by replacing the -ane of the alkane name with -yl Methane becomes a methyl group methane methyl CH4 group ©2020 McGraw-Hill Education  Ethyl Groups For ethane, all 6 H’s are equivalent Removing one H generates the ethyl group All 3 structures shown at right are the same: Ethyl groups ethan = e ©2020 McGraw-Hill Education  Names and Formulas of the First Five Alkyl Groups Table 10.5 Names and Formulas of the First Five Continuous-Chain Alkyl Groups Alkyl Group Structure Name —CH3 Methyl —CH2CH3 Ethyl —CH2CH2CH3 Propyl —CH2CH2CH2CH3 Butyl —CH2CH2CH2CH2CH3 Pentyl ©2020 McGraw-Hill Education  Alkyl Group Classification Alkyl groups are classified according to the number of carbons attached to the carbon atom that joins the alkyl group to a molecule All continuous chain alkyl groups are 1 degree Isopropyl and sec-butyl are 2 degrees groups ©2020 McGraw-Hill Education  Iso- Alkyl Groups Propane gives two propyl groups depending on whether an end (1 degree) or interior (2 degrees) H is removed ©2020 McGraw-Hill Education  Sec- Alkyl Groups Butane gives two butyl groups depending on whether an end (1 degree) or interior (2 degrees) H is removed ©2020 McGraw-Hill Education  Structures and Names of Some Branched-Chain Alkyl Groups ©2020 McGraw-Hill Education  More Alkyl Group Classification Isobutane gives two butyl groups depending on whether a 1 degree or 3 degrees H is removed ©2020 McGraw-Hill Education  Nomenclature The IUPAC (International Union of Pure and Applied Chemistry) is responsible for chemical names Before learning the IUPAC rules for naming alkanes, the names and structures of eight alkyl groups must be learned These alkyl groups are historical names accepted by the IUPAC and integrated into modern nomenclature ©2020 McGraw-Hill Education  Carbon Chain Length and Prefixes Table 10.7 Carbon Chain Length and Prefixes Used in the IUPAC Nomenclature System Carbon Chain Prefix Alkane Name Length 1 Meth- Methane 2 Eth- Ethane 3 Prop- Propane 4 But- Butane 5 Pent- Pentane 6 Hex- Hexane 7 Hept- Heptane 8 Oct- Octane 9 Non- Nonane 10 Dec- Decane ©2020 McGraw-Hill Education  IUPAC Names for Alkanes 1. The base or parent name for an alkane is determined by the longest chain of carbon atoms in the formula The longest chain may bend and twist, it is seldom horizontal Any carbon groups not part of the base chain are called branches or substituents These carbon groups are also called alkyl groups ©2020 McGraw-Hill Education  IUPAC Names for Alkanes – Rule 1 Rule 1 applied Find the longest chain in each molecule 8 Carbon 7 Carbon chain octane chain ©2020 McGraw-Hill Education heptane  IUPAC Names for Alkanes – Rule 2 2.Number the carbon atoms in the chain starting from the end with the first branch If both branches are equally from the ends, continue until a point of difference occurs ©2020 McGraw-Hill Education  IUPAC Names for Alkanes – Rule 3 3. Write each of the branches/substituents in alphabetical order before the base/stem name (longest chain) Halogens usually come first Indicate the position of the branch on the main chain by prefixing its name with the carbon number to which it is attached Separate numbers and letters with a ©2020 McGraw-Hill Education hyphen  IUPAC Names for Alkanes: Example Name : 4-ethyl-2-methylhexane ©2020 McGraw-Hill Education  Write Name for Branched Alkane Hyphenated and number prefixes are not considered when alphabetizing groups Name the compound below: 5-sec-butyl-4-isopropylnonane ©2020 McGraw-Hill Education  Write IUPAC Name for Alkane Using Substituent Prefix Rule When a branch/substituent occurs more than once Prefix the name with di tri tetra Then list the number of the carbon branch for that substituent to the name with a separate number for each occurrence Separate numbers with commas e.g., 3,4-dimethyl or 4,4,6-triethyl ©2020 McGraw-Hill Education  Write IUPAC Name for Alkane Using Substituent Alphabetizing Rule 5-ethyl-2,3-dimethylheptane for order: ethyl before dimethyl ©2020 McGraw-Hill Education  Practice: Write IUPAC Name 6-ethyl-6-isobutyl-3,3-dimethyldecane ©2020 McGraw-Hill Education  Practice: Draw from IUPAC Name 1 Draw the structural formula for 1-bromo-4- methylhexane. Begin by drawing the 6-carbon parent chain, showing the 4 bonds to each carbon: Add the substituents: ©2020 McGraw-Hill Education  Practice: Draw from IUPAC Name 2 Draw the structural formula for 1-bromo-4- methylhexane. Add in H atoms to complete the structure Draw the condensed formulas: ©2020 McGraw-Hill Education  Structural Isomers Constitutional/Structural Isomers differ in how atoms are connected Two isomers of butane have different physical properties The carbon atoms are connected in different patterns Butane Isobutane Bp –0.4 oC Bp –12 oC Mp –139 oC Mp –145 oC ©2020 McGraw-Hill Education  10.4 Cycloalkanes Cycloalkanes have two less hydrogens than the corresponding chain alkane Hexane=C6H14 versus cyclohexane=C6H12 To name cycloalkanes, prefix cyclo- to the name of the corresponding alkane Place substituents in alphabetical order before the base name as for alkanes For multiple substituents, use the lowest possible set of numbers; a single substituent requires no number ©2020 McGraw-Hill Education  Cycloalkane Structures ©2020 McGraw-Hill Education  Naming a Substituted Cycloalkane Name the two cycloalkanes shown Parent below 6 carbon ring 5 carbon ring chain cyclohexane cyclopentane 1 chlorine a methyl group Substitue atom methyl nt chloro Methylcyclopent Chlorocyclohex ane Name ane ©2020 McGraw-Hill Education  cis-trans Isomers Atoms of an alkane can rotate freely around the carbon-carbon single bond having an unlimited number of arrangements Rotation around the bonds in a cyclic structure is limited by the fact that all carbons in the ring are interlocked Formation of cis-trans isomers, or geometric isomers, is a consequence of the lack of free rotation Stereoisomers are molecules that have the same structural formulas and bonding patterns, but different arrangements of atoms in space cis-trans isomers of cycloalkanes are stereoisomers whose substituents differ in spatial arrangement ©2020 McGraw-Hill Education  cis-trans Isomers in Cycloalkanes Two groups may be on the same side (cis) of the imagined plane of the cycloring or they may be on the opposite side (trans) Geometric isomers do not readily interconvert, only by breaking carbon- carbon bonds can they interconvert ©2020 McGraw-Hill Education  10.5 Conformations of Alkanes Conformations differ only in rotation about carbon-carbon single bonds Two conformations of ethane and butane are shown The first (staggered form) is more stable (energetically favorable) because it allows hydrogens to be farther apart and thus, the atoms are less crowded ©2020 McGraw-Hill Education  Two Conformations of Cyclohexane Chair Boat conformation conformation (more stable) (less stable) ©2020 McGraw-Hill Education  10.6 Reactions of Alkanes Alkanes, cycloalkanes, and other hydrocarbons can be: Oxidized (by burning) in the presence of excess molecular oxygen, in a process called combustion Reacted with a halogen (usually chlorine or bromine) in a halogenation reaction ©2020 McGraw-Hill Education  Combustion Complete combustion produces Carbon dioxide and water CH4 + 2O2 → CO2 + 2H2O + heat energy Incomplete combustion produces Carbon monoxide and water Carbon monoxide is a poison that binds irreversibly to red blood cells 2CH4 + 3O2 → 2CO + 4H2O + heat energy ©2020 McGraw-Hill Education  Halogenation Halogenation is a type of substitution reaction, a reaction that results in a replacement of one group for another Products of this reaction are: Alkyl halide or haloalkane Hydrogen halide This reaction is important in converting unreactive alkanes into many starting materials for other products Halogenation of alkanes ONLY occurs in the presence of heat and/or light (UV) ©2020 McGraw-Hill Education  Halogenation Reaction Equations ©2020 McGraw-Hill Education