Chapter 24 and Beyond Organic Chemistry: Nomenclature and Reactions
Organic Chemistry • What does this branch of chemistry deal with? • Compounds that contain carbon (and hydrogen), called hydrocarbons • Aliphatic – Chains • Aromatic – Resonating rings of delocalized electrons • Very specific hydrocarbon naming system - IUPAC • Different types are separated according to certain functional groups
Aliphatic Hydrocarbons • What are the three main types of aliphatic hydrocarbons? • Based on the types of bonds: • Alkane – only single bonds • Saturated • i.e. hard to breakdown • Alkene – At least one double bond • Unsaturated • i.e. easy to breakdown • Alkyne – At least one triple bond • Unsaturated
Notes About Drawing • What are the guidelines for drawing organic structures? • Structural Diagrams • Shows all atoms, bonds and structure • Structural Formulas • Shows all atoms and suggests structure CH3CH(OH)CH2CH3 • Skeletal Diagrams
Structural Formula • How are structural formulas different from molecular and empirical? • Structural formulas show the basic structure and location of functional groups • CH3CH2CH2CH3 • Molecular formulas simply show the number of atoms • C4H10 • Empirical formulas are simplified molecular formulas • C2H5
International Union of Pure and Applied Chemistry (IUPAC) • What is IUPAC? • IUPAC is an organization that has determined the internationally adopted way to name chemicals • Nomenclature – fancy word for naming • System is based on the longest hydrocarbon chain and the Greek prefixes
IUPAC Nomenclature for Alkanes • What is the first rule? • Determine the parent chain and name • Find the longest hydrocarbon chain • May not be a straight line • Use the appropriate prefix • Meth – 1 • Eth – 2 • Prop – 3 • But – 4 • Pent – 5 • Hex – 6 • Hept – 7 • Oct – 8 • Non – 9 • Dec – 10
IUPAC Nomenclature for Alkanes • If there are only single bonded carbons use the suffix – ane • Ex.
IUPAC Nomenclature for Alkanes • What is the second rule? • If an alkane has a hydrocarbon (alkyl) group, determine its name and number • Use the suffix -yl • Make sure to assign it so that it has the lowest number possible • Ex.
IUPAC Nomenclature for Alkanes • What is the third rule? • If more than one alkyl group exists then you must assign the lowest numbers possible
IUPAC Nomenclature for Alkanes • What is the fourth rule? • If there is more than one of the same group, use the prefixes di-, tri- and tetra- • Must also be in alphabetical order • Ex.
IUPAC Nomenclature for Alkanes • Please name the following compounds.
IUPAC Nomenclature for Alkanes • Please draw the following compounds. • 2-methyl heptane • 4-ethyl-3,4-dimethyl octane • 4-ethyl-2,2-dimethyl hexane • 2,4,4-trimethyl heptane • 3,3-diethyl-2,5-dimethyl nonane • 4-propyl-3-methyl heptane
IUPAC Nomenclature for Alkanes • Please build the following compounds. • propane • 2-methyl butane • 2,2-dimethyl pentane
Alkenes and Alkynes • How do we name hydrocarbons with a double or triple bond? • Double and triple bonds MUST have the lowest number possible • Determine the lowest number where the bond begins and place in or in front of the parent chain • Suffix added to the parent name • Alkenes use the suffix –ene • Alkynes with the suffix –yne • Ex.
IUPAC Nomenclature for Alkanes • What is a functional group? • Functional group Anything that is not a C-C or H-C single bond OR not part of the main chain • Substituent Something that is substituted in for a H • Ex. -Br, -OH, -CH3,etc. • Alkyl Group A hydrocarbon substituent • Ex. Methyl or ethyl group
Functional Groups • How do we identify and name a(n)... • Alcohol • General Formula: R-OH • Naming: -e at the end of alkane replaced by –ol • Ex. Ethanol • Can also use hydroxy prefix • Halogenoalkane • General Formula: R-X • X=F, Cl, Br, I • Naming: fluoro-, chloro-, bromo-, iodo- place before parent chain • Ex. 2-chloro-propane
Functional Groups • How do we identify and name a(n)... • Aldehyde • General Formula: R-CHO • Naming: -e at the end of alkane replaced by –al • Ex. Propanal • Ketone • General Formula: R-COR’ • Naming: -e at the end of alkane replaced by –one • Ex. 2-Butanone or Butan-2-one
Functional Groups • How do we identify and name a(n)... • Carboxylic Acid • General Formula: R-COOH • Naming: -e at the end of alkane replaced by –oic acid • Ex. Propanoic Acid
Functional Groups How do we identify an... • Amine • General Formula: R-NH2 • Ex. Propyl amine • Ester • General Formula: R-COOR’ • Ex. Ethyl ethanoate
Homologous Series • What is a homologous series? • A series of organic compounds with the same general formula, but that vary by a single carbon atom • Ex. Methane, Ethane, Propane, etc.
Structural Isomer • What are structural isomers? • Organic molecules that have the same molecular formula, but are connected/bonded differently • Ex. C4H10
Chapter 24 and Beyond Reactivity of Alkanes
Reactivity of Alkanes • Why are alkanes very unreactive? • Strong C-C and C-H bonds • Very low polarity • Can only undergo combustion and halogen substitution reactions
Combustion of Alkanes • What are the requirements for combustion? • All hydrocarbons burn with large amounts of oxygen • When completely combusted they always produce two products: • Carbon dioxide • Water
Combustion of Alkanes • Why is this reaction exothermic? • C=O and O-H bonds are stronger than C-C and C-H, so energy is released • For this reason, alkanes (natural gases) are good fuel sources • Ex. Propane, Butane, Gasoline, Diesel, etc.
Combustion of Alkanes • What happens when there is not enough oxygen? • Incomplete combustion • CO and other harmful chemicals are now made in addition to CO2 and water • Motor vehicles use catalytic converters to minimize this effect
Alkane Substitution Reactions • What is a substitution reaction? • A reaction where a functional group replaces a hydrogen • In this case, a halogen will replace a hydrogen • Typically Br2 or Cl2 • This cannot happen without a high energy catalyst, ultraviolet light
Mechanism of Chlorination of Methane • What is a reaction mechanism? • Breaks down the different parts of a reaction and shows the movement of electrons • Single electron movement • Electron pair movement
Mechanism of Chlorination of Methane • What are the different types of chemical cleavage? • A bond can break: • Heterolytically • Both electrons go to one atom • Homolytically • One electron goes to each
Mechanism of Chlorination of Methane • What is unique about homolytic cleavage? • It does NOT create ions, but something new called… FREE RADICALS! • Radicals are VERY reactive and play a large role in atmospheric chemistry, global warming and ozone depletion
Mechanism of Chlorination of Methane • What is the mechanism for the chlorination of methane? • Initiation – radicals created through UV light • Cl2homolytically cleaves • Propagation – chain reaction where radicals create more radicals • Radical Cl removes H from CH4 • Cl2 cleaves and a Cl radical attaches to the methane radical • Termination – two radicals combine to form a non-radical • Two Cl radicals combine with each other • One Cl radical attaches to the methane radical • Two methane radicals combine with each other
Mechanism of Chlorination of Methane • What can be done with your chloromethane product? • It can continue to be substituted in the same manner to produce dichloromethane, trichloromethane and tetrachloromethane
Chapter 24 and Beyond Reactivity of Alcohols
Properties of Alcohols • What functional group is associated with alcohols? • Please draw and build ethane… • Please draw and build ethanol… • NOTE: No number means its on the first carbon in the chain • The –OH (hydroxy) functional group
Alcohol Combustion • What is the balanced reaction for the complete combustion of 1-butanol? • Unbalanced: • C4H9OH + O2 → CO2 + H2O • Balanced: • C4H9OH + 6O2 → 4CO2 + 5H2O
Oxidation of Alcohols • What is a common application of alcohol oxidation? • Old breathalyzers • A suspect exhales on an acidified oxidizer • If the suspects blood alcohol content (BAC) exceeds 0.08 g/dL, he or she is arrested
Oxidation of Ethanol • What oxidizer is required for these reactions? • Potassium/Orange dichromate • Written… • Cr2O72- • Only effective in acidic conditions, so we include H+ • Cr2O72-/H+ • Sometimes abbreviated as [O]
Types of Alcohols • What are the three different types of alcohols? • Based on how many other carbons are attached to the substituted carbon • Primary • Secondary • Tertiary
Types of Alcohols • Primary • Secondary • Tertiary
Alcohol Oxidation • What products are formed when primary alcohols are oxidized? • First oxidation = aldehyde • Second oxidation = carboxcylic acid
Alcohol Oxidation • Using your ethanol molecule, draw, name and build the product after one oxidization. • Using your ethanal molecule, draw, name and build the product after a second oxidization. Ethanal Ethanoic acid
Alcohol Oxidation • What products are formed when secondary alcohols are oxidized? • …tertiary alcohols? • Ketones • NO REACTION! • No hydrogens to remove or replace
Alcohol Oxidation • How do we separate ethanal from ethanoic acid? • Ethanal can be distilled because of its low boiling point • If carboxylic acid is required, ethanal can be trapped using reflux • Reflux condenses the ethanal and returns it to the mixture so it can be oxidized again
Chapter 24 and Beyond Nucleophilic Substitution
Nucleophilic Substitution • What is the polarity of a simple halogenoalkane? • What is a nucleophile? • Polar • Partial + charge on C • Partial – charge on halogen • A reactant that has a lone pair of electrons • Negatively charged • Attracted to partially positive carbon • Ex. Hydoroxide (-OH)
Nucleophilic Substitution • What is a reaction mechanism again? • Shows all the steps of a reaction and each individual step is called an elementary reaction • Remember, a curvy double headed arrow is used to show the movement of a pair of electrons
Nucleophilic Substitution • What are the two types of nucleophilic substitution reactions? • SN2 • One step • Reaction rate based on both reactants • Primary halogenoalkanes • (X=Br or Cl) • SN1 • Two steps • Reaction rate is based on only the halogenoalkane • Teritaryhalogenoalkanes • (X=Br or Cl)