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Foundation Science CHM403 Foundation Chemistry II Organic Chemistry Lecture 1 Naming Hydrocarbons (nomenclature) Hydrocarbons: IUPAC names Objectives 1. What is organic chemistry? 2. What are hydrocarbons? What structural features identify alkanes? Alkenes? Alkynes? Aromatic hydrocarbons? 3. How are alkanes, alkenes, alkynes, and aromatic hydrocarbons named using IUPAC nomenclature? 4. What are the physical and chemical properties of alkanes, alkenes, alkynes, and aromatic hydrocarbons? 5. What is an alkyl group? 6. What are some products from reactions of alkanes? How are they formed? 7. What are the major reactions of alkenes? What are the products of those reactions? Division of Organic Chemicals Groupings of Organic Compounds Organic Comounds Aliphatic compounds Aromatic compounds contain straight or branched chains or carbon-based rings or multi-rings with rings containing single carbon bonds alternating single & double carbon bonds Introduction • Organic chemistry is the study of carbon-containing compounds – especially compounds containing C-C bonds • The field of organic chemistry is very important for a wide variety of reasons. – A huge number of carbon-containing compounds are known. • More than 16 million known compounds • About 90% of new compounds made each year contain carbon Introduction • Most of the advances in the pharmaceutical industry are based on a knowledge of organic chemistry. – Many drugs are organic compounds • Life as we know it is based on organic chemistry. – Most biologically important compounds contain carbon: • DNA, RNA • proteins • carbohydrates Hydrocarbons • The simplest organic compounds are the hydrocarbons: – organic compounds that contain only carbon and hydrogen – four general types: • alkanes • alkenes • alkynes • aromatic hydrocarbons Hydrocarbons • Alkanes: – hydrocarbons that contain only single bonds • Examples: – Methane CH4 – ethane H H H–C–C–H H H Hydrocarbons • Alkenes: – hydrocarbons that contain a C = C double bond H2C = CH2 (ethylene) • Alkynes: – hydrocarbons that contain a C C triple bond H – C C – H (acetylene) Hydrocarbons • Aromatic hydrocarbons: – contain a planar ring structure in which the carbon atoms are connected by a combination of both s and p bonds H C H-C C-H benzene H-C C-H C H Naming: common vs. IUPAC • Common names used in the 1800’s are still used for some compounds today: O O H C C H C Acetylene C H OH H3C CH3 Formic acid Acetone • The International Union of Pure and Applied Chemistry (IUPAC) was established in 1900s • Frequent revisions to nomenclature • Systematic method allows an infinite number of compounds to be named given a few rules Mnemonic for first four prefixes First four prefixes • Meth- Monkeys • Eth- Eat • Prop- Peeled • But- Bananas Other prefixes • Pent- Decade ? Decimal • Oct- • Dec- Decathalon • Hex-, Hept-, Non- Hydrocarbons • Compounds containing only two elements – Carbon and hydrogen Alkanes: Structures and Names • Objectives – Identify an alkane – Determine what an isomer of an alkane is – Identify different types of alkanes Alkanes • Saturated Hydrocarbons • Called saturated because each carbon is bonded to four other atoms • Only single bonds • Methane • Ethane • Propane Homology • Related compounds • Homologs – Have properties that vary in a regular and predictable manner – A manner of organization – Similar to P.T. Isomers • Different compounds having the same molecular formula • Butane • Isobutane (isolated branched chain) • Another name? Isomers • Pentane • Isopentane • Neopentane Alkanes • CnH2n+2 • Representation – Structural Formulas – Condensed Structural Formulas – Butane Alkyl Group • A group of atoms that results when one hydrogen atom is removed from an alkane • CnH2n+1 • Change –ane ending to –yl • Methyl • Ethyl • Propyl IUPAC Nomenclature • Define IUPAC • Examine the rules for IUPAC naming • Determine the correct names of alkanes IUPAC Nomenclature • Geneva, Switzerland 1892 • International Union of Pure and Applied Chemistry • IUPAC System of Nomenclature – (isobutane, isopentane are common names) IUPAC Rules • 1. Name the longest chain in the parent compound. End in –ane. (Root name) – Number each carbon – See Example • 2. Note the alkyl groups attached • 3. Number the carbon that the group is attached to. – Must use the lowest number possible. – See Example IUPAC Rules Con’t • 4. Use prefixes to indicate the amount of attached groups – See Example • 5. If there are more than two or more different substituents, list them in alphabetical order. If at equal points, lower alphabetical order given lowest number – See Example Name each of the following Name each of the following A. B. C. D. Draw the structural formulas for each of the following • 4-propylheptane • 3-ethyl-2-methylpentane • 3-isopropyl-3-methyloctane Properties of Alkanes • Objectives – Determine the physical and physiological properties of alkanes Physical Properties • Nonpolar – Insoluble in water • Less dense than water – Less than 1.0g/ml • Related to one another – See chart • Boiling points – Increase with higher molar mass Physiological Properties • Gases serve as anesthetics • Liquid alkanes – Light liquids – Harmful to lungs – Heavy liquids • Mineral oil • Petroleum jelly Chemical Properties: Reactions of Alkanes • Objectives – Determine the chemical properties of alkanes Chemical Properties • Do not react with many laboratory agents • Usually very flammable – Undergo combustion reactions CH4 + 2 O2 CO2 + 2 H2O + Heat 2 CH4 + 3 O2 2 CO + 4 H2O (Harmful carbon monoxide reaction) Halogenated Hydrocarbons • Objectives – Define what halogenated hydrocarbons are – Name halogenated hydrocarbons using common and IUPAC names Halogenated Hydrocarbons • Have one or more hydrogen atoms replaced by halogen atoms – Usually these are formed under UV light or very high temps – Results in an alkyl halide Common Names • First part of name is alkyl group • Second part is the halogen, ending in –ide • Name these: – CH3CH2Br – (CH3)2CHCl – CH3I – CH3CH2CH2F IUPAC Names • Rules similar to those used for naming alkanes • Substitute in the prefixes fluoro-, chloro-, bromo-, and iodo- Give the IUPAC name for each of the following compounds Cycloalkanes • Define what a cycloalkane is • Name and draw cycloalkanes Cycloalkanes • Carbon atoms that are joined in a ring or circle • Simplest: cyclopropane • Another: cyclohexane Naming • Add cyclo- • Otherwise fairly similar to regular naming • Draw structures for the following compounds – Cyclooctane – Ethylcyclohexane – 1,1,2-trimethylcyclobutane Draw these structures • Cyclopentane • 1-ethyl-2-methylcyclopentane • 1-ethyl-1,2,5,5- tetramethylcycloheptane Alkenes • Objectives – Define alkene – Name alkenes using IUPAC rules Alkenes • End in -ene • Unsaturated hydrocarbons • Have a double bond (CH3=CH2) IUPAC Rules 1. Name the longest chain. 2. Indicate the position of the double bond with the lowest number possible. 3. Substituent groups named like alkanes 5-methyl-2-hexene Name each of the following Draw the structure for the following • 3,4-dimethyl-2-pentene • 3-ethyl-2-methyl-1-hexene • 3-isopropylcyclopentene Properties of Alkenes • Objectives – Determine the properties of alkenes Properties of Alkenes • Similar to alkanes • Occur widely in nature • Ethylene – Triggers fruit ripening – Can be used artifically • Others – Carotene • Vitamin A – Fruit coloring Chemical Properties: Reactions of Alkenes • Define addition reactions • Discuss hydrogenation and hydration • Write equations for reactions between alkenes and other substances Addition Reactions • One of the bonds in the double bond is broken and each of the involved carbon atoms then bonds to another atom or group • Hydrogenation—addition of hydrogen to an unsaturated molecule Halogen addition • Alkenes readily add halogen molecules Hydration • Addition of water to an alkene Equations • Write equations for the reaction between CH3CH=CHCH3 and each of the following • H2 • Br2 • H2O (H2SO4 catalyst) • Write equations for the reaction of with each of the following. • H2 (Ni catalyst) • Cl2 • H2O (H2SO4 catalyst) Alkynes • Define alkyne • Name alkynes using IUPAC naming rules Alkynes • Carbon atoms share 3 pairs of electrons, forming a triple bond • Acetylene • Alkynes have similar properties to those of alkanes and alkenes • Naming is the same, except they end in -yne THE END
"Foundation Science Lecture 1A 2011"