Chapter 13: Unsaturated Hydrocarbons Unsaturated Hydrocarbons - PDF document

Chemistry 121(01) Winter 2009 Introduction to Organic Chemistry and Biochemistry Introduction to Organic Chemistry and Biochemistry Instructor Dr. Upali Siriwardane (Ph.D. Ohio State) E-mail: upali@chem.latech.edu Office: 311 Carson Taylor Hall ; Phone: 318-257-4941; Chapter 13: Unsaturated Hydrocarbons Unsaturated Hydrocarbons Chapter 13: Office Hours: MTW 9:00 am - 11:00 am; TR 9::00 - !0:00 am & 1:00-2:00 pm. December 19, Test 1 (Chapters 12-14) Sections 4.1- Sections 4.1 -4.5 4.5 January 2 Test 1 (Chapters 15-16) February 6 (Chapters 17-19) February 27, (Chapters 20-22) March 2, 2009, Make Up Exam: Bring Scantron Sheet 882-E Chemistry 121, Winter 2008, LA Tech Chemistry 121, Winter 2008, LA Tech 1-1 Chemistry 121, Winter 2008, LA Tech Chemistry 121, Winter 2008, LA Tech 1-2 Chapter 13: Unsaturated Hydrocarbons Unsaturated Hydrocarbons Unsaturated hydrocabons Unsaturated hydrocabons Chapter 13: 13.2 Characteristics of Alkenes and 13.2 Characteristics of Alkenes and Cycloalkenes Cycloalkenes Hydrocarbons with carbon- Hydrocarbons with carbon -carbon double bonds carbon double bonds 13.3 Names for Alkenes and 13.3 Names for Alkenes and Cycloalkenes Cycloalkenes and triple bonds and triple bonds 13.4 Line- 13.4 Line -Angle Formulas for Alkenes Angle Formulas for Alkenes 13.5 Isomerism in Alkenes 13.5 Isomerism in Alkenes double bonds: alkenes double bonds: alkenes 13.6 Naturally Occurring Alkenes 13.6 Naturally Occurring Alkenes 13.7 Physical Properties of Alkenes 13.7 Physical Properties of Alkenes triple bonds: alkynes triple bonds: alkynes 13.8 Chemical Reactions of Alkenes 13.8 Chemical Reactions of Alkenes 13.9 Polymerization of Alkenes: Addition Polymers 13.9 Polymerization of Alkenes: Addition Polymers three alternating double bond in 6 carbon ring: three alternating double bond in 6 carbon ring: 13.10 Alkynes 13.10 Alkynes aromatics aromatics 13.11 Aromatic Hydrocarbons 13.11 Aromatic Hydrocarbons 13.12 Names for Aromatic Hydrocarbons 13.12 Names for Aromatic Hydrocarbons 13.13 Aromatic Hydrocarbons: Physical Properties and Sources 13.13 Aromatic Hydrocarbons: Physical Properties and Sources 13.14 Chemical Reactions of Aromatic Hydrocarbons 13.14 Chemical Reactions of Aromatic Hydrocarbons 13.15 Fused 13.15 Fused- -Ring Aromatic Compounds Ring Aromatic Compounds Chemical Connections: Chemical Connections: Ethene Ethene: A Plant Hormone and High : A Plant Hormone and High- -Volume Volume Industrial Chemical; Industrial Chemical; Cis Cis- -Trans Isomerism and Vision; Trans Isomerism and Vision; Carotenoids Carotenoids: A : A Source of Color; Fused- Source of Color; Fused -Ring Aromatic Hydrocarbons and Cancer Ring Aromatic Hydrocarbons and Cancer Chemistry 121, Winter 2008, LA Tech Chemistry 121, Winter 2008, LA Tech 1-3 Chemistry 121, Winter 2008, LA Tech Chemistry 121, Winter 2008, LA Tech 1-4

Units of Unsaturation Unsaturation Units of Unsaturated Hydrocarbons: Unsaturated Hydrocarbons: Compounds that have have fewer hydrogens than saturated hydrocarbons (C n H 2n+2 ). Two hydrogen are H Alkenes Alkynes Arenes considered as unit of unstauration C H H C C C C Cycloalkane ring ring C n H 2n (one unit of unsat.) Cycloalkane H H C H Unsaturated hydrocarbons: Unsaturated hydrocarbons: ethene ethyne benzene C 2 H 4 C 2 H 2 C 6 H 6 bond C n H 2n (one unit of unsat.) C n H 2n C n H 2n − 2 C n H n bond C n H 2n − 2 (two units of unsat.) unsaturated unsaturated Aromatic alkene alkyne Arene Chapters 13 Chapters 13 Chapter 13 Chemistry 121, Winter 2008, LA Tech Chemistry 121, Winter 2008, LA Tech 1-5 Chemistry 121, Winter 2008, LA Tech Chemistry 121, Winter 2008, LA Tech 1-6 Structure of Alkenes Planar Structure of Alkenes Structure of Alkenes Planar Structure of Alkenes According to the orbital overlap model, a double bond According to the orbital overlap model, a double bond • • Alkene Alkene: contains a carbon-carbon double bond and has consists of consists of the general formula C n H 2n 2 hybrid σ bond formed by overlap of • a a σ bond formed by overlap of sp sp 2 hybrid orbitals orbitals • The two carbon atoms of a double bond and the four • a π π bond formed by overlap of parallel • a bond formed by overlap of parallel 2 2 p p orbital orbital atoms bonded to them lie in a plane, with bond angles • Rotating by 90° Rotating by 90 °breaks the breaks the pi pi bond bond of approximately 120° 121.7° 124.7° H H H CH 3 C C C C H H H H Propene Ethylene Chemistry 121, Winter 2008, LA Tech Chemistry 121, Winter 2008, LA Tech 1-7 Chemistry 121, Winter 2008, LA Tech Chemistry 121, Winter 2008, LA Tech 1-8

Structure of Alkynes Structure of Alkynes Alkenes Alkenes The functional group of an The functional group of an alkyne alkyne is a carbon is a carbon- -carbon triple carbon triple bond bond A triple bond consists of A triple bond consists of Second members of the hydrocarbon family. Second members of the hydrocarbon family. • one σ bond formed by the overlap of sp hybrid orbitals • contain only hydrogen and carbon • two π bonds formed by the overlap of sets of parallel 2p • have single bonds and at least one C=C double orbitals bond All members have the general formula of All members have the general formula of C n H 2n C n H 2n Twice as Twice as ma many ny hy hydr drogen ogen Twice as ma Twice as many ny hy hydr drogen ogen as carbo as carbon as carbo as carbon Chemistry 121, Winter 2008, LA Tech Chemistry 121, Winter 2008, LA Tech 1-9 Chemistry 121, Winter 2008, LA Tech Chemistry 121, Winter 2008, LA Tech 1-10 Alkenes: Naming and Structures Alkenes: Naming and Structures IUPAC Nomenclature of Alkenes and Alkynes IUPAC Nomenclature of Alkenes and Alkynes name the longest continuous carbon chain containing the name the longest continuous carbon chain containing the • • multiple bond(s multiple bond(s) (parent chain). If cyclic, ring is the parent. ) (parent chain). If cyclic, ring is the parent. One simple class of compound is the alkene alkene One simple class of compound is the use the infix - -en en- - to show the presence of a carbon to show the presence of a carbon- -carbon carbon use the infix • • which has only C, H and single bonds. which has only C, H and single bonds. double bond double bond • ethene propene 2- butene use the infix use the infix - -yn yn- - to show the presence of a carbon to show the presence of a carbon- -carbon carbon • • • C 2 H 4 C 3 H 6 C 4 H 8 triple bond triple bond • CH 2 CH 2 CH 3 CH 2 CH 2 CH 3 CH 2 CHCH 3 number the parent chain to give the 1st carbon of the number the parent chain to give the 1st carbon of the • • double/triple bond the lower number double/triple bond the lower number If both double and triple are present and cannot have the If both double and triple are present and cannot have the • • same #, then double bonds take priority. same #, then double bonds take priority. follow follow IUPAC IUPAC general rules for numbering and naming general rules for numbering and naming • • substituents substituents for a cycloalkene cycloalkene, the double bond must be numbered 1,2 , the double bond must be numbered 1,2 for a • • Chemistry 121, Winter 2008, LA Tech Chemistry 121, Winter 2008, LA Tech 1-11 Chemistry 121, Winter 2008, LA Tech Chemistry 121, Winter 2008, LA Tech 1-12

IUPAC Nomenclature of Alkynes IUPAC Nomenclature of Alkynes Example of IUPAC Nomenclature of Alkenes Example of IUPAC Nomenclature of Alkenes • use the infix -yn yn- to show the presence of a carbon- Cycloalkanes Cycloalkanes carbon triple bond • number the parent chain to give the 1st carbon of the 1 5 triple bond the lower number 3 2 6 2 4 6 4 2 4 5 3 5 3 1 1 • follow IUPAC rules for numbering and naming 1-Hexene 4-Methyl-1-hexene substituents 2-Ethyl-3-methyl- 1-pentene 1 1 2 3 4 2 2 5 4 CH 3 4 1 3 CH 3 3 3 6 7 5 4 CH 3 6 1 2 5 3-Methyl-1-butyne 6,6-Dimethyl-3-heptyne 3-Methylcyclo- 1,6-Dimethylcyclo- pentene hexene Chemistry 121, Winter 2008, LA Tech Chemistry 121, Winter 2008, LA Tech 1-13 Chemistry 121, Winter 2008, LA Tech Chemistry 121, Winter 2008, LA Tech 1-14 Nomenclature of Alkenes: Common Names Nomenclature of Alkenes: Common Names Alkenes Alkenes Some alkenes, particularly low- -molecular molecular- -weight ones, are weight ones, are Some alkenes, particularly low First four members of the alkanes alkanes First four members of the known almost exclusively by their known almost exclusively by their common names common names Name # of C Condensed formula Name # of C Condensed formula CH 3 = CH 2 = CH 2 =CH 2 CH 3 CH=CH 2 CH 3 C=CH 2 Ethene Ethene 2 2 CH CH 2 CH 2 2 IUPAC: Ethene Propene 2-Methylpropene = CH CH = Propene Propene 3 3 CH 3 CH 3 CH CH 2 Common: Ethylene Propylene Isobutylene 2 2- 2 -Butene Butene 4 4 CH CH 3 3 CH=CHCH CH=CHCH 3 3 Called a Called a homologous series homologous series • “Members differ by number of CH 2 groups” Chemistry 121, Winter 2008, LA Tech Chemistry 121, Winter 2008, LA Tech 1-15 Chemistry 121, Winter 2008, LA Tech Chemistry 121, Winter 2008, LA Tech 1-16