Dr. Wolf's CHM 201 & IUPAC Nomenclature of Unbranched Alkanes

Dr. Wolf's CHM 201 & Retained: methaneCH 4 ethaneCH 3 CH 3 propaneCH 3 CH 2 CH 3 butaneCH 3 CH 2 CH 2 CH 3 IUPAC Names of Unbranched Alkanes

Dr. Wolf's CHM 201 & Note: n-prefix is not part of IUPAC name of any alkane. For example: n-butane is "common name" for CH 3 CH 2 CH 2 CH 3 ; butane is "IUPAC name." Others: Latin or Greek prefix for number of carbons + ane suffix IUPAC Names of Unbranched Alkanes

Dr. Wolf's CHM 201 & Number of carbons NameStructure 5pentaneCH 3 (CH 2 ) 3 CH 3 6hexaneCH 3 (CH 2 ) 4 CH 3 7heptaneCH 3 (CH 2 ) 5 CH 3 8octaneCH 3 (CH 2 ) 6 CH 3 9nonaneCH 3 (CH 2 ) 7 CH 3 10decaneCH 3 (CH 2 ) 8 CH 3 IUPAC Names of Unbranched Alkanes

Dr. Wolf's CHM 201 & Number of carbons NameStructure 11undecaneCH 3 (CH 2 ) 9 CH 3 12dodecaneCH 3 (CH 2 ) 10 CH 3 13tridecaneCH 3 (CH 2 ) 11 CH 3 14tetradecaneCH 3 (CH 2 ) 12 CH 3 15pentadecaneCH 3 (CH 2 ) 7 CH 3 16hexadecaneCH 3 (CH 2 ) 8 CH 3 IUPAC Names of Unbranched Alkanes

Dr. Wolf's CHM 201 & Applying the IUPAC Rules: The Names of the C 6 H 14 Isomers

Dr. Wolf's CHM 201 & CH 3 CH 2 CH 2 CH 2 CH 2 CH 3 (CH 3 ) 2 CHCH 2 CH 2 CH 3 (CH 3 CH 2 ) 2 CHCH 3 (CH 3 ) 2 CHCH(CH 3 ) 2 (CH 3 ) 3 CCH 2 CH 3 The C 6 H 14 Isomers

Dr. Wolf's CHM 201 & CH 3 CH 2 CH 2 CH 2 CH 2 CH 3 The IUPAC name of the unbranched alkane with a chain of 6 carbons is hexane. Hexane The C 6 H 14 Isomers

Dr. Wolf's CHM 201 & Step 1) Find the longest continuous carbon chain and use the IUPAC name of the unbranched alkane as the basis. Step 2) Add name of substituent as a prefix. Step 3) Number the chain from the end nearest the substituent, and identify the carbon to which the substituent is attached by number. IUPAC Nomenclature of Branched Alkanes

Dr. Wolf's CHM 201 & (CH 3 ) 2 CHCH 2 CH 2 CH 3 (CH 3 CH 2 ) 2 CHCH 3 2-Methylpentane 3-Methylpentane The C 6 H 14 Isomers

Dr. Wolf's CHM 201 & (CH 3 ) 2 CHCH(CH 3 ) 2 (CH 3 ) 3 CCH 2 CH 3 2,3-Dimethylbutane 2,2-Dimethylbutane Use replicating prefixes (di-, tri-, tetra-, etc.) according to the number of identical substituents attached to the main chain. The C 6 H 14 Isomers

Dr. Wolf's CHM 201 & Alkyl Groups

Dr. Wolf's CHM 201 & Methyl and Ethyl Groups Methyl Ethyl C C HHHH H CH 3 CH 2 C HHH CH 3 or or

Dr. Wolf's CHM 201 & Unbranched Alkyl Groups If potential point of attachment is at the end of the chain, take the IUPAC name of the corresponding unbranched alkane and replace the -ane ending by -yl. R HR

Dr. Wolf's CHM 201 & Butyl If potential point of attachment is at the end of the chain, take the IUPAC name of the corresponding unbranched alkane and replace the -ane ending by -yl. R HR CH 3 CH 2 CH 2 CH 2 C C HHHH H C C HH H H or Unbranched Alkyl Groups

Dr. Wolf's CHM 201 & Hexyl CH 3 (CH 2 ) 4 CH 2 CH 3 (CH 2 ) 5 CH 2 CH 3 (CH 2 ) 16 CH 2 Heptyl Octadecyl Unbranched Alkyl Groups

Dr. Wolf's CHM 201 & The C 3 H 7 Alkyl Groups CH 3 CH 2 CH 2 C C H HH H H C H H or and CH 3 CHCH 3 C C H HH H H C H H or

Dr. Wolf's CHM 201 & CH 3 CH 2 CH 2 C C H HH H H C H H or IUPAC name: Propyl Common name: n-Propyl The C 3 H 7 Alkyl Groups

Dr. Wolf's CHM 201 & Naming Alkyl Groups (Table 2.7) Step 1:Identify longest continuous chain starting at point of attachment. Step 2: Drop -ane ending from name of unbranched alkane having same number of carbons as longest continuous chain and replace by -yl. Step 3:Identify substituents on longest continuous chain. Step 4:Chain is always numbered starting at point of attachment.

Dr. Wolf's CHM 201 & IUPAC name: 1-Methylethyl Common name: Isopropyl CH 3 CHCH 3 C C HHHH C H H or H The C 3 H 7 Alkyl Groups

Dr. Wolf's CHM 201 & CH 3 CH 2 CH 2 C C HHHH H C H H or Classification: Primary alkyl group Alkyl groups are classified according to the degree of substitution at the carbon that bears the point of attachment. A carbon that is directly attached to one other carbon is a primary carbon. The C 3 H 7 Alkyl Groups

Dr. Wolf's CHM 201 & Classification: Secondary alkyl group Alkyl groups are classified according to the degree of substitution at the carbon that bears the point of attachment. A carbon that is directly attached to two other carbons is a secondary carbon. CH 3 CHCH 3 C C HHHH C H H or H The C 3 H 7 Alkyl Groups

Dr. Wolf's CHM 201 & IUPAC name: Butyl Common name: n-Butyl Classification: Primary alkyl group CH 3 CH 2 CH 2 CH 2 C C HHHH H C C HH H H or The C 4 H 9 Alkyl Groups

Dr. Wolf's CHM 201 & IUPAC name: 1-Methylpropyl Common name: sec-Butyl Classification: Secondary alkyl group CH 3 CHCH 2 CH 3 C C H HH H H C C HH H H or12 3 The C 4 H 9 Alkyl Groups

Dr. Wolf's CHM 201 & IUPAC name: 2-Methylpropyl Common name: Isobutyl Classification: Primary alkyl group C H CH 2 CH 3 The C 4 H 9 Alkyl Groups

Dr. Wolf's CHM 201 & IUPAC name: 1,1-Dimethylethyl Common name: tert-Butyl Classification: Tertiary alkyl group 1 2 C CH 3 The C 4 H 9 Alkyl Groups

Dr. Wolf's CHM 201 & IUPAC Names of Highly Branched Alkanes

Dr. Wolf's CHM 201 & Branched alkanes Octane

Dr. Wolf's CHM 201 & Ethyloctane Branched alkanes

Dr. Wolf's CHM 201 & Ethyl-3-methyloctane List substituents in alphabetical order. Branched alkanes

Dr. Wolf's CHM 201 & Ethyl-3,5-dimethyloctane List substituents in alphabetical order. But don't alphabetize di-, tri-, tetra-, etc. Branched alkanes

Dr. Wolf's CHM 201 & First Point of Difference Rule The chain is numbered in the direction that gives the lower locant to the substituent at the first point of difference in the names. Don't add locants! 2,2,6,6,7-Pentamethyloctane? 2,3,3,7,7-Pentamethyloctane? What is correct name?

Dr. Wolf's CHM 201 & First Point of Difference Rule The chain is numbered in the direction that gives the lower locant to the substituent at the first point of difference in the names. Don't add locants! 2,2,6,6,7-Pentamethyloctane? What is correct name?

Dr. Wolf's CHM 201 & CnH2nCnH2nCnH2nCnH2n 2.15 Cycloalkane Nomenclature

Dr. Wolf's CHM 201 & CycloalkanesCycloalkanes Cycloalkanes are alkanes that contain a ring of three or more carbons. Count the number of carbons in the ring, and add the prefix cyclo to the IUPAC name of the unbranched alkane that has that number of carbons. CyclopentaneCyclohexane

Dr. Wolf's CHM 201 & Ethylcyclopentane CycloalkanesCycloalkanes CH 2 CH 3 Name any alkyl groups on the ring in the usual way.

Dr. Wolf's CHM 201 & Name any alkyl groups on the ring in the usual way. List substituents in alphabetical order and count in the direction that gives the lowest numerical locant at the first point of difference. 3-Ethyl-1,1-dimethylcyclohexane CH 2 CH 3 H3CH3CH3CH3C CH 3 CycloalkanesCycloalkanes

Dr. Wolf's CHM 201 & Sources of Alkanes and Cycloalkanes

Dr. Wolf's CHM 201 & Crude oil

Dr. Wolf's CHM 201 & Crude oil Refinery gas C 1 -C 4 Light gasoline (bp: °C) Light gasoline (bp: °C) C 5 -C 12 Naphtha (bp °C) Naphtha Kerosene (bp: °C) Kerosene C 12 -C 15 Gas oil (bp: °C) Gas oil (bp: °C) C 15 -C 25 ResidueResidue

Dr. Wolf's CHM 201 & Cracking converts high molecular weight hydrocarbons to more useful, low molecular weight ones Reforming increases branching of hydrocarbon chains branched hydrocarbons have better burning characteristics for automobile engines Petroleum Refining

Dr. Wolf's CHM 201 & Physical Properties of Alkanes and Cycloalkanes

Dr. Wolf's CHM 201 & Boiling Points of Alkanes governed by strength of intermolecular attractive forces alkanes are nonpolar, so dipole-dipole and dipole-induced dipole forces are absent only forces of intermolecular attraction are induced dipole-induced dipole forces

Dr. Wolf's CHM 201 & Induced dipole-Induced dipole attractive forces + – + – two nonpolar molecules center of positive charge and center of negative charge coincide in each

Dr. Wolf's CHM 201 & – + – movement of electrons creates an instantaneous dipole in one molecule (left) Induced dipole-Induced dipole attractive forces

Dr. Wolf's CHM 201 & – + – temporary dipole in one molecule (left) induces a complementary dipole in other molecule (right) Induced dipole-Induced dipole attractive forces

Dr. Wolf's CHM 201 & – + – temporary dipole in one molecule (left) induces a complementary dipole in other molecule (right) Induced dipole-Induced dipole attractive forces

Dr. Wolf's CHM 201 & – + – the result is a small attractive force between the two molecules Induced dipole-Induced dipole attractive forces

Dr. Wolf's CHM 201 & – + – the result is a small attractive force between the two molecules Induced dipole-Induced dipole attractive forces

Dr. Wolf's CHM 201 & increase with increasing number of carbons more atoms, more electrons, more opportunities for induced dipole-induced dipole forces decrease with chain branching branched molecules are more compact with smaller surface area—fewer points of contact with other molecules Boiling Points

Dr. Wolf's CHM 201 & increase with increasing number of carbons more atoms, more electrons, more opportunities for induced dipole-induced dipole forces Heptane bp 98°C Octane bp 125°C Nonane bp 150°C Boiling Points

Dr. Wolf's CHM 201 & decrease with chain branching branched molecules are more compact with smaller surface area—fewer points of contact with other molecules Octane: bp 125°C 2-Methylheptane: bp 118°C 2,2,3,3-Tetramethylbutane: bp 107°C Boiling Points

Dr. Wolf's CHM 201 & All alkanes burn in air to give carbon dioxide and water Chemical Properties: Combustion of Alkanes

Dr. Wolf's CHM 201 & increase with increasing number of carbons more moles of O 2 consumed, more moles of CO 2 and H 2 O formed Heats of Combustion

Dr. Wolf's CHM 201 & kJ/mol 5471 kJ/mol 6125 kJ/mol 654 kJ/mol Heptane Octane Nonane Heats of Combustion

Dr. Wolf's CHM 201 & increase with increasing number of carbons more moles of O 2 consumed, more moles of CO 2 and H 2 O formed decrease with chain branching branched molecules are more stable (have less potential energy) than their unbranched isomers Heats of Combustion

Dr. Wolf's CHM 201 & kJ/mol 5466 kJ/mol 5458 kJ/mol 5452 kJ/mol 5 kJ/mol 8 kJ/mol 6 kJ/mol Heats of Combustion

Dr. Wolf's CHM 201 & Isomers can differ in respect to their stability. Equivalent statement: Isomers differ in respect to their potential energy. Differences in potential energy can be measured by comparing heats of combustion. Important Point

Dr. Wolf's CHM 201 & CO 2 + 9H 2 O 5452 kJ/mol 5458 kJ/mol 5471 kJ/mol 5466 kJ/mol O2O2O2O O2O2O2O O2O2O2O O2O2O2O Figure 2.14