Naming Alkanes 2/19/2016Dr Seemal Jelani Chem-1601

1. Root name: name of longest continuous C chain (parent chain) 2 equally long? Choose the one with more branches 2. Number C atoms in chain, starting at end with first branch 2/19/2016Dr Seemal Jelani Chem ethyl-3,5-dimethyloctane ethyl 3-methyl and 5-methyl = 3,5-dimethyl Octane

1. Identify substituents, give each a number (C it is connected to) Two or more identical substituents: use prefixes (di-, tri-, tetra-, etc.) 2. List substituents alphabetically before root name Do not alphabetize prefixes 3. Punctuation: commas separate numbers from each other hyphens separate numbers from names no space between last substituent & root name 2/19/2016Dr Seemal Jelani Chem-1603

2/19/2016Dr Seemal Jelani Chem-1604 isopropyl isobutyl sec-butyl tert-butyl alphabetized as “i” alphabetized as “b” R R R R R R R R Remember that R = any carbon chain “iso” indicates symmetry 3 carbons 4 carbons 2o2o 2o2o Secondary carbonTertiary carbon 3o3o 3o3o

H CH H H C CC H H HHH C H H H 2 - methylbutane butane 2/19/2016Dr Seemal Jelani Chem-1605 Expanded Structure Line Structure

H C CCC H H CH 3 H H H C C H H H H H hexane 3,3-dimethyl hexane 4,4-dimethyl Lowest sum of numbers is correct 2/19/2016Dr Seemal Jelani Chem-1606 Line Structure

Alkanes are written with structural formulas that are  expanded to show each bond (Lewis Structure).  condensed to show each carbon atom and hydrogen atoms attached to that carbon. Expanded (Lewis) Condensed H H C H CH 4, methane H 2/19/2016Dr Seemal Jelani Chem-1607

2/19/2016Dr Seemal Jelani Chem-1608

Condensed formulas are written for expanded structural formula by showing each carbon and the attached hydrogen atoms. Expanded Condensed H H H H │ │ │ │ H─C ─C ─C ─C ─ H CH 3 ─CH 2 ─CH 2 ─CH 3 │ │ │ │ H H H H 2/19/2016Dr Seemal Jelani Chem-1609

The names of alkanes  are determined by the IUPAC (International Union of Pure and Applied Chemistry) system.  end in –ane.  with 1-4 carbons in a chain use prefixes as follows. Name # Carbons Structural Formula Methane1CH 4 Ethane2CH 3 CH 3 Propane3CH 3 CH 2 CH 3 Butane4CH 3 CH 2 CH 2 CH 3 2/19/2016Dr Seemal Jelani Chem-16010

Alkanes with 5-10 carbon atoms in a chain use Greek prefixes. Name # Carbons Structural Formula Pentane 5 CH 3 CH 2 CH 2 CH 2 CH 3 Hexane 6 CH 3 CH 2 CH 2 CH 2 CH 2 CH 3 Heptane 7 CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 3 Octane 8 CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 3 Nonane 9 CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 3 Decane 10 CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 3 Know the 1 st eight alkanes (name and structure) 2/19/2016Dr Seemal Jelani Chem-16011

A. Write the condensed formula for: H H H H H H C C C C C H H H H H H B. What is its molecular formula? (Gives total # of each atom, does not indicate how they are arranged) C. What is its name? 2/19/2016Dr Seemal Jelani Chem CH 3 ─CH 2 ─CH 2 ─CH 2 ─CH 3 C 5 H 12 pentane

2/19/2016Dr Seemal Jelani Chem-16013

Hexane  is an alkane with six carbon atoms in a continuous chain.  has a “zig-zag” look because each carbon atom is at the center of a tetrahedron.  is represented by a ball-and-stick model as shown below. 2/19/2016Dr Seemal Jelani Chem-16014

 They are cyclic  have two hydrogen atoms fewer than the open chain. (remember each carbon has 4 bonds)  are named by using the prefix cyclo- before the name of the alkane chain with the same number of carbon atoms. 2/19/2016Dr Seemal Jelani Chem-16015

The structural formulas of cycloalkanes are usually represented by geometric figures, Cyclopropane CH 2 CH 2 CH 2 Cyclobutane CH 2 CH 2 CH 2 2/19/2016Dr Seemal Jelani Chem-16016

Cyclopentane CH 2 CH 2 CH 2 CH 2 Cyclohexane CH 2 2/19/2016Dr Seemal Jelani Chem-16017

2/19/2016Dr Seemal Jelani Chem methylpropane or

 On piece of your own paper, draw AND name ALL of the isomers for the following alkanes: 2/19/2016Dr Seemal Jelani Chem Formulas isomers Pentane Hexane Heptane C 5 H 12 C 6 H 14 C 7 H

2/19/2016Dr Seemal Jelani Chem pentane 2-methylbutane 2,2-dimethylpropane

2/19/2016Dr Seemal Jelani Chem hexane 2-methylpentane 3-methylpentane 2,3-dimethylbutane 2,2-dimethylbutane

2/19/2016Dr Seemal Jelani Chem heptane 2-methylhexane 3-methylhexane 2,2-dimethylpentane 2,3-dimethylpentane

2/19/2016Dr Seemal Jelani Chem ,4-dimethylpentane 3,3-dimethylpentane 3-ethylpentane 2,2,3-trimethylbutane

C 5 H 12 2/19/2016Dr Seemal Jelani Chem (Same formula, different structure) More branching → weaker London dispersion forces 36.0pentane methylbutane 9.52,2-dimethylpropane Boiling point (°C) Name Structure BP/MP of Linear alkanes > BP/MP of branched alkanes

2/19/2016Dr Seemal Jelani Chem Formulas # isomers C4H9IC4H9I C 3 H 6 Cl 2 C 5 H 11 Br C 4 H 8 Cl

2/19/2016Dr Seemal Jelani Chem iodobutane 2-iodo-2-methylbutane 2-iodobutane 1-iodo-2-methylbutane I I I I

2/19/2016Dr Seemal Jelani Chem ,1-dichloropropane 1,3-dichloropropane 1,2-dichloropropane 2,2-dichloropropane

2/19/2016Dr Seemal Jelani Chem bromopentane 2-bromopentane 1-bromo-3-methylpentane 3-bromopentane

2/19/2016Dr Seemal Jelani Chem bromo-2-methylbutane 2-bromo-3-methylbutane 1-bromo-2,2-dimethylbutane 2-bromo-2-methylbutane

2/19/2016Dr Seemal Jelani Chem ,1-dichlorobutane 1,2-dichlorobutane 1,3-dichlorobutane 1,4-dichlorobutane

2/19/2016Dr Seemal Jelani Chem ,2-dichlorobutane 1,1-dichlorobutane 2,3-dichlorobutane 1,2-dichloro-2-methylpropane 1,3-dichloro-2-methylpropane

2/19/2016Dr Seemal Jelani Chem Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings

Alkanes are  nonpolar.  insoluble in water.  less dense than water.  flammable in air. 2/19/2016Dr Seemal Jelani Chem-16033

Alkanes with 1-4 carbon atoms are  methane, ethane, propane, and butane.  gases at room temperature.  used as heating fuels. 2/19/2016Dr Seemal Jelani Chem-16034

Alkanes with 5-8 carbon atoms are  liquids at room temperature.  pentane, hexane, heptane, and octane.  very volatile.  used to make gasoline. Alkanes with 9-17 carbon atoms  are liquids at room temperature  have higher boiling points.  are found in kerosene, diesel, and jet fuels. 2/19/2016Dr Seemal Jelani Chem-16035

Alkanes with 5-8 carbon atoms are  liquids at room temperature.  pentane, hexane, heptane, and octane.  very volatile.  used to make gasoline. Alkanes with 9-17 carbon atoms  are liquids at room temperature  have higher boiling points.  are found in kerosene, diesel, and jet fuels. 2/19/2016Dr Seemal Jelani Chem-16036

2/19/2016 Dr Seemal Jelani Chem

Combustion  exothermic reaction  alkanes used as fuel source 2/19/2016Dr Seemal Jelani Chem C 4 H 10 + ___ O 2  ___ CO 2 + ___ H 2 O / 2 Incomplete Combustion with insufficient O 2 produces CO Poor ventilation, cigarettes C 4 H 10 + ___ O 2  ___ CO + ___ H 2 O 4 5 9/29/2 CO is poisonous because it binds to the hemoglobin in the blood, preventing the absorption of O 2

 In excess oxygen alkanes burn according to the following equation:  C n H 2n+2 +(1.5n+0.5)O 2  nCO 2 +(n+1)H 2 O  This is called complete combustion, however if there is insufficient oxygen present incomplete combustion can occur.  C n H 2n+2 +(n+0.5)O 2  n CO +(n+1)H 2 O  With even less oxygen soot is formed. 2/19/2016Dr Seemal Jelani Chem-16039

In combustion reactions,  alkanes react with oxygen.  CO 2, H 2 O and energy are produced. Alkane + O 2 CO 2 + H 2 O + heat 2/19/2016Dr Seemal Jelani Chem-16040

 Mechanism ◦ How the reaction occurs through multiple steps (most reactions actually occur in many steps)  Chain Reaction ◦ Reactions that occur on their own after some initiating event  Free Radicals ◦ Atoms that have one free electron—highly reactive 2/19/2016Dr Seemal Jelani Chem-16041

 Initiation Step ◦ Step where a bond is split by heat/light, producing free radicals  Propagation Step ◦ Step where free radicals react with non-radicals, producing more free radicals and continuing the “chain reaction”  Termination Step ◦ Step where free radicals react with each other, producing non-radicals and terminating the “chain reaction” 2/19/2016Dr Seemal Jelani Chem-16042

Initiation Propagation Termination Radical Halogenation of Alkanes 2/19/2016Dr Seemal Jelani Chem Mechanism (chain reaction): Step 1Cl 2 ⇌ Cl· + Cl · Step 2Cl· + CH 4  CH 3 · + HCl Step 3CH 3 · + Cl 2  CH 3 Cl + Cl· Step 4Cl· + Cl·  Cl 2 Overall reaction: CH 4 + Cl 2  CH 3 Cl + HCl Halogenated product is a haloalkane Naming: halogen atom is a substituent, replace –ine ending with –o -F fluoro-Cl chloro-Br bromo-I iodo  chloromethane hh (Free Radicals) Why not 1-chloromethane? Type of Step CH 4 + Cl 2  CH 3 Cl + HCl

Halogen substitutes for hydrogen in alkane →multiple results 2/19/2016Dr Seemal Jelani Chem CH 4 CH 3 ClCH 2 Cl 2 CHCl 3 CCl 4 Cl 2  Cl 2  Cl 2  Cl 2  Compound CH 3 Cl CH 2 Cl 2 CHCl 3 CCl 4 IUPAC Name Chloromethane Dichloromethane Trichloromethane Tetrachloromethane Common Name Methyl chloride Methylene chloride Chloroform Carbon tetrachloride All are liquids at room temperature Heavy Cl atoms increase LDF Polar C-Cl bonds – can have polar molecules

Chemistry: An Intro to General, Organic and Biological Chemistry by Timberlake (Green/Tan Book) 2/19/2016Dr Seemal Jelani Chem-16045

/19/2016Dr Seemal Jelani Chem chloro-2-fluorohexane 2-chloro-5-fluorohexane 2-chloro-4-fluoro-2,3-dimethylpentane 2-bromo-3-ethyl-4-iodopentane 2-bromo-4-chloro-3-isopropylpentane Two equal numbering options? Number based on alpha order

2/19/2016Dr Seemal Jelani Chem ? + Cl 2 → OR 1-chloropropane 2-chloropropane + Br 2 → OR 1-bromo-2-methylbutane 2-bromo-2-methylbutane Remember that any H on the alkane can be replaced by a halogen OR 3-chloropropane? + HCl ? ?

2/19/2016Dr Seemal Jelani Chem Br 2 → OR 1-bromo-2-methylbutane 2-bromo-3- methylbutane 1-bromo-3- methylbutane 1-bromo-2- methylbutane 2-bromo-2-methylbutane