Chapter 11 Introduction to Organic Chemistry: Alkanes 11.1 Organic Compounds Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Organic Compounds An organic compound Is a compound made from carbon atoms. Has one or more C atoms. Has many H atoms. May also contain O, S, N, and halogens.

Properties of Organic Compounds Typical organic compounds Contain carbon. Have covalent bonds. Have low melting points. Have low boiling points. Are flammable. Are soluble in nonpolar solvents. Are not soluble in water. Oil (organic) and water (inorganic) Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Organic vs. Inorganic Propane, C3H8, is an organic compound used as a fuel. NaCl, salt, is an inorganic compound composed of Na+ and Cl− ions. Why is propane an organic compound, but NaCl is not? Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Comparing Organic and Inorganic Compounds TABLE 11.1 Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Learning Check Identify each characteristic as most typical of compounds that are (I) inorganic or (O) organic. 1. Has a high melting point 2. Is not soluble in water 3. Has a formula CH3─CH2─CH3 4. Has a formula MgCl2 5. Burns easily in air 6. Has covalent bonds

Solution Identify each characteristic as most typical of compounds that are (I) inorganic or (O) organic. I 1. Has a high melting point O 2. Is not soluble in water O 3. Has a formula CH3─CH2─CH3 I 4. Has a formula MgCl2 O 5. Burns easily in air O 6. Has covalent bonds

Writing Formulas for Carbon Compounds In carbon compounds Carbon has 4 valence electrons and hydrogen has 1. • • C • H • To achieve an octet, C forms four bonds. H H   H  C  H H C H H H CH4 , methane

Tetrahedral Structure of Carbon VSEPR theory predicts that a carbon atom with four single, covalent bonds has a tetrahedral shape. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Organic Compounds with More Carbon Atoms In organic molecules with more carbon atoms, Valence electrons are shared. Covalent bonds form between carbon and carbon atoms. Covalent bonds form between carbon and hydrogen atoms. H H H H • • • • H  C  C  H H C C H H H H H ethane, CH3─CH3

Tetrahedral Structure of Carbon In molecules with two or more carbon atoms, each carbon atom with four single bonds has a tetrahedral shape. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Chapter 11 Introduction to Organic Chemistry: Alkanes 11.2 Alkanes Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Names of Alkanes The names of alkanes Are determined by the IUPAC (International Union of Pure and Applied Chemistry) system. Use a prefix to indicate the number of carbons in a chain. End in –ane.

IUPAC Names for Alkanes TABLE 11.2 The names of organic compounds are determined by the IUPAC rules (International Union of Pure and Applied Chemistry). The stem of the name states the number of carbon atoms in the carbon chain of the compounds. The suffix, in this case –ane, indicates the alkane family. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Learning Check A. Give the name of each compound: 1) CH3—CH3 2) CH3—CH2—CH3 3) CH3—CH2—CH2—CH2—CH2—CH3 B. Write the condensed structural formula of pentane.

Solution A. Give the name of each compound: 1) CH3—CH3 ethane 2) CH3—CH2—CH3 propane 3) CH3—CH2—CH2—CH2—CH2—CH3 hexane B. Write the condensed structural formula of pentane. CH3—CH2—CH2—CH2—CH3

Structural Formulas Alkanes are written with structural formulas that are Expanded to show each bond. Condensed to show each carbon atom and its attached hydrogen atoms. Expanded Condensed H H C H CH4 , methane In methane, CH4 the four valence electrons of carbon are shared with the single electrons of four hydrogen (H) atoms. Each pair of electrons is a single bond, which can be drawn as a line. When a structure is drawn to show each bond, it is called a complete structural formula.

Writing Structural Formulas Carbon atoms in a chain Maintain tetrahedral shape. Are connected in a zig-zag pattern. Are drawn as 2-dimensional. Can be written in several conformations.

Expanded and Condensed Structures TABLE 11.3 Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Line-Bond Formulas Because each C atom has a tetrahedral arrangement, the order of atoms is not a straight line, but a zigzag pattern. A line-bond formula abbreviates the carbon atoms and shows only the zigzag pattern of bonds from carbon atom to carbon atom.

Conformations The groups attached to a C-C single bond Rotate around the bond, Give different relative arrangements called conformations. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Conformations of Butane Rotation of the end CH3- provides different conformations for butane. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cumming

Some Structures for Butane TABLE 11.3 Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Hexane has Six Carbon Atoms Is an alkane with 6 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 Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Learning Check 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? C. What is its name?

Solution A. CH3CH2CH2CH2CH3 B. C5H12 C. pentane

Learning Check Write the condensed structural formula for A. ethane B. heptane

Solution Write the condensed structural formula for A. ethane CH3─CH3 B. heptane CH3─CH2─CH2─CH2─CH2─CH2─CH3

Cycloalkanes Cycloalkanes Are cyclic alkanes. Have 2H fewer than the open chain. Are named by using the prefix cyclo- before the name of the alkane chain with the same number of carbon atoms.

Cycloalkanes The structural formulas of cycloalkanes are usually represented by geometric figures, Cyclopropane CH2 CH2 CH2 Cyclobutane CH2 CH2 CH2 CH2

More Cycloalkanes Cyclopentane CH2 CH2 CH2 CH2 CH2 Cyclohexane CH2

Learning Check Name the following: A. CH3─CH2─CH2─CH3 B. C. CH3─CH2─CH2─CH2─CH2─CH2─CH2─CH3 D.

Solution Name the following: A. CH3─CH2─CH2─CH3 butane B. cyclopropane C. CH3─CH2─CH2─CH2─CH2─CH2─CH2─CH3 octane D. cyclohexane

Chapter 11 Introduction to Organic Chemistry: Alkanes 11.3 Alkanes with Substituents Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Isomers of Butane Isomers Have the same molecular formula. Have different atom arrangements. Of butane (C4H10) consist of a straight chain and a branched chain each with 4 carbon atoms. branch Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Alkyl groups Alkyl groups are Alkanes that are missing one H. Substituents attached to carbon chains. Named with a –yl ending. H H C CH3 methyl H H H C C CH3 CH2 ethyl

Naming Substituents In the IUPAC system, A carbon branch is named as an alkyl group. Halogen atoms are named as halo.

Naming Substituents IUPAC Common methyl ethyl propyl n-propyl Isopropyl butyl n-butyl 1-methylpropyl sec-butyl 2-methylpropyl Isobutyl 1,1-dimethylethyl tert-butyl or t-butyl

Naming Substituents IUPAC Fluoro Chloro Bromo Iodo Hydroxy

Alkanes with Alkyl Groups CH3 CH3 CH CH3 methylpropane methyl groups CH3 CH3 CH3 CH CH2 CH CH3 2,4-dimethylpentane

Naming Alkanes with Substituents Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Guide to Naming Alkanes Give the name of CH3 CH3   CH3─CH─CH─CH3 STEP 1 Longest chain is butane. STEP 2 Number chain. CH3 CH3   1 2 3 4 STEP 3 Locate substituents and name. 2,3-dimethylbutane

Learning Check Write the IUPAC name for Cl CH3   CH3─CH2─CH─CH─CH3

Solution STEP 1 Longest chain is pentane. STEP 2 Number chain from end nearest substituent. Cl CH3 (nearest end)   CH3─CH2─CH─CH─CH3 5 4 3 2 1 STEP 3 Locate substituents and name alphabetically. 3-chloro-2-methylpentane

Learning Check Give the IUPAC name for each of the following: A. CH3 CH3 | | CH3─CH─CH2 ─CH─CH2─CH3 B. Cl CH3 CH3─CH2─CH─CH2─C─CH2─CH3 | Cl

Solution A. CH3 CH3 | | CH3─CH─CH2 ─CH─CH2─CH3 2,4-dimethylhexane | | CH3─CH─CH2 ─CH─CH2─CH3 2,4-dimethylhexane 1 2 3 4 5 6 B. Cl CH3 more substituents on C3 CH3─CH2─CH─CH2─C─CH2─CH3 | Cl 7 6 5 4 3 2 1 3,5-dichloro-3-methylheptane

Drawing Alkane Structures Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

What is In A Name? The structural formula is drawn from the IUPAC name. 2, 4-dimethylhexane 2, 4 dimethyl hexane Location of Two CH3- groups 6 carbon main chain branches on attached with single C-C bonds main chain

Learning Check Draw the condensed structural formula for 2-bromo-4-chlorobutane.

Solution STEP 1 Longest chain has 4 carbon atoms. C─C─C─C STEP 2 Number chain and add substituents. Br  C ─ C ─ C ─ C ─ Cl 1 2 3 4 STEP 3 Add hydrogen to complete 4 bonds to each C. CH3─CH─CH2─CH2─Cl

Naming Cycloalkanes with Substituents The name of a substituent is placed in front of the cycloalkane name. CH3 methylcyclobutane Number ring with two substituents 1-bromo-2-chlorocyclopentane Br Cl

Learning Check Name each of the following: 1. CH3 CH2─CH3 2. Cl

Solution Name each of the following: 1. methylcyclopropane 2. 3-chloro-1-ethylcyclohexane

Learning Check Write three isomers of C5H12 and name each.

Solution A chain of 5 carbon atoms CH3─CH2─CH2─CH2─CH3 pentane A chain of 4 carbon atoms and 1 carbon branch CH3 │ CH3─CH─CH2─CH3 2-methylbutane A chain of 3 carbon atoms and 2 carbon branches CH3─CH─CH3 2,2-dimethylpropane

Chapter 11 Introduction to Organic Chemistry: Alkanes 11.4 Properties of Alkanes Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Some Properties of Alkanes The properties of alkanes include being Nonpolar. Insoluble in water. Less dense than water Flammable in air. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Alkanes with 1-4 Carbon Atoms Alkanes with 1-4 carbon atoms are Methane, ethane, propane, and butane. Gases at room temperature. Used as heating fuels. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Alkanes with 5-17 Carbon Atoms 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.

Alkanes with 18 or more Carbon Atoms Have high molar masses. Are waxy solids at room temperature. Used in waxy coatings of fruits and vegetables. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Boiling Points of Pentanes BPs of alkanes Are lowest of organic compounds. Increase with larger molecules due to increased dispersion forces. Decrease for branched alkanes. Increase for cycloalkanes.

Learning Check For the following pairs of hydrocarbon, which one has the higher boiling point? Why? 1. butane or octane 2. hexane or 2,3-dimethylbutane

Solution For the following pairs of hydrocarbon, which one has the higher boiling point? Why? 1. butane or octane octane has more carbon atoms 2. hexane or 2,3-dimethylbutane hexane is not branched

Crude Oil The hydrocarbons in crude oil are Separated by boiling points. Heated to higher temperatures to produce gases that can be removed and cooled. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Classification of Carbon Atoms The classification of carbon atoms indicates the number of carbon atoms attached. A primary carbon (1°) bonds to one carbon atom. A secondary carbon (2°) bonds to two carbon atoms. A tertiary carbon (3°) bonds to three carbon atoms. CH3 | CH3 —CH2—CH2—CH3 CH3—CH—CH3 primary secondary tertiary

Combustion of Alkanes Alkanes Undergo combustion by reacting with oxygen to produce carbon dioxide, water, and energy. Are typically not very reactive due to strong C-C single bonds. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings alkane + O2 CO2 + H2O + energy

Balancing A Combustion Equation Write the equation C5H12 + O2 CO2 + H2O Balance C C5H12 + O2 5CO2 + H2O Balance H C5H12 + O2 5CO2 + 6H2O Balance O with O2 C5H12 + 8O2 5CO2 + 6H2O balanced

Learning Check Propane is used to provide heat for cooking or warming a room. Write a balanced equation for the complete combustion of propane. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Solution Unbalanced equation C3H8 + O2 CO2 + H2O Balance C Balance H C3H8 + O2 3CO2 + 4H2O Balance O C3H8 + 5O2 3CO2 + 4H2O (Balanced) To balance the atoms in the formula C3H8, we place a coefficient of 3 in front of CO2 and a coefficient of 4 in front of H2O. The total O in the products is 10 O (6 O in 3CO2 and 4 O in 4 H2O). To balance the 10 O, a coefficient of 5 is placed in front of the O2.

Learning Check Write a balanced equation for the reaction for the complete combustion of heptane C7H16.

Solution C7H16 + O2 CO2 + H2O C7H16 + O2 7CO2 + 8H2O Balanced equation: C7H16 + 11O2 7CO2 + 8H2O

Learning Check Write the combustion reaction for ethane and balance.

Solution ethane CH3CH3 = C2H6 C2H6 + O2 2CO2 + 3H2O Write the combustion reaction for ethane and balance. ethane CH3CH3 = C2H6 C2H6 + O2 2CO2 + 3H2O C2H6 + 7 O2 2CO2 + 3H2O C2H6 + 7/2 O2 2CO2 + 3H2O Multiply through by 2 to clear 2C2H6 + 7O2 4CO2 + 6H2O balanced

Halogenation of Alkanes (Substitution) When alkanes react with halogens, The reaction is called substitution, one or more H atoms are replaced with a halogen usually Cl or Br. Light or heat is required. A mixture of halogenated products result, but we write the equation with the monosubstituted product. Example: ethane and chloride light CH3—CH3 + Cl2 CH3—CH2 —Cl

Learning Check Give the structures and names of the possible monosubstituted products for the reaction of propane with bromine in the presence of light.

Solution CH3—CH2—CH2— Br 1-bromopropane; propyl bromide Br | Give the structures and names of the possible monosubstituted products for the reaction of propane with bromine in the presence of light. CH3—CH2—CH2— Br 1-bromopropane; propyl bromide Br | CH3—CH—CH3 2-bromopropane; isopropyl bromide

Chapter 11 Organic Chemistry 11.5 Functional Groups Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Elements in Organic Compounds In organic molecules, C atoms form bonds Mostly with H and other C atoms. Sometimes atoms of O, N, S, and halogens F, Cl, and Br.

Functional Groups Functional groups are A characteristic feature of organic molecules that behave in a predictable way. Composed of an atom or group of atoms. Groups that replace a H in the corresponding alkane. A way to classify families of organic compounds.

Some Functional Groups

Alkenes and Alkynes Alkenes contain a double bond between adjacent carbon atoms. Alkynes contain a triple bond. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Alcohols and Ethers An alcohol contains the hydroxyl (-OH) functional group. In an ether, an oxygen atom is bonded to two carbon atoms –C–O–C– . Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

More Functional Groups

Aldehydes and Ketones An aldehyde contains a carbonyl group (C=O), which is a carbon atom with a double bond to an oxygen atom, attached to at least one hydrogen. In a ketone, the carbon of the carbonyl group is attached to two other carbon atoms. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Carboxylic Acids and Esters Carboxylic acids contain the carboxyl group, which is a carbonyl group attached to a hydroxyl group. O  — C—OH An ester contains the carboxyl group between carbon atoms. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Amines and Amides In amines, the functional group is a nitrogen atom. | —N — In amides, the hydroxyl group of a carboxylic acid is replaced by a nitrogen group. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Summary of Functional Groups

Functional Groups in Everyday Items Methyl amine (fish) Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Learning Check 1) CH3–CH2–CH2–OH 2) CH3–O–CH2–CH3 3) CH3–CH2–NH2 O O Classify each of the following as alcohol, ether, aldehyde, ketone, carboxylic acid, ester, or amine. 1) CH3–CH2–CH2–OH 2) CH3–O–CH2–CH3 3) CH3–CH2–NH2 O O || || 4) CH3–C–OH 5) CH3–C–O–CH3

Solution 1) CH3─CH2─CH2─OH 2) CH3─O─CH2─CH3 alcohol ether Classify each of the following as alcohol, ether, aldehyde, ketone, carboxylic acid, ester, or amine. 1) CH3─CH2─CH2─OH 2) CH3─O─CH2─CH3 alcohol ether 3) CH3─CH2─NH2 amine O O || || 4) CH3─C─OH 5) CH3─C─O─CH3 carboxylic acid ester