Chapter 24 Introduction to Organic Chemistry: Alkanes Organic Compounds

Organic Chemistry 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 usually has carbon written first

Organic Compounds Typical organic compounds have covalent bonds have low melting points have low boiling points are flammable are soluble in nonpolar solvents are not soluble in water Vegetable oil is an organic compound and not soluble in water.

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 organic, but NaCl is not?

Comparing Organic and Inorganic Compounds

Learning Check Identify each characteristic as most typical of compounds that are inorganic or organic. A. Has a high melting point B. Is not soluble in water C. Has the formula CH3CH2CH3 D. Has the formula MgCl2 E. Burns easily in air F. Has covalent bonds

Solution Identify each characteristic as most typical of compounds that are inorganic or organic. A. Has a high melting point inorganic B. Is not soluble in water organic C. Has the formula CH3CH2CH3 organic D. Has the formula MgCl2 inorganic E. Burns easily in air organic F. Has covalent bonds organic

Bonding in Organic Compounds carbon has 4 valence electrons and hydrogen has 1 carbon achieves an octet by forming four bonds, with each line representing 2 electrons CH4, methane

Tetrahedral Structure of Carbon CH4 VSEPR theory predicts that a carbon atom with four single, covalent bonds has a tetrahedral shape. Methane is represented using different models: (a) tetrahedron, (b) ball-and- stick model, (c) space-filling model, (d) expanded structural formula.

Tetrahedral Structure of Carbon C2H6 In ethane, each carbon forms covalent bonds to another carbon and three hydrogen atoms each carbon atom retains its tetrahedral shape Ethane, CH3─CH3

Tetrahedral Structure of Carbon C2H6 In molecules with two or more carbon atoms, each carbon atom with four single bonds has a tetrahedral shape. Representations of ethane: (a) tetrahedral shape of each carbon, (b) ball-and-stick model, (c) space-filling model, (d) expanded structural formula.

Learning Check In the butane molecule, C4H10, predict the shape around each carbon atom.

Solution In the butane molecule, C4H10, predict the shape around each carbon atom. Each carbon atom has four single covalent bonds and therefore a tetrahedral shape.

Chapter 10 Introduction to Organic Chemistry: Alkanes 10.2 Alkanes

Alkanes Alkanes are organic molecules containing primarily C–C single bonds commonly used as fuels for heaters and cooktops whose names end in ane named by using the number of carbon atoms connected in a continuous chain

IUPAC Naming of the First Ten Alkanes

Condensed Structural Formulas In a condensed structural formula, each carbon atom and its attached hydrogen atoms are written as a group a subscript indicates the number of hydrogen atoms bonded to each carbon atom of butane, four carbon atoms are attached in a straight line CH3CH2CH2CH3 butane

Condensed 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 Expanded Condensed

Writing Structural Formulas Carbon atoms in a chain maintain tetrahedral shape are connected in a zigzag pattern are drawn as two-dimensional can be written in several conformations

Expanded, Condensed, and Skeletal Structures A hexane molecule can be represented in several ways: a molecular formula a ball-and-stick model an expanded structural formula a condensed structural formula a skeletal formula

Expanded, Condensed, and Skeletal Structures for C4H10

Learning Check 1. Write the expanded structural formula for the following: 2. What is its molecular formula? 3. What is its condensed structural formula? 4. What is its name?

Solution 1. Write the expanded structural formula for the following: 2. What is its molecular formula? C5H12 3. What is its condensed structural formula? CH3CH2CH2CH2CH3 4. What is its name? 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

Sample Problem 10.1 Drawing Expanded and Condensed Structural Formulas for Alkanes Draw the expanded structural formula, condensed structural formula, and skeletal formula for pentane. Solution In the expanded structural formula, five carbon atoms are connected to each other and to hydrogen atoms using single bonds to give each carbon atom a total of four bonds. In the condensed structural formula, each carbon atom and its attached hydrogen atoms are written as CH3– or –CH2–.The skeletal formula shows the carbon skeleton as a zigzag line where the ends and corners represent C atoms. Study Check 10.1 Draw the condensed structural formula and give the name for the following skeletal formula:

Cycloalkanes Cycloalkanes are cyclic alkanes have two less hydrogen atoms 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 propane, C3H8 cyclopropane, C3H6

Formulas of Cycloalkanes

Learning Check Give the IUPAC name for each of the following compounds: A. B.

Solution Give the IUPAC name for each of the following compounds: A. An alkane with eight continuous carbon atoms is octane. B. A cyclic molecule with five carbons is cyclopentane.

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

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

Sample Problem 10.2 Naming Alkanes Give the IUPAC name for each of the following: a. b. Solution a. A chain with eight carbon atoms is octane. b. The ring of six carbon atoms is named cyclohexane. Study Check 10.2 What is the IUPAC name of the following compound?

Chapter 10 Introduction to Organic Chemistry: Alkanes 10.3 Alkanes with Substituents

Isomers of Butane Isomers have the same molecular formula with different atom arrangements of butane (C4H10) are a straight chain and a branched chain The isomers of butane have the same number and type of atoms, but the atoms are bonded in a different order.

Sample Problem 10.3 Isomers Identify each pair of condensed structural formulas as isomers or the same molecule. a. b. Solution a. Although the carbon chain has different angles due to rotation, these condensed structural formulas represent the same molecule. The two formulas represent thesame molecule because each has four C atoms in a continuous chain. b. The molecular formula of both these condensed structural formulas is C6H14. However, they represent isomers because the C atoms are bonded in a different order; they have different arrangements. In one, there is a –CH3 group attached to a five-carbon chain, and in the other there are two –CH3 groups attached to a four-carbon chain. Study Check 10.3 Why is the following condensed structural formula an isomer of the molecules in Sample Problem 10.3, part b?

Substituents and Alkyl Groups Substituents are atoms or groups of atoms attached to the carbon chain and include alkyl and halo groups. Alkyl groups are carbon branches attached to carbon chains named with a yl ending Halo substituents are halogens attached to the carbon chain named as fluoro, chloro, bromo, or iodo

Substituents and Alkyl Groups

Guide to Naming Alkanes with Substituents

Write IUPAC Names for Alkanes with Substituents Give the IUPAC name for the following compound: Step 1 Write the alkane name of the longest chain of carbon atoms. The longest chain has five carbons, pentane.

Write IUPAC Names for Alkanes with Substituents Step 2 Number the carbon atoms starting from the end nearer a substituent. Step 3 Give the location and name of each substituent (in alphabetical order) as a prefix to the name of the main chain. 2-chloro-3-methylpentane

Learning Check Give the IUPAC name for the following compound:

Solution Give the IUPAC name for the following compound: Step 1 Write the alkane name of the longest chain of carbon atoms. The longest chain has four carbons, butane.

Solution Step 2 Number the carbon atoms starting from the end nearer a substituent. Step 3 Give the location and name of each substituent (in alphabetical order) as a prefix to the name of the main chain. 1,2-dibromo-3-methylbutane

Sample Problem 10.4 Writing IUPAC Names for Alkanes with Substituents Give the IUPAC name for the following alkane: Solution Step 1 Write the alkane name of the longest chain of carbon atoms. In this alkane, the longest chain has six carbon atoms, which is hexane. Step 2 Number the carbon atoms starting from the end nearer a substituent. The numbering of the carbon chain begins at carbon 1 at the end of the carbon chain closer to the methyl group (CH3–)and continues in the same direction.

Sample Problem 10.4 Writing IUPAC Names for Alkanes with Substituents Continued Solution Step 3 Give the location and name of each substituent (alphabetical order) as a prefix to the name of the main chain. The substituents, which are bromo and methyl groups, are listed in alphabetical order. A hyphen is placed between the number on the carbon chain and the substituent name. When there are two or more of the same substituent, a prefix (di, tri, tetra) is used in front of the name. Then commas are used to separate the numbers for the locations of the substituents. Study Check 10.4 Give the IUPAC name for the following compound:

Naming Cycloalkanes with Substituents Give the IUPAC name for the following cycloalkane. Step 1 Write the alkane name of the longest chain of carbon atoms. The longest chain is a six-member ring, cyclohexane.

Solution Step 2 Number the carbon atoms starting from the end nearer a substituent. Step 3 Give the location and name of each substituent (in alphabetical order) as a prefix to the name of the main chain. For cycloalkanes with just one substituent, there is no need to give the location of the substituent: ethylcyclohexane

Sample Problem 10.5 Naming Haloalkanes Freon-11 and Freon-12 are compounds, known as chlorofluorocarbons (CFCs), previously used as refrigerants and aerosol propellants. What are their IUPAC names? Solution Freon-11, trichlorofluoromethane; Freon-12, dichlorodifluoromethane Study Check 10.5 A haloalkane used as a fumigant has two carbon atoms with one bromine atom attached to each carbon. What is its IUPAC name?

Drawing Formulas for Alkanes Draw the structure for 1-chloro-1,2-dimethylheptane heptane – 7-carbon chain methyl group on carbon 1 and 2 chlorine on carbon 1

Guide to Drawing Formulas for Alkanes

Learning Check Draw the condensed structural formula for 3-bromo-1-chlorobutane.

Solution Draw the condensed structural formula for 3-bromo-1-chlorobutane. Step 1 Draw the main chain of carbon atoms. The longest chain in butane has four carbon atoms. CCCC Step 2 Number chain and place the substituents on the carbons indicated by the numbers. 1 2 3 4 3-bromo: Br goes on carbon 3. CCCC Cl Br 1-chloro: Cl goes on carbon 1.

Solution Draw the condensed structural formula for 3-bromo-1-chlorobutane. Step 3 Add hydrogen to complete four bonds to each carbon. CH2CH2CHCH3   Cl Br 3-bromo-1-chlorobutane

Learning Check Name each of the following cycloalkanes. A. B. C.

Solution Name each of the following cycloalkanes. A. methylcyclopropane B. ethylcyclobutane C. chlorocyclopentane

Sample Problem 10.6 Drawing Condensed Structures from IUPAC Names Draw the condensed structural formula and skeletal formula for 2,3-dimethylbutane. Solution We can use the following guide to draw the condensed structural formula: Step 1 Draw the main chain of carbon atoms. For butane, we draw a chain of four carbon atoms. C–C–C–C Step 2 Number the chain and place the substituents on the carbons indicated by the numbers. The first part of the name indicates two methyl groups (CH3–),one on carbon 2 and one on carbon 3. Step 3 Add the correct number of hydrogen atoms to give four bonds to each C atom. Study Check 10.6 What is the condensed structural formula and skeletal formula for 2-bromo-4-methylpentane?

Chapter 10 Introduction to Organic Chemistry: Alkanes 10.4 Properties of Alkanes

Some Uses of Alkanes Alkanes with one to four carbons are gases at room temperature and are widely used as heating fuels. methane, ethane, propane, butane Butane has four carbons: Alkanes with five to eight carbons are highly volatile liquids at room temperature, making them useful in fuels such as gasoline. pentane, hexane, heptane, octane Octane has eight carbons:

Some Uses of Alkanes Alkanes with 9−17 carbons are liquids with higher boiling points and are found in motor oils, mineral oil, kerosene, diesel, and jet fuels. Decane has 10 carbons:

Some Uses of Alkanes Alkanes with 18 or more carbon atoms have high molar masses are waxy solids at room temperature are used in waxy coatings of fruits and vegetables

Solubility and Density of Alkanes Alkanes are nonpolar insoluble in water less dense than water flammable in air The crude oil in oil spills floats on top of the water, forming a thin layer on the surface because it is less dense than water.

Combustion of Alkanes Alkanes have strong CC bonds react with oxygen gas to make carbon dioxide and water in combustion reactions release energy when CC bonds are broken in combustion reactions CH4(g) + 2O2(g)  CO2(g) + 2H2O(g) + energy

Alkane Mixtures in Crude Oil An oil refinery turns crude oil into usable fuel, producing natural gas, gasoline, kerosene, lubricant oils, and asphalt.

Alkane Mixtures in Crude Oil

Learning Check Propane is a fuel often used in barbeques. Write a balanced equation for the complete combustion of propane.

Solution Unbalanced equation: C3H8 + O2 CO2 + H2O Balance C: C3H8 + O2 3CO2 + H2O Balance H: C3H8 + O2 3CO2 + 4H2O Balance O: C3H8 + 5O2 3CO2 + 4H2O (balanced)

Chapter 10 Introduction to Organic Chemistry: Alkanes 10.5 Functional Groups

Elements in Organic Compounds In organic molecules, carbon atoms bond with four bonds mostly with H and other C atoms sometimes to O, N, S sometimes to halogens F, Cl, and Br

Elements in Organic Compounds

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 hydrogen atom in the corresponding alkane a way to classify families of organic compounds

Alkenes, Alkynes, and Aromatic Compounds Alkenes contain a double bond between adjacent carbon atoms. Alkynes contain a triple bond. Aromatic compounds contain a ring of six carbon atoms called benzene.

Comparing Alkenes, Alkynes, and Aromatic Compounds

Learning Check Identify the following compounds as an alkene, alkyne, or aromatic compound. A. B. C.

Solution Identify the following compounds as an alkene, alkyne or aromatic compound. A. aromatic B. alkene C. alkyne

Alcohols, Thiols, and Ethers An alcohol contains the hydroxyl (−OH) functional group. A thiol contains the thiol (−SH) functional group. An ether contains an oxygen atom bonded to two carbon atoms (COC) functional group.

Aldehydes and Ketones An aldehyde contains a carbonyl group (C=O), which is a carbon atom with a double bond to an oxygen atom. The carbonyl carbon is attached to a hydrogen. In a ketone, the carbon of the carbonyl group (C=O) is attached to two carbon atoms.

Carboxylic Acids and Esters Carboxylic acids contain the carboxyl group, which is a carbonyl group attached to a hydroxyl group. COOH An ester contains the carboxyl group between carbon atoms. COOCH3

Amines Amines have a functional group that contains a nitrogen atom are derivatives of ammonia, NH3, in which one, two, or three hydrogen atoms are replaced with carbons

Amides Amides have an amine group instead of an OH group on the carbonyl carbon are an important biological functional group, the simplest amide being urea

Classification of Organic Compounds

Learning Check Classify each of the following as an alcohol, ether, aldehyde, ketone, carboxylic acid, ester, amine, or amide. A. B. C. D. E.

Solution Classify each of the following as an alcohol, ether, aldehyde, ketone, carboxylic acid, ester, amine, or amide. A. B. C. D. E. alcohol ether amine carboxylic acid ester

Concept Map – Organic Compounds

Sample Problem 10.7 Classifying Organic Compounds Classify the following organic compounds according to their functional groups: a. CH3–CH2–CH2–CH2–OH b. CH3–CH2–NH–CH3 c. d. Solution a. alcohol b. amine c. ketone d. carboxylic acid Study Check 10.7 Classify the following organic compound according to its functional group: