introduction to organic chemistry - alkanes

Organic CompoundsAn 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 CompoundsTypical organic compoundsContain 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. InorganicPropane, C3H8, is an organic compound used as a fuel.NaCl, salt, is an inorganic compound composed of Na+ and Cl ions.

Why is propane anorganic compound, butNaCl is not?Copyright 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Learning CheckIdentify each characteristic as most typical ofcompounds that are (I) inorganic or (O) organic. 1. Has a high melting point 2. Is not soluble in water3. Has a formula CH3CH2CH34. Has a formula MgCl25. Burns easily in air6. Has covalent bonds

SolutionIdentify 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 CH3CH2CH3 I 4. Has a formula MgCl2 O 5. Burns easily in air O 6. Has covalent bonds

Writing Formulas for Carbon CompoundsIn 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 CarbonVSEPR 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 HH C C H H H H H

ethane, CH3CH3

Tetrahedral Structure of CarbonIn 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 AlkanesCopyright 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Names of AlkanesThe 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.

Learning CheckA. Give the name of each compound: 1) CH3CH3 2) CH3CH2CH3 3) CH3CH2CH2CH2CH2CH3

B. Write the condensed structural formula of pentane.

SolutionA. Give the name of each compound: 1) CH3CH3ethane 2) CH3CH2CH3propane 3) CH3CH2CH2CH2CH2CH3hexaneB. Write the condensed structural formula of pentane.CH3CH2CH2CH2CH3

Structural FormulasAlkanes are written with structural formulas that areExpanded to show each bond.Condensed to show each carbon atom and its attached hydrogen atoms. Expanded Condensed H H C HCH4 , methane

H

Writing Structural FormulasCarbon atoms in a chainMaintain tetrahedral shape.Are connected in a zig-zag pattern.Are drawn as 2-dimensional. Can be written in several conformations.

Line-Bond FormulasBecause 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.

ConformationsThe 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

Hexane has Six Carbon Atoms Hexane 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


Learning Check A. Write the condensed formula for: H H H H H

H C C C C C H H H H H HB. What is its molecular formula?C. What is its name?

Solution A.CH3CH2CH2CH2CH3

B. C5H12

C. pentane

Learning CheckWrite the condensed structural formula for

A. ethane

B. heptane

SolutionWrite the condensed structural formula for

A. ethane CH3CH3

B. heptane CH3CH2CH2CH2CH2CH2CH3

CycloalkanesCycloalkanesAre 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.

CycloalkanesThe structural formulas of cycloalkanes are usually represented by geometric figures,

Cyclopropane CH2

CH2 CH2

CyclobutaneCH2 CH2

CH2 CH2

More CycloalkanesCyclopentane CH2 CH2 CH2CH2 CH2Cyclohexane CH2CH2 CH2CH2 CH2 CH2

Learning CheckName the following:

A. CH3CH2CH2CH3

B.

C. CH3CH2CH2CH2CH2CH2CH2CH3

D.

Isomers of ButaneIsomersHave 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.

Copyright 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings branch

Alkyl groups Alkyl groups areAlkanes that are missing one H. Substituents attached to carbon chains.Named with a yl ending. H

H C CH3methyl H H H H C C CH3CH2ethyl H H

Alkanes with Alkyl Groups CH3

CH3 CH CH3 methylpropanemethyl groups CH3 CH3

CH3 CH CH2 CH CH3 2,4-dimethylpentane

Guide to Naming AlkanesGive the name of CH3 CH3 CH3CHCHCH3

STEP 1 Longest chain is butane.

STEP 2 Number chain. CH3 CH3 CH3CHCHCH3 1 2 3 4STEP 3 Locate substituents and name. 2,3-dimethylbutane

Learning CheckWrite the IUPAC name for

Cl CH3 CH3CH2CHCHCH3

SolutionSTEP 1 Longest chain is pentane.

STEP 2 Number chain from end nearest substituent. Cl CH3 (nearest end) CH3CH2CHCHCH3 5 4 3 2 1

STEP 3 Locate substituents and name alphabetically. 3-chloro-2-methylpentane

What is In A Name?The structural formula is drawn from the IUPAC name.2, 4-dimethylhexane

2, 4 dimethyl hexaneLocation of Two CH3- groups 6 carbon main chainbranches on attachedwith single C-C bondsmain chain

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

SolutionSTEP 1 Longest chain has 4 carbon atoms.CCCCSTEP 2 Number chain and add substituents. Br C C C C Cl 1 2 3 4STEP 3 Add hydrogen to complete 4 bonds to each C. Br CH3CHCH2CH2Cl

Naming Cycloalkanes with SubstituentsThe name of a substituent is placed in front of thecycloalkane name. CH3methylcyclobutane

Number ring with two substituents1-bromo-2-chlorocyclopentane Br Cl

Learning CheckName each of the following:

1. CH3

CH2CH32.

Cl

SolutionName each of the following:

1. methylcyclopropane

2. 3-chloro-1-ethylcyclohexane

Learning CheckWrite three isomers of C5H12 and name each.

SolutionA chain of 5 carbon atoms CH3CH2CH2CH2CH3 pentaneA chain of 4 carbon atoms and 1 carbon branch CH3 CH3CHCH2CH3 2-methylbutane

A chain of 3 carbon atoms and 2 carbon branches CH3 CH3CHCH3 2,2-dimethylpropane CH3

Some Properties of AlkanesThe properties of alkanes includebeingNonpolar.Insoluble in water.Less dense than waterFlammable in air.


Alkanes with 1-4 Carbon Atoms Alkanes with 1-4 carbon atoms areMethane, ethane, propane, and butane.Gases at room temperature.Used as heating fuels.


Alkanes with 5-17 Carbon Atoms Alkanes with 5-8 carbon atoms areLiquids at room temperature.Pentane, hexane, heptane, and octane.Very volatile.Used to make gasoline.

Alkanes with 9-17 carbon atoms Are liquids at room temperatureHave higher boiling points.Are found in kerosene, diesel, and jet fuels.

Alkanes with 18 or more Carbon Atoms Alkanes with 18 or more carbon atomsHave 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 PentanesBoiling points of alkanesAre lowest of organic compounds.Increase with larger molecules due to increased dispersion forces.Decrease for branched alkanes.Increase for cycloalkanes.TABLE 11.6

Learning CheckFor the following pairs of hydrocarbon, which one hasthe higher boiling point? Why?

1. butane or octane

2. hexane or 2,3-dimethylbutane

SolutionFor the following pairs of hydrocarbon, which one hasthe higher boiling point? Why?

1. butane or octane octane has more carbon atoms

2. hexane or 2,3-dimethylbutane hexane is not branched

Crude OilThe hydrocarbons incrude oil areSeparated by boiling points.Heated to higher temperatures to produce gases that can be removed and cooled.


Classification of Carbon AtomsThe 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 CH2CH2CH3 CH3CHCH3primary secondary tertiary

Combustion of AlkanesAlkanes 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.

alkane + O2 CO2 + H2O + energy


Balancing A Combustion EquationWrite the equationC5H12 + O2 CO2 + H2OBalance C C5H12 + O2 5CO2 + H2OBalance H C5H12 + O2 5CO2 + 6H2OBalance O with O2 C5H12 + 8O2 5CO2 + 6H2O balanced

Learning CheckPropane is used to provide heat forcooking or warming a room. Write abalanced equation for the completecombustion of propane.


Solution Unbalanced equationC3H8 + O2 CO2 + H2OBalance CC3H8 + O2 3CO2 + H2OBalance HC3H8 + O2 3CO2 + 4H2OBalance OC3H8 + 5O2 3CO2 + 4H2O (Balanced)

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

SolutionC7H16 + O2 CO2 + H2OC7H16 + O2 7CO2 + 8H2OC7H16 + O2 7CO2 + 8H2OC7H16 +11O2 7CO2 + 8H2O

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

Learning CheckWrite the combustion reaction for ethane and balance.

SolutionWrite the combustion reaction for ethane and balance.ethane CH3CH3 = C2H6C2H6 + O22CO2 + 3H2O

C2H6 + 7 O22CO2 + 3H2O

C2H6 + 7/2 O22CO2 + 3H2O Multiply through by 2 to clear

2C2H6 + 7O24CO2 + 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 lightCH3CH3 + Cl2 CH3CH2 Cl

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

SolutionGive the structures and names of the possible monosubstituted products for the reaction of propane with bromine in the presence of light.CH3CH2CH2 Br1-bromopropane; propyl bromide Br |CH3CHCH3 2-bromopropane; isopropyl bromide

Chapter 11 Organic Chemistry

11.5 Functional Groups


Elements in Organic CompoundsIn organic molecules, C atoms form bondsMostly with H and other C atoms.Sometimes atoms of O, N, S, and halogens F, Cl, and Br.

TABLE 11.8Copyright 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Functional GroupsFunctional groups areA 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.

Alkenes and AlkynesAlkenes contain a double bond between adjacent carbon atoms.

Alkynes contain a triple bond.


Alcohols and EthersAn alcohol contains the hydroxyl (-OH) functional group.

In an ether, an oxygen atom is bonded to two carbon atoms COC . Copyright 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Aldehydes and KetonesAn 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 EstersCarboxylic acids contain the carboxyl group, which is a carbonyl group attached to a hydroxyl group. O COHAn ester contains the carboxyl group between carbon atoms.Copyright 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Amines and AmidesIn 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

Learning CheckClassify each of the following as alcohol, ether, aldehyde, ketone, carboxylic acid, ester, or amine.1)CH3CH2CH2OH2) CH3OCH2CH3

3) CH3CH2NH2

O O || || 4) CH3COH 5) CH3COCH3

SolutionClassify each of the following as alcohol, ether, aldehyde, ketone, carboxylic acid, ester, or amine.1)CH3CH2CH2OH 2) CH3OCH2CH3 alcohol ether3) CH3CH2NH2 amine O O || || 4) CH3COH 5) CH3COCH3 carboxylic acid ester

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.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.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.

introduction to organic chemistry - alkanes

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