© 2007 Thomson Learning, Inc. All rights reserved HFCC Science Division Principles of Organic Chemistry Unit 3 SCH 4C.

© 2007 Thomson Learning, Inc. All rights reservedHFCC Science Division

Principles of Organic Principles of Organic ChemistryChemistry

Unit 3SCH 4C


Organic ChemistryOrganic Chemistry• Organic chemistry:Organic chemistry: the study of the compounds that contain carbon as the building blocks.• Organic compounds are made up of carbon and only a few other elements.

• chief among these are hydrogen, oxygen, and nitrogen

• also present are sulfur, phosphorus, and halogens


Importance of Organic Importance of Organic ChemistryChemistry• Organic chemicals affect virtually Organic chemicals affect virtually every facet of our lives:every facet of our lives:• Products such as clothes, foods, medicines, gasoline, refrigerants, and soaps are composed almost solely of organic compounds

• Carbohydrates, lipids, proteins, enzymes, nucleic acids, hormones, vitamins, and almost all other chemicals in living systems are organic compounds.


Learning Check:Learning Check:

Which of the following Which of the following represents an organic compound? represents an organic compound? Why?Why?

a) CH3OH b) C6H12O6

c) NaOH d) NaHCO3

e) C5H12 f) HCN


Organic StructureOrganic Structure• Molecular formula: Molecular formula: indicates the type and number of atoms present in a molecule; ie) C2H2

• Structural formula:Structural formula: shows the atoms present in a molecule as well as how the bonds connect them



Provide the molecular formula Provide the molecular formula for each of the following for each of the following

organic compounds.organic compounds.


Characteristics of Organic Characteristics of Organic CompoundsCompounds

1.All organic compounds contain carbon atoms and most contain hydrogen atoms.

• Carbon always forms four covalent bonds.

• Hydrogen always forms one covalent bond.



2.Carbon forms single, double, and triple bonds to other carbon atoms.



Carbon forms single and double bonds to oxygen atoms.



Fill in all the H’s and lone Fill in all the H’s and lone pairs in each compound.pairs in each compound.

a) C−C=C−C

b) C−C−O−C−C

c) O=C−C−C



Provide two possible structures Provide two possible structures for each of the following for each of the following molecules.molecules.

a) C2H6O

b) C5H10

c) C3H7N

Start by drawing the carbon chain!


Drawing Organic Molecules:Drawing Organic Molecules:Condensed StructuresCondensed Structures

In a condensed structure, all of the atoms are drawn in, but the two-electron bond lines and lone pairs on oxygen are generally omitted.

• A carbon bonded to 3 H’s becomes CH3

• A carbon bonded to 2 H’s becomes CH2


Drawing Organic Molecules:Drawing Organic Molecules:Condensed StructuresCondensed Structures

• A carbon bonded to 1 H becomes CH

• Some bond lines can be drawn in for effect or to show specific bonding.



Provide a condensed structure Provide a condensed structure for each of the following for each of the following molecules.molecules.


Drawing Organic Molecules:Drawing Organic Molecules:Skeletal or Line StructuresSkeletal or Line Structures

When drawing a skeletal or line structure:

• assume there is a carbon atom at the junction of any two lines or at the end of any line (every end and every bend) • assume there are enough hydrogens around each carbon to give it four bonds• draw in all atoms other than carbon and the hydrogens directly bonded to them



Provide a skeletal structure Provide a skeletal structure for each of the following for each of the following molecules.molecules.



Provide a structural formula Provide a structural formula for the following skeletal for the following skeletal structures.structures.


HydrocarbonsHydrocarbons


HydrocarbonsHydrocarbons• Hydrocarbon:Hydrocarbon: a compound composed of only carbon and hydrogen.


AlkanesAlkanes• Alkanes:Alkanes: hydrocarbons containing only carbon-carbon single bonds.

• All alkanes are considered saturated hydrocarbons because they have the maximum number of H atoms per C atom.

• Alkanes that contain chains of C atoms but no rings are acyclic alkanes and have the general formula CnH2n+2

• The first two alkanes are methane and ethane.


AlkanesAlkanes• line-angle formula:line-angle formula:

• A line represents a carbon-carbon bond and a vertex and a line terminus represent a carbon atom.

• Hydrogen atoms are not shown in line-angle formulas.


Constitutional IsomerismConstitutional Isomerism• Constitutional isomers:Constitutional isomers: compounds that have the same molecular formula but different structural formulas (different connectivity).• For the molecular formulas CH4, C2H6, and C3H8, only one structural formula is possible; there are no constitutional isomers for these molecular formulas.

• For the molecular formula C4H10, two constitutional isomers are possible. We can attach the atoms together in two different ways.


ConformationConformation•The following two representations of propane are equivalent:

•The bends in a carbon chain don’t matter when it comes to identifying different compounds.•Molecules which have the same molecular formula, are connected the same way but are drawn differently, differ in conformationconformation.


Constitutional IsomerismConstitutional Isomerism• Problem:Problem: do the structural formulas in each set represent the same compound or constitutional isomers?


Constitutional IsomerismConstitutional Isomerism• Problem:Problem: draw structural formulas for the five constitutional isomers of molecular formula C6H14


Alkenes and AlkynesAlkenes and Alkynes• AlkeneAlkene:: a hydrocarbon that contains one or more carbon-carbon double bonds.• ethylene is the simplest alkene.

• AlkyneAlkyne:: a hydrocarbon that contains one or more carbon-carbon triple bonds.• acetylene is the simplest alkyne.


Alkenes and AlkynesAlkenes and Alkynes

AlkenesAlkenes and alkynesalkynes are two families of organic molecules that contain multiple bondsmultiple bonds.

Alkenes have the general formula

CnH2n

Alkynes have the general formula

CnH2n–2


Alkenes and Alkynes:Alkenes and Alkynes:Condensed Structural FormulaCondensed Structural Formula

•When drawing the condensed structures of alkenes and alkynes we keep the multiple-bond


Naming Acyclic Hydrocarbons:Naming Acyclic Hydrocarbons:

The name of a hydrocarbon has three parts:

• Indicates the name of the branch and its location on the main carbon chain

• Indicates the number of carbon atoms in the main chain

• Indicates the functional group or type of hydrocarbon• ane – alkane

• ene – alkene

• yne - alkyne

Prefix Root Suffix+ +


IUPAC NamesIUPAC Names• The IUPAC name of an alkane with an unbranched chain of carbon atoms consists of two parts: • (1) a root: the number of carbon atoms in the chain.

• (2) the suffix -ane-ane: shows that the compound is a saturated hydrocarbon.


IUPAC Names IUPAC Names ((Unbranched Alkanes)Unbranched Alkanes)


• The name of an alkane with a branched chain of carbon atom consists of:• The root and suffix: the longest chain of carbon atoms and the ending –ane.

• substituent names: the groups bonded to the parent chain

IUPAC Names IUPAC Names ((Branched Alkanes)Branched Alkanes)


IUPAC NamesIUPAC Names• Alkyl group:Alkyl group: a substituent group derived from an alkane by removal of a hydrogen atom.• named by dropping the -aneane from the name of the parent alkane and adding the suffix -ylyl.


IUPAC Naming RulesIUPAC Naming Rules

1. The name for an alkane with an unbranched chain of carbon atoms consists of a root showing the number of carbon atoms and the ending -aneane..

2. For branched-chain alkanes, the longest chain of carbon atoms is the parent chain and its name is the root name.

3. Name and number each substituent on the parent chain; use a hyphen to connect the number to the name.


IUPAC Naming Rules (con’t)IUPAC Naming Rules (con’t)

4. If there is one substituent, number the parent chain from the end that gives the substituent the lower number.


IUPAC Naming Rules (con’t)IUPAC Naming Rules (con’t)5. If the same substituent occurs more than once:• Number the parent chain from the end that gives the lower number to the substituent encountered first.

• Indicate the number of times the substituent occurs by a prefix di-, tri-, tetra-, penta-, hexa-, and so on.

• Use a comma to separate position numbers.


IUPAC Naming Rules (con’t)IUPAC Naming Rules (con’t)6. If there are two or more different substituents:• list them in alphabetical order.• number the chain from the end that gives the lower number to the substituent encountered first.

• If there are different substituents in equivalent positions on opposite ends of the parent chain, give the substituent of lower alphabetical order the lower number.


Learning Check:Learning Check:Give the IUPAC name for the following compounds.


Nomenclature of Alkenes and Nomenclature of Alkenes and AlkynesAlkynes

HOW TO Name an Alkene or Alkyne

Give the IUPAC name of the following alkene and alkyne.

Step [1] Find the longest chain that contains the double or triple bond.


Nomenclature of Alkenes and Nomenclature of Alkenes and AlkynesAlkynesHOW TO Name an Alkene or Alkyne

Step [1]•Find the longest chain that contains the double or triple bond.

•Compounds containing a carbon-carbon double bond end with “ene”

•Compounds containing a carbon-carbon triple bond end with “yne”

Step [2]•Number the carbon chain from the end that gives the multiple bond the lower number.

Step [3] •Number and name the substituents•Arrange side groups alphabetically and write the name.


Alkenes - IUPAC NamesAlkenes - IUPAC Names• Examples


Alkynes - IUPAC NamesAlkynes - IUPAC Names• follow the same rules as for alkenes, but use the ending -yneyne to show the presence of the triple bond.


Nomenclature: Nomenclature:

• Provide a IUPAC name for each of the following.


Sample QuestionsSample Questions

• Provide a IUPAC name for each of the following.


Physical PropertiesPhysical Properties• The most important physical property of alkanes and cycloalkanes is their almost complete lack of polarity.


• Melting and boiling points• Alkanes are nonpolar compounds and the only interaction between their molecules are the very weak London dispersion forces.

• Boiling points of alkanes are lower than those of almost any other type of compound of the same molecular weight.

• In general, the boiling points and melting points of alkanes increase with increasing lengths carbon chains.

• Smaller alkanes are gases at room temperature, whereas larger alkanes are liquids.

Physical PropertiesPhysical Properties


Physical Properties of Physical Properties of Some Unbranched Some Unbranched AlkanesAlkanes


Physical PropertiesPhysical Properties• Alkanes that are constitutional isomers are different compounds and have different physical and chemical properties.


Physical PropertiesPhysical Properties• Solubility: a case of “like dissolves like”.• Alkanes are not soluble in water; they are unable to form hydrogen bonds with water.

• Alkanes are soluble in each other.• Alkanes are also soluble in other nonpolar organic compounds, such as toluene and diethyl ether.

• Density• The average density of the liquid alkanes listed in Table 11.4 is about 0.7 g/mL; that of higher-molecular-weight alkanes is about 0.8 g/mL.

• All liquid and solid alkanes are less dense than water (1.0 g/mL) and, because they are insoluble in water, they float on water.


Focus on the EnvironmentFocus on the EnvironmentFossil FuelsFossil Fuels

• Natural gas is used as a fuel source for cooking and heating• Petroleum is a complex mixture that must be separated it into usable fractions


Physical Properties of Physical Properties of Unsaturated HydrocarbonsUnsaturated Hydrocarbons• Alkenes and alkynes are nonpolar compounds.• The only attractive forces between their molecules are London dispersion forces.

• Their physical properties are similar to those of alkanes with the same carbon skeletons.

• Alkenes and alkynes are insoluble in water but soluble in one another and in nonpolar organic liquids.

• Alkenes and alkynes that are liquid or solid at room temperature have densities less than 1.0 g/mL; they float on water.


Reactions of AlkanesReactions of Alkanes• Oxidation (combustion)

• Oxidation of hydrocarbons, including alkanes is the basis for their use as energy sources for heat [natural gas, liquefied petroleum gas (LPG), and fuel oil] and power (gasoline, diesel fuel, and aviation fuel).


Question:Question:Provide a balanced chemical equation for the complete combustion of:

a) 2-methylbutane

b)


ReactionsReactions• Reaction with halogens (halogenation)

• Halogenation of an alkane is a substitution reaction.


Question:Question:Show the two possible organic products from the chlorination of butane:


Reactions of AlkenesReactions of Alkenes• The most common reaction is addition


Addition of a HalideAddition of a Halide• Addition of HX (HCl, HBr, or HI) to an alkene gives a haloalkane. • H adds to one carbon of the C=C and X to the other.

• reaction is regioselective.regioselective.• Markovnikov’s rule:Markovnikov’s rule: H adds to the less substituted carbon and X to the more substituted carbon.


Sample QuestionsSample Questions

• Draw the structural formula of the product and name the alkene and alkane in each of the following addition reactions:


Addition of HAddition of H22OO Addition of water is called hydrationhydration• hydration is acid catalyzed, most commonly by H2SO4

• H adds to the less substituted carbon and OH adds to the more substituted carbon.

© 2007 Thomson Learning, Inc. All rights reserved HFCC Science Division Principles of Organic Chemistry Unit 3 SCH 4C.

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