Chapter 10 Organic Chemistry Copyright McGraw-Hill 2009

10.1 Why Carbon Is Different Electron configuration: [He]2s22p2 effectively prohibits ion formation Small atomic radius gives rise to short, strong CC bonds and stable compounds Hybridized atoms (sp- and sp2-) can form strong p bonds with unhybridzed p orbitals Catenation to form chains and rings containing single, double and triple bonds. Copyright McGraw-Hill 2009

Copyright McGraw-Hill 2009 Examples of Single and Multiple Bonds Copyright McGraw-Hill 2009

Copyright McGraw-Hill 2009 Carbon’s lack of d electrons enhances stability Copyright McGraw-Hill 2009

Copyright McGraw-Hill 2009 Examples of catenation Copyright McGraw-Hill 2009

10.2 Classes of Organic Compounds The seemingly limitless variety of organic compounds results from: Carbon’s ability to form chains by bonding to itself Presence of elements other than carbon and hydrogen Functional groups – a group of atoms that determines many of a molecule’s properties Multiple bonds Copyright McGraw-Hill 2009

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How are Organic Compounds Named? Alkanes Identify the longest continuous carbon chain to get the parent name. Number the carbons in the continuous chain, beginning at the end closest to the substituent. Identify the substituent and use a number and a prefix to specify location and identity, respectively. Copyright McGraw-Hill 2009

Name the compound shown below. Copyright McGraw-Hill 2009

Copyright McGraw-Hill 2009 3,3-dimethylhexane Copyright McGraw-Hill 2009

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Copyright McGraw-Hill 2009 Examples of functional groups Copyright McGraw-Hill 2009

Copyright McGraw-Hill 2009 Examples of alcohols Copyright McGraw-Hill 2009

Copyright McGraw-Hill 2009 Electrostatic maps of selected functional groups Copyright McGraw-Hill 2009

Naming Specific Functional Groups Alcohols Identify the longest chain that includes the –OH group. Change the –e ending to -ol. Number to give the –OH the lowest number. When the chain also contains an alkyl substituent, give the –OH the lowest number. Copyright McGraw-Hill 2009

Copyright McGraw-Hill 2009 Carboxylic Acids Identify the longest chain that includes the carboxyl group. Change the –e ending to –oic acid. Number starting with the carbonyl (C=O) carbon. Use numbers and prefixes to indicate the position and identity of any substituents. Esters Name as derivatives of carboxylic acids by replacing the –ic acid ending with -oate. Copyright McGraw-Hill 2009

Copyright McGraw-Hill 2009 Aldehydes Identify the longest chain that includes the carbonyl group. Change the –e ending to -al. Number starting with the carbonyl (C=O) carbon. Use numbers and prefixes to indicate the position and identity of any substituents. Copyright McGraw-Hill 2009

Copyright McGraw-Hill 2009 Ketones Identify the longest chain that includes the carbonyl group. Change the –e ending to -one. Number to give the carbonyl group the lowest possible number. Use numbers and prefixes to indicate the position and identity of any substituents. Copyright McGraw-Hill 2009

Copyright McGraw-Hill 2009 Primary Amines Identify the longest chain that includes the –NH2 group. Change the –e ending to -amine. Number starting with the carbon to which the –NH2 group is bonded. Use numbers and prefixes to indicate the position and identity of any substituents. Primary Amides Can be named as derivatives of carboxylic acids. Or, by replacing the –e ending with –amide. Copyright McGraw-Hill 2009

Compounds with More Than One Substituent Prefixes of di, tri, tetra, penta and so forth are used to denote the number of substituents. Substituent names are alphabetized. Numbers are used to indicate position of the alphabetized substituents. Prefixes are not used in alphabetization. Copyright McGraw-Hill 2009

Name the following compounds. Copyright McGraw-Hill 2009

Copyright McGraw-Hill 2009 2-pentanone 3-methylbutanoic acid Copyright McGraw-Hill 2009

Copyright McGraw-Hill 2009 Identify the functional groups in the following compound. Copyright McGraw-Hill 2009

Copyright McGraw-Hill 2009 amine ester carboxylic acid Copyright McGraw-Hill 2009

10.3 Representing Organic Molecules Condensed structural formula (Condensed Structure): shows the same information as a structural formula but in condensed form. CH3(CH2)6CH3 Kekulé structures: similar to Lewis structure but without showing lone pairs Copyright McGraw-Hill 2009

Copyright McGraw-Hill 2009 Skeletal Structures: Consist of straight lines that represent carbon-carbon bonds. Heteroatoms (atoms other than carbon or hydrogen) are shown explicitly Resonance: repositioning of electrons shown by curved arrows NH2 Copyright McGraw-Hill 2009

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Copyright McGraw-Hill 2009 Write the molecular formula and a structural formula for the following. O Copyright McGraw-Hill 2009

Copyright McGraw-Hill 2009 CH3COCH2CH3 C4H8O Copyright McGraw-Hill 2009

Copyright McGraw-Hill 2009 Draw the resonance structures for ozone. O3 Copyright McGraw-Hill 2009

Copyright McGraw-Hill 2009 10.4 Isomerism Constitutional (structural) isomerism occurs when the same atoms can be connected in two or more different ways. Stereisomerism occurs when atoms are bonded in identical ways but differ in the orientation of those bonds in space. Geometrical Isomers Optical Isomers Copyright McGraw-Hill 2009

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Copyright McGraw-Hill 2009 Geometrical isomers occur in compounds that have restricted rotation around a bond. cis (same side) trans (opposite side) Copyright McGraw-Hill 2009

Copyright McGraw-Hill 2009 Optical Isomers are nonsuperimposable mirror images of one another. Such molecules are termed chiral. A pair of such mirror-image molecules are called enantiomers. An equimolar mixture of the enantiomers is called a racemic mixture. Copyright McGraw-Hill 2009

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Copyright McGraw-Hill 2009 Bond designations to indicate stereochemistry Copyright McGraw-Hill 2009

Measurement of Optical Activity Dextrorotatory – plane of polarization is rotated to the right. Levorotatory – plane of polarization is rotated to the left. Copyright McGraw-Hill 2009

Copyright McGraw-Hill 2009 10.5 Organic Reactions Important terms Electrophile – a species with a region of positive or partial positive charge electron-poor Nucleophile a species with a region of negative or partial negative charge electron-rich Copyright McGraw-Hill 2009

Copyright McGraw-Hill 2009 Addition Reactions Reaction involving the addition of a molecule or an ion to another molecule Electrophilic addition – adding species is an electrophile Nucleophilic addition – adding species is a nucleophile Copyright McGraw-Hill 2009

Example: electrophilic addition Copyright McGraw-Hill 2009

Copyright McGraw-Hill 2009 Text Figure 1038 Copyright McGraw-Hill 2009

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Example: nucleophilic addition Copyright McGraw-Hill 2009

Comparison of electrophilic and nucleophilic addition Copyright McGraw-Hill 2009

Substitution Reactions Reaction when one group is replaced by another. Electrophilic substitution – an electrophile attacks an aromatic molecule and replaces a hydrogen atom Nucleophilic substitution – a nucleophile replaces another group on a carbon atom Copyright McGraw-Hill 2009

Electrophilic Substitution Reaction Copyright McGraw-Hill 2009

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Nucleophilic Substitution Reaction Copyright McGraw-Hill 2009

Comparison of electrophillic and nucleophillic substitution Copyright McGraw-Hill 2009

Other Types of Organic Reactions Elimination – reaction in which a double bond forms and small molecule is removed Oxidation-reduction – involve the loss and gain of electrons Isomerization – one isomer is converted to another Copyright McGraw-Hill 2009

Copyright McGraw-Hill 2009 Examples Elimination Oxidation-reduction Copyright McGraw-Hill 2009

Copyright McGraw-Hill 2009 Isomerization Copyright McGraw-Hill 2009

Copyright McGraw-Hill 2009 Draw the mechanism for the nucleophilic addition of CN to CH3CHO. Copyright McGraw-Hill 2009

Copyright McGraw-Hill 2009 Draw the mechanism for the nucleophilic addition of CN to CH3CHO. Copyright McGraw-Hill 2009

Copyright McGraw-Hill 2009 10.6 Organic Polymers Polymers – molecular compounds made up of many repeating units called monomers Types Addition polymers form when monomers join end to end Condensation polymers form when two different functional groups combine in an elimination reaction Often are copolymers which are made of two or more different monomers Copyright McGraw-Hill 2009

Addition polymerization Copyright McGraw-Hill 2009

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Condensation polymerization Copyright McGraw-Hill 2009

Ester and Ether Formation by Condensation Copyright McGraw-Hill 2009

Copyright McGraw-Hill 2009 Biological Polymers Naturally occurring polymers include Proteins – polymers of amino acids Polysaccharides – polymers of sugars Nucleic acids – polymers of nucleotides DNA (deoxyribonucleic acid) RNA (ribonucleic acid) Copyright McGraw-Hill 2009

Copyright McGraw-Hill 2009 Protein formation Peptide bonds are also called amide linkages since they contain an amide functional group. Very long chains are called proteins while shorter chains are called polypeptides. Copyright McGraw-Hill 2009

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Copyright McGraw-Hill 2009 Carbohydrates with different linkages b linkage a linkage Copyright McGraw-Hill 2009

Copyright McGraw-Hill 2009 Structure of a nucleotide (found in DNA) Copyright McGraw-Hill 2009

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Copyright McGraw-Hill 2009 Key Points Unique features of carbon Classes of organic compounds Naming organic compounds Isomerism Constitutional isomerism Stereoisomerism Geometrical isomers Optical isomers Copyright McGraw-Hill 2009

Copyright McGraw-Hill 2009 Key Points Organic reactions Addition reactions Electrophilic addition Nucleophilic addition Substitution reactions Electrophilic substitution Nucleophilic substitution Elimination reactions Oxidation-reduction reactions Isomerization reactions Copyright McGraw-Hill 2009

Copyright McGraw-Hill 2009 Key Points Polymers Addition Condensation Biological Proteins Carbohydrates Nucleic Acids Copyright McGraw-Hill 2009