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Lecture PowerPoint

ChemistryThe Molecular Nature of

Matter and ChangeSixth Edition

Martin S. Silberberg

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

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Chapter 15

Organic Compounds and the

Atomic Properties of Carbon

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Organic Compounds and the Atomic Properties of Carbon

15.1 The Special Nature of Carbon and the Characteristics of Organic Molecules

15.2 The Structures and Classes of Hydrocarbons

15.3 Some Important Classes of Organic Reactions

15.4 Properties and Reactivities of Common Functional Groups

15.5 The Monomer-Polymer Theme I: Synthetic Macromolecules

15.6 The Monomer-Polymer Theme II: Biological Macromolecules

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Bonding Properties of Carbon

• Carbon forms covalent bonds in all its elemental forms and compounds.

– The ground state electron configuration of C is [He]2s22p2; the formation of carbon ions is therefore energetically unfavorable.

– C has an electronegativity of 2.5, which is midway between that of most metals and nonmetals. C prefers to share electrons.

• Carbon exhibits catenation, the ability to bond to itself and form stable chain, ring, and branched compounds.

– The small size of the C atom allows it to form short, strong bonds.

– The tetrahedral shape of the C atom allows catenation.

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Figure 15.1 The position of carbon in the periodic table.

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Comparison of Carbon and Silicon

• As atomic size increases down the group, bonds between identical atoms become longer and weaker.

– A C–C bond is much stronger than a Si–Si bond.

• The bond energies of a C–C bond, a C–O bond, and a C–Cl bond are very similar.

– C compounds can undergo a variety of reactions and remain stable, while Si compounds cannot.

• Si has low energy d orbitals available for reaction, allowing Si compounds to be more reactive than C compounds.

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Diversity and Reactivity of Organic Molecules

• Many organic compounds contain heteroatoms, atoms other than C and H.

– The most common of these are O, N, and the halogens.

• Most reactions involve the interaction of electron rich area in one molecule with an electron poor site in another.

– C–C bonds and C–H bonds tend to be unreactive.

– Bonds between C and a heteroatom are usually polar, creating an imbalance in electron density and providing a site for reactions to occur.

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Figure 15.2 Heteroatoms and different bonding arrangements lead to great chemical diversity.

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Carbon Skeletons

Each C atom can form a maximum of 4 bonds.

Groups joined by a single bond can rotate, so there are often several different arrangements of a given carbon skeleton that are equivalent:

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Figure 15.3 Some five-carbon skeletons.

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Drawing Carbon Skeletons

Each C atom can form a maximum of four bonds.These may be four single bonds, OR one double and two single bonds, OR one triple and one single bond.

The arrangement of C atoms determines the skeleton, so a straight chain and a bent chain represent the same skeleton.

Groups joined by a single bond can rotate freely, so a branch pointing down is the same as one point up.

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Figure 15.4 Adding the H-atom skin to the C-atom skeleton.

A C atom single-bonded to one other atom gets three H atoms.

C C

H

H

HA C atom single-bonded to two other atoms gets two H atoms.

C C

H

C

H

A C atom single-bonded to three other atoms gets one H atom.

C C

H

C

C

A C atom single-bonded to four other atoms is already fully bonded (no H atoms).

C C C

C

C

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Figure 15.4 continued

A double-bonded C atom is treated as if it were bonded to two other atoms.

C C H

H

A double- and single-bonded C atom or a triple-bonded C atom is treated as if it were bonded to three other atoms.

C C

H

C

C C H

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Sample Problem 15.1 Drawing Hydrocarbons

PLAN: In each case, we draw the longest carbon chain first and then work down to smaller chains with branches at different points along them. Then we add H atoms to give each C a total of four bonds.

PROBLEM: Draw structures that have different atom arrangements for hydrocarbons with

(a) Six C atoms, no multiple bonds, and no rings

(b) Four C atoms, one double bond, and no rings

(c) Four C atoms, no multiple bonds, and one ring

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Sample Problem 15.1

(a) Six carbons, no rings

H C C C C C C

H

H

H

H

H

H

H

H

H

H

H

H

H6-C chain

H C C C C C H

H

H

HC

H

H

H

H

H H

HH

H

5-C chain

H C C C C H

H

H

HC

C

H

H H

HH

H

H H

H

C C C C H

H

H

H

C

C

HH H

H

H

H

H

H H

H

4-C chains

H C C C C C H

H

H

H

C

H

H

H

H

H

HH H

H

5-C chain

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Sample Problem 15.1

(b) Four C atoms, one double bond, and no rings

H C

H

H

C C

H

H

CH H

H

3-C chain

H C C C C

H

H

H H H

H

H

C C

H

H

H

H

H

C C H

HH

4-C chains

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Sample Problem 15.1

(c) Compounds with four C atoms and one ring

C C

CC

H

H

H

H

H

H

H

H

C C

C

H H

C

H

H

HHH

H

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Alkanes

Hydrocarbons contain only C and H. Alkanes are hydrocarbons that contain only single bonds and are referred to as saturated hydrocarbons.

The general formula for an alkane is CnH2n+2, where n is any positive integer.

Alkanes comprise a homologous series, a group of compounds in which each member differs from the next by a –CH2– group.

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Naming Organic Compounds

The root name of the compound is determined from the number of C atoms in the longest continuous chain.

The name of any organic compound is comprised of three portions:

PREFIX + ROOT + SUFFIX

The prefix identifies any groups attached to the main chain.

The suffix indicates the type of organic compound, and is placed after the root.The suffix for an alkane is –ane.

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Table 15.1 Numerical Roots for Carbon Chains and Branches

Roots Number of C Atoms

meth- 1

eth- 2

prop- 3

but- 4

pent- 5

hex- 6

hept- 7

oct- 8

non- 9

dec- 10

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Table 15.2 Rules for Naming an Organic Compound

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Figure 15.5 Ways of depicting the alkane 3-ethyl-2-methylhexane.

C C C C C

H

H

H

C

C

HH H

C

H

H

H

H H

H

H H

H

C

H

H

H

H

H

Expanded formula

CH3 CH

CH3

CH

CH2

CH3

CH2 CH2 CH3

Condensed formula

Carbon-skeleton formula Ball-and-stick model Space-filling model

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Figure 15.6 Depicting cycloalkanes.

Cyclopropane

C

C C

H H

H

H

H

H

Cyclobutane

C

C C

C

H

H H

H

H

H

H

H

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Cyclopentane

C

C C

CC

H H

H

H

H

HHH

H

H

Cyclohexane

C

CC

C

CC

H H

H H

H

H

H

H

H

H

H

Figure 15.6 Depicting cycloalkanes.

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Constitutional Isomers

Constitutional or structural isomers have the same molecular formula but a different arrangement of the bonded atoms.

A straight-chain alkane may have many branched structural isomers.

Structural isomers are different compounds and have different properties.If the isomers contain the same functional groups, their properties will still be similar.

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Table 15.3 The Constitutional Isomers of C4H10 and C5H12

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Figure 15.7 Formulas, molar masses (in g/mol), structures, and boiling points (at 1 atm pressure) of the first 10 unbranched alkanes.

Alkanes are nonpolar and their physical properties are determined by the dispersion forces between their molecules.

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Chiral Molecules

Stereoisomers are molecules with the same arrangement of atoms but different orientations of groups in space.

Optical isomers are mirror images of each other that cannot be superimposed.

A molecule must be asymmetric in order to exist as a pair of optical isomers. An asymmetric molecule is termed chiral.Typically, a carbon atom is a chiral center if it is bonded to four different groups.

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Figure 15.8 An analogy for optical isomers.

If two compounds are mirror images of each other that cannot be superimposed, they are called optical isomers.

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Figure 15.9 Two chiral molecules.

optical isomers of 3-methylhexane

optical isomers of alanine

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Optical Activity

Optical isomers have identical physical properties, except that they rotate the plane of polarized light in opposite directions.

A chiral compound is optically active; i.e., it rotates the plane of polarized light.

A compound that rotates the plane of light clockwise is called dextrorotatory, while a compound that rotates the plane of light counterclockwise is called levorotatory.

In their chemical properties, optical isomers differ only in a chiral (asymmetric) environment.

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Figure 15.10 The rotation of plane-polarized light by an optically active substance.

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Figure 15.11 The binding site of an enzyme.

An enzyme provides a chiral environment and therefore distinguishes one optical isomer from another. The shape of one optical isomer fits the binding site, but the mirror image shape of the other isomer does not.

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Naproxen

Many drugs are chiral molecules. One optical isomer has a certain biological activity while the other has a different type of activity or none at all.

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Alkenes

A hydrocarbon that contains at least one C=C bond is called an alkene.

Alkenes are unsaturated and have the general formula CnH2n.

To name an alkene, the root name is determined by the number of C atoms in the longest chain that also contains the double bond.The C chain is numbered from the end closest to the double bond.The suffix for alkenes is –ene.

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Geometric Isomers

The double bond of an alkene restricts rotation, so that the relative positions of the atoms attached to the double bond are fixed.

Alkenes may exist as geometric or cis-trans isomers, which differ in the orientation of the groups attached to the double bond.

Geometric isomers have different physical properties.

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Table 15.4 The Geometric Isomers of 2-Butene

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Figure 15.12 The initial chemical event in vision and the change in the shape of retinal.

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Alkynes

An alkyne is a hydrocarbon that contains at least one CΞC triple bond.

Alkynes have the general formula CnH2n-2 and they are also considred unsaturated carbons.

Alkynes are named in the same way as alkenes, using the suffix –yne.

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Sample Problem 15.2 Naming Alkanes, Alkenes, and Alkynes

PROBLEM: Give the systematic name for each of the following, indicate the chiral center in part (d), and draw two geometric isomers for part (e).

CH3 C

CH3

CH3

CH2 CH3

(a) (b)

CH3 CH2 CH

CH3

CH

CH2

CH3

CH3

(c)

(d)

CH3 CH2 CH

CH3

CH CH2

(e)

CH3 CH2 CH C

CH3

CH CH3

CH3

PLAN: For (a) to (c), we find the longest continuous chain (root) and add the suffix –ane because there are only single bonds. Then we name the branches, numbering the C chain from the end closest to the first branch. For (d) and (e) the longest chain must include the double bond.

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Sample Problem 15.2

SOLUTION:

2,3-dimethylbutane

(b)

CH3 CH2 CH

CH3

CH

CH2

CH3

CH3

methyl

1

23456

hexane

methyl

3,4-dimethylhexanemethyl

12

34

5

(c)

ethyl

1-ethyl-2-methylcyclopentane

CH3 C

CH3

CH3

CH2 CH3

(a)

butane

methyl

methyl1 2 3 4

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Sample Problem 15.2

3-methyl-1-pentene

(d)

CH3 CH2 CH

CH3

CH CH2

methyl

12345

chiral center

1-pentene

(e)

12

3456

C CCH3

CH

H

CH2

CH3

CH3CH3

12

34

56 C CCH3

CH

CH2

H

CH3

CH3

CH3

methyl

methyl

methyl

methyl

3-hexene

cis-2,3-dimethyl-3-hexene trans-2,3-dimethyl-3-hexene

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Figure 15.13 Representations of benzene.

Resonance forms having alternating single and double bonds.

or

Resonance hybrid shows the delocalized electrons as either an unbroken or a dashed circle.

Benzene is an aromatic hydrocarbon.

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methylbenzene(toluene)

bp = 110.6°C

1,2-dimethylbenzene(o-xylene)

bp = 144.4°C

1,3-dimethylbenzene(m-xylene)

bp = 139.1°C

1,4-dimethylbenzene(p-xylene)

bp = 138.3°C

O2N NO2

NO2

2,4,6-trinitromethylbenzene(trinitrotoluene, TNT)

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Tools of the Laboratory Nuclear Magnetic Resonance (NMR) Spectroscopy

Figure B15.1 The basis of proton spin resonance.

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Tools of the Laboratory

Figure B15.2 The 1H-NMR spectrum of acetone.

Nuclear Magnetic Resonance (NMR) Spectroscopy

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Tools of the Laboratory

Figure B15.3 The 1H-NMR spectrum of dimethoxymethane.

Nuclear Magnetic Resonance (NMR) Spectroscopy

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Tools of the Laboratory

Figure B15.4 An MRI scan showing a brain tumor.

Nuclear Magnetic Resonance (NMR) Spectroscopy

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Types of Organic Reactions

An addition reaction occurs when an unsaturated reactant becomes a saturated product:

R CH CH R + X Y R CH CH R

X Y

The C=C, CΞC, and C=O bonds commonly undergo addition reactions.In each case, it is the π bond that breaks, leaving the σ bond intact.

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CH2 CH2 + H Cl H CH2 CH2 Cl

Reactants (bonds broken)

1 C=C = 614 kJ

4 C–H = 1652 kJ

1 H–Cl = 427 kJ

Total = 2693 kJ

Products (bonds formed)

1 C–C = -347 kJ

5 C–H = -2065 kJ

1 C–Cl = -339 kJ

Total = -2751kJ

H°rxn = H°bonds broken + H°bonds formed = 2693 kJ + (-2751 kJ) = -58 kJ

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Figure 15.14 A color test for C=C bonds.

This compound has no C=C bond, so the Br2 does not react.

C C + Br2 C C

Br

Br

Br2 (in pipet) reacts with a compound that has a C=C bond, and the orange-brown color of Br2 disappears.

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Types of Organic Reactions

An elimination reaction occurs when a saturated reactant becomes an unsaturated product.This reaction is the reverse of addition.

The groups typically eliminated are H and a halogen atom or H and an –OH group.

R CH CH R + X YR CH CH R

X Y

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The driving force for an elimination reaction is the formation of a small, stable molecule such as HCl (g) or H2O.

R CH CH R + H OHR CH CH R

OH HH2SO4

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Types of Organic Reactions

A substitution reaction occurs when an atom or group from an added reagent substitutes for one attached to a carbon in the organic reagent.

The C atom at which substitution may be saturated or unsaturated, and X and Y can be many different atoms.

R C X + Y R C Y + X

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CH3 C

O

Cl + HO CH2 CH2 CH

CH3

CH3 CH3 C

O

O CH2 CH2 CH

CH3

CH3

+ H Cl

The main flavor ingredient in banana oil is formed through a substitution reaction:

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Sample Problem 15.3 Recognizing the Type of Organic Reaction

PLAN: We determine the type of reaction by looking for any change in the number of atoms bonded to C.

• An addition reaction results in more atoms bonded to C.• An elimination reaction results in fewer atoms bonded to C.•If there are the same number of atoms bonded to C, the reaction is a substitution.

PROBLEM: State whether each reaction is an addition, elimination, or substitution:

CH3 CH2 CH2 Br CH3 CH CH2 + HBr(a)

(c) CH3 C

O

Br + CH3CH2OH CH3 C

O

OCH2CH3 + HBr

(b) + H2

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Sample Problem 15.3

SOLUTION:

CH3 CH2 CH2 Br CH3 CH CH2 + HBr(a)

This is an elimination reaction; two bonds in the reactant, C–H and C –Br, are absent in the product.

(b) + H2

This is an addition reaction; two more C–H bonds have formed in the product.

(c) CH3 C

O

Br + CH3CH2OH CH3 C

O

OCH2CH3 + HBr

This is a substitution reaction; the reactant C–Br bond has been replaced by a C–O bond in the product.

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Functional Groups

Organic compounds are classified according to their functional groups, a group of atoms bonded in a particular way.

The functional groups in a compound determine both its physical properties and its chemical reactivity.

Functional groups affect the polarity of a compound, and therefore determine the intermolecular forces it exhibits.

Functional groups define the regions of high and low electron density in a compound, thus determining its reactivity.

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Table 15.5 Important Functional Groups in Organic Compounds

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Table 15.5 Important Functional Groups in Organic Compounds

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Alcohols

The alcohol functional group consists of a carbon bonded to an –OH group.

C O H

Alcohols are named by replacing the –e at the end of the parent hydrocarbon name with the suffix –ol.

Alcohols have high melting and boiling points since they can form hydrogen bonds between their molecules.

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Reactions of Alcohols

Alcohols undergo elimination and substitution reactions.OH

H+

cyclohexanol cyclohexene

+ H2O dehydration (elimination)

CH3 CH2 CH

OH

CH3

K2Cr2O7

H2SO4

CH3 CH2 C

O

CH3

OH O

2-butanol 2-butanone

oxidation (elimination)

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Figure 15.15 Some molecules with the alcohol functional group.

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Haloalkanes

Haloalkanes or alkyl halides contain a halogen atom bonded to carbon.

Haloalkanes are named by identifying the halogen with a prefix on the hydrocarbon name. The C bearing the halogen must be numbered.

C X

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Reactions of Haloalkanes

Haloalkanes undergo substitution and elimination reactions.

CH3 CH2 CH2 CH2 Br + OH- CH3 CH2 CH2 CH2 OH + Br-

1-bromobutane 1-butanol

CH3 C

CH3

Cl

CH3 CH3 CH2 O-K++ CH3 C

CH3

CH2 + KCl + CH3 CH2 OH

2-chloro-2-methylpropane

potassium ethoxide 2-methylpropene ethanol

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Figure 15.16 A tetrachlorobiphenyl, one of 209 polychlorinated biphenyls (PCBs).

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Amines

The amine functional group contains a N atom.

The systematic name for an amine is formed by dropping the final –e of the alkane and adding the suffix –amine.

C N

Common names that use the name of the alkyl group followed by the suffix –amine are also widely used.

CH3CH2NH2

ethanamine ORethylamine

CH3CH2 NH CH2CH3

diethylamine

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Figure 15.17 General structures of amines.

Amines are classified according to the number of R groups directly attached to the N atom.

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Figure 15.18 Some biomolecules with the amine functional group.

Lysine (1° amine)amino acid found in proteins

Adenine (1° amine)component of nucleic acids

Epinephrine (adrenaline; 2° amine)neurotransmitter in brain; hormone released during stress

Cocaine (3° amine)brain stimulant; widely abused drug

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Properties and Reactions of Amines

Primary and secondary amines can form H bonds; therefore they have higher melting and boiling points than hydrocarbons or alkyl halides of similar mass.

Amines of low molar mass are fishy smelling, water soluble, and weakly basic.

Tertiary amines cannot form H bonds between their molecules because they lack a polar N–H bond.

Amines undergo a variety of reactions, including substitution reactions.

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Sample Problem 15.4 Predicting the Reactions of Alcohols, Alkyl Halides, and Amines

PLAN: We first determine the functional group(s) of the reactant(s) and then examine any inorganic reagent(s) to decide on the reaction type. Keep in mind that, in general, these functional groups undergo substitution or elimination.

PROBLEM: Determine the reaction type and predict the product(s) for each reaction:

(a) CH3 CH2 CH2 I + NaOH

(b) CH3 CH2 CH2 Br + 2 CH3 CH2 CH2 NH2

(c) CH3 CH

OH

CH3

Cr2O72-

H2SO4

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SOLUTION:

Sample Problem 15.4

(a) In this reaction the OH of the NaOH reaction substitutes for the I in the organic reagent:

CH3 CH2 CH2 OH + NaI

(b) This is a substitution reaction:

CH3 CH2 CH2 NH

CH2CH3

+ CH3 CH2 CH2 NH2Br

(c) This is an elimination reaction since acidic Cr2O72- is a strong

oxidizing agent:CH3 C

O

CH3

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Alkenes

Alkenes contain the C=C double bond:

Alkenes typically undergo addition reactions. The electron-rich double bond is readily attracted to the partially positive H atoms of H3O+ ions and hydrohalic acids.

C C

CH3

C CH2CH3 + H3O+

CH3

C CH3CH3

OH

OH

+ H+

2-methylpropene 2-methyl-2-propanol

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Aromatic Hydrocarbons

Benzene is an aromatic hydrocarbon and is a resonance hybrid. Its bond electrons are delocalized.

Aromatic compounds are unusually stable and although they contain double bonds they undergo substitution rather than addition reactions.

+ Br2

FeBr3

Br

+ HBr

benzene bromobenzene

15-75

Figure 15.19 The stability of benzene.

Benzene releases less energy during hydrogenation than expected, because it is already much more stable than a similar imaginary alkene.

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Aldehydes and Ketones

Aldehydes and ketones both contain the carbonyl group, C=O.

Aldehydes are named by replacing the final –e of the alkane name with the suffix –al.

Ketones have the suffix –one and the position of the carbonyl must always be indicated.

R and R′ indicate hydrocarbon groups.

H C

O

Raldehyde

R C

O

R'ketone

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Figure 15.20 Some common aldehydes and ketones.

Methanal (formaldehyde) Used to make resins in plywood, dishware, countertops; biological preservative

Ethanal (acetaldehyde) Narcotic product of ethanol metabolism; used to make perfumes, flavors, plastics, other chemicals

2-Propanone (acetone) Solvent for fat, rubber, plastic, varnish, lacquer; chemical feedstock

2-Butanone (methyl ethyl ketone) Important solvent

Benzaldehyde Artificial almond flavoring

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Figure 15.21 The polar carbonyl group.

The C=O bond is electron rich and is also highly polar. It readily undergoes addition reactions, and the electron-poor C atom attracts electron-rich groups.

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Reactions of Aldehydes and Ketones

Reduction to alcohols is an example of an addition reaction:

O

reduction

OH

cyclobutanone cyclobutanol

Organometallic compounds, which have a metal atom covalently bonded to C, add to the electron-poor carbonyl C:

R C

O

H + R' Li+-

+

-

R CH

OH

R' + LiOH

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Sample Problem 15.5 Predicting the Steps in a Reaction Sequence

PLAN: For each step we examine the functional group of the reactant and the reagent above the yield arrow to decide on the most likely product.

PROBLEM: Fill in the blanks in the following reaction sequence:

CH3 CH2 CH

Br

CH3OH- Cr2O7

2-

H2SO4

CH3-Li H2O

SOLUTION: The first step involves an alkyl halide reacting with OH-, so this is probably a substitution reaction, which yields an alcohol. In the next step the alcohol is oxidized to a ketone and finally the organometallic reagent adds to the ketone to give an alcohol with one more C in its skeleton:

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Sample Problem 15.5

CH3 CH2 CH

Br

CH3OH- Cr2O7

2-

H2SO4

CH3-Li

H2O

CH3 CH2 CH

OH

CH3

substitution oxidation(elimination)

CH3 CH2 C

O

CH3

addition

CH3 CH2 C

OH

CH3

CH3

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Carboxylic Acids

Carboxylic acids are named by replacing the –e of the alkane with the suffix –oic acid.

Carboxylic acids contain the functional group –COOH, or

Carboxylic acids are weak acids in water, and react with strong bases:

C

O

OH

CH3 C

O

OH (l) + NaOH (aq) CH3 C

O

O- (aq) + Na+ (aq) + H2O (l)

methanoic acid methanoate anion

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Figure 15.22 Some molecules with the carboxylic acid functional group.

Methanoic acid (formic acid) An irritating component of ant and bee stings

Butanoic acid (butyric acid) Odor of rancid butter; suspected component of monkey sex attractant

Octadecanoic acid (stearic acid) Found in animal fats; used in making candles and soaps

Benzoic acid Calorimetric standard; used in preserving food, dyeing fabric, curing tobacco

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Esters

The ester group is formed by the reaction of an alcohol and a carboxylic acid.

Ester groups occur commonly in lipids, which are formed by the esterification of fatty acids.

CH3 C

O

OH O CH3H+ CH3 C

O

O CH3 + HOH

ethanoic acid methanol methyl ethanoate

Esterification is a dehydration-condensation reaction.

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Figure 15.23 Some lipid molecules with the ester functional group.

Cetyl palmitate The most common lipid in whale blubber

Lecithin Phospholipid found in all cell membranes

Tristearin Typical dietary fat used as an energy store in animals

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Saponification

Ester hydrolysis can be carried out using either aqueous acid or aqueous base. When base is used the process is called saponification.This is the process used to make soaps from lipids.

R C

O

O CH2

CH

CH2O

O

C

O

R"

C

O

R'

a triglyceride

3NaOH

HO CH2

CH

CH2HO

HO

R C

O

O- Na+

R' C

O

O- Na+

R" C

O

O- Na+

3 soaps(salts of fatty acids)

glycerol

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Amides

An amide contains the functional group:

C

O

N

Amides, like esters, can be hydrolyzed to give a carboxylic acid and an amine.

The peptide bond, which links amino acids in a protein, is an amide group.

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Lysergic acid diethylamide (LSD-25)A potent hallucinogen

Figure 15.24 Some molecules with the amide functional group.

N,N-Dimethylmethanamide (dimethylformamide)Major organic solvent; used in production of synthetic fibers

AcetaminophenActive ingredient in nonaspirin pain relievers; used to make dyes and photographic chemicals

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Sample Problem 15.6 Predicting the Reactions of the Carboxylic Acid Family

PROBLEM: Predict the product(s) of the following reactions:

(a) CH3 CH2 CH2 C

O

OH CH3 CH

OH

CH3+H+

(b) CH CH2 CH2 C

O

NH

CH3

CH3 CH2CH3

NaOH

H2O

PLAN: We identify the functional groups in the reactant(s) and see how they change. In (a), a carboxylic acid reacts with an alcohol, so the reaction must be a substitution to form an ester. In (b), an amide reacts with aqueous base, so hydrolysis occurs.

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Sample Problem 15.6

SOLUTION:

(a) CH3 CH2 CH2 C

O

OH CH3 CH

OH

CH3+H+

CH3 CH2 CH2 C

O

O CH

CH3

CH3

+ H2O

(b) CH CH2 CH2 C

O

NH

CH3

CH3 CH2CH3

NaOH

H2OCH CH2 CH2 C

OCH3

CH3 O- Na+

CH2CH3

+NH2

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Figure 15.25 The formation of carboxylic, phosphoric, and sulfuric acid anhydrides.

P and S form acids, anhydrides and esters that are analogous to organic compounds.

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Figure 15.26 A phosphate ester and a sulfonamide.

Glucose-6-phosphateSulfanilamide

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Functional Groups with Triple Bonds

Alkynes contain the electron rich –CΞC– group, which readily undergoes addition reactions:

C CHCH3

H2

propyne

CH CH2CH3

propene

H2CH2 CH3CH3

propane

Nitriles contain the group –CΞN and are made by a substution reaction of an alkyl halide with CN- (cyanide):

CH2 ClCH3 + NaCN CH2 CCH3 N + NaCl

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Sample Problem 15.7

SOLUTION:

Recognizing Functional Groups

PLAN: Use Table 15.5 to identify the various functional groups.

PROBLEM: Circle and name the functional groups in the following molecules:

(a)C

O

OH

O C

O

CH3

(b)

CH

OH

CH2 NH CH3

(c) O

Cl

(a)C

O

OH

O C

O

CH3

(b)

CH

OH

CH2 NH CH3

(c) O

Cl

carboxylic acidester

aromatic ring

aromatic ring

alcohol

2° amine

ketone

alkenehaloalkane

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Polymers

Addition polymers, also called chain-growth polymers form when monomers undergo an addition reaction with each other.The monomers of most addition polymers contain an alkene group.

Condensation polymers are formed when monomers link by a dehydration-condensation type reaction.The monomers of condensation polymers have two functional groups, and each monomer can link to two others.

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Figure 15.27 Steps in the free-radical polymerization of ethylene.

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Table 15.6 Some Major Addition Polymers

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Table 15.6 Some Major Addition Polymers

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Figure 15.28 The formation of nylon-66.

Nylon-66 is a condensation polymer, made by reacting a diacid with a diamine. The polyamide forms between the two liquid phases.

HO C

O

(CH2)4 C

O

OH + nH2N (CH2)6 NH2

HO C

O

(CH2)4 C

O

NH (CH2)6 NH Hn

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Figure 15.29 The structure of glucose in aqueous solution and the formation of a disaccharide.

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Figure 15.30 The common amino acids.

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Figure 15.30 The common amino acids.

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Figure 15.31 The structural hierarchy of proteins.

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collagen silk fibroin

Figure 15.32 The shapes of fibrous proteins.

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Figure 15.33 Nucleic acid precursors and their linkage.

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Figure 15.34 The double helix of DNA and a section showing base pairs.

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Figure 15.35 Key stages in protein synthesis.

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Figure 15.36 Key stages in DNA replication.

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Chemical Connections

Figure B15.5 Nucleoside triphosphate monomers.

Chemical Connections

Figure B15.5 Nucleoside triphosphate monomers.

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A. B.

C. D.

Chemical Connections

Figure B15.6 Steps in the Sanger method of DNA sequencing.

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Chemical Connections

Figure B15.7 STR analysis of DNA in the blood of seven suspects and that in blood found at a crime scene.