Chapter 20 - Highline Community College

Transcript Chapter 20 - Highline Community College

Chemistry: A Molecular Approach

, 2nd Ed.

Nivaldo Tro

Chapter 20 Organic Chemistry

Roy Kennedy Massachusetts Bay Community College Wellesley Hills, MA Copyright  2011 Pearson Education, Inc .

Odors

• • • • • Our sense of smell helps us identify food, people, and other organisms, and alerts us to dangers such as polluted air or spoiled food Odorants must be volatile However, many volatile substances have no scent at all Most common smells are caused by organic molecules The study of compounds containing carbon combined with one or more of the elements hydrogen, nitrogen, oxygen, and sulfur, including their properties and their reactions, is known as

organic chemistry

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What Is Organic Chemistry?

• • Organic chemistry is a branch of chemistry that focuses on compounds that contain carbon  except CO, CO 2 , carbonates, and carbides Even though organic compounds only contain a few elements, the unique ways carbon atoms can attach together to form molecules leads to millions of different organic compounds Tro: Chemistry: A Molecular Approach, 2/e 4 Copyright  2011 Pearson Education, Inc .

The Chemistry of Life

• • • Life as we know it is because of organic chemistry Organic molecules can be very large and complex It is this complexity of large organic molecules that allows the complex functions of the cells to occur Tro: Chemistry: A Molecular Approach, 2/e 5 Copyright  2011 Pearson Education, Inc .

Differences Between Organic and Inorganic Compounds

• • Organic compounds are easily decomposed into simpler substances by heating, but inorganic substances are not Inorganic compounds were readily synthesized in the lab, but synthesis of organic compounds in the lab is hard Tro: Chemistry: A Molecular Approach, 2/e 6 Copyright  2011 Pearson Education, Inc .

What’s Special About Organic Compounds?

• • • • Organic compounds tend to be molecular Mainly composed of just six nonmetallic elements  C, H, O, N, S, and P Compounds found in all three states  solids, liquids, and gases  solids tend to have low melting points Solubility in water varies depending on which of the other elements are attached to C and how many there are  CH 3 OH is miscible with water; C 10 H 21 OH is insoluble Copyright  2011 Pearson Education, Inc .

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What’s So Special About Carbon?

• Carbon atoms can do some unique things that other atoms cannot • • • • • Carbon can bond to as many as four other atoms Bonds to carbon are very strong and nonreactive Carbon atoms can attach together in long chains Carbon atoms can attach together to form rings Carbon atoms can form single, double, or triple bonds Copyright  2011 Pearson Education, Inc .

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Bond Energies and Reactivities

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Carbon Bonding

• • • • Carbon forms four bonds When C has four single bonds, the shape is tetrahedral When C has one triple + one single or two double bonds, the shape is linear When C has two single + one double bond, the shape is trigonal planar Tro: Chemistry: A Molecular Approach, 2/e 10 Copyright  2011 Pearson Education, Inc .

Practice – Predict the shape and hybridization around each C aAtom CH 3 CN

linear, sp

CH 3 CH 2 CH 3

all tetrahedral, sp

H 2 CNH Tro: Chemistry: A Molecular Approach, 2/e 11

trigonal planar, sp

Hydrocarbons

• Hydrocarbons contain only C and H  aliphatic or aromatic • Insoluble in water  no polar bonds to attract water molecules • Aliphatic hydrocarbons  saturated or unsaturated aliphatics  saturated = alkanes, unsaturated = alkenes or alkynes  may be chains or rings  chains may be straight or branched • Aromatic hydrocarbons Copyright  2011 Pearson Education, Inc .

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Uses of Hydrocarbons

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Physical Properties of Aliphatic Hydrocarbons

• Boiling points and melting points increase as the size of the molecule increases  nonpolar molecules  main attractive forces are dispersion forces • • Less dense than water Insoluble in water Tro: Chemistry: A Molecular Approach, 2/e 15 Copyright  2011 Pearson Education, Inc .

Saturated Hydrocarbons

• A saturated hydrocarbon has all C ─C single bonds  it is saturated with hydrogens • Saturated aliphatic hydrocarbons are called

alkanes

• Chain alkanes have the general formula • C n H 2n+2 Ring alkanes have all C ─C single bonds, but have fewer hydrogens than a chain with the same number of carbons Tro: Chemistry: A Molecular Approach, 2/e 16 Copyright  2011 Pearson Education, Inc .

Unsaturated Hydrocarbons

• • • Unsaturated hydrocarbons have one or more C=C double bonds or C  C triple bonds Unsaturated aliphatic hydrocarbons that contain C=C are called

alkenes

 the general formula of a monounsaturated chain alkene is C n H 2n  remove two more H for each additional double bond Unsaturated aliphatic hydrocarbons that contain C  C are called

alkynes

 the general formula of an alkyne with one triple bond is C n H 2n −2  remove four more H for each additional triple bond Copyright  2011 Pearson Education, Inc .

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Aromatic Hydrocarbons

• • Aromatic hydrocarbons contain a ring structure that seems to have C=C, but doesn’t behave that way The most prevalent example is

benzene

 C 6 H 6  Other compounds have the benzene ring with other groups substituted for some of the Hydrogens Tro: Chemistry: A Molecular Approach, 2/e 18 Copyright  2011 Pearson Education, Inc .

alkanes 19 Copyright  2011 Pearson Education, Inc .

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Practice —Assuming only chains with a maximum of one unsaturation, decide if each of the following molecular formulas represents an alkane, alkene, or alkyne C 14 H 28 Alkene C 25 H 52 Alkane C 12 H 22 Alkyne Tro: Chemistry: A Molecular Approach, 2/e 21 Copyright  2011 Pearson Education, Inc .

• • •

Formulas

Molecular formulas just tell you what kinds of atoms are in the molecule, but they don’t tell you how they are attached Structural formulas show you the attachment pattern in the molecule Models not only show you the attachment pattern, but give you an idea about the shape of the molecule Tro: Chemistry: A Molecular Approach, 2/e 22 Copyright  2011 Pearson Education, Inc .

Condensed Structural Formulas

• • • Attached atoms listed in order  central atom with attached atoms Follow normal bonding patterns  use to determine position of multiple bonds () used to indicate more than one identical group attached to same previous central atom  unless () group listed first in which case attached to next central atom Tro: Chemistry: A Molecular Approach, 2/e 23 Copyright  2011 Pearson Education, Inc .

Example – Write the structural and condensed formula for the n-Alkane C

H

18 • • • Connect the C atoms in a row  Carbon backbone Add H to complete four bonds on each C.

 middle C gets 2 Hs  end C gets 3 Hs The condensed formula has the H attached to each C written directly after it Copyright  2011 Pearson Education, Inc .

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Example – Draw a complete structural formula for CH

CHCH

CH(CH

)CH

CH

3 Tro: Chemistry: A Molecular Approach, 2/e 25 Copyright  2011 Pearson Education, Inc .

Practice – Write a complete structural formula for the straight chain isomer of C 7 H 16 Tro: Chemistry: A Molecular Approach, 2/e 26 Copyright  2011 Pearson Education, Inc .

Practice – Draw a complete structural formula for CHCCH

C(CH

)

CH

3 Tro: Chemistry: A Molecular Approach, 2/e 27 Copyright  2011 Pearson Education, Inc .

Carbon Skeleton Formulas

• • • Each angle, and beginning and end, represent a C atom H omitted on C  included on functional groups Multiple bonds indicated  double line is double bond, triple line is triple bond Tro: Chemistry: A Molecular Approach, 2/e 28 Copyright  2011 Pearson Education, Inc .

Practice – Draw a complete structural formula for each of the following Tro: Chemistry: A Molecular Approach, 2/e 29 Copyright  2011 Pearson Education, Inc .

Formulas

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• • •

Isomerism

Isomers

are different molecules with the same molecular formula

Structural isomers

are isomers that have a different pattern of atom attachment  aka Constitutional Isomers

Stereoisomers

are isomers with the same pattern of atom attachments, but the atoms have a different spatial orientation Tro: Chemistry: A Molecular Approach, 2/e 31 Copyright  2011 Pearson Education, Inc .

Structural Isomers of C

H

10 Butane, BP = 0 °C Isobutane, BP = −12 °C Tro: Chemistry: A Molecular Approach, 2/e 32 Copyright  2011 Pearson Education, Inc .

Rotation about a Bond Is Not Isomerism

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Possible Structural Isomers

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Example 20.1: Write the structural formula and carbon skeleton formula for C 6 H 14 start by connecting the carbons in a line determine the C skeleton of the other isomers Tro: Chemistry: A Molecular Approach, 2/e 35 Copyright  2011 Pearson Education, Inc .

Example 20.1: Write the structural formula and carbon skeleton formula for the 5 structural isomers of C 6 H 14 fill in the H to give each carbon four bonds Tro: Chemistry: A Molecular Approach, 2/e 36 Copyright  2011 Pearson Education, Inc .

Example 20.1: Write the structural formula and carbon skeleton formula for the 5 structural isomers of C 6 H 14 convert each to a carbon skeleton formula – each bend and the ends represent C atoms 2-methylpentane BP 60 ºC n-hexane BP 69 ºC 3-methylpentane BP 63 ºC 2,2-dimethylbutane BP 50 ºC Tro: Chemistry: A Molecular Approach, 2/e 37 2,3-dimethylbutane BP 58 ºC Copyright  2011 Pearson Education, Inc .

Practice – Draw the three structural isomers of pentane

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Stereoisomers

• • •

Stereoisomers

are different molecules whose atoms are connected in the same order, but with a different spatial direction

Optical isomers

are stereoisomers that are nonsuperimposable mirror images of each other

Geometric isomers

not optical isomers are stereoisomers that are Copyright  2011 Pearson Education, Inc .

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Nonsuperimposable Mirror Images

the mirror image cannot be rotated so all its atoms align with the same atoms of the original molecule Tro: Chemistry: A Molecular Approach, 2/e 40 Copyright  2011 Pearson Education, Inc .

Chirality

• • • Any molecule with a nonsuperimposable mirror image is said to be

chiral

Any carbon with 4 different substituents will be a chiral center A pair of nonsuperimposable mirror images are called a pair of

enantiomers

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Optical Isomers of 3-methylhexane

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Practice – Draw the mirror image of the molecule and decide if they are enantiomers Tro: Chemistry: A Molecular Approach, 2/e Enantiomers 43 Copyright  2011 Pearson Education, Inc .

Plane Polarized Light

• Light that has been filtered so that only those waves traveling in a single plane are allowed through Tro: Chemistry: A Molecular Approach, 2/e 44 Copyright  2011 Pearson Education, Inc .

•

Optical Activity

Enantiomers have all the same physical properties except one – the direction they rotate the plane of plane-polarized light  each one of the enantiomers will rotate the plane the same amount, but in opposite directions  dextrorotatory = rotates the plane to the right  levorotatory = rotates the plane to the left Tro: Chemistry: A Molecular Approach, 2/e 45 Copyright  2011 Pearson Education, Inc .

Mixtures of Enantiomers

• • • An equimolar mixture of a pair of enantiomers is called a

racemic mixture

Because half the molecules are rotating the plane to the left and the other half are rotating it to the right, the rotations cancel, and the racemic mixture does not rotate the plane If the mixture is non-racemic, the amount of rotation can be used to determine the percentages of each enantiomer in the mixture Copyright  2011 Pearson Education, Inc .

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Chemical Behavior of Enantiomers

• • A pair of enantiomers will have the same chemical reactivity in a non-chiral environment But in a chiral environment they may exhibit different behaviors  enzyme selection of one enantiomer of a pair Tro: Chemistry: A Molecular Approach, 2/e 47 Copyright  2011 Pearson Education, Inc .

Alkanes

• • • • • Aka paraffins Aliphatic General formula C

H 2n+2 for chains Very unreactive Come in chains or/and rings  CH 3 groups at ends of chains, CH 2 the middle groups in • • Saturated Branched or unbranched Copyright  2011 Pearson Education, Inc .

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Physical Properties of

–Alkanes

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Alkane Boiling Points

• • Branched chain alkanes have lower boiling points than straight chain alkanes Ring alkanes have higher boiling points than straight chain alkanes Copyright  2011 Pearson Education, Inc .

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Naming

• Each name consists of three parts  prefix  indicates position, number, and type of branches  indicates position, number, and type of each functional group  parent  indicates the length of the longest carbon chain or ring  suffix  indicates the type of hydrocarbon o ane, ene, yne  certain functional groups Copyright  2011 Pearson Education, Inc .

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Naming Alkanes

1. Find the longest continuous carbon chain 2. Number the chain from end closest to a branch  if first branches equal distance use next in 3. Name branches as

alkyl groups

 locate each branch by preceding its name with the carbon number on the chain 4. List branches alphabetically  do not count

n-, sec-, t-

, count iso 5. Use prefix if more than one of same group present   di, tri, tetra, penta, hexa do not count in alphabetizing Copyright  2011 Pearson Education, Inc .

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Prefixes

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Alkyl Groups

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More Alkyl Groups

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Examples of Naming Alkanes

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Example – Name the alkane

1. Find the longest continuous C chain and use it to determine the base name because the longest chain has 5 C the base name is pentane Tro: Chemistry: A Molecular Approach, 2/e 58 Copyright  2011 Pearson Education, Inc .

Example – Name the alkane

2. Identify the substituent branches there are 2 substituents both are 1 C chains, called methyl Tro: Chemistry: A Molecular Approach, 2/e 59 Copyright  2011 Pearson Education, Inc .

Example – Name the alkane

Number the chain and substituents a) determine the end closest to a substituent branch  if first substituents equidistant from end, go to next substituent in b) then assign numbers to each substituent based on the number of the main chain C it is attached to 1 2 3 4 5 both substituents are equidistant from the end 2 4 60 Copyright  2011 Pearson Education, Inc .

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Example – Name the alkane

4. Write the name in the following order a) substituent

number

followed by dash of first alphabetical substituent b) substituent

name

followed by a dash of first alphabetical substituent   if it is the last substituent listed, no dash use prefixes to indicate multiple identical substituents c) repeat for other substituents alphabetically d) name of main chain 2,4 – dimethylpentane 2 4 Tro: Chemistry: A Molecular Approach, 2/e 61 Copyright  2011 Pearson Education, Inc .

Practice – Name the following

3-ethyl-2-methylpentane Tro: Chemistry: A Molecular Approach, 2/e 62 Copyright  2011 Pearson Education, Inc .

Practice – Draw and name all nine structural isomers of heptane

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Practice – Draw and name all nine structural isomers of heptane

• • The prefix

hept-

means 7, so the molecular formula is C 7 H 16 Start by drawing the carbon skeleton of the straight chain isomer Tro: Chemistry: A Molecular Approach, 2/e 64 Copyright  2011 Pearson Education, Inc .

Practice – Draw and name all nine structural isomers of heptane

• • Take one C off the right end of the straight chain isomer and attach it to the second C in from the left end Then keep moving it down the chain, but not past the halfway point Tro: Chemistry: A Molecular Approach, 2/e 65 Copyright  2011 Pearson Education, Inc .

Practice – Draw and name all nine structural isomers of heptane

• • Take one C off the right end of each one-branch chain isomer and attach it to the second C in from the left end Then keep moving it down the chain  always keep checking to ensure you do not duplicate Tro: Chemistry: A Molecular Approach, 2/e 66 already have Copyright  2011 Pearson Education, Inc .

Practice – Draw and name all nine structural isomers of heptane

• • • Take one C chain off the right end of 2,2-branch isomer and attach it to the third C in from the left end Then keep moving it down the chain Repeat with other two branch isomers if necessary Tro: Chemistry: A Molecular Approach, 2/e 67 Copyright  2011 Pearson Education, Inc .

• •

Practice – Draw and name all nine structural isomers of heptane

Take two C chain off the right end of straight chain isomer and attach it to the third C in from the left end Then keep moving it down the chain, but not beyond halfway Tro: Chemistry: A Molecular Approach, 2/e 68 Copyright  2011 Pearson Education, Inc .

Practice – Draw and name all nine structural isomers of heptane

• Continue the process until you’ve drawn all the isomers Tro: Chemistry: A Molecular Approach, 2/e 69 Copyright  2011 Pearson Education, Inc .

Practice – Draw and name all nine structural isomers of heptane

• Find the base name of each main chain

Heptane Hexanes Pentanes

Butane

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•

Practice – Draw and name all nine structural isomers of heptane

Number the main chain from end closest to a substituent 1 2 3 4 5 6 7 1 2 3 4 5 6 1 2 3 4 5 1 2 3 4 5 6

Hexanes

1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 Tro: Chemistry: A Molecular Approach, 2/e 71 1 2 3 4 Copyright  2011 Pearson Education, Inc .

Practice – Draw and name all nine structural isomers of heptane

• Name and number the alkyl groups

heptane 2-methylhexane 3-methylhexane 2,2-dimethylpentane 2,3-dimethylpentane 2,4-dimethylpentane 3,3-dimethylpentane

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3-ethylpentane

2,2,3-trimethylbutane

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•

Practice – Draw and name all nine structural isomers of heptane

Fill in the hydrogens so each C has four bonds Tro: Chemistry: A Molecular Approach, 2/e 73 Copyright  2011 Pearson Education, Inc .

Drawing Structural Formulas

• • • Draw and number the base chain carbon skeleton Add the carbon skeletons of each substituent on the appropriate main chain C Add in required H’s 4-ethyl-2-methylhexane Copyright  2011 Pearson Education, Inc .

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Practice – Draw the structural formula of 4-isopropyl-2-methylheptane

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Alkenes

• • • • • Also known as olefins Aliphatic, unsaturated  C=C double bonds Formula for one double bond = C

H 2

 subtract 2 H from alkane for each double bond Trigonal shape around C  flat Polyunsaturated = many double bonds Tro: Chemistry: A Molecular Approach, 2/e 76 Copyright  2011 Pearson Education, Inc .

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•

Double Bonds

2 , trigonal planar  shorter bond lengths  alkene angles a little larger than 120 ° • • • No free rotation around double bond Composed of 1sigma (s) and 1 pi ( p ) bond Not twice as strong as single bond, therefore less stable and more reactive Tro: Chemistry: A Molecular Approach, 2/e 78 Copyright  2011 Pearson Education, Inc .

ethene = ethylene H H C C H H

Alkenes

propene = propylene H H C C H CH 3 produced by ripening fruit used to make polyethylene Tro: Chemistry: A Molecular Approach, 2/e 79 used to make polypropylene Copyright  2011 Pearson Education, Inc .

Physical Properties of Alkenes

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Physical Properties of Alkenes

• pi bond electrons not held as tight as sigma, therefore alkenes are more polarizable than alkanes • • • cis generally more polar than trans trans lower boiling point more carbon groups attached to the double bond = higher boiling point  for equal numbers of C • • densities similar to alkanes trans higher melting point than cis  molecules are more symmetrical and pack better Tro: Chemistry: A Molecular Approach, 2/e 81 Copyright  2011 Pearson Education, Inc .

Alkynes

• • • • Also known as acetylenes Aliphatic, unsaturated C  C triple bond Formula for one triple bond = C

H 2

n −

2  subtract 4 H from alkane for each triple bond • • • Linear shape Internal alkynes have both triple bond carbons attached to C Terminal alkynes have one carbon attached to H Copyright  2011 Pearson Education, Inc .

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Triple Bonds

• • • • •

hybrid  50% “

” character Linear, 180 ° Composed of 2 pi bonds and 1 sigma Shorter than C –C and C=C Stronger than C –C, but not 3x as strong  C  C = 836 kJ/mol, C –C = 368 kJ/mol Copyright  2011 Pearson Education, Inc .

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Alkynes

both used in welding torches Tro: Chemistry: A Molecular Approach, 2/e 85 Copyright  2011 Pearson Education, Inc .

Physical Properties of Alkynes

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Physical Properties of Alkynes

• Higher boiling points than similar sized alkenes  similar size = same number of carbons  more pi bond = more polarization = higher boiling point • • • Slightly higher densities than similar alkenes There are no alkyne cis or trans isomers Internal alkynes have higher boiling points than terminal alkynes  with the same number of C Copyright  2011 Pearson Education, Inc .

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Naming Alkenes and Alkynes

• • Change suffix on main name from

ane

for base name of alkene, or to

yne

to for the

ene

base name of the alkyne • Number chain from end closest to multiple bond Number in front of main name indicates first carbon of multiple bond Tro: Chemistry: A Molecular Approach, 2/e 88 Copyright  2011 Pearson Education, Inc .

Examples of Naming Alkenes

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Examples of Naming Alkynes

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Name the Alkene

1. Find the longest, continuous C chain that contains the double bond and use it to determine the base name Because the longest chain with the double bond has 6 C the base name is hexene Tro: Chemistry: A Molecular Approach, 2/e 91 Copyright  2011 Pearson Education, Inc .

Name the Alkene

2. Identify the substituent branches there are 2 substituents one is a 1 C chain, called methyl the other one is a 2 C chain, called ethyl Tro: Chemistry: A Molecular Approach, 2/e 92 Copyright  2011 Pearson Education, Inc .

Name the Alkene

3. number the chain and substituents  a) determine the end closest to the double bond if double bond equidistant from both ends, number from end closest to the substituents b) then assign numbers to each substituent based on the number of the main chain C it is attached to 3 4 4 3 2 1 Tro: Chemistry: A Molecular Approach, 2/e 5 93 6 Copyright  2011 Pearson Education, Inc .

Name the Alkene

4. Write the name in the following order a. substituent number of first alphabetical substituent – substituent name of first alphabetical substituent –  use prefixes to indicate multiple identical substituents b. repeat for other substituents c.

number of first C in double bond – name of main chain 3 3 –ethyl–4–methyl–2–hexene 4 4 3 2 1 5 6 Tro: Chemistry: A Molecular Approach, 2/e 94 Copyright  2011 Pearson Education, Inc .

Practice – Name the following

3 4 5 6 2 1 3,4-dimethyl-3-hexene Tro: Chemistry: A Molecular Approach, 2/e 95 Copyright  2011 Pearson Education, Inc .

Name the Alkyne

1. Find the longest, continuous C chain that contains the triple bond and use it to determine the base name Because the longest chain with the triple bond has 7 C the base name is heptyne Tro: Chemistry: A Molecular Approach, 2/e 96 Copyright  2011 Pearson Education, Inc .

Name the Alkyne

2. Identify the substituent branches there are 2 substituents one is a 1 C chain, called methyl the other one is called isopropyl Tro: Chemistry: A Molecular Approach, 2/e 97 Copyright  2011 Pearson Education, Inc .

Name the Alkyne

3. number the chain and substituents a.

 determine the end closest to the triple bond if triple bond equidistant from both ends, number from end closest to the substituents b. then assign numbers to each substituent based on the number of the main chain C it is attached to 7 6 6 5 4 4 3 2 1 Copyright  2011 Pearson Education, Inc .

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Name the Alkyne

4. write the name in the following order a) substituent number of first alphabetical substituent – substituent name of first alphabetical substituent –  use prefixes to indicate multiple identical substituents b) repeat for other substituents c) number of first C in triple bond – name of main chain 7 6 6 5 4 4 3 2 1 4 –isopropyl–6–methyl–2–heptyne Copyright  2011 Pearson Education, Inc .

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Practice – Name the Following

3 2 1 4 5 3,3-dimethyl-1-pentyne Tro: Chemistry: A Molecular Approach, 2/e 100 Copyright  2011 Pearson Education, Inc .

Geometric Isomerism

• • • • Because the rotation around a double bond is highly restricted, you will have different molecules if groups have different spatial orientation about the double bond  stereoisomers This is often called

cis –trans isomerism

When groups on the doubly bonded carbons are cis, they are on the same side of the double bond When groups on the doubly bonded carbons are trans, they are on opposite sides Copyright  2011 Pearson Education, Inc .

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Cis –Trans Isomerism

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Free Rotation Around C ─C: No Cis –Trans Isomerism

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No Free Rotation C=C: Cis-Trans Isomerism

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Cis-Trans Isomerism

The cis and trans isomers are different molecules with different properties.

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Reactions of Hydrocarbons

• • All hydrocarbons undergo combustion Combustion is always exothermic  about 90% of U.S. energy generated by combustion 2 CH 3 CH 2 CH 2 CH 3 (

) + 13 O 2 (

) → 8 CO 2 (

) + 10 H 2 O(

) CH 3 CH=CHCH 3 (

) + 6 O 2 (

) → 4 CO 2 (

) + 4 H 2 O(

) 2 CH 3 C  CCH 3 (

) + 11 O 2 (

) → 8 CO 2 (

) + 6 H 2 O(

) Tro: Chemistry: A Molecular Approach, 2/e 107 Copyright  2011 Pearson Education, Inc .

Chemical Energy

• • • Burning hydrocarbons releases heat and light energy  Combustion Alkane + oxygen  carbon dioxide + water Larger alkane, more heat released Tro: Chemistry: A Molecular Approach, 2/e 108 Copyright  2011 Pearson Education, Inc .

Other Alkane Reactions

• Substitution  replace H with a halogen atom  initiated by addition of energy in the form of heat or ultraviolet light  to start breaking bonds  generally get multiple products with multiple substitutions Tro: Chemistry: A Molecular Approach, 2/e 109 Copyright  2011 Pearson Education, Inc .

Predict the Products and Balance the Equations

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Other Alkene and Alkyne Reactions: Addition

• • Adding a molecule across the multiple bond Hydrogenation = adding H 2  converts unsaturated molecule to saturated  alkene or alkyne + H 2  → alkane generally requires a catalyst • • Halogenation = adding X 2 Hydrohalogenation = adding HX  HX is polar 

when adding a polar reagent to a double or triple bond, the positive part attaches to the carbon with the most H’s

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Addition Reactions

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Practice — Predict the products

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Aromatic Hydrocarbons

• • Contain benzene ring structure Even though they are often drawn with C=C, they do not behave like alkenes Tro: Chemistry: A Molecular Approach, 2/e 114 Copyright  2011 Pearson Education, Inc .

Resonance Hybrid

• The true structure of benzene is a resonance hybrid of two structures Tro: Chemistry: A Molecular Approach, 2/e 115 Copyright  2011 Pearson Education, Inc .

Naming Monosubstituted Benzene Derivatives

• (name of substituent)benzene  halogen substituent = change ending to “o” • or name of a common derivative Tro: Chemistry: A Molecular Approach, 2/e 116 Copyright  2011 Pearson Education, Inc .

Naming Benzene as a Substituent

• When the benzene ring is not the base name, it is called a

phenyl

group Tro: Chemistry: A Molecular Approach, 2/e 117 Copyright  2011 Pearson Education, Inc .

Naming Disubstituted Benzene Derivatives

• Number the ring starting at attachment for first substituent, then move toward second  order substituents alphabetically  use “di” if both substituents are the same Tro: Chemistry: A Molecular Approach, 2/e 118 Copyright  2011 Pearson Education, Inc .

Naming Disubstituted Benzene Derivatives

• Alternatively, use relative position prefix 

ortho-

= 1,2;

meta-

= 1,3;

para-

= 1,4 2-chlorotoluene

ortho

-chlorotoluene

-chlorotoluene 3-chlorotoluene

meta

-chlorotoluene

-chlorotoluene 4-chlorotoluene

para

-chlorotoluene

-chlorotoluene Tro: Chemistry: A Molecular Approach, 2/e 119 Copyright  2011 Pearson Education, Inc .

Practice – Name the Following

1-chloro-4-fluorobenzene 1,3-dibromobenzene or

meta

-dibromobenzene or

-dibromobenzene Tro: Chemistry: A Molecular Approach, 2/e 120 Copyright  2011 Pearson Education, Inc .

Polycyclic Aromatic Hydrocarbons

• Contain multiple benzene rings fused together  fusing = sharing a common bond Tro: Chemistry: A Molecular Approach, 2/e 121 Copyright  2011 Pearson Education, Inc .

Functional Groups

• • Other organic compounds are hydrocarbons in which functional groups hydrogens have been substituted for A functional group is a group of atoms that show a characteristic influence on the properties of the molecule  generally, the reactions that a compound will perform are determined by what functional groups it has  because the kind of hydrocarbon chain is irrelevant to the reactions, it may be indicated by the general symbol

CH 3 —OH R group functional group Copyright  2011 Pearson Education, Inc .

Tro: Chemistry: A Molecular Approach, 2/e 122

Tro: Chemistry: A Molecular Approach, 2/e 123 Copyright  2011 Pearson Education, Inc .

• • • •

Alcohols

R —OH Ethanol = CH 3 CH 2 OH  grain alcohol = fermentation of sugars in grains   alcoholic beverages  proof number = 2x percentage of alcohol gasohol Isopropyl alcohol = (CH 3 ) 2 CHOH    2-propanol rubbing alcohol poisonous Methanol = CH 3 OH    wood alcohol = thermolysis of wood paint solvent poisonous Copyright  2011 Pearson Education, Inc .

Tro: Chemistry: A Molecular Approach, 2/e 124

Naming Alcohols

• • • • Main chain contains OH Number main chain from end closest to OH Give base name ol ending and place number of C on chain where OH attached in front Name as

hydroxy

group if higher precedence group present 1 2 3 4 5 6 4-ethyl-4-methyl-3-hex-5-enol Tro: Chemistry: A Molecular Approach, 2/e 125 Copyright  2011 Pearson Education, Inc .

Practice – Name the following

1 2 3 4 5 6 3-ethyl-1-hexanol 5 4 3 2 1 1-pent-4ynol Tro: Chemistry: A Molecular Approach, 2/e 126 Copyright  2011 Pearson Education, Inc .

Reactions of Alcohols

Nucleophilic substitution CH 3 ─OH + HCl  CH 3 Cl + H 2 O Acid catalyzed elimination (dehydration) CH 3 ─ CH 2 H 2 SO 4 OH  CH 2 ═CH 2 + H 2 O Tro: Chemistry: A Molecular Approach, 2/e 127 Copyright  2011 Pearson Education, Inc .

Reactions of Alcohols

CH 3 CH 2 OH  Oxidation CH 3 −2 H CHO  CH 3 COOH a common oxidizing agent is Na 2 Cr 2 O 7 Alcohols with very active metals 2 CH 3 ─OH + 2 K  2 CH 3 O − K + + H 2 Tro: Chemistry: A Molecular Approach, 2/e 128 Copyright  2011 Pearson Education, Inc .

Practice − Complete each reaction

Tro: Chemistry: A Molecular Approach, 2/e 129 Copyright  2011 Pearson Education, Inc .

Practice − Complete each reaction

Tro: Chemistry: A Molecular Approach, 2/e 130 Copyright  2011 Pearson Education, Inc .

Aldehydes and Ketones

• • • • • • • Contain the

carbonyl

group Aldehydes = at least 1 side H Ketones = both sides R groups Many aldehydes and ketones have pleasant tastes and aromas Some are pheromones Formaldehyde = H 2 C=O  pungent gas  formalin = a preservative  wood smoke, carcinogenic Acetone = CH 3 C(=O)CH 3  nail-polish remover Tro: Chemistry: A Molecular Approach, 2/e 131 Copyright  2011 Pearson Education, Inc .

Aldehyde Odors and Flavors

• butanal = butter • vanillin = vanilla • benzaldehyde = almonds • cinnamaldehyde = cinnamon Copyright  2011 Pearson Education, Inc .

Tro: Chemistry: A Molecular Approach, 2/e 132

Ketone Odors and Flavors

• acetophenone = pistachio • carvone = spearmint • ionone = raspberries • muscone = musk Copyright  2011 Pearson Education, Inc .

Tro: Chemistry: A Molecular Approach, 2/e 133

Naming Aldehydes and Ketones

• • • • Main chain contains C=O  unless COOH present Number main chain from end closest to C=O For

aldehydes

, give base name al ending  always on C1 For

ketones

, give base name one ending and place number of C on chain where C=O attached in front Tro: Chemistry: A Molecular Approach, 2/e 134 Copyright  2011 Pearson Education, Inc .

Practice – Name the following

5 4 3 2 1 4-methyl-3-hexenal 1 2 3 4 5 6 5-hydroxy-3-isopropyl-4-methyl-2-hexanone Tro: Chemistry: A Molecular Approach, 2/e 135 Copyright  2011 Pearson Education, Inc .

•

Reactions

Aldehydes and ketones are generally synthesized by the oxidation of alcohols • Therefore, reduction of an aldehyde or ketone results in an alcohol • Common reducing agents are H 2 with a Ni catalyst, NaBH 4 , and LiAlH 4 Tro: Chemistry: A Molecular Approach, 2/e 136 Copyright  2011 Pearson Education, Inc .

Carbonyl Group

C=O group is highly polar many reactions involve addition across C=O, with positive part attached to O Tro: Chemistry: A Molecular Approach, 2/e 137 Copyright  2011 Pearson Education, Inc .

Addition to C=O

polar molecules add across the C=O, with the positive part attaching to O d+ d − Tro: Chemistry: A Molecular Approach, 2/e 138 Copyright  2011 Pearson Education, Inc .

Practice − Complete each reaction

Tro: Chemistry: A Molecular Approach, 2/e 139 Copyright  2011 Pearson Education, Inc .

Carboxylic Acids

• • • • • • RCOOH Sour tasting Weak acids Citric acid  found in citrus fruit Ethanoic acid = acetic acid  vinegar Methanoic acid = formic acid  insect bites and stings Copyright  2011 Pearson Education, Inc .

Tro: Chemistry: A Molecular Approach, 2/e 140

Synthesis of Carboxylic Acids

• Made by the oxidation of aldehydes and alcohols Tro: Chemistry: A Molecular Approach, 2/e 141 Copyright  2011 Pearson Education, Inc .

Naming Carboxylic Acids

• • • Carboxylic acid group always on end of main chain  has highest naming precedence of functional groups C of group always C1  position not indicated in name Change ending to

oic acid

Tro: Chemistry: A Molecular Approach, 2/e 142 Copyright  2011 Pearson Education, Inc .

Examples of Naming Carboxylic Acids

Tro: Chemistry: A Molecular Approach, 2/e 143 Copyright  2011 Pearson Education, Inc .

Practice – Name the following

hexanoic acid (aka caproic acid, which causes foot odor) Tro: Chemistry: A Molecular Approach, 2/e 144 2-hydroxy-3-methylbutanoic acid Copyright  2011 Pearson Education, Inc .

Esters

• • • R –COO–R Sweet odor Made by reacting carboxylic acid with an alcohol R a COOH + R b OH  R a COOR b + H 2 O Tro: Chemistry: A Molecular Approach, 2/e 145 Copyright  2011 Pearson Education, Inc .

Naming Esters

• • • • Carboxylic acid group always on end of main chain  unless carboxylic acid group present C of ester group on C1  position not indicated in name Begin name with alkyl group attached to O Name main chain with oate ending Tro: Chemistry: A Molecular Approach, 2/e 146 Copyright  2011 Pearson Education, Inc .

Naming Esters

Tro: Chemistry: A Molecular Approach, 2/e 147 Copyright  2011 Pearson Education, Inc .

Practice – Name the following

isopropyl butanoate Tro: Chemistry: A Molecular Approach, 2/e 148 Copyright  2011 Pearson Education, Inc .

• • •

Condensation Reactions

A condensation reaction is any organic reaction driven by the removal of a small molecule, such as water reaction between 2 carboxylic acid molecules  the reaction is driven by heat R O C OH + H O O C R' R O C O O C R' + HOH Tro: Chemistry: A Molecular Approach, 2/e 149 Copyright  2011 Pearson Education, Inc .

Synthesis of Aspirin (Acetylsalicylic Acid)

Tro: Chemistry: A Molecular Approach, 2/e 150 Copyright  2011 Pearson Education, Inc .

Practice – Complete the reaction

Tro: Chemistry: A Molecular Approach, 2/e 151 Copyright  2011 Pearson Education, Inc .

Ethers

• • • • • R –O–R Ether = diethyl ether = CH 3 CH 2 OCH 2 CH 3  anesthetic Polar molecules Used for solvents To name ethers, name each alkyl group attached to the O, then add the word

ether

Tro: Chemistry: A Molecular Approach, 2/e 152

Practice – Name the following

isopropyl methyl ether Tro: Chemistry: A Molecular Approach, 2/e 153 Copyright  2011 Pearson Education, Inc .

Amines

• • • • • N containing organic molecules Very bad smelling Form when proteins decompose Organic bases Name alkyl groups attached to the N, then add the word

amine

to the end Tro: Chemistry: A Molecular Approach, 2/e 154 Copyright  2011 Pearson Education, Inc .

Practice – Name the following

isopropyl methyl amine Tro: Chemistry: A Molecular Approach, 2/e 155 Copyright  2011 Pearson Education, Inc .

• •

Amines

Many amines are biologically active  dopamine – a neurotransmitter  epinephrine – an adrenal hormone  pyridoxine – vitamin B 6

Alkaloids

are plant products that are alkaline and biologically active  toxic  coniine from hemlock  cocaine from coca leaves  nicotine from tobacco leaves  mescaline from peyote cactus  morphine from opium poppies Copyright  2011 Pearson Education, Inc .

Tro: Chemistry: A Molecular Approach, 2/e 156

Amine Reactions

• • Weak bases  react with strong acids to form ammonium salts RNH 2 + HCl → RNH 3 + Cl − React with carboxylic acids in a condensation reaction to form

amides

RCOOH + H —NHR’  RCONHR’ + H 2 O Tro: Chemistry: A Molecular Approach, 2/e 157 Copyright  2011 Pearson Education, Inc .

Practice – Complete the reaction

Tro: Chemistry: A Molecular Approach, 2/e 158 Copyright  2011 Pearson Education, Inc .

Polymers

Tro: Chemistry: A Molecular Approach, 2/e 159 Copyright  2011 Pearson Education, Inc .

Macromolecules

• • • • • Polymers are very large molecules made by repeated linking together of small molecules  monomers Natural polymers are polymers found in both the living and nonliving environment Modified natural polymers are natural polymers that have been chemically altered Synthetic polymers are polymers made in a lab from one, two, or three small molecules linked in a repeating pattern  plastics, elastomers (rubber), fabrics, adhesives Composites are materials made of polymers mixed with various additives  additives such as graphite, glass, metallic flakes Tro: Chemistry: A Molecular Approach, 2/e 160 Copyright  2011 Pearson Education, Inc .

• • • • • • • •

Natural Polymers

Polysaccharides – polymers made of repeating small sugar molecule units  cellulose (cotton)  starch Proteins – polymers made of repeating amino acid units Nucleic acids (DNA) nucleotide units – polymers made of repeating Natural latex rubber – polyisoprene Shellac – a resin secreted by lac bugs Gutta-percha  – a polyisoprene latex from the sap of the gutta-percha plant used to fill space for root canal Amber, lignin, pine rosin – resins from trees Asphalt – polymeric petroleum Copyright  2011 Pearson Education, Inc .

Tro: Chemistry: A Molecular Approach, 2/e 161

Modified Natural Polymers

• • • • Cellulose acetate – an ester of cellulose and acetic acid  rayon  film Vulcanized rubber – latex rubber hardened by cross linking with sulfur Nitrocellulose  gun cotton – an ester of cellulose with nitric acid  celluloid  ping-pong balls Casein treating cow’s milk with acid  – a polymer of the protein casein made by buttons, mouldings, adhesives Copyright  2011 Pearson Education, Inc .

Tro: Chemistry: A Molecular Approach, 2/e 162

Polymerization

• • • Polymerization is the process of linking the monomer units together There are two processes by which polymerization may proceed –

addition polymerization

and

condensation polymerization

Monomer units may link head-to-tail, or head-to head, or tail-to-tail during polymerization  head-to-tail most common  regular pattern gives stronger attractions between chains than random arrangements Tro: Chemistry: A Molecular Approach, 2/e 163 Copyright  2011 Pearson Education, Inc .

Tro: Chemistry: A Molecular Approach, 2/e 164 Copyright  2011 Pearson Education, Inc .

Addition Polymerization

• • • Monomers add to the growing chain in such a manner that all the atoms in the original monomer wind up in the chain  no other side products formed, no atoms eliminated First monomer must “open” to start reaction  done with heat, or the addition of an

initiator

The process is a chain reaction  each added unit ready to add another Copyright  2011 Pearson Education, Inc .

Tro: Chemistry: A Molecular Approach, 2/e 165

Addition Polymerization of Vinyl Chloride

Tro: Chemistry: A Molecular Approach, 2/e 166 Copyright  2011 Pearson Education, Inc .

Condensation Polymerization

• Monomer units are joined by removing small molecules from the combining units  polyesters, polyamides lose water • • • No initiator needed The process is a chain reaction Each monomer has two reactive ends, so chain can grow in two directions Tro: Chemistry: A Molecular Approach, 2/e 167 Copyright  2011 Pearson Education, Inc .

Condensation Polymerization

Tro: Chemistry: A Molecular Approach, 2/e 168 Copyright  2011 Pearson Education, Inc .

• • •

Plastics

Plastics are polymer materials capable of being molded or shaped.

 Round, hard balls; thin, flexible threads; intricate molds; or flat sheets.

Plastics have molar mass from 10,000 to 1,000,000 amu Many plastics are in the “glass” or amorphous solid state  solid that has semi-fluid characteristics  glass transition temperature states is where an amorphous polymer is converted between rubbery and glassy  plastics do not melt like an ice cube, they rubberize Copyright  2011 Pearson Education, Inc .

Tro: Chemistry: A Molecular Approach, 2/e 169

Characteristics of Plastics

• • • • • • • • • Transparent or translucent Chemical resistance Thermal and electrical insulators Low density Varying strengths  Kevlar Mold or extrude Elasticity  regain original shape if quick stress applied Foamed Tend to soften when heated  rather than quickly melt Copyright  2011 Pearson Education, Inc .

Tro: Chemistry: A Molecular Approach, 2/e 170

Synthetic Polymers

Polyethylene HDPE LDPE Polypropylene Polyvinyl chloride Polyesters polyethylene terephthalate Polyamides nylon Kevlar Tro: Chemistry: A Molecular Approach, 2/e 171 Copyright  2011 Pearson Education, Inc .

Polyethylene Terephthalate (PET)

• Condensation copolymer of ethylene glycol + terephthalic acid  A polyester • • • • • Transparent High-impact strength Nonreactive with acid and atmospheric gases Doesn’t stretch Used for soda bottles, Dacron  , Mylar  1 Copyright  2011 Pearson Education, Inc .

Tro: Chemistry: A Molecular Approach, 2/e 172

High Density Polyethylene (HDPE)

• • • • • • • • • • • Addition polymer with linear chains Opaque Denser than LDPE Mechanically stronger than LDPE More rigid than LDPE  more crystalline Higher heat resistance than LDPE Nonreactive to acids and bases Absorbs oils and softens Oxidizes on exposure to air and sunlight Subject to cracking Used for containers, caps, bullet-proof vests, synthetic ice 2 Tro: Chemistry: A Molecular Approach, 2/e 173 Copyright  2011 Pearson Education, Inc .

Poly Vinyl Chloride (PVC)

• • • • • • • • • Addition polymer Transparent to opaque Flame resistant Low heat resistance Good chemical resistance High-impact strength Quite rigid Many additives used to modify properties  plasticizer adds flexibility Used in food wrap, pipes, flooring and wall covering, toys, hoses, auto trim, squeeze tubes, and appliance housings 3 Copyright  2011 Pearson Education, Inc .

Tro: Chemistry: A Molecular Approach, 2/e 174

Low Density Polyethylene (LDPE)

• • • Addition polymer with branched chains Lower density, strength, heat resistance (100 –125 °C), and rigidity than HDPE Used in food, trash, and grocery bags as well as in electrical wire insulation 4 Copyright  2011 Pearson Education, Inc .

Tro: Chemistry: A Molecular Approach, 2/e 175

• • • • • • • • Addition polymer Opaque

Polypropylene (PP)

High stretching strength High heat resistance (170 °C) Excellent chemical resistance Flexed almost indefinitely without tearing Smooth surface with high luster Used in carpets and upholstery; chemical resistant pipes, containers, and tanks; margarine tubs; and medicine bottles 5 Copyright  2011 Pearson Education, Inc .

Tro: Chemistry: A Molecular Approach, 2/e 176

Polystyrene (PS)

• • • • • • • Addition polymer Low-impact resistance Fair strength and stiffness Poor chemical resistance Transparent, glassy, sparkling clarity Moderate heat resistance (90 °C) Used in model cars, computer housing, Styrofoam  , clear drinking cups, and hard-molded parts 6 Copyright  2011 Pearson Education, Inc .

Tro: Chemistry: A Molecular Approach, 2/e 177

Acrylics

• • • • • • • • • Polymethylmethacrylate, PMMA Low-impact resistance Good strength and stiffness Excellent transparency Excellent scratch resistance Moderate heat resistance Addition polymer of methyl methacrylate Uses include Plexiglas  , Lucite  , lighting fixtures, lenses, fiber optic filament, appliance faceplates, decorative signs, and paints Also, reduces oil viscosity Copyright  2011 Pearson Education, Inc .

Tro: Chemistry: A Molecular Approach, 2/e 178

• • • • • • • •

Polycarbonates (PC)

Excellent physical properties Excellent toughness Very good heat resistance Fair chemical resistance Transparent Condensation copolymer of Bisphenol A and phosgene Lexan  , Calibre  , Makrolon  , Panlite  Used in equipment housings, exterior auto parts, outdoor light fixtures, non-auto vehicle windows, structural parts, medical supply parts, scratch-resistant coatings, eye wear, bullet-proof glass, and DVDs Copyright  2011 Pearson Education, Inc .

Tro: Chemistry: A Molecular Approach, 2/e 179

Nylon

• • • • • Condensation copolymer of a diamine with a diacid  polyamides  nylon 6,6  made by condensing 1,6 –hexandiamine, H 2 N –(CH 2 ) 6 –NH 2 , with hexandioic acid, HOOC –(CH 2 ) 4 –COOH Good physical properties  affected by moisture Very good heat resistance Excellent chemical resistance Excellent wear resistance Tro: Chemistry: A Molecular Approach, 2/e 180 Copyright  2011 Pearson Education, Inc .

Tro: Chemistry: A Molecular Approach, 2/e 181 Copyright  2011 Pearson Education, Inc .