Chemistry: A Molecular Approach

, 1 st Ed.

Nivaldo Tro

Chapter 20 Organic Chemistry

Roy Kennedy Massachusetts Bay Community College Wellesley Hills, MA 2008, Prentice Hall

Structure Determines Properties

• Organic compounds all contain carbon  CO, CO 2 , carbonates and carbides are inorganic  other common elements are H, O, N, (P, S) • Carbon has versatile bonding patterns  chains, rings, multiple bonds  chain length nearly limitless • Carbon compounds generally covalent  molecular; gases, liquids, or low melting solids; varying solubilities; nonconductive in liquid • C - C bonds unreactive (very stable) Tro, Chemistry: A Molecular Approach 2

Bond Energies and Reactivities C-C S-S Si-Si N-N O-O 347 kJ 214 kJ 213 kJ 159 kJ

H 3 C-CH

HS-SH H

3

Si-SiH

3 3 NONREACTIVE IN AIR EXTREMELY REACTIVE SPONTANEOUS BURNS IN AIR H 2 N-NH 2 EXTREMELY REACTIVE

138 kJ HO-OH

REACTIVE Tro, Chemistry: A Molecular Approach 3

Allotropes of Carbon - Diamond

Tro, Chemistry: A Molecular Approach 4

Allotropes of Carbon - Graphite

Tro, Chemistry: A Molecular Approach 5

Carbon Bonding

• • mainly forms covalent bonds C is most stable when it has 4 single covalent bonds, but does form double and triple bonds  C=C and C≡C are more reactive than C−C  C with 4 single bonds is tetrahedral,  2 singles and 1 double is trigonal planar  2 doubles or 1 triple and 1 single is linear Tro, Chemistry: A Molecular Approach 6

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 Tro, Chemistry: A Molecular Approach 7

Number of C atoms

Uses of Hydrocarbons

State Major Uses 8

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 Tro, Chemistry: A Molecular Approach 9

Unsaturated Hydrocarbons

• • • unsaturated hydrocarbons have one of 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 2 more H for each additional unsaturation unsaturated aliphatic hydrocarbons that contain C  C are called

alkynes

 the general formula of a monounsaturated chain alkyne is C n H 2n-2  remove 4 more H for each additional unsaturation Tro, Chemistry: A Molecular Approach 10

H 3 C

Unsaturated Hydrocarbons

H C H 3 C C H C CH 3 C Tro, Chemistry: A Molecular Approach H 3 C CH 3 CH C 3 C CH 3 H 2 C H 2 C H 2 CH 3 H 2 C C CH 2 C H C H C CH 2 C H 2 H 2 C C H 2 H 2 C C C H 2 H C 2 H 2 C CH 2 CH 2 H C 2 CH 2 C H 2 11

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 12

H 3 C H 3 C C C C H C CH 3 CH 3 H 3 C H 2 3 C 2 C C H 2 C C H 2 3 CH 2 3 C H 2 H C C 2 C H 2 H C 2 H C H C 2 2 C C H 2 CH 2 2 H 2 C CH 2 C H CH 2 2 Tro, Chemistry: A Molecular Approach 13

Tro, Chemistry: A Molecular Approach 14

• • •

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 15

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 1 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 16

Line-Angle 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 17

Formulas

Tro, Chemistry: A Molecular Approach 18

C 2 H 6 CH 4 CH 3 CH 3

Formulas

H H H C H H H C H H C H H C 3 H 8 C 4 H 10 C 4 H 10 CH 3 CH 2 CH 3 CH 3 CH 2 CH 2 CH 3 C(CH 3 ) 2 Tro, Chemistry: A Molecular Approach H H H C H H C H H C H H C H H C H H C H H H C H H H H C H H H C C H H C H H H 19

• • •

Isomers

Isomerism

= different molecules with the same molecular formula

Structural Isomers

attachment = different pattern of atom  Constitutional Isomers

Stereoisomers

= same atom attachments, different spatial orientation Tro, Chemistry: A Molecular Approach 20

H H C H H H H H H H H C H C C H H H H H H Butane, BP = 0 H °C H C

Structural Isomers of C

4

H

10 H H H H H C H H H H Isobutane, BP = -12 H H H °C C C H H C H H C H C H C C C H H H C H H H H H H C H H C H H H H Tro, Chemistry: A Molecular Approach 21

Rotation about a bond is not isomerism

Tro, Chemistry: A Molecular Approach 22

Possible Structural Isomers

Carbon Content 4 5 6 7 8 9 10

Tro, Chemistry: A Molecular Approach

Molecular Formula C 4 H 10 C 5 H 12 C 6 H 14 C 7 H 16 C 8 H 18 C 9 H 20 C 10 H 22 Possible Isomers 2 3 5 9 18 35 75

23

Ex 20.1 – Write the structural formula and carbon skeleton formula for C 6 H 14 start by connecting the carbons in a line C C C C C C C C C C C C C determine the C skeleton of the other isomers Tro, Chemistry: A Molecular Approach 24

Ex 20.1 – Write the structural formula and carbon skeleton formula for C 6 H 14 H H H H H H fill in the H to give each C 4 bonds H H H H H H H H H H H H H H H H H H H H H H H H H C C H H H H H H C C H H C C H H H H H H H H H H H H H H C C H H H H H H H H C C C C C C C C H H C C H H C H C H H H H

Ex 20.1 – Write the structural formula and carbon skeleton formula for C 6 H 14 H H H H H H convert each to a carbon skeleton formula – each bend and the ends represent C atoms H H C H H H C C H H H H C H H H C H H C H H H C H H C H H C H H C H C H C H H H C H H C H H C H C H H H H C H C C H H C H H H C H C H H C H H H C C C C H H H C H H H H H C H H H C H H H H

Stereoisomers

• •

stereoisomers

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

optical isomers

are molecules that are nonsuperimposable mirror images of each other

geometric isomers

are stereoisomers that are not optical isomers Tro, Chemistry: A Molecular Approach 27

Nonsuperimposable Mirror Images

mirror image cannot be rotated so all its atoms align with the same atoms of the original molecule Tro, Chemistry: A Molecular Approach 28

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

Tro, Chemistry: A Molecular Approach 29

Optical Isomers of 3-methylhexane

Tro, Chemistry: A Molecular Approach 30

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 31

• •

Optical Activity

a pair of enantiomers have all the same physical properties except one – the direction they rotate the plane of plane polarized light  each will rotate the plane the same amount, but in opposite directions   dextrorotatory = rotate to the right levorotatory = rotate to the left an equimolar mixture of the pair is called a

racemic mixture

 rotations cancel, so no net rotation Tro, Chemistry: A Molecular Approach 32

• •

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 33

Alkanes

• • • • • aka paraffins aliphatic general formula C

n

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  chains may be straight or branched • saturated • branched or unbranched Tro, Chemistry: A Molecular Approach 34

Name Methane Ethane Propane Butane Pentane Hexane Lewis Structure

H H C H H H H H C C H H H H H H H C C C H H H H H H H H H C C C C H H H H H H H H H H H H C C C C C H H H H H H H H H H H H C H C H C H C H C C H H H Tro, Chemistry: A Molecular Approach CH CH 3

Formula

CH CH 3 CH CH 3 2 CH 3 CH CH 2 CH CH 4 2 2 3 CH 2 CH CH 3 2 3 CH 3 CH 3 CH 2 CH 2 CH 2 CH 2 CH 3

Boiling Point

-162°C -89°C -42°C 0°C 36°C 69°C 35

Naming

• each name consists of 3 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 – ane, ene, yne  certain functional groups Tro, Chemistry: A Molecular Approach 36

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 37

H H C H H H H H C C H H H H H C C C H H H

Alkyl Groups

CH3-, METHYL CH3CH2-, ETHYL CH3CH2CH2-, PROPYL H H CH3 C C H H Tro, Chemistry: A Molecular Approach (CH3)2CH-, ISOPROPYL 38

H

More Alkyl Groups

H H H H C C C C H H H H CH3CH2CH2CH2-, n-BUTYL H H H CH3 C C C H H H H H C H CH3 C H C H H H3C CH3 C CH3 Tro, Chemistry: A Molecular Approach CH3CH2(CH3)CH-,

sec

-BUTYL (CH3)2CHCH2-, ISOBUTYL (CH3)3C-, BUTYL 39

Examples of Naming Alkanes

2-methylpentane H H H H H H C C C C C H H CH 3 H H H 3-isopropyl-2,2-dimethylhexane Tro, Chemistry: A Molecular Approach H CH 3 H H H H H C C C C C C H H CH 3 CH H H H CH 3 CH 3 40

Example – Name the alkane

CH 3 CHCH 2 CHCH 3 1) CH 3 CH 3 find the longest continuous C chain and use it to determine the base name CH 3 CHCH 2 CHCH 3 CH 3 CH 3 since the longest chain has 5 C the base name is pentane Tro, Chemistry: A Molecular Approach 41

Example – Name the alkane

CH 3 CHCH 2 CHCH 3 2) CH 3 CH 3 identify the substituent branches CH 3 CHCH 2 CHCH 3 CH 3 CH 3 there are 2 substituents both are 1 C chains, called methyl Tro, Chemistry: A Molecular Approach 42

Example – Name the alkane

3) number the chain from the end closest to a  substituent branch if first substituents equidistant from end, go to next substituent in then assign numbers to each substituent based on the number of the main chain C it’s attached to 1 2 3 4 5 CH 3 CHCH 2 CHCH 3 both substituents are equidistant from the end CH 3 CH 2 4 3 Tro, Chemistry: A Molecular Approach 43

Example – Name the alkane

4) 1) write the name in the following order substituent

number

followed by dash of first alphabetical substituent 2) 3) 4) substituent

name

by dash  of first alphabetical substituent followed if it’s the last substituent listed, no dash  use prefixes to indicate multiple identical substituents repeat for other substituents alphabetically name of main chain CH 3 CHCH 2 CHCH 3 2,4 – dimethyl pentane CH 3 CH 3 2 4 Tro, Chemistry: A Molecular Approach 44

Practice – Name the Following

CH 3 CH 3 CHCHCH 2 CH 3 CH 2 CH 3 Tro, Chemistry: A Molecular Approach 45

Practice – Name the Following

CH 3 CH 3 CHCHCH 2 CH 3 CH 2 CH 3 3-ethyl-2-methylpentane Tro, Chemistry: A Molecular Approach 46

Drawing Structural Formulas

4-ethyl-2-methylhexane • • • 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 C C C C C C 1 2 3 4 5 6 C C C C C C C C C CH 3 CH CH 2 CH CH 2 CH 3 H 2 C CH 3 CH 3 Tro, Chemistry: A Molecular Approach 47

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

Tro, Chemistry: A Molecular Approach 48

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

CH 3 CH CH 2 CH CH 2 CH 2 CH 3 CH 3 HC CH 3 CH 3 Tro, Chemistry: A Molecular Approach 49

Alkenes

• • • • • • also known as olefins aliphatic, unsaturated  C=C double bonds formula for one double bond = C

n

H

2n

 subtract 2 H from alkane for each double bond trigonal shape around C  flat much more reactive than alkanes polyunsaturated = many double bonds Tro, Chemistry: A Molecular Approach 50

Tro, Chemistry: A Molecular Approach 51

ethene = ethylene

Alkenes

H H C H C H propene H H C C H CH 3 Tro, Chemistry: A Molecular Approach 52

Name

ethene propene 1-butene 1-pentene 1-hexene 1-heptene 1-octene 1-nonene 1-decene

Physical Properties of Alkenes

Formula

CH 2 =CH 2 CH 2 =CHCH 3 CH 2 =CHCH 2 CH 3 CH 2 =CH(CH 2 ) 2 CH 3 CH 2 =CH(CH 2 ) 3 CH 3 CH 2 =CH(CH 2 ) 4 CH 3 CH 2 =CH(CH 2 ) 5 CH 3 CH 2 =CH(CH 2 ) 6 CH 3 CH 2 =CH(CH 2 ) 7 CH 3

Molar Mass BP, °C Density, g/cm 3

28 -104 0.52

42 56 -47 -6 0.59

0.59

70 84 98 112 126 140 30 64 93 122 146 171 0.64

0.68

0.70

0.72

0.73

0.74

Tro, Chemistry: A Molecular Approach 53

Alkynes

• • • • also known as acetylenes aliphatic, unsaturated C  C triple bond formula for one triple bond = C

n

H

2n-2

 subtract 4 H from alkane for each triple bond • • linear shape more reactive than alkenes Tro, Chemistry: A Molecular Approach 54

Tro, Chemistry: A Molecular Approach 55

Alkynes

ethyne = acetylene propyne H C C H H C C CH 3 Tro, Chemistry: A Molecular Approach 56

Name

ethyne propyne 1-butyne 1-pentyne 1-hexyne 1-heptyne 1-octyne 1-nonyne 1-decyne

Physical Properties of Alkynes

Formula

CH  CH CH  CCH 3 CH  CCH 2 CH 3 CH  C(CH 2 ) 2 CH 3 CH  C(CH 2 ) 3 CH 3 CH  C(CH 2 ) 4 CH 3 CH  C(CH 2 ) 5 CH 3 CH  C(CH 2 ) 6 CH 3 CH  C(CH 2 ) 7 CH 3

Molar Mass BP, °C Density, g/cm 3

28 -104 0.52

42 -47 0.59

56 70 84 -6 30 64 0.59

0.64

0.68

98 112 126 140 93 122 146 171 0.70

0.72

0.73

0.74

Tro, Chemistry: A Molecular Approach 57

Naming Alkenes and Alkynes

• change suffix on main name from

ane

to -

ene

for base name of alkene, or to

yne

for the 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 58

Examples of Naming Alkenes

2-methyl-1-pentene H H H H C C C C C H H CH 3 H H H H CH 3 H H 3-isopropyl-2,2-dimethyl-3-hexene H C C C C C C H Tro, Chemistry: A Molecular Approach H CH 3 CH H H H CH 3 CH 3 59

Examples of Naming Alkynes

3-methyl-1-pentyne H H H H C C C C C H CH 3 H H H CH 3 H H 4-isopropyl-5,5-dimethyl-2-hexyne H C C C C C C H H CH 3 CH H CH 3 CH 3 Tro, Chemistry: A Molecular Approach 60

Name the Alkene

1) find the longest, continuous C chain that contains the double bond and use it to determine the base name H 3 C CH H 2 C H 2 C C CH 3 CH 3 CH CH 3 since the longest chain with the double bond has 6 C the base name is hexene Tro, Chemistry: A Molecular Approach 61

Name the Alkene

2) identify the substituent branches H 3 C CH H 2 C H 2 C C CH 3 CH 3 CH CH 3 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 62

Name the Alkene

3) number the chain from the end closest to the double bond then assign numbers to each substituent based on the number of the main chain C it’s attached to 4 H 3 C CH 4 H 2 C 5 3 H 2 C C 3 CH 3 6 CH 2 3 CH CH 3 1 Tro, Chemistry: A Molecular Approach 63

Name the Alkene

4) 1) 2) write the name in the following order substituent number of first alphabetical substituent – substituent name of first alphabetical substituent –  use prefixes to indicate multiple identical substituents repeat for other substituents 3) number of first C in double bond – name of main chain 4 H 3 C CH 4 H 2 C 5 3 H 2 C C 3 CH 3 6 CH 3 CH CH 3 2 Tro, Chemistry: A Molecular Approach 1 3–ethyl– 4–methyl–2–hexene 64

Practice – Name the Following

H 3 C C H 2 C CH 3 C CH 2 CH 3 CH 3 Tro, Chemistry: A Molecular Approach 65

Practice – Name the Following

H 3 C 3 C H 2 C 2 CH 3 C 4 CH 3 1 CH 2 5 CH 6 3,4-dimethyl-3-hexene 3 Tro, Chemistry: A Molecular Approach 66

Name the Alkyne

1) find the longest, continuous C chain that contains the triple bond and use it to determine the base name CH 3 CH CH 2 CH CH 3 HC C CH 3 CH 3 C CH 3 since the longest chain with the triple bond has 7 C the base name is heptyne Tro, Chemistry: A Molecular Approach 67

Name the Alkyne

2) identify the substituent branches CH 3 CH CH 2 CH CH 3 C HC CH 3 CH 3 C CH there are 2 substituents one is a 1 C chain, called methyl the other one is called isopropyl 3 Tro, Chemistry: A Molecular Approach 68

Name the Alkyne

3) number the chain from the end closest to the triple bond then assign numbers to each substituent based on the number of the main chain C it’s attached to CH 7 3 CH 6 6 CH 3 CH 5 2 CH 4 C 3 HC 4 CH 3 CH 3 C 2 CH 1 3 Tro, Chemistry: A Molecular Approach 69

Name the Alkyne

4) 1) 2) write the name in the following order substituent number of first alphabetical substituent – substituent name of first alphabetical substituent –  use prefixes to indicate multiple identical substituents repeat for other substituents 3) number of first C in double bond – name of main chain CH 7 3 CH 6 6 CH 3 CH 5 2 CH 4 C 3 C 2 CH 1 3 HC 4 CH 3 CH 3 4–isopropyl–6–methyl–2–heptyne Tro, Chemistry: A Molecular Approach 70

Practice – Name the Following H

3

C CH

3

C C CH

2

CH

3

CH

Tro, Chemistry: A Molecular Approach 71

Practice – Name the Following CH

3

H

3

C C

3

C

2

CH

2

CH

3 4 5

CH

1 3,3-dimethyl-1-pentyne Tro, Chemistry: A Molecular Approach 72

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 this is often called

cis-trans isomerism

when groups on the doubly bonded carbons are cis, they are on the same side when groups on the doubly bonded carbons are trans, they are on opposite sides Tro, Chemistry: A Molecular Approach 73

Free Rotation Around C─C

Tro, Chemistry: A Molecular Approach 74

Cis-Trans Isomerism

Tro, Chemistry: A Molecular Approach 75

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 (

g

) + 13 O 2 (

g

) → 8 CO 2 (

g

) + 10 H 2 O(

g

) CH 3 CH=CHCH 3 (

g

) + 6 O 2 (

g

) → 4 CO 2 (

g

) + 4 H 2 O(

g

) 2 CH 3 C  CCH 3 (

g

) + 11 O 2 (

g

) → 8 CO 2 (

g

) + 6 H 2 O(

g

) Tro, Chemistry: A Molecular Approach 76

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 H H C H H C H H + Cl Cl heat or UV light H H C H Cl C H H Tro, Chemistry: A Molecular Approach 77

Other Alkene and Alkyne Reactions

• Addition reactions  adding a molecule across the multiple bond • Hydrogenation = adding H 2  converts unsaturated molecule to saturated  alkene or alkyne + H 2 → alkane • • 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

78

H H C C

Addition Reactions

H

+

CH 3 3 3  + + H-Cl 2 2  H H H C C H CH 3 3 Cl Tro, Chemistry: A Molecular Approach 79

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 80

Resonance Hybrid

• the true structure of benzene is a resonance hybrid of two structures Tro, Chemistry: A Molecular Approach 81

•

Naming Monosubstituted Benzene Derivatives

(name of substituent)benzene  halogen substituent = change ending to “o” F CH 2 CH 2 CH 3 fluorobenzene propylbenzene • or name of a common derivative CH 3 NH 2 OH HC CH 2 toluene Tro, Chemistry: A Molecular Approach aniline phenol styrene 82

Naming Benzene as a Substituent

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

phenyl

group H 2 C CH CH 2 CH CH 2 4-phenyl-1-hexene CH 3 Tro, Chemistry: A Molecular Approach 83

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 the same F 3 2 1 CH 3 2 CH 3 1 Br 1-bromo-3-fluorobenzene 1,2-dimethylbenzene Tro, Chemistry: A Molecular Approach 84

Naming Disubstituted Benzene Derivatives

• alternatively, use relative position prefix 

ortho-

= 1,2;

meta-

= 1,3;

para-

= 1,4 CH 3 CH 3 CH 3 Cl Cl 2-chlorotoluene

ortho

-chlorotoluene

o

-chlorotoluene Tro, Chemistry: A Molecular Approach 3-chlorotoluene

meta

-chlorotoluene

m

-chlorotoluene Cl 4-chlorotoluene

para

-chlorotoluene

p

-chlorotoluene 85

Practice – Name the Following

F Br Br Cl Tro, Chemistry: A Molecular Approach 86

Practice – Name the Following

F Br Br Cl 1-chloro-4-fluorobenzene 1,3-dibromobenzene or

meta

-dibromobenzene or

m

-dibromobenzene Tro, Chemistry: A Molecular Approach 87

Polycyclic Aromatic Hydrocarbons

• contain multiple benzene rings fused together  fusing = sharing a common bond Tro, Chemistry: A Molecular Approach 88

Reactions of Aromatic Hydrocarbons

• most commonly, aromatic hydrocarbons undergo substitution reactions – replacing H with another atom or group Tro, Chemistry: A Molecular Approach 89

Functional Groups

• • other organic compounds are hydrocarbons in which functional groups have been substituted for hydrogens 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  since the kind of hydrocarbon chain is irrelevant to the reactions, it may be indicated by the general symbol

R

CH 3 —OH R group functional group Tro, Chemistry: A Molecular Approach 90

91

Alcohols

• • R-OH ethanol = CH 3 CH 2 OH  grain alcohol = fermentation of sugars  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 Tro, Chemistry: A Molecular Approach 92

Naming Alcohols

• • • • main chain contain 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 present group if other higher precedence CH 3 2 CH 2 3 OH CH 4 CH 3 C 5 CH CH 2 CH 2 CH 3 4-ethyl-4-methyl-3-hex-5-enol Tro, Chemistry: A Molecular Approach 93

CH 3

Reactions of Alcohols

Nucleophilic Substitution OH + HCl  CH 3 Cl + H 2 O Acid Catalyzed Elimination (Dehydration) CH 3 CH 2 OH H 2  4 CH 2 CH 2 + H 2 O CH 3 CH 2 OH  Oxidation CH 3 CHO  CH 3 COOH CH 3 with Reactive Metals OH + Na  CH 3 O − Na + + ½ H 2 Tro, Chemistry: A Molecular Approach 94

• • • • • • •

Aldehydes and Ketones

contain the

carbonyl

group O aldehydes = at least 1 side H ketones = both sides R groups C 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 formaldehyde acetone Tro, Chemistry: A Molecular Approach 95

•

Aldehyde Odors and Flavors

butanal = butter O H C O CH 2 CH 2 CH 3 O • vanillin = vanilla HO H HO • benzaldehyde = almonds O H C • cinnamaldehyde = cinnamon O H C C C H H 96

Ketone Odors and Flavors

• • • • acetophenone = pistachio O C H 3 C carvone = spearmint H 3 C O C CH 2 CH 3 ionone = raspberries H 3 C CH 3 O C H H C C CH 3 CH 3 muscone = musk O CH 3 97

Reactions

• aldehydes and ketones are generally synthesized by the oxidation of alcohols • therefore, reduction of an aldehyde or ketone results in an alcohol Tro, Chemistry: A Molecular Approach 98

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 99

Addition to C=O

Tro, Chemistry: A Molecular Approach 100

• • • • • •

Carboxylic Acids

O RCOOH CH 2 C OH sour tasting weak acids HO O C C OH citric acid  found in citrus fruit CH 2 C O OH ethanoic acid = acetic acid  vinegar CH 3 O C methanoic acid = formic acid  insect bites and stings H OH O C OH Tro, Chemistry: A Molecular Approach 101

Carboxylic Acids

• • • • made by the oxidation of aldehydes and alcohols  OH on the end of the chain O C H always on main chain benzaldehyde  has highest precedence OH C of group always C1  position not indicated in name H 3 C CH 2 ethanol change ending to

oic acid

oxidation oxidation O C OH benzoic acid O H 3 C C OH ethanoic acid Tro, Chemistry: A Molecular Approach 102

Naming Carboxylic Acids

Tro, Chemistry: A Molecular Approach 103

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 name alkyl group from alcohol, then acid name with

oate

ending  precedence over carbonyls, but not carboxylic acid  number from end with ester group methyl butanoate O C OH O C O aspirin CH 3 104 Tro, Chemistry: A Molecular Approach

Naming Esters

Tro, Chemistry: A Molecular Approach 105

• • •

Condensation Reactions

a condensation reaction is any organic reaction driven by the removal of a small molecule, like water R O C OH + H O O C R' Tro, Chemistry: A Molecular Approach R O C O O C R' + HOH 106

Synthesis of Aspirin (Acetylsalicylic Acid)

Tro, Chemistry: A Molecular Approach 107

Ethers

• • • R– O – R ether = diethyl ether = CH 3 CH 2 OCH 2 CH 3  anesthetic to name ethers, name each alkyl group attached to the O, then add the word

ether

to the end

diethyl ether

Tro, Chemistry: A Molecular Approach 108

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 NH 2 H 3 C NH H 3 C CH ethylamine 2 H 3 C CH 2 ethylmethylamine Tro, Chemistry: A Molecular Approach H 2 NCH 2 CH 2 CH 2 CH 2 NH 2 putrescine H 2 NCH 2 CH 2 CH 2 CH 2 CH 2 NH 2 cadaverine 109

• •

Amines

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

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 N CH 2 CH 2 NH 2 dopamine N CH 3 nicotine Tro, Chemistry: A Molecular Approach 110

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 + HNHR’  RCONHR’ + H 2 O Tro, Chemistry: A Molecular Approach 111

Macromolecules

• • • • • polymers are very large molecules made by repeated linking together of small molecules  monomers natural modified natural polymers synthetic  plastics, elastomers (rubber), fabrics, adhesives composites  additives such as graphite, glass, metallic flakes Tro, Chemistry: A Molecular Approach 112

Natural Polymers

• • • • • • • polysaccharides  cellulose (cotton)  starch proteins nucleic acids (DNA) natural latex rubber, etc.

shellac amber, lignin, pine rosin asphalt, tar Tro, Chemistry: A Molecular Approach 113

Modified Natural Polymers

• • • • • • Cellulose Acetate  Rayon  film Vulcanized Rubber Gun Cotton Celluloid  ping-pong balls Gutta Percha  fill space for root canal Casein  buttons, mouldings, adhesives Tro, Chemistry: A Molecular Approach 114

Polymerization

• • • the process of linking the monomer units together two processes are addition polymerization and condensation polymerization monomers may link head-to-tail, or head-to-head, or tail-to-tail  head-to-tail most common  regular pattern gives stronger attractions between chains than random arrangements Tro, Chemistry: A Molecular Approach 115

H H H H H C C C C Cl H Cl H Head Tail Head Tail H H C H C H C H C H Tail Cl Cl H Head Head Tail

Head-to-Tail Head-to-Head, Tail-to-Tail

116

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 addition of an

initiator

chain reaction  each added unit ready to add another Tro, Chemistry: A Molecular Approach 117

initiator

Addition Polymerization

etc.

H H H H Cl H C H C C Cl C H H H H + Cl initiator H C C H H C Cl H C Cl H C H H C Cl H C + H H Cl C C H H H C • H H H H C Cl H C H C H Cl H C • H H C Cl H C H H C Cl H C H H C Cl H C • H

Condensation Polymerization

• monomer units are joined by removing small molecules from the combining units  polyesters, polyamides lose water • • • no initiator needed chain reaction each monomer has two reactive ends, so chain can grow in two directions Tro, Chemistry: A Molecular Approach 119

Condensation Polymerization

HO O C + + O C OH + H O CH2 CH2 OH H O O C Tro, Chemistry: A Molecular Approach O C O CH2 CH2 OH + H 2 O 120

• • • • • •

Nylon

polyamides good physical properties  affected by moisture very good heat resistance excellent chemical resistance excellent wear resistance 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

O O HN (CH2)6 NH C

Tro, Chemistry: A Molecular Approach

(CH2)4 C

121

Tro, Chemistry: A Molecular Approach 122