Bài soạn Chapter 20 Organic Chemistry

Structure Determines Properties• Organic compounds all contain carbon  CO, CO2 , carbonates and carbides are inorganic  other common elements are H, O, N, P, S • Carbon has versatile b

Overview

Structure Determines Properties

• Organic compounds all contain carbon

 CO, CO2 , 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)

Overview

• Carbon uses sp3, sp2, and sp

hybridization in forming the four bonds per carbon atom common to almost all carbon compounds

• With sp hybridization, there are two (2)

 bonds and 2  bonds.

• With sp2 hybridization there is one (1)

 bond and 3  bonds.

Chemistry, Julia Burdge, 2 nd e., McGraw Hill.

Why Carbon

chemistry is the making of carbon-carbon bonds, C-X, C-O, C-N, and C-S bonds to make new molecules

Inorganic molecules like CO, and

CO 3 -2 are not considered organic molecules.

Chemistry, Julia Burdge, 2 nd e., McGraw Hill.

Bond Energies and Reactivities

Allotropes of Carbon - Diamond

Chemistry, Julia Burdge, 2 nd e., McGraw Hill.

Allotropes of Carbon - Graphite

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

Chemistry, Julia Burdge, 2 nd e., McGraw Hill.

 saturated or unsaturated aliphatics

 saturated = alkanes, unsaturated = alkenes or alkynes

 may be chains or rings

 chains may be straight or branched

Uses of Hydrocarbons

Number of

1-4 gas heating and cooking fuel

5-7 (low boiling)liquids, solvents, gasoline

12-24 liquids jet fuel; camp stove fuel

18-50 (high boiling)liquids, diesel fuel, lubricants,

heating oil 50+ solids petroleum jelly, paraffin wax

1-4 gas heating and cooking fuel

5-7 (low boiling)liquids, solvents, gasoline

12-24 liquids jet fuel; camp stove fuel

18-50 (high boiling)liquids, diesel fuel, lubricants,

heating oil 50+ solids petroleum jelly, paraffin wax

Saturated Hydrocarbons

bonds

it is saturated with hydrogens

alkanes

Tro, Chemistry: A Molecular Approach 14

 the general formula of a monounsaturated chain alkene is CnH2n

 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

CnH2n-2

 remove 4 more H for each additional unsaturation

CH2 H H2C

C C C

H2C

H2C

H2C

Tro, Chemistry: A Molecular Approach 16

Aromatic Hydrocarbons

they do not behave like alkenes

H C H

H C

CH2C

H2

C H C

H2 H2C

CH2C

H

C C C

H2C

H2C

H2C

Tro, Chemistry: A Molecular Approach 18

• 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 20

Condensed Structural Formulas

 central atom with attached atoms

 use to determine position of multiple bonds

group attached to same previous central

atom

 unless () group listed first in which case

attached to next central atom

Line-Angle Formulas

atom

included on functional groups

double line is double bond, triple line is triple bond

Tro, Chemistry: A Molecular Approach 22

Formulas

H H H H

C2H6 CH3CH3 C

H C H H

H H H

C3H8 CH3CH2CH3 C

H C H H

H C H

H H H

C4H10 CH3CH2CH2CH3 C

H C H H

H C H

H C H

H H H

C H C(CH )

H H H

Tro, Chemistry: A Molecular Approach 26

Structural Isomers of C4H10

Butane, BP = 0°C Isobutane, BP = -12°C

C C C C

H H

H H

H

C H C

C

H

Rotation about a bond is not isomerism

Tro, Chemistry: A Molecular Approach 28

Possible Structural Isomers

Carbon Content

Molecular Formula

Possible Isomers

Ex 20.1 – Write the structural formula and carbon

skeleton formula for C6H14

H H H

H

C C C C C

C H H

H H H

H

H H H

H

H H

H H

C C C C C C H

Ex 20.1 – Write the structural formula and carbon

skeleton formula for C6H14

H

H H

C H

H H

C C C C C C

C C C C C C

C C C C C

C

C C C C C

H H

H H

H

H H H

H H H

H

C C C C C

C H H

H H H

H

H H H

H

H H

H H

C C C C C C H

Ex 20.1 – Write the structural formula and carbon

skeleton formula for C6H14

H H H

C H

H H

H H

H

Tro, Chemistry: A Molecular Approach 32

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

Nonsuperimposable Mirror Images

mirror image cannot be rotated so all its atoms align

Tro, Chemistry: A Molecular Approach 34

Chirality

a chiral center

Optical Isomers of 3-methylhexane

Tro, Chemistry: A Molecular Approach 36

Plane Polarized Light

waves traveling in a single plane are allowed

through

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 38

Chemical Behavior of Enantiomers

chemical reactivity in a non-chiral environment

different behaviors

enzyme selection of one enantiomer of a pair

• come in chains or/and rings

 CH 3 groups at ends of chains, CH 2 groups in the middle

 chains may be straight or branched

• saturated

Tro, Chemistry: A Molecular Approach 40

H

H C H 4 - 1 6 2 ° C

E t h a n e

C H

H C H

H C H

H

H C H 3 C H 2 C H 3 - 4 2 ° C

B u t a n e H CH

H C H

H C H

H C H

H

H C H 3 C H 2 C H 2 C H 3 0 ° C

P e n t a n e

C H H

H C H

H C H

H C H

H C H

H

H C H 3 C H 2 C H 2 C H 2 C H 3 3 6 ° C

H e x a n e H CH

H C H

H C H

H C H

H C H

H C H

H

H C H 3 C H 2 C H 2 C H 2 C H 2 C H 3 6 9 ° C

• 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

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

H H H H

H H

H H

H

H CH3

CH3-, METHYL CH3CH2-, ETHYL CH3CH2CH2-, PROPYL

(CH3)2CH-, ISOPROPYL

Tro, Chemistry: A Molecular Approach 44

More Alkyl Groups

H H

H H

H H

H

H H

H

H H CH3

CH3 CH3 H3C

C C CH3 C

H H

H H

H H

(CH3)2CHCH2-, ISOBUTYL

CH3CH2(CH3)CH-, sec-BUTYL

CH3CH2CH2CH2-, n-BUTYL

(CH3)3C-, tert-- BUTYL

Examples of Naming Alkanes

Tro, Chemistry: A Molecular Approach 46

Example – Name the alkane

to determine the base name

Example – Name the alkane

Tro, Chemistry: A Molecular Approach 48

CH3CHCH2CHCH3

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

both substituents are

equidistant from the end

1 2 3 4 5

2 4

then assign numbers to each substituent based

on the number of the main chain C it’s attached to

Example – Name the alkane

4) write the name in the following order

1) substituent number of first alphabetical substituent followed by dash 2) substituent name of first alphabetical substituent followed by dash

 if it’s the last substituent listed, no dash

 use prefixes to indicate multiple identical substituents 3) repeat for other substituents alphabetically

4) name of main chain

2,4 – dimethylpentane

Tro, Chemistry: A Molecular Approach 50

Practice – Name the Following

CH3CHCHCH2CH3

CH3

CH2CH3

Practice – Name the Following

CH3CHCHCH2CH3

CH3

CH2CH3

3-ethyl-2-methylpentane

Tro, Chemistry: A Molecular Approach 52

Drawing Structural Formulas

• draw and number the

base chain carbon

skeleton

• add the carbon skeletons

of each substituent on the

appropriate main chain C

Practice – Draw the structural formula of

4-isopropyl-2-methylheptane

Tro, Chemistry: A Molecular Approach 54

Practice – Draw the structural formula of

C=C double bonds

subtract 2 H from alkane for each double bond

flat

Tro, Chemistry: A Molecular Approach 56

C C

H H

ethene = ethylene

C C

CH3H

propene

Tro, Chemistry: A Molecular Approach 58

Name Formula Molar Mass BP, °C Density, g/cm 3

subtract 4 H from alkane for each triple bond

Tro, Chemistry: A Molecular Approach 60

ethyne = acetylene propyne

C C H

Tro, Chemistry: A Molecular Approach 62

Physical Properties of Alkynes

Name Formula Molar Mass BP, °C Density, g/cm 3

Saturated Hydrocarbon C Saturated –vs- Unsaturated15H32

Unsaturated Hydrocarbon

Contains either double and/or triple bonds

Notice how the chains do not line up

Naming Alkenes and Alkynes

name of the alkyne

carbon of multiple bond

Tro, Chemistry: A Molecular Approach 66

Examples of Naming Alkenes

Examples of Naming Alkynes

Tro, Chemistry: A Molecular Approach 68

Name the Alkene

1) find the longest, continuous C chain that

contains the double bond and use it to determine the base name

since the longest chain with the double bond has 6 C

the base name is hexene

H3C CH C

H2C CH3

CH CH3

H2C CH3

Name the Alkene

there are 2 substituentsone is a 1 C chain, called methyl

the other one is a 2 C chain, called ethyl

H3C CH C

H2C CH3

CH CH3

H2C CH3

Tro, Chemistry: A Molecular Approach 70

H3C CH C

H2C CH3

CH CH3

H2C CH3

Name the Alkene

3) number the chain from the end closest to the

double bondthen assign numbers to each substituent based

on the number of the main chain C it’s attached to

1 2

3 4

4

3

Name the Alkene

4) write the name in the following order

1) substituent number of first alphabetical substituent –

substituent name of first alphabetical substituent –

 use prefixes to indicate multiple identical substituents 2) repeat for other substituents

3) number of first C in double bond – name of main chain

Tro, Chemistry: A Molecular Approach 72

Practice – Name the Following

H3C C C

CH3

CH2 CH3

H2C CH3

Practice – Name the Following

Tro, Chemistry: A Molecular Approach 74

Name the Alkyne

1) find the longest, continuous C chain that

contains the triple bond and use it to determine the base name

since the longest chain with the triple bond has 7 C

the base name is heptyne

CH3 CH CH2 CH C

CH3

C CH3

Name the Alkyne

there are 2 substituentsone is a 1 C chain, called methyl

the other one is called isopropyl

CH3 CH CH2 CH C

CH3

C CH3

Tro, Chemistry: A Molecular Approach 76

Name the Alkyne

3) number the chain from the end closest to the

triple bondthen assign numbers to each substituent based

on the number of the main chain C it’s attached to

4 6

1 2

3 4

5 6

7

Name the Alkyne

4) write the name in the following order

1) substituent number of first alphabetical substituent –

substituent name of first alphabetical substituent –

 use prefixes to indicate multiple identical substituents 2) repeat for other substituents

3) number of first C in double bond – name of main chain

1 2

3 4

5 6

7

Tro, Chemistry: A Molecular Approach 78

Practice – Name the Following

H3C C

CH3

CH2CH3

C CH

Practice – Name the Following

3

Tro, Chemistry: A Molecular Approach 80

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

Free Rotation Around

C─C

Tro, Chemistry: A Molecular Approach 82

Cis-Trans Isomerism

Reactions of Hydrocarbons

about 90% of U.S energy generated by combustion

2 CH3CH2CH2CH3(g) + 13 O2(g) → 8 CO2(g) + 10 H2O(g)

CH3CH=CHCH3(g) + 6 O2(g) → 4 CO2(g) + 4 H2O(g)

2 CH3CCCH3(g) + 11 O2(g) → 8 CO2(g) + 6 H2O(g)

Tro, Chemistry: A Molecular Approach 84

Other Alkane Reactions

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

C C

H H

H H

H H

H

H

+

Other Alkene and Alkyne Reactions

• Addition reactions

 adding a molecule across the multiple bond

• Hydrogenation = adding H2

 converts unsaturated molecule to saturated

 alkene or alkyne + H 2 → alkane

Tro, Chemistry: A Molecular Approach 86

H

CH3

H H

H

+ + H-Cl

-This is called a Markovnikov Addition

Preparation of Alkenes and Alkynes

• Acetylene aka ethyne, from calcium carbide, CaC2

• Steam cracking for the formation of ethylene, ethene, from

ethane

Addition Reactions

• Symmetrical addition is simple, but asymmetrical addition

follows Markovnikov's rule The hydrogen adds to the carbon with the most hydrogen.

• For alkynes, the addition is always two mole to one mole of alkyne, the product being a substituted alkane If hydrogen gas

is added, the process is called hydrogenation

Aromatic Hydrocarbons

they do not behave like alkenes

Tro, Chemistry: A Molecular Approach 90

Resonance Hybrid

hybrid of two structures

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 92

Naming Benzene as a Substituent

4-phenyl-1-hexene

Naming Disubstituted Benzene Derivatives

substituent, then move toward second

order substituents alphabetically

use “di” if both substituents the same

F

Br 1

Tro, Chemistry: A Molecular Approach 94

Naming Disubstituted Benzene Derivatives

ortho- = 1,2; meta- = 1,3; para- = 1,4

4-chlorotoluene

para-chlorotoluene p-chlorotoluene

Practice – Name the Following

F

Cl

Br

Br

Tro, Chemistry: A Molecular Approach 96

Practice – Name the Following

Polycyclic Aromatic Hydrocarbons

fusing = sharing a common bond

Tro, Chemistry: A Molecular Approach 98

Reactions of Aromatic Hydrocarbons

undergo substitution reactions – replacing H

with another atom or group

+ Br2

Br

+ HBr

CH3CH2CH2CH2Cl

CH2CH2CH2CH3

AlCl3

Substitution reaction Overview

Substitution reaction Overview

C C H

Tro, Chemistry: A Molecular Approach 104

Substitution reaction Overview

Substitution reaction Overview

Tro, Chemistry: A Molecular Approach 106

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