Organic Chemistry

Organic Chemistry: The chemistry of carbon

and carbon-based compoundsOrganic Chemistry in everyday life:

Smells & tastes: fruits, chocolate, fish, mintMedications: Aspirin, Tylenol, Decongestants, SedativesAddictive substances: Caffeine, Nicotine, Alcohol, NarcoticsHormones/Neurotransmitters: Adrenaline, EpinephrineFood/Nutrients: Carbohydrates, Protein, Fat, VitaminsGenetics: DNA, RNAConsumer products: Plastics, Nylon, Rayon, Polyester

Drawing Organic Structures

Butane: C4H10

C C C C

H

H

H

H

H

H

H

H

H

H

CH3 CH2 CH2 CH3

CH3CH2CH2CH3

CH3(CH2)2CH3

Shortcuts make structures easier & faster to draw

Line Structure• Only shows bonds• C atoms assumed at each end

and intersection of bonds• H atoms not shown• Assume 4 bonds to each C• Fulfill C’s 4 bonds by adding H’s

Lewis Structure

Condensed Structures

Carbon Atoms

Types of Organic CompoundsClassified according to functional group

Alkane

Alkene

Alkyne

Haloalkane

Alcohol

Ether

Ketone

Aldehyde

Carboxylic acid

Amine

Amino acid

AmideO

H

O

NH2

O

OH

O

H2NOH

O

OH

Cl

Br

NH2

C C

O

Big Idea in Organic Chemistry

Structure controls Function

Each functional group has predictable reactivity

Alkanes or Paraffins• All C atoms are tetrahedral and sp3 hybridized (only C-C

single bonds)

• General formula = CnH2n+2 (CH4, C2H6, C3H8, C4H10, etc.)

• Can have linear or branched alkanes

C5H12

• Same molecular formula, different structure: structural isomers• Branches are called substituents• Primary (1°) carbon atom: bound to one other C atom• Secondary (2°) C atom: bound to 2 other C atoms• Tertiary (3°) C atom: ” 3 ”• Quaternary (4°) C atom: ” 4 ”

C CH2H3C

H

CH3

CH33° 1°

2°

Names of Linear Alkanes and Alkyl Substituents

Alkane Alkyl substituents# ofC atoms

CH4

CH3CH3

CH3CH2CH3

CH3CH2CH2CH3

-CH3

-CH2CH3

-CH2CH2CH3

Methyl

Ethyl

Propyl

etc.

Methane

Ethane

Propane

Butane

Pentane

Hexane

Heptane

Octane

Nonane

Decane

Root: number of C atomsSuffix: functional group (-ane for alkanes) (-yl for alkyl groups)

1

2

3

4

5

6

7

8

9

10

C H

H

H

H

Methane CH4

H

CC C C

H H H

H

HHHH

H

Butane C4H10

Butyl -C4H9

Methyl-CH3

C H

H

H

?R

H

CC C C

H H H

H

HHHH

?

Where R = any other C atom or arrangement of C atoms

R

First Ten Hydrocarbons: PropertiesName

Methane

Ethane

Propane

Butane

Pentane

Hexane

Heptane

Octane

Nonane

Decane

1

2

3

4

5

6

7

8

9

10

CH4

C2H6

C3H8

C4H10

C5H12

C6H14

C7H16

C8H18

C9H20

C10H22

Number ofCarbon Atoms

Molecular Formula

Melting Point, oC

# of Isomers

Boiling Point, oC

-182.5

-183.2

-187.7

-138.3

-129.7

-95.3

-90.6

-56.8

-53.6

-29.7

-161.5

-88.6

-42.1

-0.5

36.1

68.7

98.4

125.7

150.8

174.0

1

1

1

2

3

5

9

18

35

75

Properties of Alkanes

CompoundMethaneEthanePropaneButanePentane

MW1630445872

Boiling point (°C)-164-88.6-42.1-0.5

+36.0

Linear Alkanes:1 - 4 C atoms: gas at room temp

5 - 15 C atoms: liquid at room temp>15 C atoms: solid at room temp

Larger molecular weight → Stronger London dispersion forces

Nonpolar → only London Dispersion Forces IMF

FormulaCH4

C2H6

C3H8

C4H10

C5H12

Fractional Distillation of

Crude Oil

Kelter, Carr, Scott, Chemistry A World of Choices 1999, page 429

Naming Branched Alkanes (IUPAC)

1. Root name: name of longest continuous C chain (parent chain)• 2 equally long? Choose the one with more branches

2. Number C atoms in chain, starting at end with first branch

3. Identify substituents, give each a number (C it is connected to)• Two or more identical substituents: use prefixes (di-, tri-, tetra-, etc.)

4. List substituents alphabetically before root name• Do not alphabetize prefixes

5. Punctuation: commas separate numbers from each otherhyphens separate numbers from namesno space between last substituent & root name

4-ethyl-3,5-dimethyloctane1

2

3

658

74

4-ethyl

3-methyl and 5-methyl = 3,5-dimethyl

Octane

Common Names of other Alkyl Substituents

isopropyl

isobutyl

sec-butyl

tert-butyl

alphabetized as “i”

alphabetized as “i”

alphabetized as “b”

alphabetized as “b”

CH CH2 CH3

CH3

C CH3

CH3

CH3

CH CH3CH2

CH3

CH CH3

CH3R

R

R

R

R

R

R

R

Remember that R = any carbon chain

“iso” indicates symmetry

3 carbons

4 carbons

2o

2o

Secondary carbon

Tertiary carbon

3o 3o

HC H

H

H CC C

H H

HHH

CH

HH

2 - methylbutanebutane

Naming PracticeExpanded Structure Line Structure

H C

C C C

H

H

CH3

CH3HH

H

C

C

H

H

H

H

H

hexane3,3-dimethyl

1 2 3

4

5

61

2

3

456

hexane4,4-dimethyl

Lowest sum of numbers is correct

Naming Practice

Line Structure

IsomersThe fat dog shook himself, and then rolled over on the wet rug.

The dog shook the fat rug, then rolled over and wet on himself.

These two statements use the same words...but have very different meanings!

OR

Likewise, isomers may have the same formula, but have very different structures…

Structural Isomers of C4H10

2-methylpropane

or

Structural Isomer Practice• On piece of your own paper, draw AND name

ALL of the isomers for the following alkanes:Formulas # isomers

If you complete that, try to draw and name all of the isomers for octane (C8H18). There are 18 of them!

Some of your drawings may look different, but they are only different structures (isomers) if they also have different names

Pentane

Hexane

Heptane

C5H12

C6H14

C7H16

359

Structural Isomers: Pentane (C5H12)

pentane

2-methylbutane

2,2-dimethylpropane

Structural Isomers: Hexane (C6H14)

hexane

2-methylpentane

3-methylpentane

2,3-dimethylbutane

2,2-dimethylbutane

Structural Isomers: Heptane (C7H16)

heptane

2-methylhexane

3-methylhexane

2,2-dimethylpentane

2,3-dimethylpentane

Structural Isomers: Heptane (C7H16)

2,4-dimethylpentane

3,3-dimethylpentane

3-ethylpentane

2,2,3-trimethylbutane

Comparing Structural IsomersC5H12

(Same formula, different structure)

More branching → weaker London dispersion forces

36.0pentane

27.92-methylbutane

9.52,2-dimethylpropane

Boiling point (°C)NameStructure

BP/MP of Linear alkanes > BP/MP of branched alkanes

Chemical Bingo: Naming Review• There are 27 structures or names drawn

on the next slide. Select 24 of them to be placed on your bingo card.

• Because of space issues, I would number each bingo square and then list the names or structures on a separate sheet of paper

• If I give you a name, you must match it to a structure. If I give you a structure, you must match it to a name

• Any bingo winner will be awarded 1 bonus point on the quiz (5% pts)

Chemical Bingo: Alkanes

R

R

R

R

isopropyl sec-butyl

tert-butyl isobutyl

decane nonane

2,3,4,5-tetramethylhexane

3,4-diethylhexane

3,5-diethyl-4-isopropylheptane

4-tert-butyl-3,5-dimethylheptane

4-ethyl-2,2,3,5,6,6-hexamethylheptane

Any isomer of C5H12

Any isomer of C6H14

Any isomer of C7H16

Reactions of AlkanesCombustion

• exothermic reaction• alkanes used as fuel source

C4H10 + ___ O2 ___ CO2 + ___ H2O4 513/2

Incomplete Combustion with insufficient O2 produces CO• Poor ventilation, cigarettes

C4H10 + ___ O2 ___ CO + ___ H2O4 59/2

CO is poisonous because it binds to the hemoglobin in the blood, preventing the absorption of O2

Radical Halogenation Terms• Mechanism

– How the reaction occurs through multiple steps (most reactions actually occur in many steps)

• Chain Reaction– Reactions that occur on their own after some

initiating event

• Free Radicals– Atoms that have one free electron—highly

reactive

Radical Halogenation Terms• Initiation Step

– Step where a bond is split by heat/light, producing free radicals

• Propagation Step– Step where free radicals react with non-

radicals, producing more free radicals and continuing the “chain reaction”

• Termination Step– Step where free radicals react with each

other, producing non-radicals and terminating the “chain reaction”

Initiation

Propagation

Propagation

Termination

Reactions of AlkanesRadical Halogenation of Alkanes

Mechanism (chain reaction):

Step 1 Cl2 ⇌ Cl· + Cl ·

Step 2 Cl· + CH4 CH3· + HCl

Step 3 CH3· + Cl2 CH3Cl + Cl·

Step 4 Cl· + Cl· Cl2Overall reaction: CH4 + Cl2 CH3Cl + HCl

Halogenated product is a haloalkaneNaming: halogen atom is a substituent, replace –ine ending with –o

-F fluoro -Cl chloro -Br bromo -I iodo

chloromethane

h(Free Radicals)

Why not 1-chloromethane?

Type of Step

CH4 + Cl2 CH3Cl + HCl

Radical Halogenation of AlkanesHalogen substitutes for hydrogen in alkane →multiple results

CH4 CH3Cl CH2Cl2 CHCl3 CCl4

Cl2

Cl2

Cl2

Cl2

CompoundCH3Cl

CH2Cl2CHCl3CCl4

IUPAC NameChloromethaneDichloromethaneTrichloromethaneTetrachloromethane

Common NameMethyl chlorideMethylene chlorideChloroformCarbon tetrachloride

All are liquids at room temperature• Heavy Cl atoms increase LDF• Polar C-Cl bonds – can have polar molecules

Textbook Resource

Chemistry: An Intro to General,Organic and Biological Chemistry

by Timberlake (Green/Tan Book)

Sections 10.1-10.6 already covered

Currently Section 11.2 (Haloalkanes)

Can be used as an outside reference

1 23

4 56

Naming Practice: Haloalkanes

F ClF

Cl

IBr

Cl

Br

5-chloro-2-fluorohexane

2-chloro-5-fluorohexane 2-chloro-4-fluoro-2,3-dimethylpentane

2-bromo-3-ethyl-4-iodopentane 2-bromo-4-chloro-3-isopropylpentane

Two equal numbering options? Number based on alpha order

12

34

5

6

?

Radical Halogenation: Predict the Product

ClCl

BrBr

+ Cl2 → OR

1-chloropropane 2-chloropropane

+ Br2 → OR

1-bromo-2-methylbutane 2-bromo-2-methylbutane

Remember that any H on the alkane can be replaced by a halogen

ClOR

3-chloropropane?

+ HCl?

?

Radical Halogenation: Predict the Product

BrBr

BrBr

Br

+ Br2 → OR

OROR

1-bromo-2-methylbutane

2-bromo-3-methylbutane

1-bromo-3-methylbutane

1-bromo-2-methylbutane

2-bromo-2-methylbutane

Structural IsomersWhat are the possible structural isomers of C3H7Br?

BrBr

1-bromopropane 2-bromopropane

What are the possible structural isomers of C4H9Cl?Cl

Cl

Cl

Cl

1-chlorobutane

2-chlorobutane

2-chloro-2-methylpropane

1-chloro-2-methylpropane

Structural Isomer PracticeOn piece of your own paper, draw AND name ALL of the isomers with the following formulas:

Formulas # isomers

Some of your drawings may look different, but they are only different structures (isomers) if they also have different names

C4H9IC3H6Cl2C5H11BrC4H8Cl2

4489

To be honest, there may be more…this is what I found, so try and prove me wrong! Extra Credit to anyone who can find more structures…

Structural Isomers: C4H9I

II

II

1-iodobutane

2-iodo-2-methylbutane

2-iodobutane

1-iodo-2-methylbutane

I

II

I

Structural Isomers: C3H6Cl2 Cl

ClCl

Cl

ClClClCl

1,1-dichloropropane

1,3-dichloropropane

1,2-dichloropropane

2,2-dichloropropane

Structural Isomers: C5H11Br

BrBr

BrBr

1-bromopentane 2-bromopentane

1-bromo-3-methylpentane3-bromopentane

Structural Isomers: C5H11Br

Br

Br

Br

Br

1-bromo-2-methylbutane 2-bromo-3-methylbutane

1-bromo-2,2-dimethylbutane 2-bromo-2-methylbutane

Structural Isomers: C4H8Cl2

Cl

ClCl

Cl

Cl

Cl

ClCl

1,1-dichlorobutane 1,2-dichlorobutane

1,3-dichlorobutane 1,4-dichlorobutane

Structural Isomers: C4H8Cl2

Cl Cl

Cl

Cl

ClCl

ClCl

Cl

Cl

2,2-dichlorobutane

1,1-dichlorobutane

2,3-dichlorobutane

1,2-dichloro-2-methylpropane

1,3-dichloro-2-methylpropane