Organic Chemistry

Organic Chemistry: The chemistry of carbon

and carbon-based compounds

Organic Chemistry in everyday life:

Smells & tastes: fruits, chocolate, fish, mint

Medications: Aspirin, Tylenol, Decongestants, Sedatives

Addictive substances: Caffeine, Nicotine, Alcohol,

Narcotics

Hormones/Neurotransmitters: Adrenaline, Epinephrine

Food/Nutrients: Carbohydrates, Protein, Fat, Vitamins

Genetics: DNA, RNA

Consumer 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 Compounds Classified according to functional group

Alkane

Alkene

Alkyne

Haloalkane

Alcohol

Ether

Ketone

Aldehyde

Carboxylic acid

Amine

Amino acid

Amide

O

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 # of

C 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 atoms

Suffix: 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

C C C C

H H H

H

H H H H

H

Butane

C4H10

Butyl

-C4H9

Methyl

-CH3

C H

H

H

? R

H

C C C C

H H H

H

H H H H

?

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

R

First Ten Hydrocarbons: Properties

Name

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 of

Carbon 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

Compound

Methane

Ethane

Propane

Butane

Pentane

MW

16

30

44

58

72

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

Formula

CH4

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 other

hyphens separate numbers from names

no space between last substituent & root name

4-ethyl-3,5-dimethyloctane

1

2

3

6 5

8

7 4

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

CH3

R

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

H

C H

H

H C C C

H H

H H H

C

H

H H

2 - methylbutane butane

Naming Practice

Expanded Structure Line Structure

H C

C C C

H

H

CH3

CH3 H H

H

C

C

H

H

H

H

H

hexane 3,3-dimethyl

1 2 3

4

5

6 1

2

3

4 5 6

hexane 4,4-dimethyl

Lowest sum of numbers

is correct

Naming Practice

Line Structure

Isomers

The 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

3

5

9

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 Isomers

C5H12

(Same formula, different structure)

More branching → weaker London dispersion forces

36.0 pentane

27.9 2-methylbutane

9.5 2,2-dimethylpropane

Boiling point (°C) Name Structure

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 Alkanes

Combustion

• exothermic reaction

• alkanes used as fuel source

C4H10 + ___ O2 ___ CO2 + ___ H2O 4 5 13/2

Incomplete Combustion with insufficient O2 produces CO

• Poor ventilation, cigarettes

C4H10 + ___ O2 ___ CO + ___ H2O 4 5 9/2

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 Alkanes Radical 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· Cl2

Overall reaction: CH4 + Cl2 CH3Cl + HCl

Halogenated product is a haloalkane

Naming: 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 Alkanes Halogen substitutes for hydrogen in alkane →multiple results

CH4 CH3Cl CH2Cl2 CHCl3 CCl4

Cl2

Cl2

Cl2

Cl2

Compound

CH3Cl

CH2Cl2

CHCl3

CCl4

IUPAC Name

Chloromethane

Dichloromethane

Trichloromethane

Tetrachloromethane

Common Name

Methyl chloride

Methylene chloride

Chloroform

Carbon 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 2 3

4 5

6

Naming Practice: Haloalkanes

F Cl

F

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 1

2

3 4

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

OR OR

1-bromo-2-methylbutane

2-bromo-3-

methylbutane 1-bromo-3-

methylbutane

1-bromo-2-

methylbutane

2-bromo-2-methylbutane

Structural Isomers

What 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 Practice On 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

C4H9I

C3H6Cl2

C5H11Br

C4H8Cl2

4

4

8

9

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

I I

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-methylpentane 3-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

Cl

Cl

ClCl

Cl

Cl

2,2-dichlorobutane

1,1-dichlorobutane

2,3-dichlorobutane

1,2-dichloro-2-methylpropane

1,3-dichloro-2-methylpropane