Chem 105X Monday, Dec. 5, 2011 Chapter 10, Kotz Organic Chemistry Alkynes More on hydrocarbons and petroleum products Oxidation states, and oxidation numbers, of carbon O-containing functional groups Course questionnaires

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Review for final: 201 Reichardt Sunday 12-11-11 , 4-6 PM Keller (Stoichiometry) Monday 12-12-11 , 6-8 PM Heitzler (Lewis formulas, VSEPR etc)

Review for final: 509 Gruening Saturday 12-10-11 , 2-4 PM Quinn Sawyer Tuesday 12-13-11 , 5-7 PM Quinn Sawyer

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C C C H 3 C H 2 C H 2

C H 2 C H

C H 3

C H 3

C CH3C CH2

CH2 CH

CH3

CH3

1 2 3 4

5

6 7

7-methyl-3-octyne

8

The common name of H-C≡C-H is “acetylene”

(“ethyne” is the systematic name, but is not used.)

Uses: acetylene is welding gas

larger alkynes used as synthesis intermediates because

the C≡C bond can be modified in many ways.

Some natural molecules such as dynemicin anti-cancer

drug contain C≡C bonds.

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Alkynes are used in organic synthesis reactions to

create specific isomer products.

CH3C C H + Base CH3C C + HBase

CH3C C CH2CH2CH3

Cl

CH3C C CH2CH2CH3 + Cl

C H 3 C C C H 2 C H 2 C H 3

C l

C H 3 C C C H 2 C H 2 C H 3 + Cl

C H 3 C C H + Base C H 3 C C + HBase

acetylide ion

2-hexyne

C-C bond forming reactions like this are used to make larger, more complex molecules. This is the main goal of organic chemistry: synthesis of new molecules and materials.

N

H H

Clicker question on alkyne isomers.

How many alkyne isomers exist having a formula of C6H10?

Each should contain one CC bond.

four

five s

ix

sev

en

32

16

2931

1. four

2. five

3. six

4. seven

1 2 3 4 5 6 7 8 9 10 11 12 13 14

1

15

29

43

57

71

85

99

113

127

141

155

169

183

183

197

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How many alkyne isomers exist having a formula of C6H10?

Each should contain one CC bond.

1. four

2. five

3. six

4. seven

CC C C C C

CC C C C C

CC C C C C

CC C C C

C

CC C C C

C

CC C C C

C

CC C C

C

C

6 in a row

5 in a rowtriple at end

5 in a rowtriple at C2

4 in a row

On board

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Hydrocarbon properties Boiling points vs molar mass GC separation

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See 2Hexanes.hin

Short-range attractive forces stick surfaces together. Hence, higher BPs for larger molecules.

Hydrocarbons can be separated by gas chromatography (GC). Last week in lab students used a GC-MS instrument. This uses a mass spectrometer (MS) to identify and characterize the molecules as they exit the separation column.

GC

MS

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Gas chromatogram of C1-C6 hydrocarbons

Courtesy of R. Stolzberg

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Courtesy of R. Stolzberg

Gasoline

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Courtesy of R. Stolzberg

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Distillation column similar to N. Pole refinery

Courtesy of R. Stolzberg

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Courtesy of R. Stolzberg

12/5/2011 15 (from North Pole refinery) Courtesy of R. Stolzberg

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Courtesy of R. Stolzberg

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Oxygen–containing functional groups (sp3 O)

Alcohol ethanol C

O H C

H O H

H H

H H

Ether Diethyl ether

OH H

O H H

OC C

O C C

OH3C CH3

O H 3 C C H 3

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Carbonyl (C=O)–containing functional groups

Ketone

Aldehyde

Carboxylic acid

acetone (propanone)

O

C C

O

C C H

H

H

H

H H

O

C H

O

C H

H

H

H acetaldehyde (ethanal)

O

C O H

O

C H H

H

O H acetic acid (CH3CO2H)

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Carbon oxidation numbers in different compounds can range from -4 to +4 (here, -3 to +3).

ethanol acetaldehyde acetic acid

+1

+1

+1

+1 +1

+1 +1

+1

-2

-2 -2

-2

+1 +1

+1 +1 +1

+1

-3

This C is

like C in

ethane.

-3 -3 -1

+1 +3

2-electron oxidation

2-electron oxidation

C O

H

C H 3

H

H

C

O

H 3 C

H

C

O

H 3 C

O H

C

H

H

H

C

H

H

H+1

+1

+1 +1

+1

+1

-3

-3

C

H

H

H

C

H

H

H +1

+1

+1 +1

+1

+1

-3

-3

Recall: H is almost always +1 SUM ox # = total charge

What are the oxidation numbers of methane and carbon dioxide, respectively?

-4, +

4

+4,

-4

0, +

8

-8, 0

61

3

14

31

1 2 3 4 5 6 7 8 9 10 11 12 13 14

1

15

29

43

57

71

85

99

113

127

141

155

169

183

183

197

1. -4, +4

2. +4, -4

3. 0, +8

4. -8, 0

CH4 -4 most reduced form of C CO2 +4 most oxidized form of C

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C H 2 C H 2 C H 3 C H 2 O H

+1 +1 +1 +1 +1

-2 -2

-2

-3 -1

This carbon is oxidized (Ox # increases algebraically)

This carbon is reduced (Ox # decreases algebraically)

Net effect: zero. Oxidation balances reduction in alkene hydration.

A typical organic reaction: Hydration (addition of water ) of ethylene. Analyzing organic reactions using oxidation numbers.

H-OH

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You should be able to identify some functional groups within larger, more complex organic molecules.

CH3

H3C CH3

CO2H

C H 3

H 3 C C H 3

C O 2 H

carboxylic acid

alkane

aromatic

Ibuprofen

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Paclitaxel (Taxol) (core molecule) - Discovered in bark of Pacific yew tree (1968) and in various fungi Anti-cancer drug Commercially produced by bacterial fermentation Synthesized by several chemistry labs.

C31H38O11

Alcohol Ester Aromatic

Alkane Alkene

ether

Some drug molecules, like paclitaxel , have a complex 3-dimensional structure. Their large, varied surface allows them to bind to specific sites or protein targets . Paclitaxel (taxol) binds to the tubulin protein inside cells.

See paclitaxel.hin

Electrostatic potential 3D-mapped isosurface

Student questionnaires

The End

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