12/11/2009 1

Chem 105 Friday, 12-11-09

Final Exam Preview – ACS –”First Semester General Chemistry”

Alkynes

Oxidation numbers of carbon

Oxygen-containing organic compounds

Multi-functional molecules

Amides

Proteins Monday: Review for final

Wednesday: No class

Friday 1-3 pm Final exam

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A couple of typical questions:

What is the formula of the nitrate ion?

A. NO2 B. NO3- C. NO2

2- D. NO33-

What volume of a 0.145 M MgCl2 solution must be used to

prepare 15.2 mL of a 0.100 M MgCl2 solution?

A. 2.20 x 10-4 mL B. 10.8 mL C. 0.0108 mL D. 23.5 mL

ACS exam covers Chapters 1-11 Kotz

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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

1 2 3 4

5

6 7

7-methyl-3-octyne

8

H-C≡C-H common name 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.

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

amide ion

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Draw all structural isomers of alkynes with the formula C6H10.

Each one should contain a C≡≡≡≡C bond. How many are there?

1. four

2. five

3. six

4. seven

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Draw all structural isomers of alkynes with the formula C6H10.

Each one should contain a C≡≡≡≡C bond. How many are there?

1. four

2. five

3. six

4. seven

(on board)

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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

O H H

O C C

O H 3 C C H 3

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Carbonyl (C=O)–containing functional groups

Ketone

Aldehyde

Carboxylic acid

Carboxylic ester

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)

O

C O C

O

C H

H

H

O C

H H

C H 3

O

C H

H

H

O H C

H H

C H 3 O

H

ethyl acetate

Water removed to form ester.

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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

Recall:

�H is almost always +1

�SUM ox # = total charge

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The following reaction is “hydration of an alkene” to

give an alcohol. Assign the oxidation #s in ethene

then tell whether this reaction involves..

1. Oxidation and reduction

2. Oxidation only

3. Reduction only

C H 2 C H 2 + H 2 O C H 3 C H 2 O H -1 -3

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

+1 +1 +1 +1 +1 +1

-2 -2

-2 -2

-3 -1

This carbon is oxidized (Ox # increases algebraically)

This carbon is reduced (Ox # decreases algebraically)

Net effect: zero. No redox chemistry in alkene hydration.

Why? Because one carbon bonds to a less electronegative atom (H),

while the other carbon bonds to a more electronegative atom (O).

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O,N-containing functional group: amide

amide acetamide

O

N

H

O

N H C H 3

H

remove water O

O H N

H

H carboxylic acid

amine

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Students should be able to identify most functional groups within

larger, more complex organic molecules.

C H 3

H 3 C C H 3

C O 2 H

carboxylic acid

alkane

aromatic

Ibuprofen

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N H

N H

O

N

O O

N C l

C l

N

O

H

H 3 C C H 3

N

O

H

H 3 C C H 3

H O

H

�Diazónamide A - Discovered in Pacific sea squirt (1988)

�Synthesized by Patrick Harran of U. Texas Southwest and K.C. Nicolaou of

Scripps Research Institute and their co-workers.

�Powerful anti-cancer drug.

�Kills cancer cells at 1 x 10-9 M

C40H34Cl2N6O6

Aromatic

Alkane

Amide

Alcohol

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http://www.uaf.edu/chem/105Fa09/DiazonamideA.html

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H 2 N

O

O H R H

N H

H O

O H

R H

O

H 2 N

R H

N

H O

O H

H R

Amino acid

+ H2O

peptide = two amino acids joined by amide bond

Proteins contain 20

amino acids that have

different R-groups.

(aromatic

alkane

alcohol

carboxylic acid

amine

others)

(Further details in “The Chemistry of Life: Biomolecules,”)

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Amide bonds have two resonance forms

O

N

C H 3

H

O

N

C H 3

H

This N is sp2-hybridized, which makes

the amide group trigonal planar.

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As in other resonance-bonded molecules, the

presence of resonance forms indicates the

existence of a multi-atom π-bond.

O

N H

H

H The smallest amide is “formamide”.

(I’m using a π* MO to illustrate p-orbitals.)

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Tripeptide of Alanine, Serine, and Phenylalanine

Amide bond connects 2

amino acids

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See Protein Data Bank at

http://www.rcsb.org

For 47,400 protein and DNA/RNA structures

Use RasMol to visualize. Rasmol is on all

chemistry lab computers, or you can

download your own free copy at:

http://www.umass.edu/microbio/rasmol/

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MOs, π-bonds, resonance, electron pair geometry,

molecular geometry…

…all these are important facts of life.

They control the shape, chemical reactivity, and

biological properties of all life molecules.