Organic Chemistry

Organic Chemistry Notes Page | 15

Organic Chemistry

In chemistry the word organic has a different meaning than in the grocery store. Organic chemistry is the study of ______________________________________________.

Almost everything around you is made up of carbon, so this is a big topic. We are made of carbon, and so are things like lighter fuel and plastic bags. Depending on how the carbon is bonded and what it is bonded to it can create materials with very different properties.

A. Bonding of Carbon Atoms

Whats so special about carbon anyway? It tends to form ____________ bonds with other carbon atoms to form chains. Because carbon has ___ valence electrons it can form ___ bonds.

When 1 pair of electrons is shared between two carbon atoms the bond is called a __________ covalent bond.

If carbon atoms share two pairs of electrons the bond is called a _________ covalent bond.

Carbons can even share three pairs of electrons. This bond is called a _________ covalent bond.

Saturated =

Unsaturated =

Chains of carbon atoms can be open or closed, or even form three-dimensional networks.

B. Categories of Hydrocarbons

Homologous series =

As members of a homologous series increase in molecular mass (the number of carbons increases), their boiling and melting points ___________.

Hydrocarbons are named according to their number of carbons and the type of bonds in them. Tables P and Q are used together for this purpose.

Alkanes:

Alkenes:

Alkynes:

Name the following hydrocarbons from their descriptions:

1. 9 carbons with only single bonds = _____________

2. 5 carbons with a double bond = _____________

3. 7 carbons with only single bonds = _____________

4. 5 carbons with a triple bond = _____________

5. 6 carbons with a double bond = _____________

Each homologous series has a general formula that you can follow to determine the number of hydrogens attached to a molecule.

Alkanes =

Alkenes =

Alkynes =

Where n = _____________________________

C. Naming Hydrocarbons

Ex) Methane n = ____, and the formula _______ is used, so methane = C H

Practice this by writing out the formulas of the hydrocarbons in the previous examples.

There are many ways that the makeup of a molecule can be expressed.

Methane

Ethane

Molecular Formula

Structural Formula

Condensed Formula

Ball-and-Stick Model

Space-Filling Model

D. Drawing Structural Formulas of Hydrocarbons

Alkanes

1. Determine the number of carbons and draw that many in a row

2. Because the molecule name ends in ane you know that there are only single bonds. Connect all of the carbons with a single line.

3. Each carbon atom must have 4 bonds connected to it. Add enough hydrogens so that each carbon has 4 total bonds connected to it.

4. Use the molecular formula to make sure that you have the correct number of hydrogens.

Draw the structural formula for propane:

Alkenes

1. Determine the number of carbons and draw that many in a row connected by a single line.

2. Because the molecule name ends in ene you know that there is a double bond. The name of the molecule will tell you where that bond is located. For example, 2-butene will tell you that there are 4 carbons and the double bond is located after the second one. Add another line for the double bond.

3. Each carbon atom must have 4 bonds connected to it. Add enough hydrogens so that each carbon has 4 total bonds connected to it.

4. Use the molecular formula to make sure that you have the correct number of hydrogens.

Draw the structural formula for 3-hexene:

Alkynes follow the same rules as alkenes, except there is a triple bond, not a double bond.

Draw the structural formula for 2-butyne:

19. Write the molecular formula for 1-octene and draw its structural formula:

20. Write the molecular formula for 2-pentyne and draw its structural formula:

E. Isomers

As the number of carbon atoms increases, the number of possible isomers _____________.

The letter n before the name of a hydrocarbon signifies that it is the ___________, or straight chain isomer. Branched isomers must have different names.

Naming Isomers

The rules for naming organic compounds are governed by the International Union of Pure and Applied Chemistry (IUPAC).

C - C - C - C| C

C - C - C - C| C -butane

C - C - C - C| C methylbutane

C1 - C2 - C3 - C4 | C 2-methylbutane

Naming Procedure: Example

1. Find the longest continuous chain of carbons and use its name as the base. (Example: 4 carbons = butane)

Alkane

Alkyl Group

Methane

Methyl

Ethane

Ethyl

Propane

Propyl

2. Count the number of carbons in the side branch and assign a prefix based on the name of the corresponding alkane. (Example: 1 carbon = methane = methyl)

3. If necessary, the location of the side branch (alkyl group) is shown by assigning numbers to the carbons in the longest chain. Numbering should begin at the end that has the side chain attached to the lowest number possible. (Example: 2-methylbutane, not 3-methyl butane)

4. If more than 1 side branch is attached commas are used to separate the numbers in the name and prefixes are used to denote more than one of the same group, such as 2,2-dimethylbutane:

Isomer Naming Practice

Name the following molecules:

Example: 2,2,4-trimethyl pentane

Draw the following molecules:

5. 2,3-dimethylpentane 6. 4,4-diethylheptane

F. Functional Groups - Organic compounds in which one or more hydrogen atoms of a hydrocarbon are replaced by other elements

1. Halocarbons (Halides)

- Organic compounds in which one or more hydrogen atoms are replaced by a halogen

(Group 17 element)

Naming ( Same as hydrocarbons, but add a prefix to signify which halogen is attached.

Example:

- 5 carbons, singly bonded = _____________

- Bromine is present on the __st and __th carbons.

- Why wouldnt we say the 2nd and 4th carbons?

- There are __ Bromines.

- Well, the first half would be named 1, 4 dibromo ________

- The final name is _________________________

Name the following halocarbons:

a. b.

___________________

______________________________

2. Alcohols

Organic compounds in which one or more hydrogen atoms are replaced by an

-OH group. (No more than one OH can be attached to a carbon)

They are not bases! (Do not form -OH ions in aqueous solution!)

Naming ( Same as hydrocarbons, but drop the e ending and add ol

(For example: methanol, 2,2-dimethylbutanol. . .)

Primary alcohols

One OH group is attached to a carbon on the end of a chain.

Represented by R-OH, where R is a hydrocarbon chain of any length

Typical example = propanol = CH3CH2CH2OH

3 carbons -OH

Name the following alcohols:

a. CH3CH2OH________________ b. CH3CH2CH2OH______________

Draw the following molecules:

1. 2-chloro, 2-propanol

2. 2-fluoro, 1,2-butanediol

3. Carbonyl Group

One of the most important functional groups in chemistry, which consists of a carbon atom connected to an oxygen atom by a double bond.

a. Organic Acids

A family of organic compounds containing the functional group COOH.

Organic acids are formed by:

1. Dropping the final e of the alkane member.

2. Replace the e with - oic .

3. Then add the word acid .

Example: Methane ( Methanoic Acid

Ethane ( Ethanoic Acid

Name this acid:

__________________

b. Aldehydes

- The carbon of the carbonyl group is bonded to at least one hydrogen atom.

- Named by adding the suffix -al to the name of the parent hydrocarbon.

Name this aldehyde:

_________________

c. Ketones

- Has no hydrogen atoms directly attached to the carbonyl group

- Named by adding the suffix -one to the name of the parent hydrocarbon.

Name this ketone:

__________________

d. Esters

Made from an organic acid and an alcohol, resulting in:

Naming ( use the names of the component alcohol and acid and add the suffix -oate.

Have strong aromas; responsible for the odors of many foods and flavorings

Example: = Methylpropanoate

Practice Problems:

4. Ethers

- General formula R1 O R2 where each R represents a carbon chain

- Commonly named by naming the two branches first and adding the word ether

Example:

= diethyl ether

Name this ether:

___________________

5. Amines

Formed when 1 or more hydrogens in ammonia (NH3) are replaced by an alkyl group

- Named by changing the e ending of the alkane name to amine and adding a number to show the location of the amine group

Example: = dimethylamine

Name this amine: ______________________

6. Amides

Basically organic acids where the OH is replaced by an amine group

- Named by changing the e ending of the alkane name to amide

and adding a number to show the location of the amine group

Example: = ethanamide

Name this amide:

______________________

G. Organic Reactions

Organic Reactions

Generally occur ____________ than inorganic reactions because existing bonds must be broken before making new ones.

1. Combustion (__________________)

When saturated hydrocarbons (like methane) react with oxygen at a high temperature they produce carbon dioxide and water complete combustion

CH4 + 2O2 ( CO2 + 2H2O

If there is insufficient oxygen, carbon monoxide is produced incomplete combustion.

2CH4 + 3O2 ( 2CO + 4H2O

Write the balanced reaction for the complete combustion of propane:

2. Substitution

The replacement of one kind of atom or group by another kind of atom or group.

An example of this occurs in saturated hydrocarbons where a hydrogen is replaced.

If the hydrogen is replaced by a halogen (F,Cl, Br, I, At) halogenation is said to have occurred.

Name these compounds:

______________

________________

3. Addition

The adding of one or more atoms or groups at a double or triple bond.

The double or triple bond is changed to a single (saturated) bond or double bond.

If hydrogen is added, the process is referred to as hydrogenation. This reaction is done on unsaturated hydrocarbons, such as vegetable oils, to make the oils solidify at room temperature: saturated fats tend to be solid at higher temperatures than unsaturated fats.

Name these compounds: ______________

________________

4. Esterification

Organic acids (COOH) react with alcohols to produce an ester plus water.

The process is reversible and slow:

Esterification = acid + alcohol (( ester + water

Esterification is also referred to as a hydrolysis (adding water) and is considered to be a dehydration reaction (removing water) or condensation (water product).

Name these compounds:

______________ + ____________ ( ______________ + water

5. Saponification

The hydrolysis of an ester such as fat with an inorganic base to produce an alcohol and a soap.

(

What would the IUPAC name for glycerol be? ______________________

6. Fermentation

Chemical process where molecules are broken down.

For example, zymase, an enzyme (which act as catalysts) from yeast, breaks down glucose to form ethanol and carbon dioxide (carbonation.)

7. Polymerization

A polymer is a large molecule composed of many repeating units called monomers.

In polymerization, a number of smaller monomers join to form a larger polymer.

Natural polymers: proteins, cellulose, starch

Synthetic polymers: polyethylene, nylon and polyester.

a. Condensation Polymerization

Monomers are joined by a dehydration reaction of two alcohols whereby water is released and an ester linkage is formed.

This will continue to grow as additional monomers attach to the dimer.

Polyester is formed this way.

b. Addition Polymerization

Joining of unsaturated monomers to form long chains

The double or triple bonds are reduced to single or double bonds just like we learned earlier in addition reactions.

The letter n is used to denote that the monomer unit repeats.

Polymer Questions:

Practice Problems:

C

1 Carbon

Alkane

Example: Pentane

Example: 2-Pentene

3.