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Organic Chemistry

CHEM 30S

Learning Booklet

Name:

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What is organic chemistry?

The word ‘organic’ has been used widely in food that has been grown without the aid of fertilizers or chemicals enhancements. In chemistry, organic compounds are compounds that contain the element carbon.

However, not all compounds that contain carbon are organic compounds. Compounds such as carbon oxides, carbides (found mostly as geological rocks), and carbonates are considered inorganic or (non-living). The

unique property of carbon being able to form 4 covalent bonds allows carbon to be very versatile. In organic chemistry, carbon is mostly combined with hydrogen (if not bonded with anything else), oxygen, nitrogen, sulfur, phosphorus and the halogens. Biochemical molecules such as carbohydrates, fats such as lipids, and

nitrogenous bases (forms DNA) are all organic molecules. The interesting thing about organic chemistry is that the carbon can form from chains of 2 to thousands. It can also form complex ring structures or even cage like

structures.

Friedrich Wohler 1800-1882

The term organic came into use in the early 1700s, and people believed that in order to create organic compounds (compounds that life uses), a ‘vital’ force must be present. Because it was believed a ‘vital force’ must be present in order for organic chemicals to form, the organic molecules are only isolated or collected and cannot be synthesized.

It was not until Wohler where he disproved of this theory by producing an organic compound by synthesis. Wohler was into synthesizing inorganic compounds until his experiments led him in discovering the possibility of creating organic compounds.

Wohler reacted ammonium chloride and silver cyanate in a double displacement reaction hoping to create ammonium cyanate, but instead he created urea, an organic compound found in urine.

NH4Cl + AgOCN AgCl + CH4N2O (Urea)

By producing urea, he proved that a ‘vital force’ was not needed to create organic compounds.

Start:

One of the most basic organic compounds is the hydrocarbons. These are simple aliphatic (long chains) of carbons bonded with hydrogen hence HYDRO-CARBON. Hydrocarbons are non-polar molecules, and insoluble in water. They are flammable in oxygen to form water and carbon dioxide. An example is propane.

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Hydrocarbons can be alkanes, alkenes or alkynes, the ending of the name (-ane,-ene,-yne) suggests the type of bonding between the carbon atoms in the chain. Alkanes represents single bonds between the carbon atoms.

Alkenes represents a double bond(s) between the carbon atoms.

Alkynes represent a triple bond(s) between the carbon atoms.

A key to remember is that a carbon can form 4 covalent bonds, so you cannot have more than 4 atoms

bonded to 1 single atom.

Drawing models to represent organic compounds: (Example Methane)

The structural formula is the most used depiction of a formula in organic chemistry. The single ‘dash’ lines

represent single bonds, while 2 dashes represent a double bond and 3 dashes represent a triple bond. The ball

Molecular Formula Structural Formula Stick Formula Ball and Stick formula

Space-filling model

CH4

Cannot be

drawn

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and stick model demonstrates the geometry (bonding angles) of the compounds while the space-filling model show a more realistic picture of the molecule.

Alkanes:

Alkanes are single bonded chains of carbon and hydrogen atoms. In order to name them, a set of rules

established by IUPAC (International Union of Pure and Applied Chemistry) is there to dictate the naming order.

Number 1 rule: All alkanes will end with –ane as their ending

Number 2 rule: The prefixes will depend on the number of carbons there are based on the table below.

Example: There are 5 carbons, and they all have single bonds. Thus, Pentane!

Example 2:

Name: ____________________

Example 3:

Number of

Carbons Prefix Number of Carbons Prefix

1 meth- 6 hex-

2 eth- 7 hept- 3 prop- 8 oct-

4 but- 9 non-

5 pent- 10 dec-

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Name: ____________________

Example 4:

Name: ____________________

To simplify the drawings without writing out all the C and Hs, the stick model is used.

To use the stick model, you draw a straight line, and each END represents a CARBON atom. Hydrogen atoms are not drawn and are assumed to be at all the carbon atoms.

Since methane only has 1 carbon, stick model cannot be used. But if we look at ethane, which has 2 carbon atoms, it can be drawn as a straight line. The stick model is often used for longer chains where you have over 2 carbon atoms.

STRUCTURAL FORMULA STICK MODEL OF ETHANE

Example 5:

Something interesting about refining hydrocarbons or separating petroleum

Hydrocarbons are obtained from petroleum (a fossile fuel). Unrefined petroleum (raw petroleum) is a thick

mixture containing more than a thousand different compounds. In order to make the petroleum useful, it has to be separated into the separate components. Separation is through a processed called Fractional distillation, where the petroleum is boiled and based on the boiling points of the different compounds in the mixture similar components with reasonably similar boiling points are collected. As the molecules are boiled in the

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chamber, there is a cooling temperature gradient where the smaller molecules condense at lower temperatures.

Fractional distillation produces more of the heavier compounds than the lighter ones. Chemists and engineer

developed the method of “cracking” where the larger molecules are broken down into smaller molecules.

Alkyl Groups:

Straight hydrocarbon chains do not just have a straight line of carbon and hydrogen atoms. Sometimes they will have a branch of another chain that stems from the main chain. These branched single bonded groups are called alkyl groups. The branch will also have single bonds only and the prefix of these groups will still follow

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the IUPAC naming of the number of carbon atoms (ie. Meth – 1 carbon, eth- 2 carbon etc..). However, the suffix or the ending will have –yl instead.

Methyl Ethyl Pentyl Octyl

-CH3 -CH2-CH4 -CH2-CH2-CH2-CH2-CH4 -CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH4

Naming branched-chain alkanes with alkyl groups:

Step 1: Count the number of carbon atoms in the longest continuous chain

Step 2: Number each carbon in parent chain where the carbon closest to the substituent (alkyl) group is position 1.

Step 3: Name each alkyl group substituent by placing the name of the group BEFORE the name of the parent

chain.

Step 4: If the same alkyl group occurs more than once as a branch on the parent structure, use a prefix (di-, tri-, tetra-, and so on) before its name to indicate how many times it appears. Ex: di-methyl 1,4 for methyl group

on carbon 1 and 4

Step 5: When different alkyl groups are attached to the same parent structure, place their names in alphabetical order. Do not consider prefixes when determining order.

Step 6: Write the entire name, using hyphens to separate numbers from words and commas to separate numbers. Do not add a space between the substituent name and the name of the parent chain.

WOW

Example 1:

Count the number of carbons in the longest continuous chain.

Thus, this is a HEPTANE

Now, add the substituents, we have 3 substituents, 1 ethyl, and 2 methyl groups.

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We need to name them with the smallest carbon atom position as possible. If we were to start from the left side, the groups would be 4 and 6 not 2 and 4.

Now, since we have 2 methyl groups, we need the prefix di- to indicate 2 methyls. Ethyl is on the 4th carbon so

we put 4- in front of ethyl.

4-ethyl-2,2-dimethyl

Finally, include the parent chain,

4-ethyl-2,2-dimethylheptane (notice no spaces)

Example 2:

CH3CH(CH3)CH2CH(CH3)CH3

The brackets represent branched substituents.

Expand it!

Count the longest carbon chain:

Number the carbons

PENTANE!

Final name: 2,4-dimethylpentane

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Example 3:

Answer: 3,3,5-trimethyloctane

Example 4:

Answer: 3-methyl-4ethylheptane

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Cyclohexane

Due to the unique properties of carbon atoms, numerous varieties of organic compounds can exist. Carbon atoms not only can form aliphatic short or long chains but can also form ring structures called cyclic

hydrocarbon. The prefix cyclo- is used with the hydrocarbon name. Thus, cyclic hydrocarbons containing only single bonds are called cycloalkanes.

Cycloalkanes can have rings of 3, 4, 5, 6 or more carbon atoms, but more commonly cyclohexane is found.

Structure of cyclohexane:

Or commonly written as

Naming cycloalkanes with substituents:

Example: name the structure on the right.

1. Count the number of carbons and determine the kind of cyclohexane. In this case, it is a cyclohexane.

2. Number the ring, starting from one of the methyl groups. Find the numbering that gives the lowest possible set of numbers for the branches.

3. Name the substituents. All three are methyl groups 4. Add prefixes, since there are three methyls, we need tri-

5. Arrange in alphabetical order (cannot be done for this structure) 6. Put the name together

1,2,4-trimethylcyclohexane

Example 2:

1. Count the number of carbons. It is a cyclohexane 2. Number the carbons.

3. Name the substituents. There are 2 methyl and 1 ethyl group 4. Add prefixes. So dimethyl 5. Arrange in alphabetical order. 4-ethyl-1,2-dimethyl

6. Finally,

4-ethyl-1,2-dimethylcyclohexane

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Alkenes and alkynes

Alkenes are unsaturated hydrocarbons because there is a double bond between 2 of the carbons in

the carbon chain. A double bond is drawn as –C=C– where two pairs of electrons are shared. Due to

the two pairs of electrons sharing, there is only 1 hydrogen atom in each of the carbon atoms instead of two found in single bonded carbon chains. The formula for alkenes is CnH2n where n is the number of carbons in the chain.

Naming alkenes:

The steps are similar to alkanes except now you will need to identify where the double bond is in the carbon chain.

Example: Name the structure CH2=CHCH2CH2CH3

1. Expand the structure.

2. Number the carbon chains starting from the side where the double bond is closest.

3. Thus, the compound is 1-pentene.

Example 2: CH3CH=CHCH2CH3

1. The example is similar to example 1 except the double bond is now on the 2nd carbon.

Thus, 2-pentene.

Example 3:

1. Expand - This is done

2. Number the carbons from the carbon that is closest to the double bond.

3.

4. Name the substituent. Here we have a methyl group on carbon #4

5. Therefore, 4-methyl-2-pentene.

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Example 4:

CH3CH2CH(CH3)CH=C(C2H5)CH2CH3

1. Expand

2. Find the longest carbon chain with the double bond.

3. Name the substituents.

We have 1 methyl group on carbon 5

We have 1 ethyl group on carbon 3

4. Arrange in alphabetical order

5. Therefore, 3-ethyl-5-methyl-3-heptene

****Check for HYPHENS (between numbers and letters) and COMMAS (between numbers)****

Alkynes:

Alkynes are also unsaturated hydrocarbons (does not have all single bonds). In alkynes, there is at least a triple

bond between two carbon atoms. To denote a triple bond, –C≡C– is used. The general molecular formula

for alkynes is CnH2n-2 where n is the number of carbons. These standard formulas will help you understand the number of carbons found in these hydrocarbons without counting them one by one.

Naming alkynes is similar to alkenes but instead of using –ene as the ending, the ending –yne is used.

Example:

Name CH3–C≡C–CH2–CH3

1. Number the carbons

2.

3. 3-pentyne

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Example 2:

Name: HC≡CCH2C(C2H5)2CH2C(CH3)CH(CH3)CH3

1. Expand

2. Find the longest carbon chain with the triple bond

3. There are 4 substituent groups, 2 ethyl groups and 2 methyl groups

4. Use prefixes for the two ethyl groups and arrange them in alphabetical order

5. 4,4-diethyl-6,7-dimethyl

6. Put it all together: 4,4-diethyl-6,7dimethyl-1-octyne

Example 1:

Draw the structural formula for 1-butyne.

1. The prefix “but-“ is for 4 carbon chain.

2. The suffix “-yne” is for alkynes

3. The 1 indicates the triple bond is on the 1 carbon.

4. Thus, HC≡C–CH2–CH3

Example 2:

Draw the structural formula for 2,2,5,5-tetramethyl-3-hexyne.

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Answer: or CH3C(CH3)2C≡CC(CH3)2CH3

Hydrocarbon isomers

Isomers are when two or more compounds have the same molecular

formula but different molecular structures. It can be broken down

further into different classes of isomers. We will focus on structural

isomers and stereoisomers.

Structural isomers are when the compounds have the same

chemical formula, but their atoms are bonded in different arrangements.

Analyze the diagram on the right, and you can see that both of the

compounds have the same number of carbon atoms and hydrogen atoms,

but the double bond is different. The change in the structure will play a

role in the properties of the compound despite having the same formula.

Stereoisomers are isomers where all atoms are bonded in

the same order but are arranged differently in space. The

diagram on the right shows that the methyl groups can

either be on the same side (cis) or across from (trans) from

Butane 2-methylpropane

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each other. The bonds must be double bonds since it restricts the rotation of the bonds. The different

arrangements can play a enormous role in biology such as drug effects.

Drawing structural isomers

When constructing or drawing structural isomers, it is a good idea to draw out all the carbon atoms without

the hydrogen atoms first. After the carbon atoms have been drawn, rearrange the carbon atoms until you

have found all the different combinations with the same molecular formula.

Example 1. Draw and name 2 structural isomers of pentane, not including pentane.

Step 1: Write the chemical formula

Pentane is a 5-carbon alkane, so its molecular formula is C5H12.

CH3–CH2–CH2–CH2–CH3

Step 2: Draw different arrangements of carbons.

We can start by taking one carbon off the end and making it a branch. Remember, we are just drawing the

carbons. Then name it.

One way is there are still 5 carbon atoms but now it is no longer a pentane. This is ok. 2-

methylbutane.

If we move the carbon to the next carbon atom, it is still the same as the one above. So, this would not work.

Try taking another carbon atom from the end and attaching it to the internal carbon atoms.

This will give 2,2-dimethylpropane. Therefore, there are 2 structural isomers.

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Naming Cis and trans stereoisomers:

1. The longest carbon chain for the diagram on the right is 5, thus, pentane.

2. Because it has a double bond, the rotation of the methyl and ethyl group is restricted, thus, an

stereoisomer.

3. For the “cis” the methyl and ethyl groups are on the same side, while the methyl and ethyl groups are

across from each other for the “trans”. The 2-pentene is still the same between both of them, now we

just have two new words (cis, and trans) to indicate where they are located.

Example 1:

Name both of the following: and

1. Both of them have 4 carbon atoms as their main chain, thus a butene.

2. The double bond is on the 2nd carbon, thus, 2-butene.

3. The first one has the ends on opposite sides, while the second one has their ends on the same side.

Therefore, trans-2-butene and cis-2-butene.

Example 2:

Name both of the following:

1. The longest carbon chain is 6 for both, thus a hexene.

2. The double bond is on carbon 3

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3. Both of them have their methyl group on carbon 4 but the first one is trans, while the second one is cis.

4. 1st one is trans-3-methyl-3-hexene and the second one is cis-3-methyl-3-hexene.

Aromatic hydrocarbons

Aromatic hydrocarbons are unsaturated (contains at least a double or triple bond). Aromatic hydrocarbons

are unusually stable compounds with ring structures in which electrons are shared by many atoms. Aromatic

hydrocarbons are associated with the basic structure of benzene where it is a 6 carbon ring with double bonds.

The molecular formula for benzene is C6H6. Aromatic hydrocarbons can give off wonderful odours such as

cinnamon, wintergreen, vanilla etc…

The structure of Benzene

or

The stick structure can also be drawn as indicating an equal sharing of electrons around all the

carbons. One unique feature of benzene is that experiments have indicated that the double bonds found in

benzene isn’t entirely double bonds but halfway between a single and double bond.

Functional groups

Now we will focus on the various derivatives that can be included in addition of hydrocarbons. These

functional groups can replace one or more hydrogen atoms with another non-hydrocarbon group. These

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functional groups are the ones that define alcohol, carboxylic acids, esters and many others. We will focus on

alcohols, carboxylic acids and esters.

Alcohols

The functional group for alcohol is –OH or the hydroxyl group. The functional group of alcohol defines what an

alcohol is, thus, all alcohols whether methanol, propanol or ethanol, have the functional group –OH in the

carbon chain. The general formula for alcohol is R-OH, where R is the carbon chain.

Naming alcohols:

Step 1: Identify the parent chain and replace the -e with –ol

Step 2: Number the carbons so the carbon containing the hydroxyl group has the lowest number.

Step 3: Name any substituent groups (alkyl) based on alphabetical order

Example 1: CH3CH2OH

1. It has an –OH, therefore it is an alcohol

2. There are 2 carbons, so it is an ethane

3. There are not other groups to add so we will skip step 3

4. The name is ethanol

Example 2:

1. It has an –OH so it is an alcohol

2. It has 5 carbons as the longest chain, so it is a pentane

3. Number the carbons with the –OH as the lowest carbon atom

4. Name any other alkyl group, in this case, the methyl group on carbon 4

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5. 4-methyl-2-pentanol

Practice

1.

2.

3. CH3CH(CH3)CH2CH2CH2CH2CH(OH)CH3

Draw the structural formula for each of the following.

a) 3-ethyl-3-methyl-1-hexanol

b) b) 2,3-dimethyl-2-butanol

c) c) 3,3,4,5-tetramethyl-2-heptanol

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Carboxylic acids

Carboyxlic acids contain the carboxyl functional group, -COOH. The –COOH is actually the condensed version

of . Small carboyxlic acids molecules are very polar

and are soluble in water.

Naming carboxylic acids

Similar to alcohol, there are some common names. When naming carboxylic acids, replace the –e with –oic

acid. Numbering the carbon chain always begins with the carbon containing the carboxyl group, but because

the functional group is attached to the carbon, we do not write the “1” for the functional group.

Example 1

1. There are two carbons, thus it will start with ethan-

2. Add –oic acid at the end to make ethanoic acid, or commonly known as acetic acid.

Example 2

CH3CH(CH3)CH2CH2COOH or

1. There are 5 carbons in the longest chain.

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2. There is a methyl group on carbon 4, so it will be 4-methylpentanoic acid.

Esters

Esters are the result of a reaction between and organic acid and alcohol. The acid and alcohol are heated in

the presence of a catalyst, usually concentrated sulfuric acid to dehydrate the reaction. Esters usually give off

a variety of scents.

In the reaction, the OH from carboxylic acid combines with the –H from the alcohol to form water. Thus, the

basic formula for esters is R-COO-R’

Naming esters

When naming esters, the alkyl group joined to the single bonded oxygen is named first, replacing the –ol (of

alcohol) with –yl. In a separate word, the acid is named with –oic acid ending to –oate.

Example 1:

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or CH3COOCH2CH2CH3

1. This compound has R-COO – R’ so it is an ester.

2. In the alcohol (the one with the single oxygen), used to be propanol, so

we will change the propanol to propyl.

3. The acid has 2 carbons, so it was ethanoic acid, now we change it to ethanoate.

4. Finally, it is propyl ethanoate.

Example 2:

1. It is an ester because it is separated by a –COO

2. On the alcohol side, there are 4 carbons, so it will be butyl (changing from butanol to butyl)

3. On the acid side, there are 6 carbons, so it will be hexanoate (changing from hexanoic acid to

hexanoate).

4. Finally, it will be butyl hexanoate.

Interesting facts…

Ethyl butanoate smells like pineapple, while pentyl ethanoate smells like bananas and octyl ethanoate smells

like oranges.

Break down summary:

Organic Chemistry

Hydrocarbon

chains Aliphatic chains Alkanes Alkenes Alkynes Naming Functional groups

Alcohol Carboxylic

acid

Esters Aromatic Benzene Isomers

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Practic

e

Day 1 Exercise:

1. Complete the chart below

Number of Carbons

Name of Alkane

Molecular Formula

Structural Formula

Condensed Structural Formula

1

2

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2. The first 10 alkanes above follow a particular general formula. Write the general formula below? What do the symbols in the formula tell you (i.e. what do they mean?)

3

4

5

6

7

8

9

10

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3. What would be the molecular formulas for a 14-carbon alkane, a 100-carbon alkane, and a 50-carbon alkane?

4. Are any of the alkanes in your chart considered unsaturated (containing at least one double or triple bond)? Why or Why not?

5. List the prefixes used to name alkanes from 1 carbon to 10 carbons?

6. What is organic chemistry?

7. Draw out the various models in how a molecule can be expressed.

Day 2 Exercise

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Day 2 Homework Exercise

1. _______________________________ 2. _______________________________

3. _______________________________ 4. _______________________________

5. _______________________________ 6. _______________________________

7. _______________________________

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Draw out the following structures by using the stick model:

1. 4-ethyl-octane

2. 2-methyl-nonane

3. 2-ethyl-2-methyl-butane

4. 2,2,3-trimethyl-butane

5. 3-ethyl-2,2-dimethyl-hexane

6. 2,3,4,5,6,7-hexamethyl-nonane

7. 3-ethyl-pentane

8. 2-butyl-3-ethyl-4-methyl-hexane

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Day 4 – Naming Alkenes

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Day 4 homework – Naming alkynes

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Day 5 – In class assignment

1. Explain the process of refining hydrocarbons from petroleum. What is fractional distillation?

2. Draw the following structures

a. Propane

b. Nonane

c. 2,2-dimethypentane

d. methylcyclohexane

e. 3-ethyl-2,4-dimethylpentane

f. ethylcyclohexane

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g. 2,3-dimethyl-1-pentene

h. 2-methyl-1-butene

i. 1,3-dimethylcyclobutane

j. 3,4-dimethyl-3-pentyne

k. 1-ethyl-2,3-dimethyl-5-nonyne

Name the following structures:

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Day 5 Homework:

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2,2,3-trimethylbutane

3-ethyl-3-methyl-1-pentyne

2,3-dimethyl-2-butene

Day 6 Exercise:

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CH3CH2CH2OH

HOCH2(CH2)2CH3

CH3CHOOH

HCOOHCH2CH3

2-methyl-2-butanol

2,3,4-trimethyl-1-pentanol

3-ethly-2,4-dimethyl-1-hexanol

3,3-diethyl-2-hexanol

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2,3-dimethyl-butanoic acid

2-methyl-propanoic acid

Day 7 – Naming esters

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Remaining days:

Organic review

Draw the molecule for the following organic compounds in the space provided.

(a) 2,2 dimethylbutanoic acid

(b) 4-methyl-3-hexanol

(c) 2-methyl-3-hexyne

(d) 2,3,3-trimethyl-pentane

1. Which of the following are structural isomers of hexane?

Name or draw the following:

CH2=CHCH2CH2OH

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Methyl propanoate

Ethanoic acid

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2-methylbutanoic acid