2.2 Representing Hydrocarbons and Simple Organic Compounds

What is Tamoxifen used for? What is it?

• Breast cancer (Estrogen Receptor positive cancer)

• An organic molecule

Where are the carbon atoms in a skeletal formula drawing?

• At the jagged angle

What is interesting of Hydrogen atoms in a skeletal formula drawing?

• Each carbon (each angle) is assumed to have the maximum possible number of Hydrogen atoms bonded to it

Hydrocarbons are a specific class of organic compounds that contain only two elements:

• Carbon and Hydrogen

What are some everyday examples of where we can find hydrocarbons?

• Natural gas in homes

• Gas for cars

• Propane in BBQs

• Butane in lighters

• Asphalt

• Candle wax

• Tar

• Plastics

Hydrocarbons are divided in how many categories? Based on what?

• 3 main categories

• Whether their Carbon atoms have single, double, or triple bonds with each other

What are the names of the 3 categories of Hydrocarbons?

1. Alkanes

2. Alkenes

3. Alkynes

Alkanes contain only-

• Single carbon-to-carbon bonds

Alkenes contain at least-

• One carbon-to-carbon double bond

Alkynes contain at least-

• One carbon-to-carbon triple bond

Define aliphatic hydrocarbons

• Organic compound made of Carbon and Hydrogen that does not have rings; has open chains

Define aromatic hydrocarbons

• Organic molecules composed of Carbon and Hydrogen that contain one or more cyclical rings

This is an example of what type of hydrocarbon?

• Alkene

This is an example of what type of hydrocarbon?

• Alkyne

This is an example of what type of hydrocarbon?

• Alkane

This is an _____ hydrocarbon

• Aromatic

These are examples of _____ hydrocarbons

• Aliphatic

The longest of the long-chain hydrocarbons tend to be _____ at room temperature

• Solid

What is an interesting trend of Hydrocarbons? Why?

• Molecules with more Carbons have higher melting and boiling points

• Because of the strong intermolecular forces in the long structures which makes the molecules attract

Many short-chain Hydrocarbons are _____ or _____ at room temperature. Why?

• Gases or liquids

• Because they have weaker intermolecular forces

Alkanes all end in _____ which immediately tells you what?

• -ane

• The compound will only have single carbon-to-carbon bonds

The prefixes of Alkanes tell you what?

• The number of Carbon atoms in the compound

Name the first 10 prefixes of Alkanes

1. Meth-

2. Eth-

3. Prop-

4. But-

5. Pent-

6. Hex-

7. Hept-

8. Oct-

9. Non-

10. Dec-

What is a phrase that will help you remember the names of Alkane prefixes?

• Monkeys Eat Peeled Bananas. Please Hand Him One. Nicely Done!

Do Alkanes only come in lines? Can they have chains branching off the main chains?

• Yes, they can have branches

A branch off an Alkane is called what?

• An Alkyl group

Branches must be named in-

• Alphabetical order

When considering large molecules, is it possible to have more than one possibility for connecting their atoms?

• Yes

Can you have two different compounds with the same molecular formula?

• Yes

Molecules that have the same molecular formula but different structures are called what?

• Structural isomers

How can you tell if two structures are isomers?

• If they have the same molecular formula but are named differently

Describe physical and chemical properties between isomers

• Physical: different

• Chemical: sometimes similar

The number of structural isomers _____ as the number of carbon atoms in the molecular formula _____

• Increases

• Increases

Alkenes are the class of Hydrocarbons that contain at least one-

• Carbon-to-Carbon double bond

• C=C

The presence of a double bond (or a triple bond) increases what?

• The reactivity of the compound compared to an Alkane with a similar number of Carbons

Why is C₂H₄ more reactive than C₂H₆?

• Because C₂H₄ has a double bond between the carbons

What is the smallest member of the Alkene family? What is its formula?

• Ethene

• C₂H₄

Ethene is a _____ at room temperature

• “gas”

What is the everyday use of Ethene?

• Manufacture of polyethylene/polythene- a plastic used in home insulation and water bottles

The Alkyne family of Hydrocarbons contain at least one-

• Carbon-to-Carbon triple bond

What does the suffix become for Alkynes?

• -yne

What is the simplest Alkyne? What is its formula?

• Ethyne

• C₂H₂

What is the common name of the Alkyne Ethyne? What is its everyday use?

• Acetylene

• Used primarily as a fuel in welding torches

Name the 3 types of reactions involving these compounds

1. Combustion

2. Addition

3. Substitution

Can all Hydrocarbon compounds undergo combustion reactions? What about all organic molecules?

• Yes

• Yes

A combustion reaction occurs when a Hydrocarbon is _____ in the presence of _____

• Heated

• Oxygen

When a Hydrocarbon undergoes combustion, what 2 things could occur?

1. It can combust quickly (explode)

2. It can combust slowly (burn, smoulder)

Describe a car’s combustion engine

1. Engine has several chambers shaped like cylinders

2. Pistons are metal plungers that slide in and out of the cylinders

3. Gas is mainly octane. When it’s ignited by a spark inside a piston chamber it explodes in the presence of oxygen. Explosion causes energy to be released

4. This energy causes the pistons to move outward. This motion, translated through gears, is the forward motion of the car

5. Energy from a nearby cylinder pushes the first piston back into the cylinder so that the process is continuous

Which are more chemically reactive- Alkenes + Alkynes or Alkanes?

• Alkenes and Alkynes

What is an addition reaction in Alkenes and Alkynes?

• One of the double or triple bonds is broken and the Carbon atoms involved are allowed to form bonds with other elements

What is a saturated Hydrocarbon? Which type of Hydrocarbon are they?

• When a Hydrocarbon is saturated with Hydrogen

• Each Carbon atom has the maximum possible number of Hydrogen atoms and no more Hydrogen atoms can be added to the compound

• Alkane

Why are Alkenes and Alkynes unsaturated Hydrocarbons?

• Because they contain less than the maximum possible number of Hydrogen atoms due to the presence of the double/triple bonds

What does “in excess” mean?

• A way to completely saturate an Alkyne

• Add Hydrogen, for example by bubbling Hydrogen gas through it

• The reaction would have H₂ (in excess) written on the left side of the equation

Can all Hydrocarbons undergo substitution reactions?

• Yes

What is required for a substitution reaction to occur?

• A catalyst

Define catalyst

• A compound that helps promote a reaction but does not get used up in the process

In a substitution reaction, a _____ atom is replaced by a different atom/group of atoms

• Hydrogen

Covalent compounds share electrons. Is this sharing equal?

• No

_____ is a physical property of compounds that results from the uneven distribution of electrons among adjacent atoms

• Polarity

What does the unequal sharing of electrons (-) mean for covalent compounds?

• Polar compounds have a slightly negative side and a slightly positive side

When looking at a compound, how could you know which element will attract the electrons more?

• By their electronegativity value

• The higher an element’s electronegativity value, the more the element pulls the electron pair close to it

Electronegativity (EN) is defined as what?

• The ability of an atom to attract electrons

On the periodic table- the trends of electronegativity show that electronegativity _____ as you go down and _____ as you move from left to right

• Decreases

• Increases

In regards to electronegativity, what is special about the noble gases?

• Since they do not react, they are rarely assigned EN values

What does this picture mean?

• You can use the difference in the electronegativity value between two atoms to classify it

Besides EN values, polarity can also be determined by looking at-

• The overall symmetry of the compound

• More symmetric means non-polar