Chemistry (Hydrocarbons and Reactions with Hydrocarbons)

Question 1

What is a hydrocarbon?

Answer 1

A substance that is solely made up of carbon and hydrogen.

Question 2

Name and Describe the three groups of hydrocarbons

Answer 2

Alkanes: substances that contain carbon and hydrogen bonded together by only single bonds.

Alkenes: substances that contain carbon and hydrogen with at least one double bond within the structure.

Alkynes: substances that contain carbon and hydrogen with at least one triple bond within the structure.

Question 3

What are the numerical prefixes of hydrocarbons (1 -10)

Answer 3

1 - meth
2 - eth
3 - prop
4 - but
5 - pent
6 - hex
7 - hept
8 - oct
9 - non
10 - dec

Single Bond: ane
Double Bond: ene
Triple Bond: yne

Question 4

What are the 4 types of cyclic hydrocarbons

Answer 4

Cycloalkanes: this is a ring structure that only contains single bonds. An example is cyclopropane which has a triangular structure.

Cycloalkenes: the is a ring structure that contains at least one double bond. An example is cyclobutene which has a square structure and a double bond.

Cycloalkynes: this is a ring structure that contains at least one triple bond. An example is cyclopentyne which has a pentagon structure and a triple bond.

Aromatics: these contain benzene rings. A benzene ring is a six-carbon ring with three double bonds within it.

Question 5

Steps to writing branched-chain hydrocarbons

Answer 5

1. Count and find the longest continuous chain of carbons.
   Number the carbons in the longest chain starting with the end that’s closest to a branching group.
2. Count the number of carbons in each group that branches from the longest chain.
3. Attach the number of the carbon in the longest chain from which each group branches to the front of the alkyl group name (e.g. 3-methyl).
4. Check for repeated alkyl groups (e.g. 3,5-dimethyl or 2,2,4-triethyl).
5. Identify any halogen atoms attached to the longest chain and name them in the same way as the alkyl groups (e.g. 1-chloro or 2,4-dibromo)
6. Place the names of the substituent groups in front of the name of the parent chain in alphabetical order.

Question 6

What are the general properties of hydrocarbons

Answer 6

The longer a hydrocarbon chain is, the higher the melting or boiling point.

The more branching that occurs in a hydrocarbon chain, the lower the melting or boiling point.

Cyclic hydrocarbons have higher melting and boiling points than straight-chain hydrocarbons with the same number of carbons.

Question 7

What is a saturated and unsaturated hydrocarbon?

Answer 7

A saturated hydrocarbon is one that contains as much hydrogen as it can possibly handle. Alkanes/cycloalkanes are saturated hydrocarbons.

An unsaturated hydrocarbon is one that could have more hydrogen atoms added to it. Alkenes/cycloalkenes and alkynes/cycloalkynes are unsaturated hydrocarbons.

Question 8

What are the different types of hydrocarbon reactions

Answer 8

• Hydrogenation Reaction
• Halogenation Reaction (Addition)
• Halogenation Reaction (Substitution)
• Combustion

Question 9

What is a hydrogenation reaction? And an example?

Answer 9

Occurs in alkenes and alkynes when hydrogen gas is added to the hydrocarbon. This turns alkenes and alkynes into alkanes. The hydrogen atoms attack where the multiple bond occurs, breaking it to provide additional bonds for the new atoms.

examples:
1-propene + hydrogen gas -> propane
C3H6 + H2 -> C3H8

cyclopropene + hydrogen gas -> cyclopropane
C3H4 + H2 -> C3H6

Question 10

What is a halogenation addition reaction? And an example?

Answer 10

Occurs in alkenes and alkynes when a halogen is added to the hydrocarbon. This turns alkenes and alkynes into haloalkanes. The halogen atoms attack where the multiple bond occurs, breaking it to provide additional bonds for the new atoms.

1-propene + chlorine gas -> 1,2-dichloropropane
C3H6 + Cl2 -> C3H6Cl2
cyclopropene + chlorine gas - 1,2-dichlorocyclopropane
C3H4 + Cl2 -> C3H4Cl2

Question 11

What is a halogenation substitution reaction? And an example?

Answer 11

Occurs in alkanes where a halogen molecule interacts with one of the hydrogen atoms at the end of the hydrocarbon molecule. One of the halogen atoms replaces the hydrogen atom which bonds with the loose halogen atom to form an acid.

propane + chlorine gas -> 1-chloropropane + hydrogen chloride (hydrochloric acid)
C3H8 + Cl2 -> C3H7Cl + HCl
cyclopropane + chlorine gas -> 1-chlorocyclopropane + hydrochloric acid
C3H6 + Cl2 -> C3H5Cl + HCl
benzene + chlorine gas -> chlorobenzene + hydrochloric acid
C6H6 + Cl2 -> C6H5Cl + HCl

Question 12

What is a combustion reaction? And an example?

Answer 12

Combustion: when a hydrocarbon reacts with oxygen gas in the presence of heat, it decomposes into carbon dioxide and water.

propane + oxygen gas -> carbon dioxide and water
C3H8 + 5O2 -> 3CO2 + 4H2O