Hydrocarbons

Introduction to Functional Groups

• the molecules are soluble in polar or non-polar solvents
• the molecules have high or low melting and boiling points
• molecules readily react with other molecules

• There are many different functional groups but they essentially consist of only 3 main components:

1. Carbon-Carbon multiple bonds (-C=C- or -C≡C-)
2. Single bonds between a Carbon atom and a more electronegative atom (eg. C-O, C-N, or C-Cl)
3. Carbon atom double bonded to an oxygen atom (-C=O)

Introduction to Hydrocarbons

• A hydrocarbon is an organic compound that only contains carbon and hydrogen atoms

Unsaturated vs Saturated Hydrocarbons

• A saturated hydrocarbon is one that has the maximum number of hydrogens added (no double or triple bonds)
• Alkanes are saturated hydrocarbons
• While alkenes and alkynes are unsaturated hydrocarbons

• Alkanes are hydrocarbons that only have single bonds between carbon atoms ... CnH2n+2
• Alkenes are hydrocarbons that have at least 1 C=C double bond ...CnH2n
• Alkynes are hydrocarbons that contain at least 1 C≡C triple bond ... CnH2n-2

• Aliphatic hydrocarbons: compounds that have a structure based on straight or branched chains or rings of carbon atoms (does not include aromatic compounds like benzene)
• Includes: alkanes, alkenes, alkynes, and cyclic hydrocarbons
• Aromatic hydrocarbons: a compound with a structure based on benzene (C6H6).
• benzene has all 6 Cs in intermediate length between a single and double bond because of resonance

Cyclic Hydrocarbons

5 Ways to Represent Alkane Structures

Properties of Alkanes, Alkenes, & Alkynes

• Are non-polar
• Soluble in non-polar solvents (Like dissolves like)
• Don't dissolve in water (polar)
• Boiling point increases as the chain gets longer due to increased intermolecular forces (London dispersion forces)
• Highly branched alkanes have lower boiling points
• *Think: tree trunk vs small branches
• Alkenes have lower boiling points than alkanes with the same number of carbon atoms
• Alkynes have higher boiling points than alkanes with the same number of carbon atoms (it has to do with the triple bond and how it creates a linear structure, which causes the atoms to attract each other more strongly, so it takes more energy to break them apart)
• Aromatic hydrocarbons have similar boiling points as aliphatic hydrocarbons with the same # of carbons
• Benzene is a liquid at room temperature
• Aromatic compounds were named this because they are "aromatic" and often have strong odours