MYP Chemistry Alkanes, Alkenes, Alcohols Notes

Introduction to Organic Chemistry

1. Organic chemistry is the study of carbon-based compounds, especially those containing C–C and C–H bonds.
2. Most molecules in living things – sugars, fats, proteins, DNA – are organic, as well as many fuels, plastics, medicines and dyes.
3. So when we study alkanes, alkenes and alcohols, we are really starting to explore the huge family of organic molecules built around carbon.

Why Carbon Is So Important

Carbon is special because it can:

1. Form four covalent bonds (it is tetravalent).
2. Bond to other carbon atoms to form long chains and rings.
3. Form single, double and triple bonds (C–C, C=C, C≡C).
4. Bond to many other elements: H, O, N, halogens, S, etc.

Homologous Series and Functional Groups

To organise this huge number of compounds, chemists use the ideas of:

1. Homologous series
2. Functional groups

Homologous Series

A homologous series is a family of organic compounds that:

1. Have the same functional group
2. Follow the same general formula
3. Differ by –CH₂– units between members
4. Show similar chemical properties
5. Show gradual trends in physical properties (e.g. boiling point increasing with chain length)

Functional Groups

1. A functional group is a specific group of atoms in a molecule that is responsible for its characteristic reactions.
2. Different functional groups → different types of reactions and uses.

Naming Organic Compounds: IUPAC Basics

1. In organic chemistry we use a systematic naming system called IUPAC nomenclature.
2. For now, we’ll focus on simple, unbranched alkanes, alkenes and alcohols.
3. You will build three key skills:
   1. Recognizing the root name (how many carbons)
   2. Identifying the functional group (what family)
   3. Using the correct suffix (-ane, -ene, -ol)

Root Names – Number of Carbon Atoms

The root tells you how many carbons are in the longest continuous chain:

For MYP level, 1–6 carbons is usually enough to start with.

Suffix – Which Functional Group?

The ending of the name (suffix) tells you which homologous series the compound belongs to:

1. Alkanes → -ane
   1. e.g. ethane, propane
2. Alkenes → -ene
   1. e.g. ethene, propene
3. Alcohols → -ol
   1. e.g. ethanol, propanol

Position Numbers (for alkenes and alcohols)

1. When the functional group can be in different positions along the chain, we add a number to show where it is.
2. Number the carbon chain so that the functional group gets the lowest possible number.

Types of Formula in Organic Chemistry

1. In organic chemistry, we often represent molecules in different ways depending on how much detail we need.
2. It’s important to recognise and move between these formula types.
3. We will mainly use:
   1. Molecular formula