Organic Compounds
Definition: Organic compounds are special types of substances that always contain carbon as one of their main building blocks. These compounds are very important because carbon can form many different shapes and bonds, which makes it easy to create a huge variety of substances.
Bonding: In organic compounds, carbon atoms don’t work alone. They make covalent bonds, which means they share electrons, with other elements such as hydrogen, oxygen, nitrogen, sulphur, and phosphorus. These bonds hold the atoms together to form stable molecules.
Origin: Many organic compounds are made naturally by living things. This means that they can be found in plants, animals, and even tiny organisms like bacteria. That’s why they are called “organic” – they usually come from organisms.
Biological examples: Some common examples of organic compounds made by living things include carbohydrates (like sugar), proteins (like those in meat and beans), and lipids (like fats and oils).
Other natural examples: Besides the big three (carbohydrates, proteins, and lipids), our bodies and other living things also make organic substances like vitamins (which help keep us healthy) and hormones (which control body activities like growth and emotions).
Fossil sources: Organic compounds are also found in the Earth, not just in living things. Things like petroleum (oil) and natural gas are made from dead plants and animals that were buried millions of years ago. That’s why they’re also called fossil fuels.
Synthetic materials: Humans have also learned how to make their own organic compounds. These include plastics (like those used in bottles and toys) and synthetic fibres (like nylon and polyester used in clothes).
Inorganic Compounds
Source: Inorganic compounds are different from organic ones because they usually come from non-living things, like rocks, minerals, and water.
Bond absence: One big difference is that inorganic compounds usually do not have carbon bonded with hydrogen. That special bond is mostly seen in organic compounds.
Carbon presence: Some inorganic compounds do have carbon, but it’s usually bonded with other things like oxygen or metals, not hydrogen.
Examples: Common inorganic compounds that contain carbon include carbon monoxide (a dangerous gas), carbon dioxide (the gas we breathe out), carbonates (like the ones in chalk and shells), and cyanides (which can be poisonous).
Hydrocarbons
Composition: Hydrocarbons are a group of organic compounds made only from two types of atoms: carbon and hydrogen. There are no other elements in them.
Classification: Hydrocarbons can be split into two main groups. Saturated hydrocarbons have only single bonds between the carbon atoms, while unsaturated hydrocarbons have one or more double or triple bonds.
Alkanes: Alkanes are a type of saturated hydrocarbon. This means that all the carbon atoms are joined by single bonds only. They are quite stable and don’t react easily.
Unsaturated types: On the other hand, unsaturated hydrocarbons are more reactive because they have at least one double or triple bond between carbon atoms.
Alkenes: Alkenes are unsaturated hydrocarbons that have at least one double bond between carbon atoms. This double bond gives them special properties.
Alkynes: Alkynes are another kind of unsaturated hydrocarbon, but they have at least one triple bond between carbon atoms, which makes them even more reactive than alkenes.
Sources: Hydrocarbons are found in nature inside crude oil, coal, and natural gas. These sources are called fossil fuels.
Petroleum content: Petroleum, or crude oil, is made up of many different hydrocarbons. That’s why it’s such an important source of energy and materials.
Fuel use: We use hydrocarbons every day as fuels. They power cars, buses, airplanes, and are also used for cooking and in factories.
Energy release: When hydrocarbons burn (combust), they react with oxygen and release energy. This energy is used for heat, light, and motion.
Alkane formula: The general formula for alkanes is CₙH₂ₙ₊₂. This means if you know how many carbon atoms (n), you can find out how many hydrogen atoms there are.
Alkene formula: Alkenes follow the formula CₙH₂ₙ. That’s because of the double bond between two carbon atoms.
Alkyne formula: Alkynes have the formula CₙH₂ₙ₋₂. The triple bond makes them lose more hydrogen compared to alkanes.
Non-Hydrocarbons
Definition: Non-hydrocarbons are organic compounds that, in addition to carbon and hydrogen, also have other elements like oxygen, nitrogen, or halogens (like chlorine).
Alcohols: Alcohols are organic compounds that contain a special group called hydroxyl (-OH). This group makes alcohols able to dissolve in water and react in special ways.
Carboxylic acids: These are organic acids that have a carboxyl group (-COOH). They taste sour and are found in vinegar and citrus fruits.
Esters: Esters are sweet-smelling compounds formed from carboxylic acids and alcohols. They are used in perfumes and flavourings.
Biological examples: Some important biological non-hydrocarbons are proteins (needed for growth), fats (used for energy), and carbohydrates (like sugar and starch, also used for energy).
Functional groups: The special groups like -OH or -COOH are called functional groups. They control how the molecule behaves and reacts with other substances.
Additional Notes
Homologous Series
Definition: A homologous series is a group of organic compounds that have a similar structure, the same functional group, and follow a general formula. They behave in similar ways during chemical reactions.
Unit difference: Each member in a homologous series differs from the next by one extra -CH₂- group. This small change makes a big difference in properties.
Property trend: As we go up the series (adding more -CH₂- units), the physical properties like melting point and boiling point change gradually.
Example trend: For example, the boiling point of each compound gets higher as we add more carbon atoms to the chain.
Isomerism
Definition: Isomers are compounds that have the same molecular formula (same number and type of atoms), but their atoms are arranged differently. This gives them different properties.
Types: There are a few types of isomerism:
- Chain isomerism: atoms arranged in different shapes.
- Positional isomerism: same groups but in different places.
- Functional isomerism: different functional groups altogether.
Reactions
Combustion: When hydrocarbons burn in the presence of oxygen, they release a lot of heat and light. This is called combustion and is why they are used as fuels.
Substitution: Alkanes can go through substitution reactions, where one of their hydrogen atoms is swapped for another atom, usually when light or heat is present.
Addition reactions: Alkenes can take part in addition reactions because of their double bond. They can add hydrogen (hydrogenation), halogens (halogenation), or water (hydration).
Alcohol production: Alcohols can be made by fermenting sugar using yeast (a natural process), or by adding water to an alkene (a chemical process).
Alcohol reactions: Alcohols can also be burned to release energy, dehydrated to form alkenes, or oxidised to become acids.
Acid reactions: Carboxylic acids can react with bases (like sodium hydroxide) to form salt and water. This is a neutralisation reaction.
Ester formation: Esters are made when a carboxylic acid reacts with an alcohol, usually with some acid added as a helper (catalyst).