Organic Chemistry - Basic Principles and Techniques
Class 11 · Chemistry
4 ideas in Class 11 Chemistry, explained in plain words, with games and quizzes to practise.
Tetravalence and Classification
Part of: Framework and Names
Carbon's four tetrahedral bonds build chains, rings and branches. Skeletons split into open and closed, saturated and unsaturated; groups like hydroxyl, carbonyl and carboxyl define families with shared chemistry.
Why it matters. Families predict reactions before memorising each molecule. Skeleton plus group names every compound.
Formulas
- Members of a homologous series differ by one CH2 group
- Alkanes follow CnH2n+2
Key words
- Tetravalence
- : Carbon always makes four covalent bonds in organic compounds.
- Catenation
- : Carbon links to itself in long stable chains, branches and rings.
- Homologous series
- : A family of compounds differing by one CH2 group with similar chemistry.
- Functional group
- : An atom group on carbon that fixes the family and its reactions.
- Saturated hydrocarbons
- : Hydrocarbons with only single carbon-carbon bonds.
- Unsaturated hydrocarbons
- : Hydrocarbons with at least one double or triple carbon bond.
Try it in two minutes
- Sort ten formulas into families.
- Spot saturated versus unsaturated.
- Circle the functional group.
Try at home. Sort home chemicals by family.
Nomenclature of Organic Compounds
Part of: Framework and Names
Longest chain parents, lowest locants, alphabetical branches, suffix for the lead group. Numbering favours principal groups, then multiple bonds, then branches; ties break alphabetically.
Why it matters. One name worldwide prevents mix-ups. Rules turn any sketch into a unique name.
Formulas
- Parent chain = longest chain carrying the principal functional group
- Number from the end giving the principal group the lowest locant
- Name pattern: prefix (branches) + root (chain) + suffix (group)
- List branches alphabetically; lowest locant set wins ties
Key words
- IUPAC nomenclature
- : Worldwide rule set giving every compound one unique name.
- Parent chain
- : Longest carbon chain that carries the main functional group.
- Locant
- : The number marking where a branch or group sits on the chain.
- Suffix
- : The ending of a name that shows the principal functional group.
- Prefix
- : The part of a name that shows attached branches or groups.
- Wrong parent selection
- : A name built from a wrongly short chain instead of the longest one.
- Alphabetical order
- : Arranging branch names from A to Z in the full name.
Try it in two minutes
- Find the longest chain in three sketches.
- Number toward the first branch.
- Order two branches alphabetically.
Try at home. Name five branched sketches.
Isomerism and Electronic Effects
Part of: Behaviour, Intermediates and Analysis
Same formula, different build: chains, positions, functions or space. Inductive pulls fade along sigma bonds; resonance shares pi electrons across frames; hyperconjugation leaks alkyl C-H into empty p. Electromeric shifts flash only during attack.
Why it matters. Same atoms, new properties. Electron shifts explain stability, acidity and directing.
Formulas
- Carbocation and free-radical stability: tertiary > secondary > primary > methyl
- Carbanion stability: methyl > primary > secondary > tertiary
- Inductive effect weakens steadily with distance along sigma bonds
Key words
- Tetravalence
- : Carbon forms four covalent bonds, giving chains, branches and rings.
- Catenation
- : Carbon links to itself in long stable chains, branches and rings.
- Isomers
- : Compounds with the same formula but different atom arrangements.
- Chain isomerism
- : Isomers differing in the carbon skeleton layout.
- Position isomerism
- : Isomers differing in the position of a group or multiple bond.
- Functional isomerism
- : Isomers belonging to different families with the same formula.
- Inductive effect
- : Electron pull through sigma bonds that fades with distance.
- Resonance
- : Sharing of pi electrons across a frame, raising stability.
Try it in two minutes
- Draw all C5H12 skeletons.
- Push arrows for resonance in aniline.
- Rank three carbocations.
Try at home. Build isomers with balls and sticks.
Reactive Intermediates, Purification and Analysis
Part of: Behaviour, Intermediates and Analysis
Charged and radical fragments rank by donation around them: tertiary beats methyl. Solids crystallise, liquids distil by boiling gaps, and chromatography parts mixtures. Lassaigne fuses elements into salts; Kjeldahl and Carius weigh nitrogen, halogens and sulphur from precipitates.
Why it matters. Stability ranks predict reaction paths. Classic tests still certify every new compound.
Formulas
- %C = 12 x m(CO2) x 100 / (44 x m sample)
- %H = 2 x m(H2O) x 100 / (18 x m sample)
- Dumas %N = 28 x V x 100 / (22400 x m sample)
- Kjeldahl %N = 1.4 x N x V / m sample
- Carius %X = atomic mass x m(AgX) x 100 / (mol mass AgX x m sample)
- Carius %S = 32 x m(BaSO4) x 100 / (233 x m sample)
Key words
- Carbocation
- : A carbon fragment left with only six electrons and a positive charge.
- Carbanion
- : A carbon fragment with a lone pair and a negative charge.
- Free radical
- : A carbon fragment with one unpaired electron and no charge.
- Heterolysis
- : Splitting that puts both bond electrons on one fragment.
- Homolysis
- : Splitting that gives each fragment one bond electron.
- Sublimation
- : Heating a solid to vapour that sets back into solid on cooling.
- Lassaigne test
- : Fusing the compound with sodium to trap N, S and halogens as salts.
- Chromatography
- : Separating mixture parts by their grip on a moving and still phase.
Try it in two minutes
- Rank four carbocations.
- Distil two liquids apart.
- Weigh nitrogen by titration math.
Try at home. Crystallise sugar from syrup.
What your child will practise
- Isomerism and Electronic Effects: Space Quick Fire (Quick Fire)
- Nomenclature of Organic Compounds: Jungle Quest (Flip and Match)
- Nomenclature of Organic Compounds: Ocean Puzzle (Clue Puzzle)
- Reactive Intermediates, Purification and Analysis: Jungle Quick Fire (Quick Fire)
- Tetravalence and Classification: Candy Puzzle (Clue Puzzle)
- Quiz: Isomerism and Electronic Effects (8 questions)
- Quiz: Nomenclature of Organic Compounds (8 questions)
- Quiz: Reactive Intermediates, Purification and Analysis (8 questions)
- Quiz: Tetravalence and Classification (8 questions)