Kit Library / Science / Organic Chemistry
⚡ Topic Learning KitShared by a Veda learner · Generated with Veda AI
Veda Bites are swipeable micro-lessons — each one teaches exactly one idea. The bites below come from this kit — swipe through them in the app.
💡 Key Idea
Single bonds only. No exceptions.
Alkanes are saturated hydrocarbons — they contain only carbon-carbon single bonds and C-H bonds, with no double or triple bonds anywhere.
↳ If a molecule has any double or triple bond, it is NOT an alkane.
📖 Definition
Latin for 'little affinity' — and it fits.
Alkanes are highly inert toward common reagents like $KMnO_4$, sodium dichromate, nitric acid, and hydrogen peroxide. This lack of reactivity earned them the name paraffins.
↳ Alkane inertness is a direct consequence of strong, stable sigma bonds.
💡 Key Idea
Every carbon sits at a tetrahedron's center.
In alkanes, each carbon is sp³ hybridized, giving a tetrahedral geometry with bond angles of about $109.5^\circ$.
↳ sp³ hybridization explains both the shape and the stability of alkanes.
➗ Formula
One formula, every alkane.
This formula defines the homologous series of alkanes — same functional behavior, different chain lengths.
↳ Plug in n to get the molecular formula of any alkane.
💡 Key Idea
Count carbons, pick the root.
↳ The root word is fixed by the number of carbons in the parent chain.
💡 Key Idea
One suffix tells you the bond.
For alkanes, the primary suffix is always -ane.
↳ Root + primary suffix = IUPAC name of the alkane.
⚙️ Process
Longest chain first. Always.
↳ Longest chain → lowest locants → alphabetical order. That's the IUPAC sequence.
✏️ Example
Left gives 11. Right gives 11. Now what?
An 8-carbon chain with methyl groups at positions 2, 3, 5, 6 from the left gives sum = 16; from the right gives 11. So numbering starts from the right.
↳ Lowest sum of locants decides the numbering direction.
⚠️ Common Mistake
Lowest first substituent beats lowest sum? Not always.
↳ One substituent → lowest single locant. Multiple → lowest sum.
⚖️ Comparison
Same formula, different boiling points.
↳ Branching reduces surface contact → weaker intermolecular forces → lower boiling point.
⭐ Important Fact
Gas → liquid → solid as carbons grow.
↳ All alkanes are colorless and odorless — only the physical state changes with size.
⭐ Important Fact
Like dissolves like — alkanes avoid water.
Alkanes are nonpolar, so they do not dissolve in polar solvents like water but dissolve readily in nonpolar solvents such as benzene, ether, and carbon tetrachloride.
↳ Nonpolar nature explains both insolubility in water and solubility in organic solvents.
⭐ Important Fact
Add one CH₂, raise the boil by 20–30 °C.
↳ Boiling point is regular; melting point is not — don't confuse the two trends.
❓ Did You Know
Even carbons pack better — and melt higher.
Alkanes with an even number of carbon atoms have higher melting points than their odd-numbered neighbors because they pack more symmetrically, allowing greater intermolecular attraction.
↳ Even-carbon alkanes pack better → higher melting point.
🎯 Exam Tip
This question appears every year.
↳ Three keywords — sp³, sigma bonds, nonpolar — earn full marks.
Alkanes are saturated hydrocarbons containing only carbon-carbon single bonds, making them inert 'paraffins'. This topic covers their sp3 structure, IUPAC nomenclature rules, and the trends in their physical properties.
Full explanation, worked examples & memory tricks in the app
All 17 questions, laddered from warm-up to topper-level, each with its answer and the reasoning behind it.
Q1. Which of the following best describes alkanes?
BeginnerAnswers and explanations are in the Veda app.
Q2. The general formula of alkanes is:
BeginnerAnswers and explanations are in the Veda app.
Q3. The hybridisation of carbon in alkanes is:
BeginnerAnswers and explanations are in the Veda app.
Q4. Which suffix indicates a carbon–carbon single bond?
BeginnerAnswers and explanations are in the Veda app.
Q5. The root word for a chain of 6 carbon atoms is:
BeginnerAnswers and explanations are in the Veda app.
Q6. Which of the following alkanes is a gas at room temperature?
BeginnerAnswers and explanations are in the Veda app.
Q7. Alkanes are called paraffins (Latin: parum = little, affinis = affinity) because of their very low chemical reactivity.
BeginnerAnswers and explanations are in the Veda app.
Q8. Alkanes are called paraffins because:
IntermediateAnswers and explanations are in the Veda app.
Q9. In the IUPAC name 2,3,5-trimethylhexane, what does 'hex' indicate?
IntermediateAnswers and explanations are in the Veda app.
Q10. A branched alkane has methyl groups at positions 2, 3 and 5 when numbered from the left, and at 5, 4 and 2 from the right. Which numbering is correct?
IntermediateAnswers and explanations are in the Veda app.
Q11. Why are alkanes inert toward reagents like $KMnO_4$ and $HNO_3$?
IntermediateAnswers and explanations are in the Veda app.
Q12. Which statement about the physical properties of alkanes is correct?
IntermediateAnswers and explanations are in the Veda app.
Q13. Why does a straight-chain alkane have a higher boiling point than its branched isomer?
AdvancedAnswers and explanations are in the Veda app.
Q14. Why do even-carbon alkanes have higher melting points than their odd-carbon neighbours?
AdvancedAnswers and explanations are in the Veda app.
Q15. Assertion (A): Alkanes are called saturated hydrocarbons. Reason (R): They contain only carbon–carbon single bonds and C–H single bonds.
AdvancedAnswers and explanations are in the Veda app.
Q16. A student names a compound '5,4,2-trimethylhexane'. What is the correct IUPAC name?
AdvancedAnswers and explanations are in the Veda app.
Q17. A branched alkane has the following substituents: a methyl group at position 2 and another methyl group at position 3 when numbered from the left, and a methyl group at position 4 when numbered from the right. What is the correct IUPAC name for this compound?
AdvancedAnswers and explanations are in the Veda app.
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