SSC CGL Chemistry · Carbon and Its Compounds
Hydrocarbons and Fuels
The general formulas of alkanes, alkenes and alkynes with names for each carbon count, old and common names, how hydrocarbons burn, boiling points, and the chemists SSC names.
Why this matters
Thirteen questions in the bank: nine from the 2023 shifts and four from the 2024 shifts. Half need one general formula to answer, so learn the three formulas and you can name any chain.
Concept 1 of 2: Alkanes, alkenes, alkynes and their names
Definition
The families:
- Alkanes (saturated): CnH(2n+2). Propane is C3H8; nonane is C9H20.
- Alkenes: CnH(2n). Ethene C2H4, propene C3H6.
- Alkynes: CnH(2n minus 2). Ethyne C2H2, propyne C3H4.
- Benzene C6H6 is unsaturated.
Names and facts:
- Olefiant gas is the old name of ethylene. 1,3-dimethylbenzene is m-xylene; toluene is methylbenzene.
- Unsaturated hydrocarbons burn with a yellow, sooty flame; saturated ones with a blue flame. Ethanol burns to CO2 and water, giving heat and light.
- For the same carbon count, alkynes boil highest. Methane boils at 111 K, chloroform at 334 K.
- Fullerene (C60) was found by Curl, Kroto and Smalley in 1985.
Practise this conceptself-check · 3 quick reps
The same idea in a real exam question:
Example 1 · Carbon and Its Compounds · Hydrocarbons and Fuels
Benzene is not saturated
Concept 2 of 2: Chemists behind the rules
Definition
The names:
- Michael Faraday isolated benzene in 1825, from illuminating gas.
- Erich Huckel (1931): a ring is aromatic if it has 4n + 2 pi electrons.
- Kharasch and Mayo (1933): the peroxide effect, HBr adding against Markovnikov's rule when peroxides are present.
- Kekule proposed the ring structure of benzene.
| Chemist | Remembered for |
|---|---|
| Faraday, 1825 | Discovered benzene |
| Kharasch and Mayo, 1933 | Peroxide effectQ |
| Kekule | Benzene ring structure |
Practise this conceptself-check · 3 quick reps
The same idea in a real exam question:
Example 2 · Carbon and Its Compounds · Hydrocarbons and Fuels
Huckel, not Kekule
Summary — formulas & gotchas at a glance
A revision cheat-sheet for the formulas and gotchas above. Click any concept name to jump back to its full explanation.
Reference tables (2)
Chemists behind the rules3 rows
| Chemist | Remembered for |
|---|---|
| Faraday, 1825 | Discovered benzene |
| Kharasch and Mayo, 1933 | Peroxide effectQ |
| Kekule | Benzene ring structure |
Watch out for (2)
- Benzene is not saturated→ Alkanes, alkenes, alkynes and their names
- Huckel, not Kekule→ Chemists behind the rules
Test yourself on Carbon and Its Compounds
10 past SSC CGL questions from this chapter, timed at 6 minutes and marked the way the exam marks it. You see your score and every answer the moment you finish. Free to start.