MHT-CET Chemistry · Teaching notes
Alkenes — MHT-CET Chemistry
Alkenes is about one question a paper in MHT-CET Chemistry, and none of its thirty-six past-year questions is HARD. Half of it is one skill — predicting what an alkene turns into — and there the reagent and its CONDITIONS decide everything: peroxide or not, cold alkaline or hot acidic KMnO₄. Names and stability come first, because the addition and elimination rules are built on carbocation and alkene stability. Every PYQ is tagged.
Every subtopic, worked example, formula and trap in one printable document — answers shown, ready to share.
Subtopic notes
Alkenes: IUPAC Names, Isomers, Hybridisation and Stability
13 PYQsAn alkene is named from the longest chain that contains its C=C, numbered to give the double bond the lowest locant; its stability grows with the number of alkyl groups on the double-bonded carbons.
Preparing Alkenes: Dehydrohalogenation and Saytzeff's Rule
3 PYQsHeating an alkyl halide with alcoholic KOH removes H and X from neighbouring carbons to give an alkene, and when more than one alkene can form the more substituted one is the major product.
Reactions of Alkenes: Addition and Its Direction, KMnO₄ Oxidation, and Ozonolysis
19 PYQsAn alkene adds reagents across its double bond — HX with Markovnikov's rule, HBr with peroxide the other way round, water through hydroboration the other way too — and is oxidised by KMnO₄ to a diol (cold, dilute, alkaline) or cleaved to acids (hot, acidic), or cleaved by ozone to aldehydes and ketones.
Formula & revision sheet
6 formulas · 5 gotchas across all subtopics — the exam-eve cheat-sheet
Formula & revision sheet
6 formulas · 5 gotchas across all subtopics — the exam-eve cheat-sheet
Formulas (2)
Watch out for (1)
- Taking the longest chain that skips the double bond→ Naming a Substituted Alkene
Watch out for (1)
- Picking the alcohol→ Dehydrohalogenation with Alcoholic KOH
Formulas (3)
Watch out for (3)
- Applying the peroxide effect to HCl→ Addition to Alkenes: Markovnikov, Peroxide Effect and Hydroboration
- '3-Bromopropane' is the paper's name for allyl bromide→ Addition to Alkenes: Markovnikov, Peroxide Effect and Hydroboration
- Stopping at cyclohexanol or cyclohexanone→ Oxidation by KMnO₄: Glycols or Cleavage
PYQ weightage by concept
7 concepts · 35 PYQs — where the marks actually sit, so you know what to drill first
PYQ weightage by concept
7 concepts · 35 PYQs — where the marks actually sit, so you know what to drill first
| Concept | PYQs | Share |
|---|---|---|
| Naming a Substituted Alkene | 5 | 14% |
| Isomers, Hybridisation and Alkadienes | 4 | 11% |
| Stability of Substituted Alkenes | 4 | 11% |
| Concept | PYQs | Share |
|---|---|---|
| Dehydrohalogenation with Alcoholic KOH | 3 | 9% |
| Concept | PYQs | Share |
|---|---|---|
| Oxidation by KMnO₄: Glycols or Cleavage | 9 | 26% |
| Addition to Alkenes: Markovnikov, Peroxide Effect and Hydroboration | 7 | 20% |
| Ozonolysis | 3 | 9% |
Test yourself on Alkenes
15 past MHT-CET questions from this chapter, timed at 14 minutes and marked the way the exam marks it. You see your score and every answer the moment you finish. Free to start.