MOST COMMON ORGANIC QUESTIONS:

1. Test for double bond / alkene 

• Bromine water 

• Turn from brown to colourless in case of carbon double bonds (alkenes)

• Type of reaction: electrophilic addition 

2. Define stereoisomerism 

• Molecules with same structural formula 

• Same molecular formula 

• Different arrangements of atoms in space 

3. Explain why X is the major product of the reaction while only small amounts of Y is produced 

• N carbocation has the least number of H atoms bonded to it, it is more stable 

• Due to positive inductive effect 

• There are more electron donating methyl groups 

• Reducing charge density on C+

4. Types of reactions

• Tollens Reagent: oxidation / reduction 

• 2,4 DNPH: condensation 

• Ketone with NaBH4: reduction / addition 

• Aldehyde and HCN: addition 

• ALKENE + steam: addition

• Alkene reactions are either electrophilic addition or redox, kmno4 reagent used are redox and the rest of the alkene are electrophilic addition.

• Halogenoalkane reactions are all nucleophilic substitution except to alkene which is elimination reaction 

5. Structural isomers 

• Same molecular formula but different structural formula/bond arrangement (types- chain, positional, functional group isomerism)

6. How does an sp2 and sp3 hybridization occurs and their bond angles in carbon atoms:

• Sp2: overlap of 2 s with 2 p atomic orbitals: 116-124

• Sp3: overlap of 2 s with all three 2 p atomic orbitals: 106-112

7. Identify the yellow pptx formed when adding alkaline aqueous iodine to a carbonyl containing organic compound 

• CHI3 - tri iodomethane

8. Explain the meaning of the term optical isomers

• Chiral centre attache to 4 different atoms or group of atom

• Non super imposable mirror image 

• Different spatial arrangement 

• Different rotations of plane polarised light  

9. Addition reaction 

• Reaction where 2 or more reactants give one product 

10. State the conditions required for chlorine to react with methane 

• UV light 

11. Role of H3PO4

• Acid, proton donor 

12. Justify why X is described as a catalyst

• It is regenerated at the end of the reaction 

• It is not chemically used up

• increases the rate of reaction

13. Suggest why an unbranched isomer has a higher boiling point than its branched isomer 

• Straight chain has stronger temporary dipole attractions

• More energy is required to break intermolecular forces 

14. Explain why X show’s geometric isomerism 

• Restricted rotation of C=C

• One of the methyl groups is on each side of C=C

15. Explain the origin of the dipole moment on X in this mechanism 

• Electrons in pi bond induce it 

• Electron density in pi bond repels 

16. Acid with NaCO3

• RCOOH + Na —> RCOONa +  H2O + CO2 

• No Reaction of Carboxylic 

17. Identify a reagent that can convert CH3OH to CH3I 

• HI (g) and I2 

18. Identify which species acts as an electrophile and explain why 

• ION with +ve charge 

• Accepts a pair of electrons 

19. Why X does not show geometric Isomerism

• Has 2 identical methyl groups on each side of the double bond  

20. When solving an absorptions question 

• Mention the functional group (e.g. Ketone AND C=O)

• Mention the absorption range 

21. When comparing X and Y in absorption questions 

• Mention what each of them lack from each other and their range 

• Mention what each of them have 

22. Explain why an organic compound X is very soluble in water

• it is polar 

• forms hydrogen bonds with water 

23. Define the term X-Alkane (X=Halogen)

• Carbon atom bonded to X is bonded to three other carbon atoms 

24. Suggest why the disposal of X is difficult (X=polymer)

• it is non biodegradable 

25. Suggest why 2-iodopropane reacts faster than 2-Bromopropane 

• C-I covalent bond is weaker 

• lower activation energy with 2 iodopropane 

• H-Cl bond is stronger than H-I

26. When reducing a Ketone you get a mixture of 2 organic compounds, why? 

• A ketone is planar, so it can be attacked from either side 

• optical isomers are formed 

27. Suggest why it might be difficult to distinguish between 2 absorptions of an organic compound (have similar bonds)

• Bonds in similar environments 

• Absorptions will overlap 

28. Describe how the composition of products differ from when an organic compound undergoes incomplete combustion 

• Production of Carbon monoxide and less carbon dioxide 

• Production of Unburnt hydrocarbons and C

29.  Remembering the ratio of halogen during NMR spectroscopy

Chlorine 3:1 and bromine 1:1

FORMULA FOR CALCULATING NO OF CARBON ATOM NMR SPECTROSCOPY

1.1/100 =[M+1] 100/1.1  x  (M+1)/M+

30. COLOUR CHANGES OF SOLUTION FOR ORGANIC TEST

• TOLLEN REAGENT

<Oxidises the aldehyde; forms (Silver mirror)

• FEHLING REAGENT 

<Oxidises the aldehyde; (red ppt)

2,4 DNPH

On presence of C=O group turns (orange)

31. Explain why methane CH4 has no overall dipole moment

• Charges cancel out 

• tetrahedral structure 

• Non polar

32. Products of some reactions 

• Alcohol + Halide → Halogenoalkane + Water 

• Acetyl chloride + Ammonia → Acyl chloride + hydrochloric acid 

• alkane + halogen → halogenoalkane + halide

• alcohol → alkene + water  

• Halogenoalkane with cyanide group + water → carboxylic acid + ammonia 

• Amide + water → carboxylic acid + ammonia