Yr 2 Organic Chemistry Tutorials 3

ORGANIC CHEMISTRY TUTORIAL 3 QUESTIONS

1. Molecular Formulas of Alkanes

• Alkanes are saturated hydrocarbons with the general formula $C_nH_{2n+2}$.
• Examples of molecular formulas:
  • Methane: $CH_4$
  • Ethane: $C_2H_6$
  • Propane: $C_3H_8$
  • Butane: $C_4H_{10}$
  • Pentane: $C_5H_{12}$
  • Hexane: $C_6H_{14}$
  • Heptane: $C_7H_{16}$
  • Octane: $C_8H_{18}$
  • Nonane: $C_9H_{20}$
  • Decane: $C_{10}H_{22}$

2. IUPAC Names for Alkanes and Cycloalkanes

• Examples of IUPAC naming:
  • For simple straight-chain alkanes:
  • $C_4H_{10}$ is butane.
  • For cycloalkanes:
  • Cyclopropane: $C_3H_6$
  • Cyclopentane: $C_5H_{10}$

3. Structural Formulas for Alkanes and Cycloalkanes

• (a) 2,2,4-Trimethylhexane:

  • Structure:
  • $CH_3$
  • $|$
  • $C(CH_3)$
  • $|$
  • $C(CH_3)$
  • $|$
  • $C(CH_3)C_2H_5$

• (b) 2,2-Dimethylpropane:

  • Structure:
  • $C(CH_3)$
  • $| </li> <li>C(CH_3)$
  • $| </li> <li>C_2H_5$

• (c) 3-Ethyl-2,4,5-trimethyloctane:

  • Structure not provided but follow similar pattern.

• (d) 5-Butyl-2,2-dimetylnonane:

  • Structure similar.

• (e) 4-(1-Methylethyl) octane:

  • Structure similar.

• (f) 3,3-Dimethylpentane:

  • Structure similar.

• (g) trans-1,3-Dimethylcyclopentane:

  • Structure includes two methyls on a cyclopentane ring.

• (h) cis-1,2-Dimethylcyclobutane:

  • Structure of cyclobutane with two methyls on adjacent carbons.

4. Incorrect IUPAC Names and Corrections

• (a) 3,1-Dimethylbutane:

  • Incorrect because nothing must be lower than 2nd position. Correct: 2,3-Dimethylbutane.

• (b) 4-Methylpentane:

  • Correct as is, no changes needed.

• (c) 2,2-Diethylbutane:

  • Incorrect. There cannot be three substituents at the second carbon. Correct name: 2,2-Dimethylbutane.

• (d) 2-Ethyl-3-methylpentane:

  • Correct as is, no changes needed.

• (e) 2-Propylpentane:

  • Incorrect because propyl must be named as 3rd carbon. Correct: 3-Propylpentane.

• (f) 2,2-Diethylheptane:

  • Incorrect due to improper substituent numbering. Correct: 2-Ethyl-2-methylheptane.

• (g) 2,2-Dimethylcyclopropane:

  • Incorrect due to too many substituents on cyclopropane. Correct: 1,1-Dimethylcyclopropane.

• (h) 1-Ethyl-5-methylcyclohexane:

  • Correct as is, no changes needed.

5. Combustion Reactions - Complete and Balance

• Hydrocarbon reactions with $O_2$ yield $CO_2$ and $H_2O$.
  • (a) Propane: $C_3H_8 + 5O_2 <br /> ightarrow 3CO_2 + 4H_2O$
  • (b) Octane: $C_8H_{18} + 12.5O_2 <br /> ightarrow 8CO_2 + 9H_2O$
  • (c) Cyclohexane: $C_6H_{12} + 6O_2 <br /> ightarrow 6CO_2 + 6H_2O$
  • (d) 2-Methylpentane: $C_6H_{14} + 9O_2 <br /> ightarrow 6CO_2 + 7H_2O$

6. Alkenes Reaction with HI

• Order of reactivity with HI:
  • 1: Least reactive
  • 2: More reactive
  • Example: comparing structures:
  • $C_2H_4$ < $C_3H_6$ < $C_6H_{10}$
• Major products drawn as structural formulas after ranking.

7. Organic Products from 2-Butene and Reagents

• Reactions predicted with products drawn:
  • (a) H2O/(H2SO4): Major product: 2-Butanol.
  • (b) Br2: Major product: 2,3-Dibromobutane.
  • (c) Cl2: Major product: 2,3-Dichlorobutane.
  • (d) Br2 in H2O: Major product: 2-Bromo-2-butanol.
  • (e) HI: Major product: 2-Iodobutane.
  • (f) Cl2 in H2O: Major product: 2-Chloro-2-butanol.

8. Acid-Catalyzed Hydration Reaction Products

• Alkene structures yielding alcohol majors:
  • (a) 3-Hexanol: Alkene structure leading to this product.
  • (b) 1-Methylcyclobutanol: Alkene structure yielding this alcohol.
  • (c) 2-Methyl-2-butanol: Specific alkene structure.
  • (d) 2-propanol: Derived structure.

9. Regioselective Reactions of 2-Methyl-2-pentene

• Products drawn for:
  • (a) HI: Major product drawn with reagents accounted.
  • (b) HBr: Product explained.
  • (c) H2O:H2SO4: Major product with regioselectivity noted.
  • (d) Br2 in H2O: Products drawn with regioselectivity.
  • (e) Hg(OAc)2 /H2O: Major product drawn.

10. Regioselectivity and Stereoselectivity of 1-Methylcyclopentene Reactions

• Products explained for:
  • (a) BH3: Major product structurally illustrated.
  • (b) Br2/H2O: Major structural product shown.
  • (c) Hg(OAc)2/H2O: Product explained and drawn.

11. Alkene Structure for Major Product Omitting Doubles

• Alkene structures drawn leading to specific products based on molecular formula.

12. Addition of HCl to 1-Bromopropene

• Mechanism explained detailing how 1-Bromo-1-chloropropane forms exclusively.

13. Alkene Structure C5H10 with Br2 Reactions

• Structural formulas illustrated for reactions producing specified products.

14. Alkene Structure C5H10 with Cl2 Reactions

• Similar structural analysis with expected products drawn accordingly.

15. Reactions of 1-Methylcyclohexane with Oxidizing Agents

• Structures of major products from:
  • (a) OsO4/H2O2: Major product illustrated.
  • (b) O3 followed by (CH3)2S: Major product shown and explained.

16. Ozone Reaction Products

• Alkenes resulting from ozonolysis products drawn in structural formulas.

17. Conversion of Cyclopentane into Various Compounds

• Structural drawings for transformations into:
  • (a) trans-1,2-Dibromocyclopentane.
  • (b) cis-1,2-Cycloentanediol.
  • (c) Cyclopentanol.
  • (d) Iodocyclopentane.
  • (e) Cyclopentane (in original form).
  • (f) Pentanedial (structurally illustrated).

18. Reactions of 3-Hexyne with Various Reagents

• Major product structures predicted for reactions:
  • (a) H2: Product structure drawn.
  • (b) H2 Lindlar catalyst: Major product shown.
  • (c) Na in NH3(l): Predictions noted.
  • (d) BH3 followed by H2O2/NaOH: Major product structure illustrated.
  • (e) BH3 followed by CH3CO