Draw skeletal (line –bond) structures for the following compounds

1.Draw skeletal (line –bond) structures for the following compounds. cyclohexane ,cyclohexene, toluene 2.Write equations for the reaction of 1-butene with the following reagents. a) Br2/CH2Cl2 b) KMnO4/ hot 3.What would you expect the difference between reactivity of a) hexane and Cyclohexane b) hexane and cyclohexene? Explain answers. 4. condensed structure of cyclohexene 5.Write equations for the reaction of cyclohexene with the following reagents. a) Br2/CH2Cl2 b) KMnO4/cold

The Correct Answer and Explanation is :

1. Skeletal (line-bond) Structures:

• Cyclohexane:
  Cyclohexane is a six-membered carbon ring with single bonds, so it is represented as a hexagon with each corner representing a carbon atom. All hydrogen atoms are implied.

       CH2
     /      \
   CH2       CH2
   |           |
   CH2       CH2
     \      /
       CH2

• Cyclohexene:
  Cyclohexene is a six-membered carbon ring with one double bond. The double bond is represented by two lines between two carbon atoms.

      CH2
    /     \
  CH2      CH2
  |         |
  CH2  = CH
    \     /
      CH2

• Toluene:
  Toluene is a benzene ring (C6H5) with a methyl group (CH3) attached.

     CH3
      |
   C6H5

2. Reactions of 1-Butene:

• a) With Br2/CH2Cl2 (Br2 in dichloromethane):
  When 1-butene reacts with bromine (Br2) in CH2Cl2, an electrophilic addition reaction occurs. The bromine adds across the double bond, resulting in a vicinal dibromide. Reaction:

  CH2=CH-CH2-CH3 + Br2 → CH2Br-CHBr-CH2-CH3

• b) With KMnO4/ hot (Potassium permanganate, hot):
  The reaction of 1-butene with hot KMnO4 leads to oxidative cleavage of the double bond. This typically results in the formation of carboxylic acids or ketones. Reaction:

  CH2=CH-CH2-CH3 + KMnO4 (hot) → 2CH3COOH (acetic acid)

3. Reactivity Comparison:

• a) Hexane vs Cyclohexane:
  Hexane is a straight-chain alkane, while cyclohexane is a cyclic alkane. In terms of reactivity, hexane is more likely to undergo combustion or substitution reactions. Cyclohexane, due to its ring structure, is relatively more stable due to ring strain, but it can undergo substitution and oxidation reactions. Cyclohexane’s chair conformation minimizes steric strain, making it quite stable compared to open-chain alkanes. Hexane, being an acyclic chain, can also form isomers, making it less reactive in some reactions.
• b) Hexane vs Cyclohexene:
  Cyclohexene has a double bond, making it much more reactive than hexane in addition reactions. The double bond in cyclohexene is a site for electrophilic attack, so reactions like bromine addition and hydrogenation are common. Hexane lacks a double bond, so it is more inert and does not readily undergo these types of addition reactions.

4. Condensed Structure of Cyclohexene:

The condensed structure of cyclohexene is:

CH2CH=CHCH2CH2CH2

5. Reactions of Cyclohexene:

• a) With Br2/CH2Cl2:
  The reaction of cyclohexene with Br2/CH2Cl2 results in a vicinal dibromide (two bromine atoms added across the double bond). Reaction:

  C6H10 + Br2 → C6H10Br2

• b) With KMnO4/cold:
  The reaction of cyclohexene with cold potassium permanganate leads to a syn-dihydroxylation, where two hydroxyl groups (-OH) are added across the double bond in a syn fashion. Reaction:

  C6H10 + KMnO4 (cold) → C6H10(OH)2

Explanation:

• The reactions involving halogenation (Br2) and potassium permanganate (KMnO4) are both typical examples of electrophilic addition and oxidation reactions that are commonly observed with alkenes (like cyclohexene and 1-butene). The electron-rich double bond acts as a nucleophile, reacting with the electrophiles (Br2 or KMnO4). The double bond provides the necessary reactive site for these reactions. When hot KMnO4 is used, cleavage of the double bond occurs, often resulting in the formation of smaller molecules like acids. Cold KMnO4 leads to milder oxidation, forming diols.