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The product of the reaction (CH3-CH=CH-CH2-CH2-CH3 + Br2) is: A. CH3-C..

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Here is the breakdown and solution for each question related to organic chemistry reactions and isomerism in the CBC curriculum for Grade 6.

Question 8: Product of (CH3-CH=CH-CH2-CH2-CH3 + Br2)

Solution

The compound given is hex-2-ene (CH3-CH=CH-CH2-CH2-CH3). When it reacts with bromine (Br2​), an addition reaction occurs across the double bond:

The double bond is between C2 and C3:

CH3-CH=CH-CH2-CH2-CH3 1 2 3 4 5 6

Bromine adds to C2 and C3:

CH3-CHBr-CHBr-CH2-CH2-CH3

Correct answer: A. CH3-CHBr-CHBr-CH2-CH2-CH3

Question 9: Catalyst for Hydrogenation of Alkenes

Solution

Hydrogenation of alkenes (adding H2​) requires a metal catalyst. Common catalysts:

  • Copper: Not commonly used for hydrogenation
  • Nickel: Commonly used
  • Aluminium: Not used
  • Zinc: Not used

Correct answer: (b) Nickel

Question 10: Cis/Trans Isomerism of Compounds

Solution

Ask: Which compounds can have cis/trans (geometric) isomerism around a double bond? Cis/trans isomerism occurs when each carbon of the double bond has two different groups attached.

a. (CH3)2C=CHCH3

  • Structure:
  • Double bond between C1 (with two CH3 groups) and C2 (with one CH3 and one H)
  • C1 does not have two different groups (both CH3)
  • Cannot have cis/trans isomerism

b. H2C=CHCH3 (Propene)

  • Double bond between C1H2 and C2
  • C1 has two identical H atoms
  • Cannot have cis/trans isomerism

c. CH3CH=CHCH3 (But-2-ene)

  • Double bond between C2 and C3
  • C2 has CH3 and H
  • C3 has CH3 and H
  • Has cis/trans isomerism

Drawing the Isomers for CH3CH=CHCH3:

Cis-2-butene:

  • CH3 groups on same side:

    CH₃ H / C=C / H CH₃

Trans-2-butene:

  • CH3 groups on opposite sides:

    H CH₃ / C=C / CH₃ H

Labels:

  • Cis: CH₃ groups together (same side)
  • Trans: CH₃ groups opposite

"Draw the structural formulas of cis-2-butene and trans-2-butene, labeling each isomer accordingly."

d. CH3CH2CH=CHBr

  • Double bond between C3 and C4
  • Attachments to C3: CH2CH3 and H
  • Attachments to C4: Br and H
  • Each carbon of the double bond has two different groups
  • Has cis/trans isomerism

Drawing the Isomers for CH3CH2CH=CHBr:

Cis-isomer:

  • Br and CH2CH3 on same side

    H CH2CH3 / C=C /

    Br H

Trans-isomer:

  • Br and CH2CH3 on opposite sides

    CH2CH3 H / C=C / H Br

Labels:

  • Cis: Br and CH2CH3 together
  • Trans: Br and CH2CH3 opposite

"Draw the structural formulas of the cis and trans isomers of CH3CH2CH=CHBr, labeling each isomer accordingly."

Summary:

  • Only (c) CH3CH=CHCH3 and (d) CH3CH2CH=CHBr have cis/trans isomerism.
  • Diagrams for both isomers for these compounds are provided above.